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2020 Sugarbeet Production Guide (A1698, Revised Jan. 2020)

The production guide will provide useful information to assist you in making timely management decisions.

Complied by Mohamed Khan, NDSU/University of Minnesota

David Franzen, NDSU; Mark Boetel, NDSU; Ashok Chanda, University of Minnesota, NWROC; Albert Sims, University of Minnesota, Crookston; Thomas Peters, NDSU/University of Minnesota


Introduction

Plan for Profitable Sugarbeet Production

This production guide will provide useful information to assist you in making timely management decisions. However, it does not give extensive details on any subject discussed. More detailed and complete discussions of weed control, soil fertility, insect and disease control, and most other aspects of sugarbeet production in Minnesota and North Dakota are presented in past issues of the Sugarbeet Research and Extension Reports, which are available on the web (www.sbreb.org).

The pesticide use suggestions in this guide are based on federal label clearances and research information from the North Dakota and Minnesota Agricultural Experiment Stations. All pesticide use suggestions are based on the assumption that all chemicals will continue to have a registered label with the Environmental Protection Agency.

The publishers do not assume any responsibility, make any guarantees or offer any warranties with regard to the results obtained from use of the data appearing in this guide.

Fertilizing SugarBeets

Nitrogen and Quality: Sugarbeet quality is dependent on the sucrose content in the roots and the level of impurities that must be removed during sugar refining. Production of high-quality sugar is especially important to growers who are paid based on extractable sugar delivered to the factories.

Proper nitrogen fertilizer use increases root and sugar yield. However, excessive nitrogen increases impurities and decreases sugar content. More precise nitrogen management within each crop in a sugarbeet rotation will help prevent overapplication and buildup of nitrogen in the subsoil.

Nitrogen Fertilizer Use Guidelines: Southern Minnesota Beet Sugar Cooperative 110 pounds (lb.) nitrogen per acre (N/A) for 4-foot depth soil sample or 80 lb. N/A for 2-foot depth soil sample

• Nitrogen fertilizer recommendations are similar for American Crystal Sugar Co. and Minn-Dak Farmers Cooperative. Use 130 lb. N/A and 100 lb. N/A when sampling to 4-foot and 2-foot soil depth, respectively. See Page 5.

• 65 lb./acre of nitrogen is required in the 0- to 2-foot soil depth to maximize early season crop growth, yield and quality. This amount is needed regardless of the quantity of residual soil nitrogen found below 2 feet.

Guidelines for Adjusting Nitrogen Recommended for Crops Following Sugar Beet

• Reduce N by 60 to 80 lb/acre next season on areas of green sugarbeet tops.

• Reduce N by 20 to 30 lb/acre next season on areas of yellow-green sugarbeet tops.

• Do not reduce N in zones within sugarbeet fields with yellow foliage.

Managing N Throughout the Rotation Using Precision Agriculture Techniques

Lower residual N levels can be achieved prior to sugarbeets through a rotation managed with precision ag techniques. Residual nitrate levels can be examined site specifically through grid or zone-based soil sampling. A composite pre-sample can be used to determine the likelihood of significant spatial variability in nitrate levels.

Choose grid soil sampling if field history is unknown, if fertility is high, when the field has a history of manure applications, when two or more fields are merged or if phosphate levels are particularly important.

Choose zone soil sampling if yield monitoring or remote imagery reveals a pattern relationship with the landscape, if no history is available or manure use has occurred, if the field has a history of relatively low phosphorus (P) rates or if mobile nutrient levels, particularly nitrate, are required.

* Subtract the amount of NO3-N in the top 2 feet of soil or top 4 feet of soil from these figures to determine the amount of N fertilizer to apply.


**Use the Olsen P test on soils with pH greater than 7. The Bray test is not recommended in North Dakota.

† Southern Minnesota Beet Sugar Cooperative recommends 80 and 110 lb N/A for 2-foot and 4-foot sampling, respectively.

‡ For Potassium in Minnesota, use the MN line. In North Dakota, ND 1 refers to soil with a smectite/illite ratio less than 3.5; ND 2 refers to soil with a smectite/illite ratio greater than 3.5. See the sugarbeet publication (www.ndsu.edu/fileadmin/soils/pdfs/Fertilizing_Sugarbeet_In_North_dakota.pdf) for map of where these are located.

Sugarbeets are a crop that is especially responsive to banded P placement. It also is a crop that is especially sensitive to fertilizer salts, so any banded starter fertilizer with the seed must be used at low rates. The following table summarizes recent broadcast and banded P research results:

Guidelines for Sugarbeet Fertilization With P

Following the above guidelines for the use of fertilizer P should address issues of fertilizer input savings with the use of banded P and maintenance of soil test P important to other rotational crops.

Micronutrients

Sugarbeets rarely respond to the use of micronutrients. Before using micronutrients on an entire field, try a test strip to determine a possible need.

Fertilizer Application: All P and potassium (K) recommendations in the fertilizer recommendation table are listed as the amount to be broadcast. We recommend that on low- to medium-testing soils, P fertilizer be applied before the deepest tillage operation. On soils testing high and very high, shallow incorporation of these rates is adequate.

Exercise caution with seed applications. Applying greater than 5 pounds per acre of N+K2O in contact with the seed can reduce plant stand emergence.

Common starter phosphorus fertilizer sources and maximum amounts suggested for seed application

Row Widths and Plant Populations

A row width of 22 inches is recommended in Minnesota and North Dakota. Research in the Red River Valley, Michigan and irrigated beet-growing areas indicates 400 to 600 pounds of sugar per acre are lost as row widths increase to 28 or 30 inches.

Higher, more uniform, plant populations are easier to establish on narrow rows. Growers interested in row widths greater than 22 inches must consider the anticipated advantages against lower yields per acre.

A good sugarbeet plant population at harvest should be about 175 to 200 uniformly spaced plants per 100 feet of row. This population should produce very good yields of high-quality sugarbeets.

Planting Rates and Seed Spacing: 22-inch Rows

Seeds and Seeding

Many varieties of seeds are available commercially in Minnesota and North Dakota. The Coded Variety Trial provides an excellent comparison of the performance of varieties in this area. Contact your agriculturist or seed company representative for more information on varieties.

Complete coded variety trial results for American Crystal Sugar Co. and Minn-Dak Farmers Cooperative are available in the Sugarbeet Research and Extension Reports (www.sbreb.org).

Sugarbeets should be planted as early as weather, soil moisture and temperature conditions permit. The potential for very high yields from early plantings usually is considered worth the risk of frost damage.

1. Plant seed 1 to 1.25 inches deep for maximum germination and emergence. Use shallow depths for earlier planting.

2. Plant sugarbeet seeds 4.5 to 5 inches apart in 22-inch rows when planting to stand.

3. A planting speed of 4 miles per hour is recommended for conventional planters and 6 to 8 mph for high-speed planters

4. Perform needed maintenance on planter prior to planting.

5. Please attend planter test stand clinic.

Planter Maintenance Checklist

1. Check the condition of hoppers, disks, drives and chains.

2. Be sure disc furrow openers are clean and turn freely.

3. Check seed ejection tubes for restrictions or blockage.

4. Be sure row spacings are correct and equal, and row markers are adjusted.

5. Lubricate the planter properly.

6. Clean seed hoppers daily.

7. Match seed sizes and planter plates carefully.

8. Test the planter on a hard surface to check the seed distribution pattern.

9. Number plates to match planter units.

10. Calibrate starter and/or fungicide application systems.

Planter Off-season Storage

1. Clean the planter with a pressure washer or high-pressure air; washing off all starter
fertilizer is especially important to prevent corrosion; flush all liquid-handling systems.

2. Remove plates and store them on a wood dowel hung horizontally.

3. Remove seed plate doors. Do not stack them on top of each other; use original boxes
for storage.

4. Release tension on press wheel springs.

5. Check for missing insecticide spoons or banders.

6. Make a list of needed repairs and parts.

7. Mouse-proof seed tubes (place fabric softener sheets in seed hoppers).

8. Save all new planter plate boxes for warranty use referral.

9. Keep track of how many acres are seeded on a set of plates (write the date of purchase
in the owners manual or on the plates).

10. Grease/protect electrical harness.

Sugarbeet Seed Specifications

 

Sugarbeet Seed Specifications

Recommendations for John Deere Maxi II Planter *

 

 

Vacuum Planter Comments

Before purchasing a new planter or different planter plates, contact your agriculturist, Norm Cattanach, or your seed salesman to discuss advantages or disadvantages.

John Deere:

1. These are the best plate combinations. Other combinations will work but may result in more skips or multiples. Adjust the vacuum as necessary.

2. Having plastic residue from the production process partially block the air holes in new plates is common. This causes skips and lower than desired population readings on the monitor. Before installing new plates, clean out obstructions by hand with a 1/16 inch drill bit. Do not enlarge the air hole.

3. Some new planters have small rough areas on casting from the production process; file them down as necessary.

4. Run units with all seals in place. Without all seals in place, a variation in vacuum levels from unit to unit will be experienced. Replace worn seals.

5. Check the monitor eye in the drop tube to make sure it is positioned properly. Seed may bounce off the monitor eye assembly if it is twisted slightly out of position.

6. In a large-tank central delivery system, remove the fuse that controls agitation in the tank. If not removed, seeds may be damaged.

7. In a large-tank central delivery system, use sorghum inserts.

8. When unfolding, check to see that all tubes have refilled with seed.

9. Replace “wipers” and knock-out wheels.

Monosem Planter Plates Recommendations

Best to buy with Plate 4025 because it plants seed from all companies

Vacuum Planter Comments

MONOSEM NG+:

1. Using plates smaller than recommended may result in seed falling off the plate when the planter bounces in the field.

2. 36-cell plates with the appropriate hole diameter will work, although increased plate turning speed may require higher vacuum levels to avoid seed falling off the plate.

3. When starting out in the field, monitor seed discs to ensure seed is staying on the plate. Increase vacuum if necessary.

White Seed Boss:

1. Use shims to obtain the proper air gap between the plant and meter.

2. Adjustment and/or modification of the tickler brush will improve performance.

3. A sugarbeet cutoff brush with metallic bristles helps remove static electricity.

Case Planter:

1. Singulators should be adjusted properly to the percentage of the hole showing and lubricated to work very freely.

2. Running it at a higher vacuum pressure may be better.

3. The planter has no agitation in the large tank; to compensate, use pure graphite or a graphite/talc blend.

Plate Recommendation

Plate Planters

 

John Deere Plate Planters

1. Plastic plates turn harder than steel, so lubricate the plate, false ring and hopper bottom lightly 
with talc. The plate should turn easily by hand.

2. Monitor the spring on the drop tube and keep it free of soil. Drop tubes should move freely up 
and down.

Seeding Rate and Plant Population Establishment (22-inch rows)*

Plant Population

Tractor Speed Calibration Chart

Weed Control

Timing of herbicide application is extremely important for maximizing weed control and recoverable sucrose per acre. Properly identify weeds and apply Roundup* to small (1- to 2-inch) weeds in Roundup Ready sugarbeets. Use maximum Roundup* rates, even in fields with weeds with low-level resistant biotypes because 1- to 2-inch weeds are easier to kill than 3- to 4-inch weeds, and dead weeds cannot produce resistant progeny. Research indicates allowing weeds at high density to get larger than 2 inches in height may reduce sugarbeet root yield.

Apply Roundup* in tank mixtures for waterhemp, kochia and ragweed control. Manage glyphosate-resistant waterhemp with residual herbicides. Apply Nortron,* Ro-Neet SB or Dual Magnum* PPI/PRE or S-metolachlor,* Warrant or Outlook* early postemergence in mixtures with Roundup* at full rates + Nortron* at 4 to 6 fluid ounces per acre (fl oz/A).

Residual herbicides applied early postemergence must be rainfall activated before waterhemp emerges in fields. Scout fields and spray Betamix (highest rate possible) + Nortron* + Roundup* or inter-row cultivate when waterhemp is 1 to 2 inches in height to control escapes.

Control 1-inch glyphosate-resistant common ragweed with Stinger* at 2 fl oz/A followed by a repeat application of Stinger at 2 fl oz/A at approximately 14-day intervals. Control 3- to 4-inch common ragweed with Stinger at 4 fl oz/A followed by Stinger at 4 fl oz/A at 14-day intervals. Tank-mixes providing effective weed control in the field across crops in sequence with sugarbeets, including corn, soybeans and wheat, is the most effective weed management strategy for control of tough weeds, including glyphosate-resistant biotypes.

Assure II* (ACC-ase-inhibitor [SOA 1] herbicide)-resistant wild oat populations are found in the Red River Valley. Manage herbicide-resistant wild oat biotypes with Far-Go (PPI) and/or Select* or Select Max* POST at full rates to small wild oats and repeat application as necessary at approximately 14- to 21-day intervals.

Maximize weed control in conventional sugarbeets by scouting fields and applying herbicide treatments when weeds are at the cotyledon to first true leaf stage. Scout the field before making the next herbicide treatment to determine the effectiveness of the previous application; make sequential herbicide applications on five- to seven-day intervals. Use full herbicide rates and effective adjuvants to kill weeds.

*Or generic equivalent

Weed Control Recommendations

The weed control suggestions in this production guide are based on the assumption that all herbicides mentioned will have a registered label with the Environmental Protection Agency. Herbicides no longer registered or that have not yet received registration for sugarbeets should not be used. Sugarbeets treated with a nonregistered herbicide may have an illegal residue which, if detected, could cause condemnation of the crop. Nonregistered herbicide use is illegal, and a user could be subject to a heavy fine, even without detectable residue.

Roundup Ready Sugarbeet

 

 

Chemical Names, Concentrations, Re-entry Interval, Preharvest Interval and Cost

 

Rainfastness Guide

Rainfall shortly after application often reduces weed control from postemergence herbicides because the herbicide is partially washed from the leaves. Herbicides vary in absorption rate and in the ease of being washed from leaves. The rainfall effect also can vary depending on rainfall amount and intensity. The approximate time between application and rainfall needed for maximum weed control is given in the following table.

Herbicide Combinations

Sugarbeet herbicides may be tank mixed legally if all herbicides in the mixture are registered for use on sugarbeets and if no prohibitions against tank mixes appear on a label. However, the user must assume liability for any resulting crop injury, inadequate weed control, or illegal and/or harmful residues. When a nonregistered combination is used, none of the manufacturers of the product used in the combination will stand behind its products.

Combinations of postemergence herbicides can improve spectrum and provide greater total weed control, compared with individual treatments. The risk of sugarbeet injury also increases with combinations, so combinations should be used with caution.

Roundup* can (and should) be tank mixed with herbicides to improve control of tough-to-control weeds in “RR” sugarbeets. Roundup* can be applied in combination with Nortron,* Betamix, Stinger* or UpBeet, depending on broadleaf weed species, to improve control in field. Roundup* also may be tank mixed with Dual-Magnum, Outlook* and Warrant to provide residual grass and small-seeded broadleaf weed control.

In general, annual grass and broadleaf control from Roundup* will not be antagonized by tank mix partners, provided Roundup* is applied at full rates. Field research in 2014 suggested that Stinger* may antagonize waterhemp control from Roundup,* although no statistical difference was found from Roundup*-alone herbicide treatments.

Adjuvant applied with postemergence herbicides in tank mixes with Roundup* is important. Roundup* is very water- soluble. High water solubility causes slow absorption through waxy plant cuticles. Nonionic surfactant (NIS) increases retention of spray droplets and improves control of hard-to-wet species such as common lambsquarters.

Most herbicides applied with glyphosate are oil-soluble. Oil adjuvants, including crop oil concentrate (COC) and methylated seed oil (MSO), greatly enhance oil-soluble herbicides but antagonize glyphosate. NIS is less effective with oil-soluble herbicides. MSO-based “high surfactant oil concentrate” adjuvants (HSMOC) contain a higher concentration of surfactant than COC and MSO, and enhance oil-soluble herbicides such as Nortron,* Betamix, Stinger* or UpBeet without decreasing Roundup* activity and, thus, should be used in tank mixes with glyphosate.

Always add ammonium sulfate (AMS) to glyphosate. AMS enhances glyphosate absorption and translocation and deactivates antagonistic hard water salts such as Na, Ca, Mg and Fe.

Glyphosate Combined With Other Pesticides

Liquid foliar insecticide and/or fungicide tank mixes do not antagonize grass or broadleaf weed control from Roundup* and are efficacious against insects and diseases, according to research conducted at NDSU. However, some tank mix products and combinations have the potential to cause sugarbeet injury under certain environmental conditions at certain growth stages and/or other circumstances.

For example, other herbicides, insecticides and/or fungicides combined with Roundup* are formulated with surfactants that may increase the potential for sugarbeet injury. Consider excluding NIS or HSMOC from insecticide containing tank mixes with Roundup*, especially when applied to cotyledon to two-leaf sugarbeets.

Tin fungicides plus sugarbeet herbicides, including Roundup* may cause more sugarbeet leaf burn than the tin fungicides alone. Injury tends to increase as the temperature and humidity at application increases. Quadris plus Roundup* (water- based) is safe to sugarbeets when applied without NIS or other oil adjuvants. However, Quadris plus other herbicides, such as Betamix, Dual Magnum* or Outlook* (oil-based) typically cause more sugarbeet injury than Quadris applied alone.

Roundup* may be applied with clear liquid fertilizers such as 28-0-0 or 10-34-0 but at less than 5% v/v because the salt solution will cause excessive leaf burn, limit translocation of glyphosate, and give erratic control of certain broadleaf and grass weeds. Do not use glyphosate with suspension-type liquid fertilizers.

Physical incompatibility may occur with herbicide, insecticide and/or fungicide tank mixtures and will result in the formulation of gels, creams, oil scums or other precipitates that may or may not be sprayable. If the incompatible tank mixture is applied over the crop, an uneven spray distribution may occur and result in unacceptable performance.

Herbicide Carryover

Herbicide residue or the persistence of phytotoxic levels of a herbicide for more than one year can be a problem with some of the herbicides used in North Dakota and Minnesota. Herbicide residues are most likely to occur following years with unusually low rainfall because chemical and microbial activity needed to degrade herbicides is limited in dry soil.

Some herbicides, such as Pursuit, Python and Raptor, carry over more in low pH soils, while other herbicides, such as the sulfonylureas Accent, Ally, Beacon and Classic, carry over more in high pH soils.

Crop damage from herbicide residues can be minimized by the application of the lowest herbicide rate that provides effective weed control, by using band rather than broadcast applications and by moldboard plowing before planting the next crop.

Moldboard plowing reduces phytotoxicity of some herbicides by diluting the herbicide residue in a large volume of soil and by providing untreated surface soil in which sugarbeets can germinate and begin growing.

The number of trade names for herbicides and herbicide combinations is increasing each year. The active ingredients of a herbicide should be identified prior to use to avoid unpleasant surprises with unexpected crop injury from carryover. Several herbicides are listed in the following table. These same herbicides could occur in mixtures under different brand names.

Rotation Restrictions for Several Crops

a  Refer to label - rotation restriction may be adjusted based on herbicide rate, rainfall, tillage, soil type, soil pH and bioassay.

B or b = Bioassay. Do not plant until field bioassay indicates it is safe. Crop rotation after atrazine* is rate and soil pH dependent. Python, Hornet and SureStart/TripleFlex = 26-month rotation + successful field bioassay. FirstRate = 30-month rotation + successful field bioassay. Pursuit = 40-month rotation + successful field bioassay.

c Requires thorough tillage and 12 inches of rain.

d days

e Above soil pH 7.9, soil bioassay must be performed.

g Cumulative precipitation between application and planting of dry beans, peas and sugarbeets is 20 inches. 10 MAA rotation interval applies to all dry bean types except red kidney and cranberry (18 MAA). Thorough tillage must precede planting of sugarbeets.

h Any rotational crop may be planted 120 days following application of dicamba at 1.5 pt/A or less, excluding days when ground is frozen. For all crops and rates greater than 1.5 pt/A, allow 45 days per 1 pt/A of dicamba used excluding days when ground is frozen.

i Crops with a nine- or 10-month rotation restriction require 15 inches of cumulative precipitation after application. Crops with a 17- or 18-month rotation restriction require 30 inches of cumulative precipitation after application. Soil at 7.5 pH or above requires crop rotation to be extended from nine or 10 months to 17 or 18 months and from 17 or 18 months to 24 months.

j Requires 15 inches of cumulative precipitation during the growing season following application. An 18-month restriction applies to Prequel and  rimsulfuron* applied above rates indicated or if drought follows application. Refer to label if higher rates are used.

k See label - 0.2 oz/A has less restrictive rotation restrictions than at higher rates. Requires 24 inches of accumulated precipitation.

m Do not plant dry beans, dry peas, soybeans or sunflowers for 18 months on soil with less than 2% OM and rainfall less than 15 inches during the  12 MAA OR may be planted 12 MAA if risk of injury is acceptable. Perform a field bioassay prior to planting for areas that receive less than 15      inches of rainfall and have less than 2% OM. Do not plant lentils, potatoes or any other broadleaf crops grown for seed for 18 months unless the      risk of injury is acceptable.

n Dry beans can be planted after nine months at Armezon/Impact rates of 0.5 fl oz/A or less. Field peas can be planted after nine months at              Armezon/Impact rates of 0.75 fl oz/A or less.

p Barley can be planted nine months after application in Cass, Grand Forks, Pembina, Towner, Traill and Walsh counties of North Dakota. In all other counties of North Dakota, allow an 18-month rotation restriction before planting barley.

s Corn can be planted only if Prowl*/H20 are applied PRE. Do not apply PPI.

t Rotation to barley is: 9 months if (greater than 18 inches water + greater than 6.2 soil pH) or (moldboard plow with less than
    18 inches water or less than 6.2 soil pH) or 18 months if (less than 18 inches water or soil pH less than 6.2).

  Rotation to potatoes is: 9 months: soil pH greater than 6.2 and rainfall is greater than 18 inches/year or 18 months: soil pH less
      than 6.2 and rainfall is less than 18 inches/year

  Rotation to sugarbeets: 18 months: soil pH greater than 6.2 or 26 months if soil pH is less than 6.2.

u Must add two months if soil pH is 7.5 or above. Wheat and barley can be planted 4 MAA following lentils or soybeans.

v Do not include time when soil is frozen. Sunflowers and safflowers are the most sensitive crops. For Verdict: Fall-seeded cereals can be planted    four months after application. All crops can be planted the spring following application.

w CRP grasses may be planted 13 MAA, but a field bioassay must be performed prior to planting CRP grasses. The manufacturer assumes no          liability for injury. Fall is recommended as the best time to plant CRP grasses.

x Do not plant corn or sorghum until soil samples analyzed for Tordon residue indicate no detectable levels present. Restriction is based on              nonlegal herbicide residue that may be found in corn and sorghum and not on crop safety.

y Oats, sorghum and annual or perennial grass crops may be planted at least 12 MAA in areas that received 20 inches or more of precipitation          during the growing season. CRP grasses may be planted 18 MAA if Treflan* is spring-applied or 21 MAA if fall- applied.

z For rotation to field peas in 10.5 months, precipitation must be greater than 7 inches during the 10.5 months following application and greater than 5.5 inches of precipitation from June 1 to Aug. 31 following application. Otherwise allow 18 months.

*Or generic equivalent.

Relative Response of Weeds to Soil Residual Herbicides Applied PPI, PRE or EPOSTa

Relative Response of Weeds to POST Herbicidesa

 

Maximizing Glyphosate (Roundup) Activity – Best Management Practices

1. Use the correct rate

A. Annual grass species: 0.77 to 0.84 lb ae/A

B. Annual broadleaf species: 0.98 to 1.125 lb ae/A

C. Perennial grass and broadleaf species: 1.125 to 3 lb ae/A

2. Apply over small, actively growing annual weeds and at the appropriate stage for perennial weeds. The larger a vegetative plant, the more difficult it is to control.

A. Annual grass and broadleaves: 1 to 2 inches

B. Perennial grass and broadleaf weeds: early bud/boot stage to early flowering or in the fall
at a minimum-sized plant

C. Biennial weed species: fall, after a light frost

3. Always add spray-grade AMS fertilizer at 8.5 to 17 lb/100 gal to increase absorption and translocation and to reduce antagonistic effects from hard water and some herbicide formulations. Use AMS replacements or water-conditioning agents at the equivalent rate of 8.5 lb/100 gal.

4. Apply during conditions when plants are growing actively and avoid fluctuation in temperature. Research data show wide temperature changes (>15 F) two to three days prior to and/or after the application are more likely to reduce weed control than consistently cool conditions. For applications to summer annual or spring applications to perennial weed species, do not apply if the daytime low temperature is below 38 F and the daytime temperature does not exceed 45 to 50 F.

5. Apply between 9 a.m. and 5 p.m., especially if velvetleaf, common or giant ragweed are present in the field.

6. Reduce dust during application by reducing travel speed because it inactivates glyphosate. Increasing spray volume and offsetting (perpendicular to first application is ideal) subsequent applications can decrease the inactivation of glyphosate caused by dust. Always allow a rain-free period after application of at least six to 12 hours, regardless of formulation. This is especially important for lambsquarters control.

7. Applying contact herbicides in a tank-mix with glyphosate may result in antagonism and reduce weed control. Increase the glyphosate rate to the highest single application rate and use a high-surfactant methylated oil concentrate (HSMOC) adjuvant when tank-mixing with a contact herbicide.

8. Always add a high-quality nonionic surfactant (NIS) at 0.25 percent v/v to fully loaded formulations (unless the label prohibits), especially to improve lambsquarters control and at 0.25 to 0.50 percent v/v to partially loaded formulations and at 0.5 to 1 percent v/v to nonloaded formulations.

9. Apply at a 5- to 10-GPA spray volume when applying alone or in combination with another systemic herbicide. Apply at a 15- to 40-GPA spray volume when applying in combination with a contact herbicide or when weeds are tall and dense.

10. Do not tank-mix foliar fertilizers unless necessary. Add spray-grade AMS when necessary to mix with foliar fertilizers.

11. Scout for glyphosate resistance. Identify glyphosate-resistant biotypes early (few plants/field) and remove surviving plants from field by hand-pulling.

12. The interval between glyphosate applications should be approximately 14 days, depending on growing conditions, and weed size and density.

13. Glyphosate products are formulated in many different acid-equivalent concentrations. Use acid- equivalent rates of glyphosate when comparing formulations to be confident of applying the correct product rate.

14. Avoid spraying with heavy dew on plants. Excessive dew on plant foliage at application may reduce weed control by diluting droplet concentration.

Insect Management

Sugarbeet Root Maggot

2020 Fly Activity Forecast

The 2020 sugarbeet root maggot (SBRM) forecast map for the Red River Valley (RRV) is shown in the figure below. The 2019 growing season marked the third consecutive year of significant increases in fly activity and SBRM feeding injury at several RRV locations. This suggests that SBRM infestations in 2020 generally will be higher than in previous years.

Areas at highest risk of damaging SBRM infestations include rural Auburn, Bathgate, Cavalier, Crystal, Glasston, Grand Forks, Merrifield, St. Thomas, Thompson and Walhalla, N.D., as well as Argyle, Crookston, Donaldson, East Grand Forks, Eldred and Stephen, Minn. Moderate risk is expected in areas bordering high-risk zones, as well as fields near Drayton, Buxton, Forest River, Hamilton, Nash, Oakwood and Reynolds, N.D., and Ada, Crookston, Eldred and Fisher, Minn. The remainder of the area is at lower risk.

Proximity to previous-year beet fields where SBRM populations were high and/or control was unsatisfactory can increase risk. Sugarbeet fields near those areas where high fly activity occurred in 2019 should be monitored closely in 2020.

Growers in high-risk areas should use an aggressive form of at-plant insecticide treatment (granular insecticide) and expect the need for a postemergence rescue insecticide (banded granules or peak fly spray). Those in moderate-risk areas using insecticidal seed treatments for at-plant protection should monitor fly activity levels closely in their area and be ready to apply additive protection if justified.

Any grower in an area with a history of SBRM problems should pay close attention to fly activity levels in late May through June to decide if postemergence treatment is needed. NDSU Entomology will continue to inform growers regarding SBRM activity levels and hot spots each year through radio reports, the NDSU “Crop & Pest Report” and notification of sugar cooperative agricultural staff
when appropriate. Root maggot fly counts for the current growing season and those from previous years can be viewed at
www.ndsu.edu/entomology/people/faculty/boetel/flycounts.

Root Maggot Management

Please note the following important terminology used in this guide:

Fly emergence pertains to the initial appearance of flies emerging from soil in previous-year beet fields where they had overwintered as larvae and

Fly activity refers to fly numbers in current-year beet fields.

The time between fly emergence from previous-year beet fields and activity in current-year fields is weather-dependent and varies among years. Forecasts and updates on these events will be provided to growers, county Extension personnel, sugar cooperative agricultural staff and other agricultural professionals by using various media outlets. However, there is no substitute for careful activity monitoring on an individual-field basis.

Cultural Control

Early planting allows for larger beet roots during the period of peak SBRM feeding activity (mid-June to mid- July). Larger roots are more able to withstand feeding injury and can avoid potential yield impacts if adequate rainfall is received.

Roots of smaller, late-planted beets are more vulnerable to feeding injury. Severe injury can kill seedlings and cause major stand reductions or result in smaller, sprangled, bulb-shaped roots at harvest.

Using a rotary hoe or field harrow across beet rows in June following egg deposition can help reduce maggot numbers. These tillage practices can move eggs away from beet seedlings and onto the soil surface, which exposes them to predators and the elements. As a result of exposure to heat and dry air, the developing maggots sometimes die before hatch. This cultural strategy works best if hot and dry weather coincides with egg deposition.

Sowing oat cover crops immediately before beet planting can reduce SBRM injury to sugarbeet roots. Cover crops provide a dense plant canopy and the shading helps keep soils moist. This condition is believed to keep larvae feeding higher in the soil profile (away from tap roots and nearer to insecticide-treated soil). Also, the dense network of oat roots may impair the ability of larvae to locate and feed on beet roots.

Added benefits of cover crops include soil stabilization, protection of beet seedlings from mechanical wind injury and reduced abrasion from wind-blown soil. Cover crops should be killed by applying a grass-killing herbicide during the last week of May or first two weeks of June to avoid sugarbeet yield losses due to competition from cover crops for water, sunlight and soil nutrients.

Chemical Control

Suggestions in this guide are based on the assumption that insecticides listed herein will have registration for the suggested use in the current production season. Remember to always read, understand and follow all label directions and precautions for the insecticide product you use. Using an insecticide in a manner inconsistent with its label is illegal, and violators may be subject to fines. Nonregistered uses also may result in condemnation of the crop.

Planting-time granular insecticides are important tools for managing sugarbeet root maggots in the Red River Valley. A few basic steps in preparation for insecticide applications can increase the probability of accuracy, effectiveness and economical use of these products. Preparation for planting should include serious attention to the following:

• accurate calibration

• unrestricted, consistent flow of granules

• even distribution of granules over the row

• adequate incorporation into soil

• protection from wind

Calibrate all of the planter’s granular applicators for the insecticide that will be used and for the exact registered rate needed. This is fairly simple because application rates on granular insecticide labels and in Extension materials are listed in ounces of product per 1,000 row feet. Reconfirming calibration settings for the desired output also is advisable at least once after planting about 50% of your anticipated acreage.

Ensure that granules will flow smoothly down the drop tubes. Incorporate insecticide granules well into the upper ¼ inch of soil.

Wind is a perennial challenge to making effective insecticide applications in the Red River Valley. Commonly, as much as 30% of the granules can be blown sufficiently far from the furrow to render them ineffective for protecting roots from insect pest injury. As a result, insecticide concentrations applied directly over the rows are greatly diminished.

If winds are too high (20+ mph), discontinue planting until winds diminish. Calm conditions are more likely to occur during evening and early morning hours, and these times can be more conducive to accurate granule placement when daytime winds are a problem.

The addition of wind shields to planter row units is a practical solution that greatly diminishes the impact of wind on granule placement. We strongly recommend that wind shields be installed on any sugarbeet planter used to apply planting-time soil insecticides.

Growers anticipating SBRM problems should consider the following management recommendations:

• Apply a granular insecticide application at planting.

• Place granules in 5-inch bands over the row or deliver via “spoon” applicator.

• Incorporate insecticide granules into the upper ¼ inch of soil during application.

Recommended Application Rates for Planting-time Soil Insecticides Based on Expected SBRM Population Level

Moderate application rates of labeled soil insecticides are recommended in areas where correspondingly moderate SBRM infestation levels are expected. These treatments should be sufficient if adequate soil moisture prevails after planting. High labeled application rates should be used in areas where SBRM populations are expected to be high (see forecast map), especially in areas where SBRM problems were evident during the preceding year.

Replanting Sugarbeets

NDSU research has shown that major yield losses due to SBRM feeding injury are likely if replanting is done without applying a second insecticide treatment in high-risk fields. Beets in replanted fields usually are smaller and more vulnerable to attack during the root maggot larval feeding period than older, more established plants. Therefore, growers in areas where high maggot populations are anticipated are advised to consider two options: 1) apply another granular material at replanting or 2) apply a postemergence liquid or granular insecticide.

Treatment with Counter 20G or Lorsban 15G (and most generic chlorpyrifos-containing granular materials) is limited to one application per year. Therefore, if one of these products was applied at initial planting, another labeled material must be used for re-planting or at postemergence. To avoid future development of insecticide-resistant root maggot strains, rotation to a different active ingredient or even a different chemical class is advised.

Postemergence Insecticides

In areas where moderate to high root maggot infestations are common, additive plant protection may be needed for adequate SBRM control, especially if an insecticidal seed treatment or a low rate of a planting-time insecticide was used for at-plant protection. Consideration of a few factors can help decide whether a postemergence insecticide is needed.

Soil moisture - Good soil moisture enhances the effectiveness of planting-time granular insecticides.

Postemergence granules work best under moist soil conditions, and liquids work better than granules in dry soils.

Sugarbeet size at peak fly activity - Early planted beets may have sufficient root development and size to withstand some maggot feeding without major yield loss. Therefore, a planting-time granular application may be sufficient. Sugarbeet fields in 10- to 14-leaf stages of development or those with an established canopy are generally large enough to withstand moderate levels of feeding. Tolerance to feeding injury can be enhanced with rainfall in early June and through July.

SBRM population level - Growers and crop advisers are encouraged to check individual fields for threatening fly activity levels and to monitor radio, DTN the NDSU “Crop & Pest Report” and other media sources for reports on fly activity levels from late May through June.

Postemergence Granules

Any of the following conditions can warrant use of a postemergence granular insecticide application:

• Replanted beet field (especially if no insecticide was applied during replanting)

• Heavy rainfall after planting (1 to 3 inches or more within first 24 hours or at least 6 inches if received in one or two rainfall events within a week after planting)

• Proximity of current-year beets to previous-year beet fields where high fly populations occurred during the preceding growing season

When a postemergence granular insecticide application is made, a few important factors should be considered.

• First, granules should be applied around late May or early June and, if possible, ahead of an anticipated rainfall.
If optimal timing is in question, erring toward applying granules early is advisable.

• Second, granules should be incorporated into the soil. If the soil surface is wet or crusted, drag chains may not sufficiently incorporate the insecticide.

• Third, moisture is required after the application to move the chemical off its granular carrier and into the soil. Without rain to activate the insecticide, control provided by a postemergence granule likely will be marginal.

Postemergence Liquids

Postemergence liquid insecticides are most beneficial and cost effective under dry conditions, especially when SBRM fly activity is high. Timing of the liquid spray application is critical. Applications made too early or too late will not produce the desired result and may not be cost effective.

Liquids work best when applied within three days of (preferably before) peak fly activity. Rain following the application can enhance the performance of foliar insecticides that also have activity against larvae in the soil (for example., chlorpyrifos-containing liquid products such as Lorsban Advanced and Lorsban 4E).

If rain is likely five to seven days before peak fly activity, the application should be made before the expected rain. These applications will be more effective if applied at least 24 hours before rain occurs.

The decision to apply liquid chlorpyrifos for fly control and larval suppression following a planting-time granular insecticide should not be made before SBRM fly numbers are estimated. Observation of posted sticky stake capture data can aid in this determination; however, it is no substitute for actual monitoring of individual fields.

If conditions warrant applying a postemergence liquid insecticide, the following recommendations are suggested:

• Apply the insecticide in 7- to 11-inch bands or as a broadcast. If broadcasting, avoid using an exceptionally low (less than 50% of labeled maximum) rate.

• Treat slightly (two to four days) before peak fly activity occurs in the current-year beet field.

• If practical, make only one application per season to minimize the likelihood of developing insecticide-resistant root maggot strains.

Insecticides Labeled for Controlling Insect Pests in Sugarbeets

Sugarbeet Root Maggot

 

Wireworms

Wireworms are smooth, somewhat hard-bodied larvae that vary in length from ½ to 1½ inches long; however, they are most damaging when they are ½ to ¾ inch in length. They range from yellowish white to bright or deep copper hues.

Wireworms feed on a wide variety of crops and weeds, and are difficult to detect and control. They tend to be more prevalent in light-textured soils and in fields that had a grassy crop the previous season or had not been in crop production for several years. Fields that had grassy weed escapes during the preceding season also are at risk.

Frequent tillage helps reduce wireworm problems.

Threshold: No economic threshold has been established for wireworms in sugarbeets; however, field history can be a good indicator of risk. The following insecticides should protect sugarbeets from wireworm injury. Refer to product labels for more information.

Cutworms

Darksided and redbacked cutworms are the most common cutworm pests of sugarbeets in the Red River Valley. Eggs of both species hatch into larvae during late May and early June. Fields should be checked frequently during early spring for wilting or dead plants because early detection of injury is essential to good control.

Cutworms can be found within 2 inches of the soil surface near bases of wilting plants. Most feeding occurs at night. Young plants often are cut off near ground level. During periods of dry weather, larvae feed just below the soil surface as they move along the row. They will feed above the soil surface if soil is excessively moist.

Applying insecticides during late afternoon is desirable because it maximizes the amount of insecticide material present during the first nighttime hours following application when larvae are often most active. Applications may be repeated as necessary during peak cutworm feeding.

Liquid formulations generally provide better control of cutworms, especially in dry soils. If severe crusting is evident in the field, the crust should be broken up before or during the insecticide application.

In 2001, variegated and black cutworm infestations caused problems in late July and August. These insects migrate into our region as moths during the spring and are capable of multiple generations within a single growing season. Variegated cutworm larvae have a distinctive row of pale yellow spots down the middle of their backs.

They are a climbing cutworm species that primarily feeds in the plant canopy during evening hours. Because variegated cutworms feed above ground, they can be managed effectively by using foliar rescue insecticide applications.

Black cutworms in late-season infestations often feed more than 2 inches below ground. Therefore, late-season control of this species can be difficult and is improbable to achieve.

Threshold: Application of an insecticide labeled for use in sugarbeets is advisable in young beets when larval cutting off of seedlings reaches from 4% to 5%. Control may be justified for late-season infestations of three to five larvae per square foot if they are feeding near or above the soil surface.

Springtails

Springtails that damage Red River Valley beet fields are tiny (1/32 to 3/32 inch long), wingless, white to cream-colored insects with fleshy, forward-pointed antennae. Species that affect valley beets are subterranean, spending their entire life below the soil surface. They are most harmful to seedlings, and injury ranges from a few brown feeding punctures to extensive root scarring, severed tap roots and seedling death. Symptoms include wilted plants and stand loss, often in patches of 0.3 to 5 acres.

Fine-textured soils with high organic matter content are conducive to springtail problems. Early planted fields, especially in years where soils remain cool and wet during early spring, can be especially vulnerable to attack. Field history is a good indicator of risk because springtails do not migrate from one field to another.

Insecticides registered for use in sugarbeets against other soil-dwelling pests can be used for springtail control; however, manufacturers are not legally bound to guarantee acceptable control if springtail control is not listed on the product label. NDSU research indicates the following:

- Counter 20G provides good springtail control at rates between 0.9 and 1.5 lb AI (4.5-7.5 lb product) per acre.

- Some growers have reported unsatisfactory control from Mustang Maxx. To maximize performance, apply it:

• Directly in-furrow at planting using conventional nozzles (not microtubes)

• At full rate of 4 oz. of product per acre and

• Tank-mixed with strained 10-34-0 starter fertilizer at a ratio of 60:1 (fertilizer to insecticide)

- Lorsban 15G and chlorpyrifos-based generics do not provide adequate protection from springtail injury.

- CruiserMaxx, NipsIt Inside and Poncho Beta seed treatments also provide good springtail control.

NOTE: Seed treatment insecticides reportedly have failed to control springtails in the MonDak area. The alleged failures could have resulted from extremely high infestations, or possibly could have involved a different springtail species from those that occur in the Red River Valley. Please report suspected failures to Mark Boetel at NDSU.

Lygus Bugs

Tarnished plant bugs, commonly referred to as Lygus bugs, occasionally have caused late-season injury to Red River Valley sugarbeet fields since the late 1990s. Most feeding injury appears on new leaves and stems emerging from the sugarbeet plant crown. Feeding symptoms include leaf curling and wilting, leaf-tip burn, feeding scars on leaf petioles and seepage of a black exudate from petioles of young leaves.

Lygus bugs are sporadic pests in this region. Two to three generations can develop during a single growing season in the Red River Valley. Mild winters or those in which frequent snowfalls provide adequate insulation for overwintering adults, followed by early spring warmups or generally warm growing seasons, increase the likelihood of a third generation being produced. Populations usually build up in other host plant habitats (for example, alfalfa, canola, small-seeded broadleaf weeds), and then adults migrate to beets in late July through August.

Threshold: Insecticide treatment may be justified if an infestation exceeds one Lygus bug per plant (nymphs and adults combined). NDSU research suggests that insecticide treatment is not likely to be economically beneficial if the application is made within three weeks of harvest. The insecticide preharvest interval is a critical factor in choosing a product for Lygus bug control because these pests usually infest beets late in the growing season.

A number of insecticides approved for use in sugarbeets have activity against Lygus bugs; however, the most common species that attack Red River Valley sugarbeet fields (Lygus lineolaris, the tarnished plant bug) is not listed as a target pest in the sugarbeet portion of those labels. Examples include Asana XL, carbaryl (Sevin XLR Plus and several generic products), Lannate LV and Lannate SP.

Applying an insecticide to sugarbeets is legal when it is labeled for use in the crop; however, if the specific target pest is not listed for sugarbeets, effective control is not implied by the manufacturer, and growers who choose to use the product assume all liability for any unsatisfactory performance.

SugarBeet Disease Management

I. Seedling and Root Diseases

Aphanomyces typically causes postemergence damping-off, and seedlings are very susceptible when they are 2 to 3 weeks old, especially when soils are wet and warm. Tachigaren (hymexazol) is highly effective against Pythium at lower rates and Aphanomyces at higher rates. Tachigaren persists for only three to four weeks and will provide protection only for the emerging seedling; it does not provide full-season protection from Aphanomyces.

Commercial seed treaters apply Tachigaren to sugarbeet seeds. Tachigaren can be used at 20 to 30 grams per unit (100,000) of seed on minimum buildup pelleted seed or 45 to 90 grams per unit of seed on standard pelleted seed. Rates greater than 45 grams of Tachigaren per unit of seed may cause phytotoxicity.

The rate of 20 to 30 grams of Tachigaren is recommended on fields with light to medium disease pressure. However, the 20- or 30-gram rate may be inadequate for medium disease pressure when the soil is warm after a heavy rainfall or when these conditions are prolonged within three weeks after planting. The rate of 45 grams of Tachigaren is recommended for fields with heavy disease pressure.

For season-long management of Aphanomyces, the best approach is to use varieties with partial resistance to Aphanomyces treated with Tachigaren. The sugar factory byproduct “waste lime” at 10 tons/acre is very effective against Aphanomyces for up to 12 years. Early planting and good drainage also may help reduce early season losses from Aphanomyces seedling disease. An Aphanomyces soil test should be done to determine if the soil is infested with Aphanomyces and the level of infection.

Rhizoctonia can cause pre- and postemergence damping-off of the seedlings when the soils are warm and moist. In severely infested fields, plant resistant varieties early, avoid “hilling” soil on sugarbeet crowns, increase the length of rotation and rotate with nonhost crops such as small grains.

Seed treatment such as Kabina ST (Penthiopyrad), Vibrance (Sedaxane) or Systiva (Fluxapyroxad) will provide early season protection for about four to five weeks. Products such as Rizolex (Toclofosmethyl) provide some level of protection. Other products may be labeled but do not provide effective control of R. solani. Quadris (azoxystrobin), including generics such as Aframe, Satori and AZteroid, and Xanthion (pyraclostrobin+ Bacillus spp.)) applied in-furrow will provide early to midseason control. In-furrow applied fungicides can affect stands under cold and dry conditions, especially when used with a starter fertilizer such as 10-34-0.

Rhizoctonia also can be managed by applying Quadris and generic azoxystrobin products such as Aframe, Satori and AZteroid, Priaxor (fluxapyroxad + pyraclostrobin) or Proline (prothiconazole) in a 7-inch band over the crowns from the four- to eight-leaf stage. Broadcast application is not as effective as band application under moderate to heavy disease pressure. These fungicides provide better protection when application is done just prior to a ¼- or ½-inch rainfall. Fields with a history of severe disease may need a second post-application in warm and wet conditions for season-long control.

Rhizomania (crazy root) is caused by the beet necrotic yellow vein virus (BNYVV), which is transmitted by the soil- borne protozoan vector Polmyxa betae. The vector can survive in soil or root debris. High soil moisture and warm temperatures will favor the vector to transmit BNYVV into plants because they infect roots.

Rhizomania is characterized by stunted taproots with masses of hairy lateral roots, giving them a bearded appearance. The root often is constricted and the vascular tissues become discolored. The leaves, with elongated petioles, become fluorescent yellow, similar to nitrogen deficiency symptoms.

Rhizomania can be managed by early planting of approved resistant varieties in well-drained fields on a three- to four- year rotation. Select varieties with high resistance levels for areas with a known history of severe Rhizomania. Recent research shows that new strains of this virus are developing; these strains may overcome the existing resistance in the current cultivars. Please let your agriculturist know if you suspect Rhizomania in your field(s).

Fusarium yellows and Fusarium yellowing decline typically are caused by the fungus Fusarium oxysporum f. sp.betae and F. secorum, respectively. Fusarium yellows/yellowing decline may cause seedling death or poor growth and even death of older plants.

Symptoms first appear on older leaves as chlorosis (yellowing) between the larger veins. As the disease progresses, younger leaves also become chlorotic, and the older, symptomatic leaves become necrotic. Occasionally, only half of a leaf is chlorotic or necrotic (a symptom more typical of Verticillium wilt, which also was identified on sugarbeets in our region). Entire leaves eventually die but remain attached to the plant and collapse in a heap around the crown.

No external root symptoms are associated with Fusarium yellows/yellowing decline. A transverse section through the root shows a grayish-brown vascular discoloration. Infection of mature plants may not cause death, but the disease causes significant reduction in root yield and recoverable sucrose. In storage, the quality of infected roots may deteriorate more rapidly, compared with non-infected roots.

The disease is favored by high soil temperatures. Fields that are waterlogged or have poor soil structure provide favorable conditions for infection. In fields with early season abiotic stress, susceptible varieties are more prone to infection and may lead to complete destruction.

Crop rotation may reduce inoculum buildup in the soil, but this practice is unreliable because the pathogens have a wide host range and chlamydospores can survive for many years. Use approved Fusarium-resistant varieties to manage this disease. See publication PP1247 for more information on Fusarium yellows of sugarbeets.

Given the long-term nature of the persistence of soil-borne diseases in soil, growers should pay utmost attention to not moving soil between fields, thoroughly cleaning the heavy equipment and having a strategy to manage tare piles in individual fields.

II. Leaf Spots

Various leaf spot diseases can affect sugarbeets. Cercospora leaf spot, caused by Cercospora beticola, is the most common and destructive disease in this area. The severity of Cercospora varies from year to year, depending on weather conditions, inoculum potential and varietal resistance. Cercospora can cause losses in susceptible varieties through reduced tonnage, reduced sucrose content, increased impurities and poorer storage after harvest when the roots are in piles.

Bacterial leaf spot generally does not cause economic damage. Bacterial leaf spot may develop in wet weather; no fungicide is registered for its control. See publication PP1244 for a comparison of Cercospora and bacterial leaf spot in sugarbeets.

Alternaria leaf spot is reported in some fields in our growing region that are favored by relatively cool temperatures and high humidity. Stressed sugarbeet plants appear to be more susceptible to Alternaria, and some sugarbeet varieties are more susceptible than others. If you have experienced flare-ups of Alternaria in your fields, talk to your seed company representative for assistance with choosing a suitable variety.

Leafspot Management

Management of Cercospora requires an integrated approach that includes early incorporation of infected debris, crop rotation, the use of varieties that are less susceptible, disease scouting, timely application of fungicide, adherence to appropriate application intervals and more frequent applications when environmental conditions are favorable for disease development. Avoid planting next to last year’s sugarbeets. This is especially important if last year’s fields had high levels of Cercospora. In high-risk situations, select approved varieties that are less susceptible than the average.

Begin checking for Cercospora in late June or early July after row closure, making sure to check near last year’s fields or shelter belts. The first fungicide application should occur when conditions first favor disease or at disease onset.

If the first application is late, control will be difficult all season, even if shorter than normal application intervals are used once applications start. When conditions favor disease or disease already is prevalent, fungicide applications must be more frequent than when disease pressure is low.

Resistance and Tolerance to Fungicides

The terms “resistance” and “tolerance” often are used interchangeably. However, in the following discussion, they are used with specific different meanings. Resistance is used to indicate that the Cercospora fungus is unaffected by a level of fungicide that previously prevented growth in the laboratory. Tolerance is used to indicate that growth of the Cercospora fungus is reduced in the laboratory by a level of fungicide that previously prevented growth in the laboratory.

Resistant isolates of Cercospora are not controlled by field applications of a fungicide. If tolerant strains are present, a reduced level of control will occur.

The systemic fungicide thiophanate methyl (benzimidazole) has federal registration for Cercospora control and is in the benzimidazole class of fungicides. Thiophanate methyl can be used in a tank mix (with TPTH, triazole or demethylation inhibitor [DMI] fungicides, or multisite fungicides) but only once in a season.

The tank mix should be used as the first or second fungicide application.

Benzimidazole-resistant isolates grow normally in the laboratory in the presence of 5 parts per million (ppm) of benzimidazole fungicide. Sensitive isolates do not grow at all in the presence of 5 ppm of benzimidazole fungicide. Some isolates of the Cercospora fungus have been found that were resistant to the benzimidazole class of fungicide and tolerant to TPTH.

Strains of Cercospora with tolerance to TPTH were confirmed for the first time in southern Minnesota and the southern Red River Valley in 1994. Tolerance was detected in fields where control was not as good as expected. Such tolerance is difficult to distinguish from inadequate application techniques or a late start in application.

Tolerance is best defined as an ability of the fungus to grow in the laboratory in the presence of TPTH at 0.2 ppm or 1 ppm. Sensitive strains do not grow at all when subjected to these levels of TPTH, but tolerant strains grow at a reduced rate, compared with growth in the absence of TPTH. Effective fungicides from different classes should be alternated to delay the development of tolerant or resistant strains of the pathogen.

C. beticola was confirmed to be resistant to QoI fungicides, especially pyraclostrobin, which is found in Headline and Priaxor. Populations resistant to QoI fungicides have the G143A mutation and are not controlled when these fungicides are applied, which may lead to field failures. Current populations are now also less sensitive to triazole fungicides such as tetraconazole, difenoconazole, propiconazole, fenbuconazole, prothioconazole and flutriafol.

Managing Cercospora Leaf Spot With Fungicides

In areas where the C. beticola population is sensitive to QoI fungicides, the fungicides Headline, Priaxor, Gem (QoIs), Proline, Inspire XT, Eminent/ Minerva, Topguard (triazoles), Lucento, Minerva Duo, Brixen and TPTH, and mixtures of TPTH and Topsin, TPTH or Topsin in mixtures with the triazoles or QoIs used in a rotation program will control Cercospora leaf spot effectively. Because C. beticola, under favorable conditions, develops resistance very rapidly to QoI fungicides, we recommend mixing QoI fungicides with a protectant or multisite fungicide for control of CLS. In mixtures, individual fungicides should be used at least at 0.75 to 0.80 times their full labeled rates or preferably at full rates.

In 2016, C. beticola populations resistant to QoI fungicides were found throughout the sugarbeet production area. Growers should not use QoI fungicides to manage populations in areas with known QoI resistance. C. beticola also has developed reduced sensitivity to triazole (DMI) fungicides. Mixtures of fungicides such as TPTH and triazoles, TPTH + Topsin, TPTH + EBDCs, TPTH + Copper, EBDCs + Copper, Triazoles + Copper and triazoles + EBDCs with different modes of action should be used in a rotation program to manage CLS in areas with known QoI resistance.

Limit the use of triazoles (DMI) and always mix with another mode of action fungicide, preferably multisite fungicides. In areas with resistance/ or reduced fungicide sensitivity, it is best to use site specific fungicides (QoIs and DMIs) at full labeled rates in mixtures. Varieties with higher CLS tolerance should be used in combination with timely fungicide applications, incorporation of infected plant debris, crop rotation, and planting away from previously infected field.

After aerial application, ensure that areas around power lines and trees are side-dressed by the use of ground equipment. Aerial applicators should use higher water volume to get better coverage. Improperly sprayed areas become focal points for Cercospora spread. Best results with ground equipment are obtained by using high pressure (100 pounds per square inch) and a high volume (20 gal/A) of water.

Preharvest Intervals (PHI): Fungicides may be needed well into September to control Cercospora in some years; stopping the application of fungicides before this time may result in late-season damage that can reduce tonnage, sucrose and quality. Do not allow the preharvest interval (PHI) to be an excuse for missing an application late in the season. Spraying a field but leaving the headland and a strip (or strips) in the middle untreated may be preferable, thereby allowing pre-pile harvest in untreated areas.

Application Intervals: Generally, the application interval for most of the fungicides recommended is 14 days. During periods of regular rainfall, shorten the application interval to 10 to 12 days. EBDCs (ethylene bisdithiocarbamates) may be required at seven- to 10-day intervals for effective control.

Variety Selection and Cercospora Management: Differences occur in Cercospora susceptibility among approved varieties. Cercospora may be somewhat easier to manage on varieties with higher than average tolerance to Cercospora. Conversely, varieties that are more susceptible than the average may need extra fungicide applications in years that are highly favorable for Cercospora. The use of more tolerant varieties can be an important part of an integrated disease management plan.

Powdery Mildew Control: Mixtures of triazoles (DMIs) or QoIs and sulfur fungicides will provide effective control. See publication PP967 for more information on powdery mildew.

Foliar Sprays – Leaf Spots

 

Rhizoctonia Root Rot Control

 

Sugarbeet Crop Record

 

Factory District Representatives

Sugarbeet Research – Extension Staff

Co-op Agriculturists’ Office and Mobile Numbers

Pesticide Safety Rules

1. Read the label carefully before using the product.

2. Store chemicals under lock and key.

3. Keep chemicals in original containers.

4. Use chemicals only on crops specified and at the correct rate and schedule.

5. Do not eat or smoke while applying pesticides.

6. Wear protective clothing and masks as directed.

7. Wash clothing and your skin immediately if chemicals should come in contact with them.

8. Avoid chemical drift from one crop to another.

9. Keep a record of materials, amounts used and the date of application.

10. Dispose of empty containers in a way that they no longer are hazardous.

11. In case of accidental poisoning, call a physician or take the patient to a hospital immediately.

12. See the inside back cover of this publication for poison control center telephone numbers.

For additional copies of this guide or  suggestions for improvements contact Mohamed Khan, 701-231-8596 or mohamed.khan@ndsu.edu Extension Sugarbeet Specialist – NDSU/University of Minnesota, 227 Walster Hall, Fargo, ND 58108-6050

Available on line at www.sbreb.org 

Funds were made available for printing this guide by the  Sugarbeet Research and Education Board of Minnesota and North Dakota.

Do not use this publication after Dec. 31, 2020.

Use of Pesticides

The pesticide recommendations in the “Sugar Beet Production Guide” are based on the assumption that all pesticides mentioned will have a registered label with the U.S. Environmental Protection Agency. Pesticides should not be used if they no longer are registered or have not yet received registration for sugar beet. Sugar beet treated with a pesticide not registered for sugar beet may have an illegal residue which, if detected, could cause condemnation of the crop. Nonregistered pesticide is illegal and a user could be subject to a heavy fine even without detectable residue.

All pesticide users should read and understand the pesticide label prior to pesticide use. Inclusion of all label details in the “Sugar Beet Production Guide” is not possible and labels sometimes are modified after the annual guide’s printing is completed.

Poison Control Centers

North Dakota statewide number: 800-732-2200

Minnesota statewide number: 800-764-7661

Fargo Poison Control number: 701-234-5575

Call the nearest poison control center for recommended treatments for any type of pesticide poisoning.

Have pesticide label information available when calling.

Published with support from

Sugarbeet Research and Education Board of Minnesota and North Dakota www.sbreb.org 

NDSU Extension does not endorse commercial products or companies even though reference may be made to trade names, trademarks or service names.

NDSU Extension is solely responsible for this content.

For more information on this and other topics, see www.ag.ndsu.edu/extension 

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