Crop & Pest Report
Another Weed of the Year (5/24/12)
Below an observant and studious disciple of the ND weed guide makes some suggestions to improve its utility. Answer to this weed in question is listed below.
“Just a thought for the next weed of the year….. foxtail
barley. We have been getting inquiries from many folks so far this year
(dealers and consultants).”
Response: We have included foxtail barley control options on page 13 in the weed guide. Intuitively folks would go to the back the of the weed guide to the weed rating sections and might not know of the information on page 13. We have received several questions at extension meetings this winter about foxtail barley control. It is certainly increasing.
“Some folks would like to see the previous Weed of the Year included in the weed guide, as they continue to deal with those problems still. So in the 2013, you might include the 2012, 2011, 2010, etc. That would make this publication even more popular than it is right now! Just a thought.”
Response: Several others have suggested the same thing. We are trying to keep the weed guide from increasing in size. As a temporary option for this suggestion we have posted all the previous Weed of the Year information on the NDSU Weed Science web page (listed on the front cover of the weed guide).
Rich Zollinger
Extension Weed Specialist
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Excellent Weed ID Resource (5/24/12)
The Michigan State University IPM Program has collaborated with weed scientists Wesley Everman, Christy Sprague, Steven Gower and Robert Richardson to post “An IPM Pocket Guide for Weed Identification in Field Crops” on-line in pdf format.
Weeds can be located in listings by common or scientific name as well as identifying characteristics.
The guide is available in pdf format at: http://www.ipm.msu.edu/weeds-field.htm. Or purchase the print pocket-sized guide at: http://bit.ly/MSUfieldGuide
Rich Zollinger
Extension Weed Specialist
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Dirt/Dust on Weed Leaves Likely will Reduce Activity of some Herbicides (5/24/12)
With the hot, dry, and windy field conditions in the last few weeks, dirt and dust has been deposited upon leaves of weeds. In addition the hot and dry weather has caused weeds to be stressed and plant growth has been reduced.
In both situations all postemergence herbicides may not control weeds as effectively as compared to the last few years during cooler and wetter conditions. Consult last week’s article by Rich Zollinger concerning the impact of hot and dry conditions on herbicide effectiveness. A reduction of herbicide activity due to dust and hot and dry conditions is not observed equally across all herbicides. Herbicide activity is most negatively affected by dust/dirt on leaves of weeds with the following herbicides: glyphosate (Roundup), Liberty, and Gramoxone. The best way to reduce this problem is to allow a rain shower to wash the dirt off the leaves, however, that may take too much time. If dry conditions persist, go ahead and apply the herbicides to the smallest possible weeds and scout to determine the effectiveness of the herbicide application to determine the next strategy if weed control is reduced. Reducing the travel speed of the sprayer during dry conditions will reduce additional deposition of dirt/dust onto weed leaves during the herbicide application.
Jeff Stachler
Agronomist - Weed Science
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Wild Cucumber Control (5/24/12)
I have received some questions about wild cucumber control. It is a vining type perennial that grows stems each spring from a huge underground woody root (about the size of a volleyball or bigger).
Stems vine around anything with the aid of tendrils. Leaves are lobed with the characteristic five lobes per leaf. Fruit of this plant have spiny pods about the size or smaller than a golf ball. The plant is found in shelterbelts, fence rows, and roadsides.
Wild cucumber is extremely tolerant to 2,4-D. Wild cucumber can be controlled with the following herbicides, however, realize that with any perennial weed it cannot be killed with just one application of anything. Herbicides for control: Glyphosate at 1.5 lb ae/A or a 0.5 to 1% solution, Tordon at 0.5 lb ae/A or a 0.5% solution, Dicamba at 1 to 2 lbs ae/A or a 1% solution, Triclopyr ester at 1 lb ae/A or a 0.5% solution, or Crossbow at 2 qt/A or a 1% solution. In my notes I have that a 3-way of Harmony Extra + 2,4-D + dicamba also controls wild cucumber but this is probably anecdotal observation.
Rich Zollinger
Extension Weed Specialist
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Weed Control Reminders for Sugarbeet Growers (5/24/12)
Thank you to those growers and dealers that have already applied herbicides to sugarbeet that are only at the 2 to 4-leaf stage. This is an excellent start however the season is not over! Scout all fields 5 to 10 days after the initial herbicide application and all later applications to determine the effectiveness of the treatment.
I have seen and have received calls about weeds surviving the initial glyphosate application in sugarbeet, especially waterhemp. If glyphosate alone was applied and waterhemp plants are the only weeds surviving, then they are likely resistant and must be controlled quickly if only using herbicides. If surviving waterhemp plants are found at 5-7 days after a glyphosate application apply the following herbicide mixture: Betamix (24 fl oz/A or as high of rate you comfortably will accept crop injury) plus Nortron (4 fl oz/A) plus Outlook (21 fl oz/A) [best option, especially if dry] or Dual Magnum or Cinch (1.5 pt/A) [can be similar to Outlook if enough rain is received] plus MSO (1.5 to 2.0 pt/A) [this is not required if using higher rates of Betamix, using Outlook (because of a higher oil content than Dual Magnum), and/or applying early in the morning on warm to hot days]. If surviving waterhemp plants are discovered > 10 days after application, then apply the mixture above and include the remaining amount of glyphosate prior to the 8-leaf sugarbeet stage. If waiting later and including the glyphosate and a MSO is included in the mixture, then use one of the following MSO (really a MSO based HSOC) products: Cide Winder, Destiny HC, Savvy, Loveland’s MSO Concentrate with Lecitech Technology or some similar product. A total of 1.96 pounds acid equivalent/A (lbs ae/A) of glyphosate can and should be applied at or before the 8-leaf sugarbeet stage. Therefore if a grower applied Roundup PowerMAX at 32 fl oz/A or a 3.0 lb ae/gal glyphosate formulation at 48 fl oz/A in the initial application, then Roundup PowerMAX and a 3.0 lba ae/gal glyphosate formulation can be applied at 24 and 35.6 fl oz/A, respectively before the 8-leaf sugarbeet stage.
If glyphosate was applied alone to Roundup Ready sugarbeet in the initial application and common or giant ragweed survived, then mix Stinger at 4.0 fl oz/A with the greatest legal rate of glyphosate prior to the 8-leaf sugarbeet stage. Scout fields 10 days after application to determine the need for additional glyphosate applications containing Stinger at 4.0 fl oz/A.
Jeff Stachler
Agronomist - Weed Science
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Herbicide Resistance in Waterhemp in MN and ND and Management in Sugarbeet, Corn and Soybean (5/24/12)
Glyphosate-resistant waterhemp continues to increase and spread in Minnesota and North Dakota based upon recent greenhouse testing.
Prior to the 2011 growing season, glyphosate-resistant waterhemp was confirmed present in the following counties: Renville, Swift, Traverse, and Yellow Medicine in MN and Richland in ND. After the 2011 growing season, glyphosate-resistant waterhemp was recently confirmed present in the following additional counties: Clay and Wilken in MN and Cass, Ransom, and Triall in ND. Glyphosate-resistant waterhemp is highly suspected to be present in the Red River Valley south of Nielsville, MN, throughout central and southern MN, and in Ransom County North Dakota.
Based upon additional greenhouse research, multiple resistant waterhemp was confirmed present at least near Holloway, MN (Swift County). In at least one field, waterhemp was confirmed resistant to glyphosate (Group 9), PPO-inhibiting herbicides (Group 14), and ALS-inhibiting herbicides (Group 2). Consult Table X1 (pages 104 and 105) in the 2012 North Dakota Weed Control Guide to know which herbicides are grouped within these herbicide mechanisms/modes of action. Multiple resistant waterhemp is believed to be present in other fields in MN and ND, but have not been confirmed resistant at this time. To reduce the selection of multiple resistant waterhemp, apply the most effective postemergence herbicides in a mixture to small (< 2”, < 1” in sugarbeet) waterhemp plants in all crops and try to apply during the best weather conditions.
Consult page 133 in the 2012 North Dakota Weed Control Guide for the best herbicide options to control waterhemp in sugarbeet, corn, and soybean. In addition, consult the Relative Herbicide Effectiveness Tables (pages 116 to 121) in the ND Weed Control Guide for control of waterhemp.
If ANY waterhemp plants remain after all herbicide applications during the growing season in all crops, please remove them by hand and/or with row cultivation. No weed seed production should be permitted in any field where herbicides were applied, otherwise herbicide resistant weeds will only increase in frequency and level of resistance!
Jeff Stachler
Agronomist - Weed Science
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Pre weed control in spring 2012 - a retrospect to 2011 (5/17/12)
How did herbicides perform in the spring of 2011?……very well. Ample rainfall (too much in many regions) activated foundation/PRE herbicides and weed control was very good. Excellent soil moisture and lack of weed stress made POST herbicides work very well also.
Many may have used reduced herbicide rates and still saw impressive weed control. Why? – because, as it say says on many herbicide labels, “Apply to actively growing plants.” Plants that are actively growing with sufficient moisture, nutrients and sunshine, but these weeds are wimpy and easier to kill.
How are PRE herbicides performing this spring?…..maybe not so good. This dry spring of 2012 is historically what most North Dakota growers remember. Dry weather and PRE herbicides do not get along at all. Academia and industry have been promoting use of residual PRE herbicides to take the pressure off glyphosate and other POST herbicides to do the entire weed control job and to delay weed resistance. Many have opted to apply a PRE foundation application this year which may cost from $10 to $20/A. Without precipitation to activate the PRE herbicides, weeds will emerge and growers may see little affect from this investment.
What can be done? If weeds emerge before activating rain remember those implements sitting in the fence rows and shelterbelts…..harrows and rotary hoes. They can be very effective in killing newly emerging (white) weeds and will help activate the PRE herbicides. Information is included in the weed guide for use of harrows and hoes for each crop: Small grains = page 82, corn = D1 on page 86, soybean = E1 on page 88, dry beans = F1 on page 91, field pea= G1 on page 91, chickpea = H1 on page 91, lentil = H2 on page 91, sunflower = J1 on page 92, and canola = L1 on page 92. Weed death from harrows and hoes is more pronounced when top soil is dry and the operation is done in the hottest part of the day causing weeds to desiccate quickly.
What will happen to the activity of POST herbicides? Dry weather causes stress on weeds (and crops). Dry weather causes weed to not grow so “actively”. Dry weather may reduce the activity of POST herbicides. The liability of reducing herbicides rates may be seen more in dry weather. If PREs don’t work and your next option is POST herbicides – use full rates, spray SMALL weeds, use superior adjuvants, and use a nitrogen source like AMS (if label allows) to improve water quality and increase herbicide absorption. Consider using two herbicides applied in a tank-mixture with different modes of action to improve weed control on the pivot weeds.
Is there an upside to lack of rain? Maybe a couple. Dry weather (= no rain) may result in fewer weed flushes. Several weed species, like nightshade and waterhemp, will produce a new flush after each rain event. Also, dry weather may reduce the mosquito population (poor consolation).
So, be nice to your wife/spouse and heck, paying a generous tithe to your local church may make divine providence shine on your efforts and improve weed control. Let’s hope for “some” timely moisture.
Rich Zollinger
Extension Weed Specialist
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Does burning stubble affect pre herbicides? (5/17/12)
The following is a question from a grower that might apply to many more growers in the state.
This might be an odd ball question but I have a grower planting Natto soybeans. We applied Authority Assist, Prowl H2O, Roundup, and 2,4-D in our burndown Preplant application a day or two ago. This is on old corn stalk ground and now my farmer wants to burn the corn stalks. I told him no, we just spend $40/acre on chemical and the heat will destroy it. Am I correct on this or what would or could happen.
Response: To begin, if you burn the stubble, you burn any residue on the stubble that hasn’t washed off to the soil. In addition, the heat may damage the active ingredients even if not burned completely. Herbicides are ‘organic’ compounds and as such contain carbon (C), hydrogen (H), and oxygen (O). The C in herbicide molecules will combust the same as the C in plant stubble or wood. We have not investigated the spontaneous decomposition temperatures for herbicide product active ingredients, but a stock stover fire is hot enough to kill weed seeds. That temperature is hotter than the flashpoint of most herbicide formulations. If it isn’t destroyed, there’s also the possibility that the herbicide could get tied up on the ash that is generated from combustion. All things considered…DON’T DO IT.
Kirk Howatt
NDSU Weed Scientist
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What are the three most important weed management goals today and into the future? (5/17/12)
All herbicides are controlling weeds less effectively than previously because of herbicide resistance. This includes the increase in multiple-resistance (resistance to 1 or more herbicide mechanisms (sites) of action). Therefore weed management practices/tactics and philosophies need to change now (this season) so as to reduce the buildup of herbicide-resistant weeds.
The three most important weed management goals in order of importance are as follows: 1. Maximize herbicide activity of all herbicides at all times; 2. Eliminate weed seed production (zero seed rain of plants prior to flowering); and 3. Practice diverse weed management (use all tools in the tool box, not just herbicides and especially a single herbicide). If these three goals are met for each individual field of a farming operation, then the opportunity to select for herbicide resistant weeds is very minimal.
The number one practice/tactic to achieving the three most important weed management goals is to scout fields early and often in order to detect any changes that may be occurring within a weed population this season compared to previous seasons. Scouting for weeds should occur prior to planting, two weeks after planting, prior to each herbicide application, 5 to 14 days after each herbicide application, just prior to flowering of any weed species, and at harvest. Scouting this frequently will allow individuals to determine if any changes may be occurring in a weed population over time and to allow for timely rescue management practice within the growing season and for future growing seasons.
What practices/tactics are necessary to maximizing herbicide activity? The following practices should be adopted to maximize herbicide activity:
1. Apply the most effective herbicide(s) for the most difficult to control and/or frequent weed species in a field. Herbicide mixtures containing two or more EFFECTIVE herbicides should provide the most effective weed control and should be used whenever possible. Mixing a less effective herbicide with a very effective herbicide likely will not maximize herbicide activity and may select for multiple resistance more rapidly, especially when applied to large plants at less than the labeled rate. The most effective herbicide mixtures are those containing two or more highly effective herbicide mechanisms of action to control the most difficult to control species in a field.
2. Apply the labeled rate of all herbicides (applied alone or in combination or soil-applied or foliar-applied) to the most difficult to control species within a field;
3. Apply all postemergence herbicides to small weeds (1-3” in height). Sugarbeet herbicides should be applied to smaller weeds (< 1” in height);
4. Include the most proven and best quality adjuvants with all herbicides applied alone or in combination. No two adjuvants perform equally. For most herbicides include a good quality methylated seed oil (MSO) in the spray mixture. When mixing a herbicide requiring a MSO adjuvant with glyphosate, use Destiny HC, Savvy, Cide Winder, Loveland’s Concentrated MSO with Lecitech technology, or a similarly tested MSO based adjuvant. These adjuvants should be included at 1.5 to 2.0 pt/A to maximize herbicide activity. Ammonium sulfate must always be mixed with glyphosate and Liberty, regardless of how good the water quality is. Include additional nonionic surfactant at 0.25%v/v to all fully-loaded glyphosate formulations to improve lambsquarters control;
5. Use the proper spray volume based upon the type of herbicide(s) being applied. For translocating herbicides such as glyphosate or Starane Ultra, apply < 10 gallons per acre of spray volume. For contact herbicides such as Liberty or Flexstar, apply >15 gallons per acre of spay volume. If contact herbicides are mixed with translocating herbicides, apply the spray volume for contact herbicides;
6. Use the proper spray droplet size for the herbicide(s) being applied. For translocating herbicides coarse spray droplets usually provide adequate coverage and subsequent control. For contact herbicides fine to medium spray droplets should be the targeted droplet size. When applying small droplet sizes, be aware these particles are more likely to drift;
7. Apply herbicides between 8:00 AM to 8:00 PM. Weed control is usually reduced for most herbicides, especially glyphosate and Liberty, when applied beyond 8:00 PM until early morning (8:00 AM);
8. Reduce sprayer travel speeds. Sprayer travel speeds between 5 and 8 mph almost always provide greater herbicide activity, especially for contact herbicides, compared to travel speeds greater than 10 mph;
9. Use a fully operational and calibrated sprayer. Regularly check for worn and clogged nozzles;
10. Apply postemergence herbicides during the best weather conditions. Warm (80 to 90° F and humid weather conditions usually maximize herbicide activity. Cold and wet conditions and hot (>95°) and dry conditions (soil and air) usually cause the least herbicide activity;
11. Apply postemergence herbicides prior to the rain free period listed on the label of all herbicides and herbicide combinations. If mixing a product having a one hour rain free period with another product having a 4 hour rain free period, apply the mixture more than 4 hours prior to rainfall. ALL glyphosate formulations require greater than a 6 hour rain free period;
12. Rotate herbicide mechanisms (sites) of action. A single herbicide mechanism of action should only be used every other year at a minimum and usage greater than 1 year is preferred;
13. Use a rotary hoe or harrow to incorporate preemergence herbicides within about 7 to 10 days after application if insufficient rainfall was received to active the herbicide;
14. Be flexible – change your weed control plans during the season and for next season based upon the weather conditions. A current example is as follows: if a soil-applied herbicide was not properly incorporated due to lack of sufficient rainfall and glyphosate-resistant waterhemp or ragweed are known to exist in your area or you suspect they may be present in your field and Roundup Ready soybeans were planted, then apply a mixture of Flexstar plus glyphosate (or Flexstar GT 3.5) [in locations allowed by the label] or Cobra (> 10 fl oz/A) to 1-2” weeds. Scout field after the application to determine the need for a second application of glyphosate plus Cobra.
The second goal is to eliminate weed seed production of all plants present following the last herbicide application. This is best accomplished by removing the plants by hand. Removing plants by hand when there are just a few plants (<10) scattered randomly and/or in a single patch of the field will greatly reduce the buildup of resistant seeds in the soil seed bank. Surviving plants need to be removed from the field prior to flowering to ensure complete destruction of plants and not allow re-rooting of pulled plants. The practice of removing plants by hand is also called zero seed rain.
Cultural and mechanical weed control practices must be utilized in conjunction with herbicides, otherwise herbicide-resistant biotypes will only increase. Cultural practices are those practices that maximize crop growth (biomass production) such as proper fertilization, narrow row spacing, high crop stand densities, and many others. Mechanical weed control must be used wisely to effectively control weeds and reduce soil erosion.
If these three weed management goals are not achieved every year starting this growing season, lost profits and reduced time to get away from the farm are likely to occur for most growers within the next 2 to 5 years.
Jeff Stachler
NDSU and U of MN Extension Agronomist – Sugarbeet / Weed Science
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Weed Control in Sugarbeet (5/10/12)
Postemergence herbicide applications in Roundup Ready sugarbeet should begin at the two-leaf sugarbeet stage or before weeds reach one inch in height.
At this stage apply glyphosate at 1.125 pounds acid equivalent/A (lbs ae/A) [Roundup at 32 fluid oz/A (fl oz/A) or a 3.0 lb ae/gallon glyphosate formulation at 48 fl oz/A] plus nonionic surfactant (NIS) at 0.25 to 1.0 %v/v (depending upon the amount of NIS in the formulation) plus ammonium sulfate (AMS) at 8.5 to 17 lbs/100 gallon of spray mixture. If common or giant ragweed is present add Stinger at 3-4 fl oz/A to proactively and/or reactively control glyphosate-resistant ragweed. If using the lower rate, three applications likely will be required to completely control glyphosate-resistant ragweed and if using the higher rate, a third application may be necessary. If glyphosate-resistant waterhemp is known to exist add Betamix (12 fl oz/A) plus Nortron (4 fl oz/A) plus Dual (1.3 to 1.6 pt/A [depending upon soil type]) or Outlook (14 fl oz/A) plus Destiny HC, Savvy, Cide Winder, Loveland MSO concentrate with Leci-tech technology or a similar proven glyphosate-friendly MSO adjuvant and do not add the NIS. Scout 5 to 10 days after application to determine the timing and need for a second herbicide application.
Jeff Stachler
NDSU and U of MN Extension Agronomist – Sugarbeet / Weed Science
NDSU Crop & Pest Report - May 24, 2012
