Crop & Pest Report
Sugarbeet Root Maggot Flies Emerging Early: Plan Post-Emergence Control Strategies Now (5/24/12)
The first sugarbeet root maggot (SBRM) flies detected by NDSU personnel in the 2012 growing season were found in a field south of St. Thomas, ND on May 11. However, activity levels have remained fairly low for several days thereafter.
Sticky-stake counts conducted on Friday, May 18 and Monday, May 21 indicated that the following areas appear to be likely hotspots for fly activity this year: Auburn, Forest River, and St. Thomas, ND. It should be noted though, that although several other areas have the potential for producing relatively high infestations. Daily and cumulative counts for all monitoring sites can be viewed at: http://www.ndsu.edu/entomology/. Just click on the “INSECT RESOURCES” link on the main page, and download the dated Adobe Acrobat (pdf) file.
SBRM fly activity is significantly impacted by weather. This has allowed us to develop a degree-day (DD) based model to predict the timing of peak activity of SBRM flies in current-year beet fields. Peak fly activity can occur at any time after the accumulation of 600 DD; however, NDSU research indicates that peak takes place, on average, at about 650 DD. It is important to note that warm weather (around 80°F), and calm to low-wind conditions are most conducive to fly activity. Flies will remain relatively inactive in cool, rainy, or windy conditions. To determine degree-day totals for fields in your area, consult the Root Maggot application on NDAWN at: http://ndawn.ndsu.nodak.edu/sugarbeet-root-maggot.html. The site also includes a “help sheet” with information on how to use the model, recommendations for whether insecticide applications are needed, and pointers on when to apply them. A preliminary, extended forecast for anticipated DD accumulations and associated peak fly activity dates in the southern, central, and northern RRV is presented in Table 1.
Growers in hotspots or high-risk areas for SBRM infestation should consider applying a postemergence insecticide, especially if an insecticidal seed treatment or a low to moderate rate of an at-plant soil insecticide was applied. Postemergence granules are usually effective if applied between 2 weeks and 5 days before peak fly, but will also likely be beneficial if applied within a 1-2 days (before or after) peak. Light to moderate rainfall after granular applications typically improves performance. Postemergence liquid insecticide applications should be targeted for peak fly, but will provide good results if applied within 2-3 days before or after peak. As Table 2 indicates, there is still plenty of time to apply either a granular or liquid material for SBRM control this season.
For more guidance on postemergence control strategies, consult the “Insect Control” section of the 2012 Sugarbeet Production Guide or the “Sugarbeet Insects” section of 2012 Field Crop Insect Management Recommendations. Online versions of these publications are located at:
http://www.sbreb.org/Production/production.htm
and
http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm
Mark Boetel
Research & Extension Entomologist
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Corn Plant Populations and Replanting (5/24/12)
This has been an exceptionally good spring for planting crops. Much of the corn in the state has now emerged. Since conditions were quite favorable for emergence, most plant stands appear to be adequate.
In a few cases, however, cold stress and/or dry soils during germination have reportedly caused disappointing stands. Fortunately, it is still early enough in the season to expect good yields if replanting is needed and it is carried out in the next few days. Before you replant, however, you should carefully assess your current stand and its yield potential, the cost of replanting, possible alternative crops and the availability of seed.
The first step towards making an informed decision on the need for replanting is to determine your current plant population. Count plants in several areas of the field that appear to be representative of the field as a whole. Counting emerged plants in a row length of 17’ 5” if using a 30” row spacing will give you the plants in 1/1000 of an acre (for 22” and 20” row spacings use a row length of 23’ 10” and 26’ 1”, respectively). Plant counts from this area can be converted to plants per acre by multiplying by 1,000. Refer to Table 1 to determine the potential yield (as a percent of optimum) of your crop at its current population and the potential yield of a crop replanted at various dates. These data apply to fields in the eastern part of North Dakota where moisture stress is typically not limiting. These data suggest that the deleterious effect of late planting (at least when planting is delayed to June) is generally greater than the deleterious effect of a reduced plant population within the range of plant populations listed. For example, a plant population of 30% of the optimal stand would be as productive as a full population when planted on June 1.
These data may also provide a rough guideline for the value of replanting fields in drier regions of the state where optimum plant populations may be as low as 20,000 plants/acre by substituting the optimum population for an environment for 36,000 in table and adjusting populations downward in a proportional.
Joel Ransom
Extension Agronomist
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Sunflower Management (5/24/12)
The annual National Sunflower Association (NSA) Field Survey was conducted in September and early October 2011. In North Dakota 77 fields were inspected.
One field was surveyed for approximately every 10,000 sunflower acres planted in each county. Agronomists, pathologists, entomologists, extension agents, and crop consultants conducted the survey. The teams were asked to assess the most limiting production factor for each field. Other observations were also taken during the survey. The North Dakota State average yield estimate for the surveyed fields was 1,651 lb/a.
Yield-limiting Factors
In North Dakota plant spacing within the row and disease were the most prominent limiting factors to higher yields in both 2010 and 2011 (Table 1). Producers should pay attention during planting to make sure the spacing between the plants and the plant population are accurate. The planter needs to be adjusted properly for the specific sunflower hybrid seed. Decreasing the planting speed will usually increase the accuracy of seeding. The sunflower seed needs to be planted at a depth of 1.5-2.5 inches with good seed to soil contact. With two seeds too close together there will usually be one dominant plant and one plant with a very small head, therefore, an even distribution of the seeds is very important. In photo 1, solid seeding resulted in too many seeds too close together with some plants having very thin stalks. These plants did not contribute to yield. On the other hand there were gaps between plants in other areas of the filed. Some diseases, like rust, can be managed and producers should scout their fields during the growing season.
Weed problems in North Dakota and NW Minnesota
The survey indicated that weeds were a limiting yield factor in 6.3% and 3.9% of the fields in 2010 and 2011, respectively. Over 29 common weeds were evaluated in the survey with the various infestation levels recorded. The data in Figure 1 provides the percent of fields found with the major weed species being present in surveys from 2007-2011. It is important to plant sunflower in clean fields and manage weeds throughout the growing season.
Reference
Kandel, H. 2012. National Sunflower Association Survey 2011 PowerPoint pdf.
http://www.sunflowernsa.com/uploads/resources/616/2011-sunflower-survey---kandel.pdf
Hans Kandel
Extension Agronomist Broadleaf Crops
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Aster Leafhopper Threat to Canola (5/24/12)
Aster leafhoppers (Macrosteles quadrilineatus) that we are observing in wheat and barley could move into canola and vector aster yellows.
The amount of aster yellows in fields would depend on the number of leafhoppers from local fields and immigrants from southern states, the percent of leafhoppers carrying the aster yellows phytoplasma and the time of arrival of the leafhoppers. Canola and other Brassica species (mustard) are not a preferred host for food and reproduction of aster leafhopper. It prefers to feed on wheat, barley and vegetable plants (lettuce and carrot), grapevines, and herbs. Aster leafhoppers may feed on young canola plants at the beginning of the season and then move to grasses and more preferred crops as the canola matures. Hot and dry conditions are not conducive to the spread of aster yellows. In contrast, abundant rainfall makes succulent plants which are more attractive to leafhoppers.
Symptoms of aster yellows in canola
take about 21-35 days to appear and sometimes plants are infected but show no
symptoms. Flowers are distorted and sterile. Flowering portions of the plant
may show excess branching and stunting (shortened internodes), resulting in a
“witches broom” appearance. Aster yellow infected canola plants are often
taller than the rest of the plants. Pods are replaced by inflated round or oval
blue-green bladder-like structures. Infected plants produce little seed, but
percent of infected plants is usually quite low (<5%) most years. However in
2007, aster yellows were observed in many canola fields in Minnesota and North
Dakota, and economic losses occurred in a few fields. Symptoms on canola can be
confused with sulfur deficiency, anthocyanin production (purpling due to crop
stress) and growth regulator herbicide damage.
To manage aster yellows in canola:
1. Plant early to reduce the incidence of aster yellows by making plant less attractive (more mature) to migrating aster leafhoppers.
2. Control perennial weeds in fields since weeds can be a good source of the aster yellows phytoplasma.
3. Due to the mobility of aster leafhoppers, any insecticide spray program would be a ‘Hit & Miss’ situation. Leafhoppers move around from field to field, crops to crops and it would be difficult to prevent aster yellows from being vectored. As in wheat and barley, there is no established economic threshold in canola. We also do not know how often we would need to spray. The residual of most pyrethroid insecticides is 7-10 days. However, the economics of multiple and frequent foliar insecticide applications is not feasible in canola as in high-value vegetable crops. In addition, flowering canola is a major source of honey for honey bees in North Dakota, and any insecticides sprayed during flowering would be deadly for honey bees. We recommend not spraying insecticides on flowering canola to protect pollinators, and only spraying insecticides when bertha armyworms or other insect pests are at economic threshold levels in fields. If foliar applied insecticides are necessary during flowering, spray in the early morning or late evening when bees are back in the hive. Research conducted in snap beans and okra suggests that the neonicotinoid seed treatments should be effective in reducing leafhopper infestations in canola for up to 30 days. There are no fungicides that will control aster yellows.
Janet J. Knodel
Extension Entomologist
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Degree Day Update for Alfalfa Weevil (5/24/12)
The alfalfa weevil DD accumulation as of May 21, 2012 is displayed in the map below (source: NDSU NDAWN – Applications – Insect Degree Days).
At 300 DD, field scouting is initiated for alfalfa weevil adult. The 300 DD base has expanded to the southern half of North Dakota and up into Grand Forks area from last week. See last issue 4 of Crop & Pest Report for more information.
Janet J. Knodel
Extension Entomologist
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Malformed Seed Potatoes May Have Glyphosate Carryover (5/24/12)
Recently, I have observed emerging and newly emerged potatoes that exhibited growth malformations. These symptoms included multiple sprouts at eyes sometimes forming a ‘cauliflower’ formation, a ‘candelabra’ growth or multiple new shoots from a single potato eye with excessive root growth, swollen shoots that have reduced growth, chlorosis on leaf margins, and auxin-like herbicide injury (such as 2,4-D or dicamba) in the leaves.
Seed pieces with this damage are randomly found in the fields, which indicates that is likely something carried over in the seed piece. These injury symptoms point towards glyphosate carryover, but this has not been confirmed. I have sent some samples to a lab to test for glyphosate.
If this is glyphosate carryover, it could be a result of glyphosate drifting onto a seed potato field or the spray tank not being properly cleaned before applying pesticides over-the-top of a seed potato field. Potatoes are sensitive to glyphosate throughout their life cycle, thus glyphosate drift at any time during the potato growing season is of concern. Precaution need to be made to not drift glyphosate when applications to nearby fields occur by using proper spraying techniques and making sure the wind direction is blowing away from sensitive areas.
It is important to scout the fields and be on the lookout for skips and plants with reduced growth and malformed leaves. In the skips, dig up potato seed pieces to see if symptomologies exist. Fields may have a small percent of plants affected, but it is unknown how this will affect yield. Please contact me if you suspect glyphosate carry-over in the seed. I would like to document how wide spread this problem may be to get a better understanding of how this is affecting potato production.
Andy Robinson
Assistant Professor, Potato Agronomist
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Small Grain Diseases (5/24/12)
Scattered rains across the state over the weekend and through last night (May 22) will increase the risk of tan spot infection in those areas seeing the most rain. Dew points averaged over 50 degrees in many areas on 5/22, indicating more favorable environment for fungal infection.
The small grain disease forecasting site (www.ag.ndsu.nodak.edu/cropdisease) indicates some risk of infection for tan spot in the last few days, as indicated in the table example for Carrington, ND, given below. Please check the site for disease risk at the nearest NDAWN location to you, as the week and crops progress.
A trace level of stripe rust was observed in “Mayville” spring wheat by a private company agronomist near Grand Forks this week. This stripe rust infection is confirmed but surprising, considering the heat and relatively dry conditions in most areas up to now. This disease has been common in KS and NE, but has not been reported in ND up until now. (see information below on rust development in KS and NE).
Marcia McMullen
Extension Plant Pathologist – Cereal Diseases
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Fusarium Head Blight (FHB = Scab) Forecasting (5/24/12)
Winter wheat is rapidly developing in North Dakota and some may be entering heading stage. Many winter wheat cultivars have considerable susceptibility to leaf diseases, leaf rust, and also Fusarium head blight.
As growers consider application of fungicides to flowering winter wheat for management of these diseases, they can estimate the risk of leaf infections at the NDSU Small Grain Disease Forecasting site, as indicated above. This site also has information on risk of Fusarium head blight (FHB) infections associated with weather at the NDAWN weather stations: the flowering growth stage must be chosen.
A broader use of additional weather information is used in the national Fusarium head blight forecasting system, found at www.wheatscab.psu.edu. At this site, the user first clicks on spring wheat, then on cultivar susceptibility level, and then on the state of ND on the map. As of Wednesday, May 23, the FHB risk for ND is very low across the whole state!
Marcia McMullen
Extension Plant Pathologist – Cereal Diseases
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NDSU Potato Blightline to Operate in 2012 (5/24/12)
The Plant Pathology Department at North Dakota State University will again be providing the potato Blightline service at no charge to the potato industry of North Dakota and western Minnesota in 2012.
Based on the amount of late blight found in 2011, there is a good chance that late blight will be present in 2012 if conditions are favorable. The NDSU Blightline is the first place to go to get the most recent blight updates and management information.
This will be the eighteenth year that this service has been provided by NDSU and sponsored by Syngenta Crop Protection. The hotline uses local weather data collected from weather stations throughout our area to forecast the occurrence and spread of late blight in fifteen non-irrigated and twelve irrigated production areas in ND and western MN. The data is processed by the North Dakota Agricultural Weather Network (NDAWN) and analyzed by a computer program (WISDOM) to forecast when conditions are favorable for late blight to occur.
The forecast information is used by plant pathologists Gary Secor and Neil Gudmestad to make late blight management and fungicide recommendations. The recommendations are made Monday, Wednesday and Friday of each week during the growing season. The first late blight hotline will be Friday June 1st, and it is anticipated that the Blightline will continue through mid-September depending on disease pressure. The Blightline will also be used to confirm reported late blight sightings and serve as clearing house for national late blight information. In addition to late blight forecasting, the hotline also provides cumulative P-values for early blight disease forecasting and management recommendations. Finally, it serves to alert growers of other disease and insect news, as well as posting messages of general interest such as potato field day dates.
The hotline recommendations can be accessed by phone or website. The toll free phone number is 888.482.7286
The NDAWN website for potato disease forecasting contains colored maps of ND to pictorially illustrate the late blight severity values (both two day and seasonal), favorable day values and P-day values for early blight throughout ND. That site is: www.ndawn.ndsu.nodak.edu Go to applications and then click the potatoes drop down box.
Current and archival information on late blight and other potato diseases, and research trial data, can also be found at http://www.ndsu.edu/potato_pathology
You can also connect to the latest blight hotline news and message update reminders by text messaging type BLIGHTND to 97063, or on Twitter follow @SyngentaSpuds.
Growers and scouts are encouraged to send suspect late blight samples to us for positive identification. Late blight is a community disease and proper identification and prompt notification is important. Leaf samples should be placed in a slightly inflated zip-lock plastic bag without a wet towel and sent to:
NOTE new mailing address: Gary Secor, NDSU Dept 7660, PO Box 6050, Fargo, ND 58108. Our phone number is 701.231.8362 and email address is gary.secor@ndsu.edu. We wish you a successful potato year.
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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
NDSU Crop & Pest Report - May 24, 2012
