Crop & Pest Report - All
Weather/Crop Phenology Maps
Associate Professor of Climatological Practices
The region’s NDAWN stations measured rainfall during May 1 to July 29 ranges from 5.7 inches (Harvey) to 9.9 inches (Oakes). Corn water use during the past week (July 23-29) ranged from 1.2-1.6 inches. There are some dry areas in counties south of Interstate 94 and intersected by Highway 281 or Highway 3. As of July 29, accumulated growing degree day units for corn planted on May 15 had -62 (Wishek) to 36 (Harvey) units compared to the 5-year average for the period.
Hay harvest continues and harvest is rapidly approaching for winter wheat and barley. Corn generally is in the tasseling to silking (VT-R1) stages. Soybean stages generally range from full flower to early pod formation (R2-3). Dry bean planted up to the first week in June are flowering and producing pods (R1-4 stages). Flowering is beginning in sunflower fields.
* The July 21 storm lodged small grain fields in Foster County but the fields are generally becoming upright again. Soybean and dry bean have ragged leaves and some bacterial disease – new foliage appears normal.
*CREC dryland spring wheat variety trial is showing significant scab (Fusarium head blight). Disease scores are being taken on the 66 varieties in the trial (see picture).
*Scout for soybean aphid as they have been found in our region (currently low densities).
*Watch for grasshopper feeding (in dry areas) in row crops as ditches are hayed and small grain fields are harvested.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center
Managing Weed Escapes in Fields
There have been several conversations with Agriculturalists regarding weed escapes, most notably waterhemp in sugarbeet in the last two weeks of July. And as I travel Eastern North Dakota and Minnesota, I am seeing weeds beginning to extend over the canopy or along the edges of soybean and sugarbeet fields. The question is, what should Producers’ do about weed escapes.
In sugarbeet, there are no chemicals that will reliably eliminate glyphosate resistant waterhemp escapes, weeds eight to twelve inch in height or taller. If you are continuing to actively scout your fields and you find waterhemp escapes, you have only two options at this point in the season. The first option is to contract with labor to eliminate weed escapes by either hand-hoeing or pulling weeds. The second option is to mow-off infested areas, if the area is too large to hand-weed. Mowing might seem extreme but it is important to stop the multiplicative expansion of weed seed and weedy areas in fields. I suggest producers also take detailed notes and make spatially accurate weed maps of fields so the information about weed escapes can be incorporated into next years’ field management plans.
Continue to actively manage ditches and the edges of fields (see picture) including areas where crops drown out due to excessive rainfall. Weeds along field edges and in drown out areas have less competition, are actively growing and will make and add seed to the weed seed bank. Weeds along field edges may also receive only a partial rate of spray which may fuel selection of resistant plants.
Proactive weeds management in July and August will ensure weeds do not produce seed that will lead to reactive measures in subsequent years.
Extension Sugarbeet Agronomist
NDSU & U of MN
Environment Impacts Crop Safety Following Sprays
Sometimes herbicides that have a history of excellent crop safety cause undesired effects in crops. Agriculturalists will study phenotypes on affected plants with focused energy, trying to solve the mystery of why we are seeing these effects. We have received several samples and examples of this in July.
Case I. A sugarbeet sample arrived at the NDSU Plant Diagnostic Lab in early July with bleaching and mottling effects on the margins of leaves. The pesticide and adjuvants were applied according to label. The effects were similar to what one might expect from a soil PPO or maybe residual of an HPPD inhibitor. We concluded a very low dose of a tank contaminates or spray residues deposited in hoses caused the injury.
Case II. Sugarbeet samples arrived at NDSU with the same visual phenotypes as ‘Case I’ the week of July 21. Fields were sprayed by air with the same commonly applied sugarbeet herbicide and adjuvants. The spray system was dedicated to one active ingredient, which eliminated the idea of residues from other pesticides. Furthermore, a partial load was sprayed on day one with no observed effects. The samples we received were from fields sprayed the second day, June 22 or when the rest of the load was applied to fields.
Case III. A soybean and a sugarbeet research trial were sprayed with commonly used products and adjuvants. Observed phenotypes in the soybean trial included puckering on some treated leaves with occasional reddish-brown lesions and some of the leaves that emerged after the treatment contained apparent chlorosis about 10 DAT. In the sugarbeet trial, leaves contained necrotic areas that may have been bleached earlier with mottling on the margins of the leaf (see photo) and were similar to the same effects we had seen on samples in ‘Case 1’ and ‘Case 2’.
We have concluded these are examples of how the environment sometimes interacts with postemergence sprays that have a history of excellent crop safety in crops. However, at writing, we are uncertain of the environmental trigger that caused the undesired phenotypes.
Extension Sugarbeet Agronomist
NDSU & U of MN
Bacterial Blights Appearing On Dry Beans
Bacterial blight is showing up on dry edible beans throughout the dry bean growing regions of North Dakota and Minnesota (Figure 1). The appearance is largely related to the high winds (and some hail) that passed through much of the region early last week. The high winds wound the plant tissue, providing an entry for these pathogens.
There are three bacterial diseases of dry beans currently active in the region; brown spot, common blight and halo blight. Early symptoms of these three diseases are similar, all begin as small greasy spots on plant tissue. Eventually, common blight will form large necrotic areas on tissue, halo blight will have a smaller necrotic lesion surrounded by a large yellow halo, and brown spot will produce numerous small necrotic spots that may coalesce to form longer lesions. Each disease is favored by plant wounding and rainfall, but optimal temperatures vary. Common blight and brown spot often are more damaging when daily high temperatures are in the 80’s F, while optimal temperatures for halo blight range from the high 60’s F to low 70’s F.
Management of bacterial diseases is difficult, and data obtained from this region are very limited. In the high plains region (Western Nebraska and Colorado), preventative copper applications are used (often Cupric Hydroxides) with some success. It is less clear how these compounds perform after bacterial blight is well established. Complicating matters, coppers are generally less effective on common blight than the other two pathogens. However, if you have high yield potential, high prices and a significant threat from bacterial blight, an application can be made to try and limit pod infection should not be ruled out. Unfortunately, we do not have data to show economic return of chemical applications at this time.
In order to limit the spread of bacterial infection, do not go into fields when they are wet. This is particularly important now that nighttime temperatures have begun to fall and heavy dews may be forming in the canopy. Under high humidity, bacterial pathogens are produced in sticky gelatinous ooze (Figure 2). This ooze is easily moved by equipment, which can spread the pathogen and cause new infections. Lastly, if you have bacterial blight infections in your crop, do not save seed. Bacterial pathogens survive in seed and can cause epidemics if planted.
A very good Colorado State University Extension publication about bacterial blights of dry beans is available at http://www.ext.colostate.edu/pubs/crops/02913.html and http://www.ext.colostate.edu/pubs/crops/02913.pdf
Extension Plant Pathologist, Broad-leaf Crops
Dry Bean and Pulse Crop Pathologist
Establishing a Residue Crop for Winter Wheat Planting this Fall
Again this year there were substantial acres that were not planted this spring due to excessive moisture. Planting winter wheat this fall on these acres can be a viable option. However, as many growers learned this past year, winter wheat survival is enhanced when it is planted into fields that catch and retain snow. Snow catch become even more critical when snowfall is limited as it was last year. Fields that were not planted this year but have standing stubble from the previous year should be ideal for direct seeded winter wheat if the residue is not completely broken down. In these fields, however, carefully manage weeds and volunteer crop plants prior to planting. Volunteer wheat plants and other grassy weeds can harbor the wheat curl mite that is the vector of the wheat streak mosaic virus. These plants must be control well in advance of planting winter wheat in order to “break” the green bridge and reduce the risk of wheat streak mosaic virus infections. For fields that were previously tilled or that have little or no stubble, establishing an effective residue crop can significantly improve the probability that there will be adequate snow cover for successful winter wheat production. To be effective, a residue crop must remain erect during the fall and winter. Cereal crops that do not reach the boot stage before being killed by frost or herbicides, for example, will lay flat on the soil and will not capture much snow. The most effective crop that can be planted this late in the season is probably flax. Flax can be established as a lightly seeded solid stand, in wide rows (i.e. 3-4 feet spacing) or as strips. Strips of flax 3 to 5 feet wide and 15 feet apart have been found to effectively trap snow while minimally depleting soil moisture. When seeding flax in strips or in wide row spacings, the drill should be set at a high seeding rate (40-60 pounds per acre) and drill spouts should be taped shut to obtain the desired spacing. Strips of flax more than 20 feet apart can be risky as they do not catch sufficient snow in most years. Flax should be seeded in late July or early August, depending on the region of the state. Though some additional weed management will be needed prior to planting, flax planted in late July or early August followed by winter wheat could be a viable and profitable option for dealing with land that was too wet to plant this spring.
Extension Agronomist for Cereal Crops
Sunflower Development Stages
Based on observations from the North Dakota Agricultural Statistics Service, 50% of the sunflower acres in ND were planted by June 6 (Table 1). This was close to average for reaching the half way mark of the planting season. Development of the sunflower plant is mainly driven by growing degree day (GGD) units. GDD for sunflower are calculated as follows: Daily Sunflower GDD = ((Daily Max Temp °F + Daily Min Temp °F)/2) - 44 °F. If the daily maximum or minimum temperature is less than 44 °F the number in the formula is set at 44 °F. Table 2 provides an indication of how many GGD’s are needed to reach a certain development stage in sunflower. The GGD’s needed to reach designated stages are based on averages and may differ between hybrids and growing conditions in the field. The model uses data from the North Dakota Agricultural Weather Network (NDAWN), however, there can be differences in the predicted development stage and the actual stage in production fields depending on field elevation, color of the soil, soil type, fertility level and moisture content of the soil, and residue levels in the field.
In Table 1, GGD’s are given for the 2014 growing season from the date of planting (first column) to July 29 including the estimated development stage for Mandan, ND. The GGD’s and estimated stages were calculated from the NDAWN sunflower GGD and development model. Sunflower development stages for any location in North Dakota can be estimated by selecting the location of the nearest weather station and the sunflower planting date and using the model mentioned above.
The model is predicting that near Mandan the sunflower has entered its reproductive phase for the 50% acres planted before June 6. Some early planted sunflower fields have already started to bloom. It is important to scout sunflowers during the reproductive phase for potential insect damage. During the 2013 sunflower survey conducted in ND, 60% of the fields had seed weevil damage and those fields with a problem had 5.7% of the seeds damaged. Banded sunflower moth damage was found in 36.3% of the samples with 3.4% of the seeds damaged. Damage due to the sunflower moth was found in 3.7% of the samples with on average 2.3% of the seeds showing damage in the fields with seed damage.
For sunflower insect management see the resources available on the Extension Entomology website. at: http://www.ag.ndsu.edu/extensionentomology/field-crops-insect-pests/sunflower.
Click the title for a descriptive pictorial description of Stages of Sunflower Development.
Extension Agronomist Broadleaf Crops
Get Ready To Scout for Red Sunflower Seed Weevils
Red sunflower seed weevil (RSSW) adults will be emerging soon and will fly to the nearest flowering sunflowers. However, I have not received any field reports of adult weevils in sunflowers yet. So, please send me your reports of locality and numbers when you start finding them. Weevils are small (2.5 to 3.1 mm long) and reddish-orange. Peak emergence will occur later in early August this year. The 2013 National Sunflower Association Sunflower Survey indicated that 60% of field surveyed in North Dakota had RSSW damage with an average of 5.7% of the seeds damaged.
Scout for adult seed weevils on the early blooming sunflower fields when the yellow ray petals are just beginning to show. A NDSU YouTube video is available on Scouting for Red Sunflower Seed Weevil in Sunflowers. Counts should continue until the economic threshold level has been reached or most plants have reached 70% pollen shed. At 70% pollen shed, plants are no longer susceptible for egg laying or significant damage. When sampling, use the X pattern and begin counting at least 70 to 100 feet into the field to avoid field margin effects. Count the number of weevils on five plants at each site for a total of 25 plants. Assuming the field is at threshold, we recommend that treatment be considered when three out of 10 plants are just beginning to shed pollen.
If you need to spray flowering sunflowers, remember to PROTECT BEES by notifying bee keepers before an insecticides application and spraying in late evening. A NDSU YouTube video is available on Protect Bees from Pesticide Poisoning.
What is the Economic Threshold (E.T.) for RSSW in oilseed sunflowers in 2014?
Oilseed Sunflower: The E.T. can be calculated using the following formula:
Threshold (weevils per head) =
Cost of Insecticide Treatment
(Market Price x 21.5) x (0.000022 x Plant Population + 0.18)
Assuming a plant population of 20,000 per acre and a market price of 19 cents per lb., the E.T would be at 4-5 weevils per head if treatment costs were $8 to $10 per acre, respectively. Other examples of threshold calculation when the cost of insecticides is $8.00 and $10.00 per acre are listed in Tables 1 &2.
Banded Sunflower Moth and Sunflower Moth Trap Update
Sunflower moth continues to be trapped at low, sub-economic levels in the IPM scouts’ pheromone traps. Using the pheromone traps, an average of 28 moths per trap per week is considered economic. IPM scouts are detecting increasing numbers of banded sunflower moths in pheromone traps, especially in the more northern regions of North Dakota. Sunflower crop development is in the R1 to R3 crop stages in surveyed fields of North Dakota. Sunflower should be scouted for banded sunflower moth eggs or adult moths when most of the plants in the field are at plant stage R3 (distinct bud elongated ¾ inch above the nearest leaf, yellow ray petals not visible). See last week’s issue 12 of Crop & Pest Report July24, 2014 for more information.
The IPM Crop Scouts surveyed 92 soybean fields last week and soybean aphids were observed in only 9% of the fields surveyed. Soybean aphids continue to be detected at low densities ranging from 0 to 16 aphids per plant; however, incidence (% of plants infested in field) increased. The high was 86% incidence in three of the positive fields. Surveyed field were in the V5 to R3 (beginning pod) crop stages. With moderate temperatures (high 70sF to low 80sF), conditions are optimal for aphid reproduction and populations can double in only 3 days in the field. So, continue to scout for soybean aphids through the R5 (beginning seed) crop stage.
Beneficial insects that eat soybean aphids also have been increasing. Ladybeetles, syrphid fly larvae and lacewing larvae have been observed in fields infested with soybean aphids. Remember to avoid early insecticide applications, since insecticides kill beneficial predators and parasites.