Crop & Pest Report - All
Soybean Aphids - Scouting Critical
Some “hotspots” soybean fields are at economic threshold (E.T. = average of 250 aphids per plant, 80% of the plants infested, and increasing populations) and will be or have been sprayed with insecticide for soybean aphid control. These fields are located near the Red River Valley area (see maps). We also are just starting to see soybean aphids in other outlier areas – Pembina and Rolette in NE, and Wells and Benson Counties in Central North Dakota. Ninety three fields were scouted by the IPM Scouts for soybean aphids last week. The IPM scouts in North Dakota and Minnesota found soybean aphids in 55% of the soybean fields surveyed. Percentage of plants infested with soybean aphids ranged from 0 to 100% with an average of 51% of plants infested, an increase from last week’s average of 39%. The average number of soybean aphids per plant ranged from 1 to 225. Our high count last week was only an average of 67 aphids per plant, so aphid populations are increasing. We are and will continue to get migratory winged aphids from neighboring states through the fall, so scouting is the best way to find and identify any fields above E.T. Scouting also is very important as the soybeans are in the susceptible reproductive stages. The USDA NASS reports that 71% of the soybeans were blooming (R1), and 23% setting pods in North Dakota (USDA NASS News Release – July 20, 2015).
The next 7 days will remind everyone that late July is climatologically the warmest period of the year. Much of the rest of this month will be dominated by an upper-level wind flow sometimes referenced as an “Omega” (Ω) pattern. There will be a trough (dip) in the jetstream along both the west and east coasts of the United States. That will create a ridge of high pressure in the Great Plains from Texas to Canada. If you examine Figure 1 you can somewhat imagine the jetstream looking like the greek letter Omega.
This shift from periodic days of cooler air over the past week to consistently warm and humid weather started yesterday (Wednesday) and is expected to continue through at least Monday. The upper-level wind will be from the west or southwest, but the near surface flow will frequently be from the south advecting Gulf of Mexico moisture into the region, meaning humid conditions are expected through early next week with above average temperatures. This will bring bountiful growing degree units to the area, but also have the potential to add disease risk with high relative humidity levels on several occasions. That will be particularly true in the eastern part of North Dakota into northwestern Minnesota.
With dew points at least in the 60s with some periods perhaps even as high as the lower 70s, any thunderstorms that do develop would have the potential to drop heavy rainfall in localized areas. There appears to be two time frames for thunderstorm development during this forecast period. One will be later today (Thursday) into Friday morning, and again early next week (later Monday into Tuesday). Although specifics for early next week are lacking, the storms that do develop today into tonight will probably have some localized severe weather potential as well as that risk for heavy downpours. The thunderstorms early next week will be associated with a brief cooling period that is expected to last only one or two days.
Projected Growing Degree Days (GDDs), base 34°, 44° and 50° for the period July 23 through July 29, 2015 are presented in Figure 2 and the number of hours expected to be at or above 85% can be found in Figure 3.
Assistant State Climatologist/Meteorologist
(701-231-8209) Twitter: @darylritchison
Crops overall are looking great. Rainfall has slowed down with most NDAWN stations in the region reporting between 0.2 and 0.5 inches of rain over the past week. Some disease is present across the region with downy mildew in sunflower and multiple diseases including tan spot, Fusarium head blight, and ergot being reported in wheat. Corn in the area is looking relatively good, especially with recent temperatures in the upper 80s.
There have been reports of crop injury from improper sprayer cleanout. Be sure to clean nozzles, screens and filters, more information on proper cleanout can be found in the NDSU weed control guide on page 70 section A8.
Area Extension Specialist/Cropping Systems
Scab is showing up in the wheat and barley fields in our region. Much of the stripe rust has gone into the black teliospore stage; however at the LREC, we still have some yellow-orange pustules present in our small grains. Also, a few leaf rust pustules can be found sporadically on these plants. Stripe rust causes the flag leaf to dry -own rapidly (see photo).
Corn growth has been excellent in last few weeks. Corn is starting to tassel in the southern and valley parts of my region. Meanwhile, we have water-affected soybean fields which can be found in high rainfall areas. These fields look chlorotic and are developing slowly. Outside these areas, we have a lush late-July soybean crop coming along.
We finished up our on-station and off-station field days on Tuesday. Thanks for all the support for our research and extension programs!
Area Extension Specialist/Agronomy
Isolated hail events have had a significant impact on some crops. Depending on location, a slight defoliation to complete defoliation of soybean has occurred. Rainfall totals for the last week have ranged from 0.2” to 1.65” in Bottineau and Rugby, respectively. The NCREC has received 0.4” of rainfall during the last week. The NCREC hosted their annual field day on July 15. Over 150 people were in attendance to hear topics focused on soybean production. Additionally, other regional field tours around the area have been well attended.
IPM scouting of wheat, barely, soybean and sunflower continues. Fusarium head blight has been quite prevalent in HRWW, HRSW and durum wheat. Corn has begun to tassel. Currently, the NCREC has accumulated 1088 GDD based on a May 1 planting. The normal accumulated GDD for this location is 1023.
Area Extension Specialist/Cropping Systems
Waterhemp is Moving North in the Red River Valley
I stated in winter meetings the ‘waterhemp line’ or fields where waterhemp could be scouted for and found in corn, sugarbeet, soybean or small grains fields was somewhere between Wahpeton and Fargo in 2014. Last week, at the Northwest Research and Outreach Center (Crookston. MN) Crop and Soils Day, I stated that I believed the waterhemp line had moved north or perhaps between Fargo and Hillsboro, ND in 2015.
I got feedback that waterhemp has been found in fields further north, perhaps as far north as US highway 2. This week I found waterhemp in fields near Ada and Hendrum, MN and received pictures that appear to be waterhemp in a field near Euclid, MN (north of US 2, north of Crookston).
How is it moving so far so fast? Scientists know waterhemp seed moves readily in water. Scientists also believe that geese and ducks feed on waterhemp and perhaps distribute seed as excrement along flyways. Finally, humans (us) unintentionally move seed, especially with our harvest equipment.
Farmers must continue to scout fields and properly identify weeds in fields. Set the expectation for zero tolerance for weed escapes and make maps of areas in fields where weed escapes occur. And finally, prepare to adapt your weeds management strategy for waterhemp. Waterhemp is easy to manage in fields planted to corn, soybean, small grains and sugarbeet when it is part of a weeds management strategy. However, it is much more difficult to manage when escapes are found in fields, especially following the first or second herbicide application. Manage weeds on the edges of fields.
Extension Sugarbeet Agronomist
NDSU & U of MN
Palmer Amaranth – A Plant Form of Cancer
In the very small chance that readers have not heard of Palmer amaranth nor heard of the devastation it can inflict, here is a summary:
Palmer amaranth is a C-4 carbon assimilating species, thrives in hot environments, and can survive, establish, and spread in the northern latitude of the U.S., including the northern plains. It was introduced to some areas (e.g. Michigan) through the spread of manure from dairy cows that were fed cotton-seed screening that included Palmer amaranth seed as a feed supplement.
Palmer amaranth seed could easily be brought into ND through various ways including:
- Custom combines moving south to north into ND.
- Contaminated crop seed used for seeding.
- Transportation of contaminated hay and forage across state borders.
- Food source for birds and bird migration. Watch for amaranth plants under power lines and anywhere birds might land.
- Water flow - Palmer amaranth seed is small, light, and floats in water which makes water movement a primary source of spread. Waterhemp, another pigweed species, has spread in ND through water flow, especially in drown-out areas where no crop competition allows weeds to grow uninhibited.
Below are reasons why it is being called “Satan” and why growers should quickly destroy any plants found.
- Biotypes of this weed are resistant to one or more of the following herbicide site of action groups: ALS (2), atrazine (5), glyphosate (9), and HPPD inhibitor (27) herbicides, leaving very few herbicide options available for management.
- One of the fastest weed growth rates known - >2 inches/day.
- Long emergence pattern from mid-May through August.
- Can exploit even slight canopy openings.
- Produces from 1 to 1.8 million seeds/plant.
- Seed is short-lived and only 2% of seed is viable after 6 years but the sheer number of seeds produced by a female plant makes eradication difficult once established.
- Female plants can grow to more than 10 feet tall with a 5-6 inch stem girth and seed heads more than 1 foot in length. Male plants are small and generally non-competitive.
- Can cause 78% yield loss in soybean, 91% in corn.
Palmer amaranth’s prolonged emergence period, rapid growth rate, prolific seed production, and propensity to evolve herbicide resistance quickly makes this the most pernicious, noxious, and serious weed threat that ND farmers have ever faced.
Extension Weed Specialist
Foxtail Barley Control
The following information is from email correspondence with Dr. Rod Lym, NDSU Weed Scientist.
Question: What are some good recommendations for control of foxtail barley in pasture - what about tips when applying Plateau and is this a good option?
Answer: There are not a lot of good options here since we lost Atrazine for pasture use. Plateau and Oust are the only two herbicides I know about for foxtail barley control in pasture, but the application window is gone for this season. Both herbicides need to be applied in late-May to early June when the plant is rapidly growing, but not yet setting seed.
Plateau should be applied at 8 to 12 oz/A. Some people split the application into 6 oz/A twice which improves control and helps prevent the plant from going to seed. The application time would be once in May and then again in June.
Oust should be applied at 1.3 to 2 oz/A. Oust is a very broad spectrum herbicide that will control many broadleaf plants in pasture and may reduce desirable grasses as well, especially during dry years.
The only other option is spot treatments with Roundup, which is only practical for small patches. I suggest the land manager flag the areas now for treatment next spring.
Extension Weed Specialist
Fusarium Head Blight (Scab) Report
The small grain crop is quickly maturing across the state and now is a good time to scout fields for any head diseases; most important Fusarium head blight (scab). Last week, the IPM survey scouts identified scab in 42% of the scouted wheat fields. Similarly, I have seen variable levels of scab at research centers and sites across the state (Figure 1).
Extension Plant Pathology, Cereal Crops