Crop & Pest Report - All
Scout for Colorado Potato Beetles
Adult Colorado potato beetles are emerging now from overwintering sites. The adult is 3/8 inch long, with oval body and a yellow-brown with 5 black stripes on each wing cover. The orange eggs are laid on the underside of leaves in clusters of 10 to 30. Larvae are 1/8 to 3/8 inch long and brick red to light orange. Both adults and larvae feed on potato foliage.
The economic threshold is to initiate treatment at 15 to 30 percent egg hatch. Best results have been achieved by flagging the first egg masses that can be located and monitoring these daily.
Degree Day Update for Leafy Spurge Flea Beetles
The updated degree day map for leafy spurge flea beetles (Aphthona species) indicates that land managers can scout and/or collect adult flea beetles in North Dakota, based on the sunflower GDD model from NDAWN. Scout at 1,000 AGDD and collect flea beetles between 1,200 and 1,600 AGDD.
Hessian Fly Infestation in SW ND
An isolated Hessian fly infestation was found in Syngenta’s hard red spring wheat variety trial near Beach in SW ND. The Hessian fly overwinters as a maggot or pupa in winter wheat, volunteer grain, and wheat stubble. Overwintering maggots pupate and emerge as adults from April to May, infesting fall and spring planted wheat. By June, maggots pupate (flaxseed stage), emerging as adults in August to lay eggs for the overwintering generation.
Winter wheat acts as a bridge to get Hessian fly from one season to the next. Delaying planting of winter wheat in the fall should reduce the risk of infestations. Suggested planting dates for ND are: September 1 – 15 in northern ND and September 15 to 30 in southern ND. Crop rotation with non-susceptible crops (oats, corn, soybean, sunflower, flax and canola) is an effective IPM strategy for reducing Hessian fly populations. Insecticide seed treatments (active ingredient - imidacloprid or thiamethoxam) labeled for wheat also help reduce the spring generation. However, population levels of this pest rarely warrant the need for insecticide treatments in North Dakota.
Spruce Sawfly Larvae Observed
Yellowheaded spruce sawflies were seen this week in the Devils Lake area. They are primarily a pest of Colorado blue spruce, where the larvae feed on expanding needles. Sometimes whole needles are eaten; in other cases, the needles are damaged to the point where the ends dry out and turn a pink/brown color (see photos). This symptom can be subtle at first, but an experienced eye will pick up on it quickly. Spruce sawflies are usually found in the central and western parts of the state.
Over the last several years, the larvae have consistently been observed at about 830 Growing Degree Days (base temp 40°F). They feed for 30-40 days total, and should be susceptible to insecticides for a least 2 more weeks. Carbaryl and acephate are both labeled for sawfly control. For a small infestation, simply picking the larvae off the tree by hand and destroying them may be easier, and is equally effective. A strong jet of water may also help reduced sawfly populations on trees.
When using insecticides, be sure to read, understand and follow all label directions.
Benson County Agent
Spraying Weeds in Less Than Optimum Environmental Conditions
Most areas of Eastern North Dakota and Minnesota have received excessive amounts of rainfall in June. The moist/wet soil conditions have created a perfect environment for weed seed germination and emergence. Growers planning postemergence sprays will first evaluate field conditions to determine if they can get spray equipment over the fields. A second consideration will be wind velocity. Some pesticide labels limit application to certain wind velocities. Growers need to abide by the label. However, there are methods for minimizing the effects of spray drift even when wind speeds are within ranges denoted on the label. Strategies for reducing spray drift include:
- Selecting nozzles that produce larger spray droplets
- Reducing boom height over target plant species
- Reducing speed of ground application equipment
The benchmark nozzle standard for many years was extended range flat fan nozzles. These nozzles allowed the operator to reduce the spray pressure to as low at 15 psi and maintain the correct spray pattern. The idea was less spray pressure equated to less droplet fines susceptible to spray drift. However, extended range flat fan nozzles still produced small droplets. There are several brands and styles of ‘air induction’ nozzles available in the marketplace, today, which reduce small spray droplet size even more than extended range flat fan nozzles. Air induction nozzles operate by drawing air into the nozzle body to create large, air-filled droplets that break and provide coverage when they come into contact with the leaf surface. There are a number of different air-induction nozzles types; careful consideration needs to be given to proper operation of these nozzles including the correct spray pressure. One should also consider the pesticide to be applied when making a decision on nozzles. For example, contact sprays require good coverage of the leaf surface to provide excellent weed control. Spray coverage is not as critical for herbicides such as glyphosate, which translocate in the plant.
Lowering the boom height and using nozzles that produce a broader pattern is a second approach for reducing drift. Reducing the distance between droplet release point and the target means less time the droplet will be in the air and susceptible to drift. However, it is not as simple as reducing the boom height. Consideration must be given to ensure the spray pattern can be maintained as the operator travels across the field and there is appropriate overlap of spray solution between spray nozzles to deliver coverage.
Speed is a third variable to consider for minimizing drift. Reducing sprayer ground speed reduces drift since there is less bounce and less sprayer vortex effect, which means droplets are aloft in air for a shorter duration of time. However, speed impacts the amount of time needed to spray a field. Ultimately the operator will need to decide on the compromise between ground speed and the number of acres one can cover in an hour and potential for spray drift.
References available for applicators
- Selecting the correct drift-reducing nozzles
- Factors that contribute to spray drift
- Impacts of temperature inversions on spray drift
- Sprayer calibration
Extension Sugarbeet Agronomist
Ag Machine Systems Specialist
Strategies for Controlling Emerged Weeds in Sugarbeet Fields
Weeds continue to emerge and are actively growing in sugarbeet fields in Eastern North Dakota and Minnesota as a result of recent widespread precipitation. The National Weather Service Climate Prediction Center forecasts above normal precipitation for June, July and August in North Dakota and Western Minnesota, which may stimulate additional flushes of weeds. In some fields, weeds may have grown larger than what is recommended for control due to saturated field conditions. So the logical question is…..how are sugarbeet growers going to stay ahead of weeds?
For sugarbeet at the 4 to 6 leaf stage, there may still be time to use layby herbicides for residual control of grasses and small seeded broadleaves including waterhemp, redroot pigweed and common lambsquarters. Apply Dual Magnum, Outlook and Warrant in combination with glyphosate to control emerged weeds in fields. Layby herbicides need rainfall for activation.
Many sugarbeet growers will continue to implement a total postemergence spray program using glyphosate as the primary component of their weed control strategy. As stated previously, apply glyphosate at maximum labeled rates, depending on weed size. Add ammonium sulfate at 8.5 to 17 gallons per 100 gallons spray solution. And depending on the type and size of weeds in field, consider a tank-mix herbicide with glyphosate. Pay particular attention to the adjuvant added with glyphosate and the tank-mix partner. Glyphosate is very water soluble and depending on adjuvant loading in the formulation, is applied with a non-ionic surfactant at 0.25% to 1% volume/volume. Most herbicides mixed with glyphosate are oil soluble and perform best in combination with oil adjuvants that antagonize glyphosate. Methylated seed oil based ‘high surfactant oil concentrate’ adjuvants contain a higher concentrate of surfactant other than oil adjuvants and enhance oil soluble herbicides without decreasing glyphosate efficacy. Consult with your agricultural retailer, your agriculturalist or write or call me if you have questions about specific adjuvants or adjuvant rates.
I consider common and giant ragweed, waterhemp, common lambsquarters and kochia tough weeds due to their weed biology and/or presence of herbicide resistant biotypes and are excellent candidates for tank-mixes with glyphosate. This especially will be true in 2014 since precipitation and wet fields have prevented growers from getting into fields in a timely manner. Stinger is an excellent tank-mix partner with glyphosate when there is common and giant ragweed in fields. Betamix, ethofumesate (Nortron) and UpBeet are excellent tank-mix partners with glyphsate for kochia, waterhemp and common lambsquarters control. Consult pages 44 and 45 of the 2014 North Dakota Weed Control Guide or the 2014 Sugarbeet Production Guide for more details or contact your ag retailer, your agriculturalist or me about specific rate recommendations that will vary depending on environmental conditions and weed and sugarbeet size.
Extension Sugarbeet Agronomist
Weed Watch: Palmer Amaranth
This may possibly be the most important Crop and Pest Report article (weeds) written in the 2014 cropping year. Palmer amaranth is the bane of agriculture in the southern U.S. This is the weed that can produce millions of seeds per plant and grow baseball bat size stems that can stop combines dead in its track. It is the weed that has forced radical changes in weed control because of its relentless ability to reproduce and spread at astounding rates. The latest information shows that glyphosate–resistant Palmer amaranth is now present in every Midwest and Plains state except Minnesota and North Dakota. Sources from Centrol consultants have indicated Palmer amaranth to be around the Aberdeen, SD area.
Palmer amaranth (Amaranthus palmeri) is a pigweed species that is not native to North Dakota or to the northern United States. It is well established in the southern U.S. It was introduced in Michigan and possibly other states through the spread of manure from dairy cows that were fed cotton by-products as a feed supplement. It could easily establish in ND through custom combines moving north into ND and several other ways of weed seed dissemination.
Palmer amaranth has not been identified in ND but has been introduced in the northern latitude of the U.S., demonstrating it could survive in the northern plains. Palmer amaranth was chosen as weed-of-the-year as a proactive approach to increase awareness of its extreme noxious and pernicious capability, to aid in identification, and to encourage land owners to keep a vigilant watch and kill all plants that may arise. Main point of this article: Let’s keep this weed out of ND – memorize the identifying characteristics of this weed, keep a steadfast watch, and if you think you find plants – KILL IT! Rephrase: Don’t even think, just kill it. In some areas in the south the only option for control is hand-weeding. Consider the choice: Hand weed a couple of plants or a small patch now or deal with a field fully infested a couple of years later. We have glyphosate resistant waterhemp, marestail, ragweed, and kochia in ND. These weeds have complicated crop production in ND but these pale to the impact that Palmer amaranth will have if established here.
Below are some 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 inhibitors (27) herbicides, leaving very few herbicide options available for weed management.
- One of the fastest weed growth rates known – near 2 inches/day.
- Long emergence pattern from mid-May through August.
- Can exploit even slight canopy openings.
- Produces more than 1 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.
- Pulled plants can re-root and produce seed.
- 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 biggest weed threat that ND farmers have ever faced. Please refer to page 136 in the 2014 North Dakota Weed Guide for management recommendation and additional information. Please contact myself or another NDSU Weed scientist to confirm positive identification.
Identifying characteristics of Palmer amaranth:
- Stem and leaf surfaces with no/few hairs
- Leaves have a symmetrical (poinsettia) arrangement
- Leaf petioles are as long as or longer than the leaf blades
- Male and female flowers are on separate plants
- Spiny bracts are at leaf axils on female plants
- Flowering structures are unbranched, and 1 to 2 feet long
- Male flowering structures are soft and spread pollen
- Female flowering structures are spiny and contain seed
Extension Weed Specialist
Soybean Iron Deficiency Chlorosis
On my way to and from Devils Lake today, nearly every field of soybean had symptoms of iron deficiency chlorosis (IDC). Therefore, a short review is in order.
To have IDC, the soil must have free lime (carbonates- calcium carbonate, magnesium carbonate, sodium carbonate or a mixture of two or three at once). The pH of these soils is always above 7. If a soil has pH below 7, then IDC is not possible and the cause of yellowing is something different. If a soil has carbonates, the next causal factor is soil moisture. Especially in our region, soil water must be sufficient to dissolve the more easily soluble salts, like chlorides, magnesium sulfate and gypsum, before the carbonate is dissolved. When carbonate dissolves, the resulting bicarbonate has the property of being able to neutralize the acidity the soybean root forms around itself to enable the activity of an iron ion reducing substance to transform Fe+3 to Fe+2, which makes iron a trillion times more soluble than it naturally occurs in an oxygen rich environment. Without the acidity around the soybean root, iron uptake is terribly restricted, and the characteristic interveinal yellowing occurs.
In his studies on IDC, Dr. Goos at NDSU has stated that if a soybean plant exhibits any IDC symptoms one can lose 5 bushels per acre right off the top. As the condition persists, yield potential continues to decrease. In our region, under extreme perpetually wet conditions or with a variety with poor tolerance to our version of IDC, the soybean can be yellow the entire season. In my experience, soybeans rarely produce more than 10 bushels per acre if they are chlorotic the entire season.
Other environmental and soil conditions that contribute to greater IDC severity are soluble salts, cool temperatures, soil nitrate, and anything that stresses the crop even a little, including a herbicide application.
There is no cure for IDC that one could apply. An application of an iron foliar fertilizer may green up the leaves that are treated, but the iron is not mobile within the leaf or the plant. A recent foliar study by Dr. Goos included a Post-It note over half a soybean leaf. The exposed half of the leaf was green following treatment, but the half under the Post-It note continued to be yellow.
Make a note of the fields with problems. A high-resolution satellite image of the field or an aerial image (this may be one possible value for the use of a drone) will help define the area for future application of an ortho-ortho-FeEDDHA fertilizer in 2015 and beyond. Other methods to reduce IDC are to plant in row widths of 20 inches to 30 inches wide, and seeding a bushel per acre of oats or barley at soybean seeding to help dry the soil more quickly and use up excess soil nitrate.
For a more detailed explanation of IDC, see the 2013 NDSU circular- Soybean Fertility
NDSU Extension Soil Specialist
Sulfur Deficiency in Valley High Clay Soils
I have stated at many meetings that the high clay soils in the Red River Valley are high enough in organic matter and have a high enough sulfatic water table that sulfur fertilization is not needed. However, in 2011 I had a corn N rate study that had a sulfur deficiency near Christine, in a Fargo-ish soil. I attributed the deficiency to nearly continuous rain over several weeks that resulted in low mineralization of S due to saturated conditions, S being leached from the surface, and a shallow root system with limited ability to extract water from deep depths. Well, if you picked me up in time in 2011 and set me down in the Valley in 2014, I would be unable to tell any difference in Valley soil conditions. Recently, a trusted crop consultant from the Hillsboro area confirmed a S deficiency. I would be amiss if I did not suggest that those that will side-dress/topdress corn/wheat this season might benefit from a 2-3 gallon per acre of ammonium thiosulfate or ammonium sulfate equivalent this season. Unusual? Yes. But what’s so unusual about that? I also checked at a local lumber yard and gopher wood is in short supply.
NDSU Extension Soil Specialist