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Insect Management Herbicide-Insecticide Combinations 2,4-D: Wheat injury but not lower wheat yield with 2,4-D amine combined with Lorsban. 2,4-D, dicamba, bromoxynil+MCPA or Curtail mixed with Asana, Cygon, Di-Syston, Warrior, or Lorsban caused no wheat injury in University of Wyoming studies. Assert: Use caution when tank-mixing organophosphate insecticides for use on barley and sunflower. Assert and Di-Syston caused barley injury in University of Wyoming research. Dicamba: Oil-based insecticides increase risk of wheat injury. Basagran: Basagran should not be tank-mixed with Scout or any organophosphate insecticide as crop injury may result. Betamix/Betanex: Increased sugar beet injury occurred from tank-mixtures with Lorsban, malathion, or Sevin XLR. Oil-based additives increase risk of sugar beet injury.Bromoxynil: Refer to label for directions on the order of adding products to the spray tank and for the complete list of insecticides that can be tank-mixed with bromoxynil. Assure II, Fusilade DX, Fusion, Poast, Prism, Select: Reduced grass control may result from tank-mixes of Fusilade DX with Lorsban, malathion, Sevin XLR, or Pydrin, or Poast mixed with Sevin XLR Plus or Pydrin. No decrease in grass control resulted from Poast tank-mixed with Lorsban or malathion. Glyphosate: No antagonism or injury to resistant crops occurred when applied in combination with Warrior, Asana, Sevin, and Capture insecticides. Sulfonylurea Herbicides (SU): Severe crop injury may result from tank-mixing SU herbicides with organophosphate insecticides. Most SU labels do not allow addition of Lorsban or malathion. SU herbicides and insecticides should be tank-mixed only when experience or research indicated crop safety. Refer to product label for directions on the order of adding products to the spray tank and for the complete list of insecticides that can be tank-mixed. Compatibility Test for Pesticide Mixture A way to test for tank-mix compatability: Get a large, clean, clear glass container, such as a quart jar. Use the same water (or other diluent) that you will use when making up the larger mixture. Add the water and each of the products in the same proportions as you will mix them. For example, each quart of pesticide that you add to 50 gallons of final spray mixture is the equivalent of about 1 teaspoon per quart of water. Unless the pesticide labeling states otherwise, add pesticides to the diluent using the “W-A-L-E” plan:
If scum forms on the surface, if the mixture clumps, or if any solids settle to the bottom (except for wettable powders), the mixture probably is not compatible. Finally, if no signs of incompatibility appear, test the mixture on a small area of the surface where it is to be applied. Resolving Incompatibility If incompatibility still persists, dispose of this mixture, clean the jar, and repeat the above steps, but add 6 drops of compatibility agent to the water before anything else is added. If the mixture is still incompatible, do not mix the chemicals in the spray tank. To overcome this problem you might consider the following alternatives: a) Use a different water supply. Hard water can contribute to incompatibility Make only one change at a time, and perform a complete test, as described above, before making another change. Do not mix the chemicals in the spray tank if incompatibility cannot be resolved. The Effect of Water pH on Insecticides Stem Maggot May Cause White Heads in Wheat With wheat stem maggot damage, the head and the stem down to the top node are dead, with the rest of the plant green. The head will pull out with a gentle tug, and usually there is evidence of insect chewing on the stem above the top node where it broke when pulled. Single heads are affected rather than the whole plant. These symptoms can be differentiated from white heads caused by common root rot. With root rot, typically the whole plant is whitened and the whole plant easily pulls from the soil, with browned or blacked roots, as well. No chemical controls are available for wheat stem maggot. Managing Grasshoppers Whenever grasshopper populations reach the threatening level, feeding damage to crops should be anticipated. Directing control efforts at nymphs in hatching sites is recommended to minimize the total area requiring insecticide treatment, and permits lower insecticide rates for effective control. Grasshopper Thresholds/Infestation Ratings
Orange Blossom Wheat Midge
Wheat is susceptible to midge infestation from the time the head emerges from the boot until 80% of the primary heads have anthers visible. Treatments are warranted when 1 or more midge are observed for every 4 or 5 heads of spring wheat, and when 1 or more midge are observed for every 7 or 8 heads of durum. Treatments after 50% of the first heads have flowered are not recommended due to reduced levels of efficacy and for the protection of a parasitic wasp that attacks the midge eggs. More information online: www.ag.ndsu.nodak.edu/aginfo/entomology/ Hessian Fly
Aphids
Soybean aphid Soybean aphids have tended to initially colonize fields near shelterbelts, southern field edges, or perhaps some other protective structure. Particular attention should be given to smaller fields (less than 30 acres) that are surrounded by wooded areas. Check field edges first to detect the earliest colonization. Surveys have indicated that it takes about 3 to 4 weeks for aphids to be detected in other areas of the field. Eventually, the larger colonies develop where initial colonization occurs. Another method of sampling developed at the University of Minnesota is a binomial sequential sampling plan or “speed scouting” recommended for use through the pod fill stage. If a plant has less than 40 aphids, consider it non-infested; however if the plant has 40 or more aphids (counting additional aphids is not necessary after 40), consider the plant infested. Based on the speed scouting sampling plan, three treatment decisions are possible: 1. Do not treat the field; 2. Treat the field; or 3. Resample the field in 3-4 days. More information about the speed sampling method on the Internet: www.soybeans.umn .edu/crop/insects/aphid/aphid_sampling.htm . An NDSU Bulletin on managing soybean aphids, revised in 2004, can be found online at www.ext.nodak.edu/extpubs/plantsci/rowcrops/e1232w.htm . Corn borer The challenge is to distinguish when egg laying and larval populations can be tolerated or if they need to be controlled. Corn should be monitored weekly for at least five weeks once plants exceed an extended leaf height of 17 inches. At this point, corn borer larvae will be able to survive on the plant. Inspect plants for the presence of egg masses, whorl feeding, and active larvae.
Observing moth activity around field margins or within the field may alert you to developing infestations. Recent corn borer infestations in N.D. developed in mid- to late-July and August as a result of the late emergence of the numerous single generation type borers. In other years, the two generation borers emerging first may contribute more to significant infestations. Field scouting worksheets and economic threshold guidelines can be found in the 2005 N.D. Field Crop Insect Management Guide, online at www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm. Cool Grain to Prevent Storage Problems
Grain should be cooled to 20-25°F for winter storage. If desired, the grain can be warmed to 35-40°F in March for storage into the summer. The goal should be to keep the grain cool to enhance its storability. Keeping the grain cool will reduce the potential for insect infestation and grain spoilage. ----------------- Insect Info on the Internet 2005 N.D. Field Crop Insect Management Guide Insect Updates for N.D. NDSU Crop Insect Publications SDSU Extension Entomology U of M Soybean Aphid Information Page Regional IPM Bugweb Insect Monitoring Network |
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