Section 4 - Insect Management

Herbicide-Insecticide Combinations

Combinations are convenientfor control of both weed and insect pests. However, some combinations have been shown to increase crop injury compared to either pesticide applied alone. Efficacy data on herbicide-insecticide mixtures are limited because of the number of potential combinations.

Non-registered tank-mixtures should be used with caution until experience or research has shown that the combination is effective and safe. The following information is based on label restrictions and/or research indicating crop injury or decreased control.

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 sugarbeet injury occurred from tank-mixtures with Lorsban, malathion, or Sevin XLR. Oil-based additives increase risk of sugarbeet 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.

Post Grass Herbicide: 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.

Compatibility Test for Pesticide Mixture

Under federal law, combining pesticides is legal unless the pesticide labeling of any of the pesticides involved instructs you not to combine them. However, not all pesticides work well when mixed together. They must be compatible — that is, mixing them together must not reduce their safety or effectiveness. The more pesticides you mix together, the greater the chance of undesirable effects.

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:

 • Add some of the diluent first

• Add Wettable and other powders and water-dispersible granules

• Agitate thoroughly and add the remaining diluent

• Add the Liquid products, such as solutions, surfactants, and flowables

• Add Emulsifiable concentrates last

Shake the jar vigorously. Feel the sides of the jar to determine if the mixture is giving off heat. If so, the mixture may be undergoing a chemical reaction and the pesticides should not be combined. Let the mixture stand for about 15 minutes and feel again for unusual heat.

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

Add 6 drops of compatibility agent and stir well. If mixture appears compatible, allow it to stand for 1 hour, stir well, and check it again. If the mixture appears incompatible, repeat one or two more times, using 6 drops of compatibility agent each time.

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

.b) Change brands or formulations of chemicals

.c) Change the order of mixing.

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

Alkaline water (containing soluble mineral salts – alkalinewaters are considered to be hard water) used in spray mixtures can seriously reduce the effectiveness of some insecticides, particularly if the mixture is left standing in the spray tank for an extended period of time. Insecticides classified as organophosphates and carbamates break down easily in high pH water. Use water of pH 7.00 or less with these insecticides. The pH of any solution will be between zero and 14, with anything below seven being alkaline. To compare, lemon juice is acidic with a pH of two. Milk of Magnesia is alkaline with a pH of 10.5, and distilled water is neutral with a pH of seven. If water having a pH of 7.0 or less is not available, use a buffering agent to alter the water pH. Buffering agents can be purchased from agricultural chemical dealers. Water pH testing kits can be bought from some ag dealers.

Insect Info on the Internet

2009 N.D. Field Crop Insect Management Guide: www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm Insect Updates for N.D.: www.ag.ndsu.nodak.edu/aginfo/entomology/entupdates/index.htm

NDSU Crop Insect Publications: www.ag.ndsu.edu/pubs/bugcrops.html

SDSU Extension Entomology: http://plantsci.sdstate.edu/ent

NWROC Crookston Entomology: http://nwes.umn.edu/html/entomology.htm

*Prevent crusting due to moisture migration by cooling grain to within 15oF of average outdoor temperature. Cooling grain by 10oF doubles its allowable storage time. (Source: Dr. Kenneth J. Hellevang, NDSU Extension Service).

Grain should be cooled to 20-25F for winter storage. If desired, the grain can be warmed to 35-40F 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.