Management of Insect and Mite Pests in Soybean

Uncontrolled soybean pest, when thresholds are exceeded, will reduce yield and quality of seed and oil. Yet soybeans have fewer serious insect pests compared to other cultivated crops, and there are many non-pest and beneficial insects that occur in soybean fields. Pesticides are not a substitute for good agronomic practices. They should not be used as “preventative insurance” because it is rarely economically or environmentally justifiable, and may disrupt the beneficial insect activity that is present. Many soybean pest problems can be avoided by implementing an Integrated Pest Management (IPM) plan that includes preventive pest management practices, such as planting high-quality, vigorous, varieties adapted for Oklahoma, planting at the proper time for optimal health and yield, providing proper fertilization and weed control, and using crop rotations. 

 

The decision to use an insecticide in soybean should be made after carefully surveying for pests and associated damage. From mid-season to pod-fill, scouting for insects that feed on foliage or pods can be conducted by shaking plants over a drop cloth or shake sheet and is particularly useful if beans planted in 30"- 40" rows. Drop cloth sampling should be conducted weekly after the plants reach 12 inches. A drop cloth can be purchased or made using a piece of white or off-white cloth measuring 24" x 42". Staple each end of the cloth to a thin strip of wood approximately ½" to 1" wide and 24" long. 

 

To begin the survey, select a site at random in the field, kneel between the two rows, and unroll the cloth from one row over to the opposite row. Extend each arm forward parallel with the row on either side. Vigorously shake the vines over the cloth. Your arms, from your elbows to your fingertips, will allow you to sample approximately 1½ row-feet of plants on each side of the row. Thus, a total of three row-feet may be sampled at each site. Count the insects that fall to the cloth. Repeat this process until approximately 10 sites have been sampled per field (up to 50 acres in size). Infestations are then evaluated as to the number of various species per 30 row-feet. 

 

Another scouting routine is the sweep net method, which can be used for beans planted in rows or drilled. Using a standard 15" diameter sweep net, make 10 consecutive sweeps (180 degrees) while walking through the field. Swing the net from side to side with each step. After 10 successive sweeps, the insects should be identified and counted as they are removed from the net. Repeat this procedure 5 times, totaling 50 sweeps and compare counts with economic thresholds established for individual pests. This method is particularly useful on seedling and drilled or broadcast beans. 

 

For foliage feeding pests, an alternative sampling strategy is to estimate percent defoliation. Determine the percent defoliation of the plants in the entire field (not on individual plants) by taking several leaves at random from several selected plants. Then estimate the amount of leaf that has been eaten by foliage feeders. This approach requires practice and a well-trained eye.

 

The information herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied. 

 

Pesticide recommendations in this publication were correct as of the “Modified Date" but always check the label that came with the purchased insecticide for the most current rates and restrictions.

 

The first name listed is the trade name of a product registered for use in corn for the listed pest. The name in (parentheses) listed below the trade name is the name of the active ingredient. The active ingredient name is provided because in many cases, there are other registered products containing the same active ingredient that may cost less, so producers should compare prices. 

 

The number [in brackets] following a product is its Mode of Action number [MOA]. The more frequently insecticides with the same MOA are used, the more likely resistance will occur. This number provides an easy way to select different modes of action to avoid selecting for pests that are resistant to a certain mode of action. 

Refer to the following OSU publications for additional information.

• EPP-7156 Field Key to Larvae in Soybeans
• EPP-7660 Seedling, Root Diseases of Soybean
• EPP-7662 Stem and Pod Diseases of Soybean
• EPP-7672 Diseases of Soybean
• EPP-7084 Pest Management Needs Assessment for Oklahoma Soybean Producers
• EPP-7196 Grasshopper Management in Rangeland, Pastures, and Crops

 

Management of Insect and Mite Pests in Soybeans I: Stem and Seedling Feeders

For the most part, stem and seedling feeders are not a problem if the grower gets a good stand of beans. They generally do most of their damage before the soybeans reach 12 inches tall. Thus growers must be ready to make a well-timed insecticide application if warranted. Isolated infestations can often be tolerated because soybeans will compensate if there are at least four plants per row-foot. 

 

 

 

Management of Insect and Mite Pests in Soybeans II: Foliage Feeders

The economic thresholds for foliage-feeding pests are considered as a group. Base threatment thresholds by estimating percent leaf loss as well as the presence of defoliators. Research from various states has shown that soybeans can withstand 35% foliage loss up to 1 week before bloom. During bloom and pod fill, the threshold falls to 15-20% defoliation, and then increases to 35-40% defoliation once pods have filled. 

 

 

Management of Insect and Mite Pests in Soybeans III: Pod Feeders

Pod feeders cause the greatest loss to soybean because plants cannot compensate readily, and the damage is direct to the seeds. Control of corn earworms is suggested if you find two or more per row-foot. Control of stink bugs is suggested when one or more per row-foot is found.

 

Levels of soybean defoliation. Check growth state to determine defoliation impact on yield.

 

 

* MOA group numbers in brackets [#] following the insecticide name are used to designate the mode of action of the insecticide according to the classification system developed by the Insecticide Resistance Action Committee (IRAC) in 2011. It is intended to help in the selection of insecticides for preventative resistance management. If you make multiple applications for a specific pest during a growing season, simply select a registered insecticide with a different number for each application. To further delay resistance from developing, integrate other control methods into your pest management programs.

 

*The pesticide information presented in this publication was current with federal and state regulations at the time of revision. READ and FOLLOW all LABEL directions. 

 

Tom A. Royer
Extension Entomologist