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Good Bugs Helping Us Out with Pest Control (08/01/19)

Thank you for sending in your insect photographs for me to identify over the last several weeks.

Thank you for sending in your insect photographs for me to identify over the last several weeks. Here are some of the highlights of the ‘good’ bugs that were emailed or texted to me. These good bugs naturally reduce our insect pest populations in field crops. A great reason not to spray any harmful insecticides, especially when insect pest densities are below the established economic threshold. Broad-spectrum insecticides kill all beneficial insects.

Parasitic Wasps:  White cocoons of parasitic wasps (Figure 1) are being observed in wheat heads. A tiny adult wasp (or parasitoid) will emerge from each cocoon, and then go to work parasitizing insect eggs, small caterpillars or soft-bodied insects, such as aphids.
In Figure 2, tan, balloon-like cereal aphids indicate a parasitized aphid by a wasp. The adult female wasps inserts one or more eggs into the aphid’s body. Aphids then become paralyzed while the wasp larva consumes the aphid from the inside out. Parasitized aphids are called ‘mummies.’ Once the larva completes pupation, they chew a small circular hole through the ballooned aphid and emerge as an adult wasp to repeat the cycle.

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Lady beetles (Figure 3):  Adults and larvae of lady beetles are generalist predators that feed on aphids, thrips and other soft-bodied insects and insect eggs. The seven-spotted lady beetle adult may consume 300 aphids per day! Pupae of lady beetles are easy to find in fields attached to leaves of many field crops (Figure 3). They are not harming the plant and often misidentified as a pest. An adult lady beetle will emerge from this puparium.

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Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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