Update on insect activity in Kansas crop fields - June 28, 2018

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Soybean Update

The first adult Dectes stem borer was detected on 23 June, from north central Kansas (specifically, DK Co.). These beetles traditionally spend approximately 7-14 days congregating or aggregating around the borders of stubble fields near where they overwintered. Then, they disperse throughout soybean and sunflower fields and begin depositing eggs in plants of either crop. Several more have been collected since the 23rd.

Bean leaf beetle adults have been and will continue chewing characteristic round or oblong holes in soybean leaves. However, at least around north central Kansas, populations seem reduced from recent years.


So far, other than a few small grasshopper nymphs, there seem to be less defoliators than usual in either alfalfa or soybeans. However, there is still time left for significant populations to develop. A few garden webworms and yellow-striped armyworms were collected from a couple of fields and many of the soybeans are still very small, in the 3-5 trifoliate stage.


Corn and Sorghum Update

Chinch bug populations continue to increase at a very disconcerting rate. Most corn throughout north central Kansas is far enough along in its development to tolerate large numbers of chinch bugs. Smaller sorghum can still be seriously stressed by growing populations of chinch bugs, especially as the hot and dry conditions return. For more information of chinch bug management in sorghum, please see the KSU 2018 Sorghum Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf742.pdf

One relatively mature fall armyworm larva was also detected. Thus, in approximately 2-3 weeks there will be a new generation of fall armyworm larva ready to start feeding, most likely, on sorghum.

Alfalfa Update

Several alfalfa fields were sampled in north central Kansas this past week. The alfalfa canopy remains an excellent habitat for many insects, especially those fields not treated for alfalfa weevils this year. Many of these insects are beneficial.

Very few pests, or potential pests, were detected although there were a few potato leafhoppers present. These small, lime green, herky-jerky, moving pests are apparently just beginning to migrate into KS, as we didn’t find any earlier in the week, and now are only finding a couple of adults. For more information relative to potato leafhopper management, please refer to the KSU 2018 Alfalfa Insect Management Guide: https://www.bookstore.ksre.ksu.edu/pubs/mf809.pdf



Jeff Whitworth, Entomology Extension Specialist

Holly Davis, Entomology Research Associate

Tags:  insects soybeans corn sorghum alfalfa