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Agronomy Update

Corn and Soybean Insect Presence in Central Indiana

Published on Monday, August 03, 2015

This week, central Indiana sales intern Christy Kettler covers the insect and disease presence she has been seeing while scouting area fields. 


Corn and Soybean Insect Presence in Central Indiana
Christy Kettler | Sales Intern | Central Indiana
July 27 - July 31, 2015

Soybean Diseases 

European corn borers (ECB) are still showing their presence in unprotected, conventional hybrids. Trap counts for this week totaled 14 ECB second generation moths. The damage they are causing include leaf feeding and boring into stalks, tassels,ears and the ear shank.

Each ECB larvae found now can account for a minimum of 7 to 10 bushels of “lost” yield potential come harvest. This second generation feeding will continue until about mid-September. In addition to potential yield loss, the second generation’s tunneling allows disease and pathogens to enter the stalk, ultimately causing stalk breakage/lodging at harvest.

The numbers of adult Japanese beetles were quite low this week as we only found one. As soon as corn pollination is complete and the silks have dried, the Japanese beetles go looking for “fresher” food sources. For the most part this means they have moved to soybeans and have begun feeding on the younger leaf tissue. Japanese beetles will “skeletonize” the leaves, creating a “lacy” appearance. Control during R1 to R5 is suggested if greater than 15% defoliation is experienced. Sometimes spot treatment is adequate if these insects are found early.

Corn Diseases

The weather has definitely taken a turn for the better, bringing more summer-like growing conditions. To date, the severity of corn diseases present hasn't spread much since last week. Gray leaf spot (GLS) and northern corn leaf blight (NCLB) are easy to spot in most fields. Fungicide applications are complete, so now we need to monitor and evaluate application effectiveness. 

Northern corn leaf blight damage

Northern corn leaf blight stalk damage


Once corn reaches the R3 stage of growth, the kernels will be yellow on the outside and the contents will be milky on the inside. This is commonly known as the roasting ear stage! Severe stress caused by such things as photosynthetic surface loss from leaf diseases can still abort kernels, but not as easily as in the earlier R2 blister stage. Once the kernels reach the early dough stage, kernel abortion is less likely.  


If you have any questions on these findings or want to learn more, please contact your local seed advisor or dealer.



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Denny Cobb

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