Issue No. 15, Article 6/July 16, 2010
Scout Alfalfa Regrowth for Potato Leafhoppers, and Don't Forget Soybean Aphids
Soybean aphid reports continue to be very few around Illinois. Russ Higgins, University of Illinois IPM extension educator, observed very low numbers of soybean aphids in his sentinel plots near Morris on July 7. He did observe lady beetles in the plots, and hopefully these natural enemies will keep the aphids at subeconomic densities. If the forecasts are accurate and the very hot weather continues over the next week to 10 days, I anticipate that soybean aphid numbers will remain low in most fields. However, don't become complacent. It's always a good idea to scout soybean fields for this insect, as densities can build very rapidly.
Potato leafhopper densities are beginning to reach impressive levels in some alfalfa stands. Kyle Cecil, University of Illinois Extension educator in the Knox County Unit, has observed significant infestations in many fields in his area. Kyle indicates that most producers have now made their second cutting, and leafhoppers are concentrating their feeding on the regrowth. These fields should be scouted and treatment decisions made. As few as 0.2 potato leafhoppers per sweep can cause economic loss when alfalfa is less than 3 inches high, so don't delay your scouting efforts. For more information about the biology, life cycle, and management of potato leafhoppers, see ipm.illinois.edu/fieldcrops/insects/potato_leafhopper.--Mike Gray