Japanese beetle adults have emerged

This week I heard the first reports of Japanese beetles (JB) becoming active throughout Iowa. I also saw a few around the Insectary in Ames. Although they are beautiful beetles, most homeowners and growers do not like to see these insects around. They have a wide host range and defoliate over 300 plants, including corn, soybean, fruit trees and many ornamentals. JB aggregate when they feed and can cause severe defoliation. Sometimes they will clip corn silks and interfere with pollination. Foliar treatments may be warranted in corn if: there are 3 or more beetles per ear, silks have been clipped to less than ½ inch, AND pollination is less than 50% complete. Treatment thresholds in soybean are based on percent defoliation (30% before bloom and 20% after bloom). JB may be clustered around field edges, so be sure to sample throughout the field to get an accurate estimation of density. A border treatment may be possible to save money and protect beneficial insects.

 

Japanese beetle adults are metallic green and bronze with white tufts along the side. Photo credit to Marlin E. Rice.

Corn rootworm egg hatch is approaching

Corn rootworm egg hatch in Iowa can occur from late May to mid June depending on soil conditions, but the average hatching date is around June 6. Research suggests about 50 percent of larval hatch occurs between 684-767 degree days (base 52°F, soil). The cool spring weather in 2011 has definitely slowed down predicted egg hatch this year. Reports from surrounding states have also indicated a delayed egg hatch. This map show the accumulated soil temperatures in Iowa this year. The southwestern region is experiencing 50 percent larval hatch now, and the rest will approach it within 7-10 days depending on the temperature.

Saturated soils will diminish overall corn rootworm pressure, and the high adoption of Bt corn should decrease populations in most fields in 2011. However, every field should be scouted for corn rootworm larval feeding regardless of the seed selection (i.e., scout even if Bt proteins are used). 

Corn rootworm rescue treatments should be made in June, but are not very practical or effective, as the corn is too tall for the product to sufficiently penetrate the soil and reach the larvae. But sampling and evaluating root systems this year will help assess corn rootworm management and seed selection for 2012.

Potato leafhoppers have arrived

For those that grow or manage alfalfa, there have been regional reports of potato leafhopper feeding.  Mike Gray noted some areas in southwestern Illinois exceeded a treatment threshold this week. Other neighboring states (e.g., Nebraska, Minnesota) have noted some leafhopper activity as well. For those that are interested in treatment thresholds, visit this ICM News article from 2009.

Potato leaf hopper nymph (top) and adult (bottom) should be active in alfalfa now. 

Photo credits Marlin E. Rice.

Try our podcast this summer!

If you are familiar with my research and extension efforts at ISU since 2009, you've probably heard me plug a podcast program for soybean aphid. Matt O'Neal (ISU soybean entomologist) and I started weekly summer podcasts in 2009 and continued the program in 2010. We've decided to continue the program in 2011 and podcasts have started again. You can listen to the podcasts in two ways. The first is easy (and free!) if you are familiar with subscribing to podcasts in iTunes. Just search for "soybean aphid" and subscribe to our program; new files will automatically get pushed to your computer as they are published. The second way is also free, but you have to remember to look us up on the web. Go to our ISU Soybean Aphid Website and the podcasts show up on the front page. You can play and replay files at your leisure.

We encourage listeners to provide questions and commentary about soybean aphid in Iowa (and beyond). Let us know how you like the podcasts and how we can improve the program.

Soybean aphids found

Over the weekend, Brian Lang (ISU field agronomist) found soybean aphids on V1 plants. He samples weekly in small plots and commercial fields in NE Iowa. He wasn't surprised when finding them, as he typically sees aphids the first week of June.

Also, high numbers of winged small grain aphids are being trapped in the suction trapping network this year. This could potentially a problem in corn later in the season.

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