AU / 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



«ECT, WEED & PLANT DISEASE SURVEY BULLETIN 



VTE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



No. 17, July 23, 1971 



This series of weekly bulletins provides a general look at the insect, weed, and -plant 

 disease situation (fruit and commercial vegetables excepted) , along with suggested, 

 abbreviated, control measures. Each individual should check his own fields to de- 

 termine local conditions. 



THE LIBRARY Or Int 



INSECTS 



SEP 3 



SOYBEAN INSECTS 



Grasshoppers have begun to migrate from fence rows and other grassy areas into bean 

 fields, where they are eating the leaves and may consume pods later. 



Green cloverworms can be found in soybean fields. This green worm with white stripes 

 springs when disturbed. Shake plants over the center of the rows and count the worms 

 on the ground. Six or more worms per linear foot of row are enough to decrease yields 

 if feeding occurs at the critical time. These pests rarely, if ever, feed on pods. A 

 fungus which infects and kills them should help reduce their numbers. Worms killed 

 by this fungus are fuzzy white and cottony in appearance. 



Bean leaf beetles are the yellow, green, or red beetles which usually, but not always, 

 have four black spots on their back and a black line as a border on the wings. When 

 disturbed, they drop to the ground and play dead. Grasshoppers and green cloverworms 

 usually consume the leaves from the edge of the leaf inward, while the bean leaf bee- 

 tle eats holes in leaves. 



Grasshoppers may be the most severe of the three, but there may be more bean leaf bee- 

 tles than normal in bean fields in August this year. 



As long as pods are not being fed upon, use leaf damage to estimate the need for chem- 

 control of leaf -feeding insects on soybeans. 



When insects eat 50 percent or more of the leaf surface of soybean plants between 

 blossom stage and early pod fill, yield losses can be quite noticeable. If this 

 feeding occurs before blossom and the pests are controlled, no harm is done. If leaf 

 destruction occurs after pod fill, there is no damage if no pods are eaten. The fol- 

 lowing guidelines to determine need of treatment can be used: (1) If defoliation 

 occurs early and the pests are expected to be present all season long, as with grass- 

 hoppers, control the pests early. If the leaf feeding is early and occurs only for 

 a short time, no control is needed. (2) If leaf damage occurs towards mid-season af- 

 ter blossom but before pod fill, apply insecticides to control the pest if 25 percent 

 of the foliage has been eaten. (3) If leaf feeding begins only after pods are well 

 formed, do not apply insecticides unless pods are being eaten. 



