Lfk. J 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



NSECT WEED & PLANT DISEASE SURVEY BULLETIN 



TATE/COUNT V/LOCAL GROUPS/US. DEPARTMENT OF AGRICULTURE COOPERATING 



MJu 6 io73 



KSITY OF ILLINOIS 



FOR IMMEDIATE RELEASE 



No. 19, July 27, 1973 



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 determine local conditions. 



INSECTS 



SOYBEAN INSECTS 



Green cloverworms were common this week (the week of July 23) on soybeans in west- 

 ern Illinois and in parts of central and northern Illinois. Only a few were found 

 on soybeans in southern, southwestern, and southeastern Illinois. These worms were 

 most common in fields that were blossoming, but were also found in less-mature 

 fields. 



Green cloverworms vary in size from about 1/16 to 1/8 of an inch long, almost hair- 

 like, to over 1-1/2 inches in length. Apparently, plenty of eggs are still hatching; 

 small worms are numerous. 



The rains may be killing the small worms. A parasitic fly deposits white globe-like 

 eggs just behind the head of the worm. A maggot which hatches from one of these eggs, 

 burrows into the worm's body. Feeding is slowed down, and the worm may die. A fungus 

 disease also kills these worms and they appear as white, moldy, dead, and almost mum- 

 ified worms. This disease spreads rapidly in the worm population during periods of 

 hot, humid weather. 



This fungus, the parasites, and hard rains are capable of eliminating the potential 

 threat from this pest. So assess the present population, the size of the worms, the 

 weather, the degree of parasitism, and the presence of dead white worms. We hope that 

 the parasites and the fungus disease together will eliminate the need for insecti- 

 cides, but a serious potential exists and each soybean field should be examined care- 

 fully. 



In some of the more mature fields this week, feeding by the worms was already well 

 advanced, and the worms had matured. Treatment may no longer be beneficial. Small 

 worms were present in some fields that were not yet in bloom. In such fields, the 

 use of an insecticide may be warranted later. 



To estimate the populations of green cloverworms, bend plants over the middle of the 

 row and shake them vigorously. Watch the soil for about five munutes to be sure you 

 have seen all the worms. Do this in several places in the field. If you find 3 or 4 

 medium-sized worms per foot of row, using an insecticide may be justified- -particularly 

 if there are also 3 or more small worms per foot of row and if the beans are in the 

 blossom to mid-pod-fill stage. 



