Liu I 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSfTY OF 

 ILLINOIS AT 

 UR B ANA-CH AMPAIG N 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



INSECT WEED & PLANT DISEASE SURVEY BULLETIN 



5TATE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



AUG 2 1373 



No. 22, AuguSTO', 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 sug- 

 gested, abbreviated, control measures. Each individual should check his own fields 

 to determine local conditions. 



INSECTS 



SOYBEAN INSECTS 



Green cloverworms were a major topic of conversation in many farm circles this week. 

 Our telephones as well as those of the County Extension Advisers rang almost con- 

 stantly. With the soybean futures as they are, we did not know whether to discourage 

 the use of insecticides or not. Although some fields may have been treated need- 

 lessly, others will show a profit from treatment. Even though dead worms were found 

 in many fields, few farmers were willing to gamble for a few more days to see what 

 would happen. 



Here is how we looked at it. If you found 3 or 4 medium-sized or larger worms per 

 linear foot of row, many tiny ones were almost always present, too. If 20 percent of 

 the foliage had been consumed, this would be approaching the level of economic damage 

 if the beans were in the early pod-set to full-pod stage . Actually, you can only 

 measure yield losses when 25 to 30 percent or more of the foliage is removed at this 

 stage of growth. 



So we said that if 4 or more medium-sized or larger worms were found per foot of row 

 and if 20 percent of the foliage had already been eaten, an insecticide should be 

 used. We also said that if 10 to 15 percent of the foliage had been consumed, you 

 may not want to wait any longer for fear you will end up making a treatment after the 

 damage had been done. 



Fungus disease has killed many worms. Without this help, some soybean fields would 

 have been defoliated. This fungus has killed worms steadily, particularly the tiny 

 worms. These tiny worms have been numerous in fields constantly since July 10, as 

 we have reported; but few have lived to be half-grown worms. Moderate weather fi- 

 nally allowed some to mature. These were the medium-sized ones we were finding. 

 Where it has rained and the weather is humid, this fungus may now finish the job . It 

 usually does . 



As high as 60 percent of the worms in some fields are now dying of fungus disease. 

 They can be found on the ground and hanging on the plants. Soon after they die, the 

 dead body disintegrates. A close watch is in order now, since the need for treatment 

 may end soon in these areas. In dry areas, green cloverworms may continue to be a 

 problem. 



