l/K'l 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



NSECT WEED & PLANT DISEASE SURVEY BULLETIN 



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



FOR IMMEDIATE RELEASE 





AT K AKJ& 



No. 21, August 10, 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 continue to be seen in many soybean fields in the northern two- 

 thirds of the state. In northern Illinois, many small worms are present with 

 very few large worms. In the central section, there are many small worms along with 

 half- to full-grown worms. This situation has remained almost constant for the past 

 three weeks. It appears that egg- laying and hatch have continued during this pe- 

 riod; and as the worms have increased in size, many have disappeared. Only a small 

 percentage of the many small worms present two weeks ago can be observed now as 

 half- to full-grown worms. Some fields have spots in them with up to 25 worms per 

 foot of row, but only 2 or 3 of these worms are half- grown or larger. There are areas 

 in the state where counts of the larger worms range up to 8 to 10 per foot of row. 



Diseased cloverworms can be found in these fields. Diseased worms which have died 

 will be chalky -white, dry, and hard. Wet or humid weather helps spread this disease. 

 Many of the larger worms are also parasitized. The parasitic fly lays small white 

 eggs behind the head of the cloverworm. These eggs can be seen easily when observ- 

 ing the worms. Diseases and parasites both increase when the populations of green 

 cloverworms are high, and both have gone up during the past week. In some fields, 

 15 to 20 percent of worm population were dead from disease. 



Continue to check soybean fields that are between the bloom stage and full-pod de- 

 velopment. If you can find an average of 4 or more half- grown or larger worms per 

 foot of soybean row , treatment is justified. An alternate method is to apply an 

 insecticide when 20 percent or more of the soybean foliage has been eaten and clover- 

 worms are still present. For control, apply carbaryl (Sevin) or malathion at 1 

 pound actual per acre as sprays over the foliage. 



CORN INSECTS 



European com borer moths have almost completely emerged in the northern section of 

 Illinois. Egg-laying for second-generation borers in most sections appears to be 

 generally light, but there are localized areas where second-generation borers could 

 be a problem. 



The moths prefer to deposit their eggs on corn in the late-whorl to early silk stage. 

 Egg- laying will continue for two to three weeks. Check late-maturing fields this 



