COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



NSECT, WEED & PLANT DISEASE SURVEY BULLETIN 



ATE/COUNTY/LOCAL GROUPS/U S. DEPARTMEMT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



No. 15, July 3, 1969 



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 . , ~,„, T . 



INSECTS 



CORN INSECTS 



C \ 1 

 USRAftX 



European corn borer moths were apparently killed by rain storms about as fast as they 

 emerged from the pupal cases during the past 2 weeks. However, some did escape, de- 

 posited eggs, and these borers did survive. Decisions about treatment should be made 

 now. 



In southern and south-central Illinois, egg-laying is over and some of the most- 

 advanced fields have up to 30 percent of the plants infested with 2 to 3 half-grown 

 borers per plant, but this is not enough to warrant use of an insecticide. The borers 

 were still behind the leaf sheaths, and had not yet bored into the stalks. This many 

 first -generation borers, although not plentiful enough to warrant control, will supply 

 plenty of moths to produce lots of second-generation borers. 



In central Illinois, there are a few borers in corn on the east side of the state, but 

 not enough to warrant control. An occasional field of the most-advanced corn on the 

 west side of the state may warrant treatment. A few egg masses can still be found in 

 these fields; survival of borers hatching from these eggs will be high. 



In northern Illinois, only a very few fields have enough corn borers to warrant chemi- 

 cal control. Moths and eggs are scarce. 



Fields with tassel ratios approaching 50 and having 40 percent or more whorl feeding 

 with an occasional egg mass still to hatch warrant use of an insecticide. Use diazinon 

 or carbaryl (Sevin) granules . 



Corn rootworms were found hatching all the way to the northern boundary of Illinois 

 this week. Have excessive rains killed newly-hatched worms? Small rootworms will 

 likely be killed, where water stands in ponds. Newly hatched rootworms will probably 

 drown in those fields where the soil is saturated and water stands between the rows 

 for a day or two. Since the hatch of worms extends over a 3-week period, these rains 

 may help reduce rootworm populations, but the rains are not likely to completely con- 

 trol rootworms. 



Rains may have decreased the effectiveness of insecticides applied at planting time. 

 Examine the roots right away. If you find 5 or more rootworms per plant, it will pay 



