J-W / 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA. ILLINOIS 



NSECT, WEED & PLANT DISEASE SURVEY BULLETIN 



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



FOR IMMEDIATE RELEASE 





No. 18, July 20, 1973 



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

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

 abbreviated, control measures. Each individual should oheok his own fields to deter- 

 mine local conditions. 



INSECTS 



CORN INSECTS 



Corn leaf aphid populations have not increased much since last week. We examined sev- 

 eral dozen fields across the central half of Illinois this week. These fields varied 

 in the stage of development, from whorl to pollination. Fields in the western half 

 had slightly greater infestations than those in the east; but even the fields with 

 the highest aphid populations had not yet reached an economic level, although a few 

 were approaching it. 



Some lady beetles and aphid lions are present. A predator, the insidious flower bug, 

 was present in moderate numbers on most plants. These tiny predators may kill sev- 

 eral aphids per day. This predation will delay or even prevent a future buildup of 

 aphids, particularly if it occurs when the number of aphids is as low as it is now. 

 However, watch for any increases in aphid numbers, since a "dry spell" may be start- 

 ing. Aphid feeding is more important in dry weather, because the plant cannot afford 

 to lose the moisture taken by the aphids. Threat of aphids maybe over in three weeks -- 

 at least fields with brown silks probably will not be severely damaged. (See Bulletin 

 No. 17, July 13, for details.) 



Do not apply phorate (Thimet) or diazinon granules to seed fields that are being de- 

 tasseled by hand. 



European corn borers are more numerous than they have been for some time. Very few 

 fields had first -generation populations great enough to cause economic losses, but many 

 fields are harboring a small number of borers. Moderate numbers of first-generation 

 borers in a reasonable number of fields may supply enough second-generation moths to 

 cause trouble. This year, we expect a noticeable increase in the number of second- 

 generation corn borers, versus the past few years. Late-maturing fields will be the 

 most attractive ones to the moths for egg-laying. 



Some moths have emerged in southern Illinois. Egg -laying should be starting there, and 

 will continue for several weeks. Late fields may be handled the same as for the first 

 generation. (See Bulletin No. 13, June 15.) A third generation is quite possible for 

 the southern third of Illinois. 



In central Illinois, we found that over 20 percent of the first -generation borers had 

 already pupated. The moths should be emerging soon- -at least by July 25. A few moths 

 may have already emerged. Egg-laying will start shortly. 



