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. DEPARTMENT OF AGRICULTURE COOPERATING 



FOR IMMEDIATE RELEASE 



TH £ LIBRARY OF THE 



WG -6 1370 



No. 16, July 17, 1970 



U AT "URSANA,CHAMPAIGN. 



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

 iisease situation (fruit and commercial vegetables excepted) , along with suggested, 

 abbreviated control measures. Each individual should check his own fields to determine 

 local conditions. 



INSECTS 



■20RN 



Corn leaf aphids are numerous in some fields; they may seem to almost "explode" within 

 the next two weeks, but this will vary greatly from hybrid to hybrid and from area to 

 area. Limited surveys indicate the possibility of a serious problem; but, as yet, we 

 cannot define any problem areas. The number of aphid predators is low, which will 

 permit a faster buildup; but a disease is killing some aphids. Also, high temperatures 

 have slowed reproduction. 



Corn in the late-whorl and early tassel stages seems to have the most aphids. Early 

 fields in which pollination is already occurring will escape damage. Corn injury us- 

 ually takes place between the pretassel and pollinating stage. Aphids suck the juices 

 from plants, causing stunting. With heavy infestations and stress conditions (partic- 

 ularly dryness), the plants will be barren, or at best produce a shrivelled ear. 



Early treatment is best. Treatments should be made prior to brown silks. Many fields 

 are in the late-whorl stage or are just now coming into tassel, and should be checked. 



Do not panic. Do not spray unless it is justified. Examine all fields carefully. If 

 50 percent or more of the plants are lightly to moderately infested with aphids, the use 

 of 1 pound of malathion or diazinon, or 1/4 pound of methyl parathion, per acre as a 

 spray will be effective. 



For best results, the spray should be applied just after the tassels begin to show. 

 \llow 5 days for malathion, 10 days for diazinon, and 12 days for methyl parathion 

 Detween treatment and harvest for grain, ensilage, or stover. Methyl parathion should 

 oe applied only by experienced applicators . 



If corn is in the late-whorl stage, 1 pound of either diazinon or phorate (Thimet) as 

 granules will be effective. Do not use phorate or parathion in seed fields that are 

 to be detasselled by hand. 



Picnic beetles are present in corn whorls in many areas. They are of little concern 

 in field corn. But in sweet corn, they are getting into the ears and destroying the 

 kernels . 



