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COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



«ECT, WEED & PLANT DISEASE SURVEY BULLETIN 



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



FOR IMMEDIATE RELEASE 



No. 14, July 2, 1971 



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

 plant disease situation (fruit and commercial vegetables expected) , along with 

 suggested, abbreviated, control measures. Each individual should check his own 

 fields to determine local conditions. 



THE LIBRARY Or i HE 



INSECTS ,, 71 



JUL 26 &n 



CORN INSECTS , LUN0 ,g. 



Mites . Spider mites are attacking the lower leaves of corn in several areas in 

 central and western Illinois. The damaged leaves have turned yellow or brown. 

 Generally, the mites are confined to the lower two or three leaves on the plants. 

 In the edges of some fields (particularly along roadsides) as the number of mites 

 has increased, they have moved upward. In such cases, damage is apparent on 

 leaves on the lower third of the plants. The mites are on the undersides of 

 corn leaves. Although tiny, they can be detected by the presence of webs. 



The extended period of hot, dry weather has been ideal for a mite buildup. We 

 have not encountered enough mite problems on corn in past years to establish 

 any guidelines for treatment. If the dry weather persists, the mites could 

 become a serious problem as they move to the upper leaves. Control is diffi- 

 cult. The spray must hit the undersides of the lower leaves to be effective. 



Two insecticides that have label clearance for controlling mites on corn are 

 carbophenothion (Trithion) and dicofol (Kelthane) . Severely affected fields 

 should be treated with 1 pound of either one per acre, mixed with enough water 

 to provide thorough coverage. Do not apply carbophenothion more than once per 

 season, and do not graze or cut forage within 21 days after application. Do 

 not apply dicofol after the ears begin to form, and do not use treated corn 

 for forage or silage. Carbophenothion should be applied only by experienced 

 commercial applicators . (NOTE: Dicofol label withdrawn. Substitute Meta-Syxtox F 

 and follow label.) 



Corn leaf aphids . These insects have been observed in the whorls of corn plants. 

 So far, only a low percentage of plants examined have been infested and the num- 

 ber is low. It is too soon to make any predictions. The presence of numerous 

 lady beetles and other predators will be very helpful in holding the aphids in 

 check. Fields of early tasseling com usually escape injury. 



To determine whether aphids are present, check several areas in fields in the 

 late-whorl or early tassel stage by pulling the corn whorls. Look for the pres- 

 ence of small, bluish-green, soft-bodied insects as you unwrap the leaves. Corn 

 leaf aphids suck the juices from the plants, causing the ears to be stunted and 

 shriveled. Injury usually occurs just before and during tasseling. If 50 per- 

 cent or more of the whorls are infested, treatment may be justified. 



