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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 



No. 15, July 9, 1971 



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 



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Spider mites continue to damage soybeans in areas that are dry. Where showers have 

 occurred, the mite problem has practically disappeared. Soybean fields adjacent to 

 clover fields are the most likely ones to be attacked, but the mites may also move 

 from grassy areas. 



Infested soybeans turn yellow and are stunted. Damage usually is most severe along 

 the edge of the field. The mites appear as small black specks on the undersides of 

 the leaves, and produce webbing. 



Mite control is often erratic. If possible, direct the spray to the undersides of 

 the leaves. Place drops between the rows and aim the nozzles toward the rows, point- 

 ing upward at a 45 -degree angle. Note: The operator should wear protective clothing 

 and avoid spray drift when using this nozzle arrangement" Use 1/2 pound of azinphos- 

 methyl (Guthion) or 3/4 pound of carbophenothion (Trithion) per acre to control the 

 mites. These should be applied by experienced commercial applicators only . Wait 21 

 days with azinphosmethyl and 7 days for carbophenothion between treatment and harvest, 

 Do not feed treated soybeans as forage to livestock. 



Green cloverworms are present in some soybean fields. These light-green worms with 

 white stripes running the length of their body feed on the leaves, not the pods or 

 blossoms. The cloverworm population is still light, but the situation will bear 

 watching. Feeding is critical on beans from the blossom to early pod fill periods. 

 Parasites and a fungus disease attack the larvae and help control them. No insecti- 

 cide treatments are needed at this time. 



CORN INSECTS 



Corn leaf aphids are beginning to appear in corn, but the number is generally low. 

 The critical stage on corn is between pretassel and pollination. It now appears 

 that by the time corn leaf aphids can build up to damaging proportions, about 60 

 to 80 percent of the corn will be beyond the critical stage. The fields that will 

 bear watching are the medium-late and late-maturing fields. Check these in about 

 two weeks. Pull 10 whorls in five places in the field and unroll them to find the 

 aphids. If 50 percent or more of the plants have a light to moderate number of 

 aphids, treatment is warranted. 



