_ Cooperative Extension Service, University of 



v'K- 7" Illinois College of Agriculture, in Cooperation with 

 the Illinois Natural History Survey and U.S.D.A. 



FOR IMMEDIATE RELEASE July 30, 1965 



INSECT SURVEY BULLETIN NO. 15 



This is the fifteenth in a series of weekly bulletins on the general insect 

 situation in Illinois (fruit insects excepted), prepared by entomologists of the Uni- 

 versity of Illinois College of Agriculture, Illinois Natural History Survey and co- 

 operating agencies. It is designed to forewarn people in Illinois of impending 

 changes in insect activity and to suggest abbreviated control measures. These reports 

 indicate only general trends. Each individual should check his own fields to deter- 

 mine local conditions. 



Fall armyworms are the brown to dull green smooth -skinned worms that can 

 be commonly found in cornfields. These worms feed in the whorl, giving plants a ragged 

 appearance as the leaves emerge. 



These fall armyworms, which appeared earlier than usual (Bulletin No. 12), 

 have increased greatly, and larvae are easy to find in 3 to 5 percent of the corn- 

 fields in the southern half of the state, with the greatest infestations south of 

 Highway 50, Fields in the pretassel or earlier stages have from 10 to 80 percent of 

 the plants infested. In some fields the worms have already matured and left the 

 plants; in others, the worms are still small; in still others, eggs, all sizes of 

 larvae, pupae and adults are present. Many fields will completely recuperate, while 

 others may be noticeably damaged. Before applying control measures, be sure that the 

 worms are still present and that most of them are not more than one inch long. If 

 the majority of the worms are one inch long or longer, they are about mature and 

 their feeding is over. 



Several materials will kill these worms if they can be reached deep in the 

 whorl. Carbaryl (Sevin) granules or diazinon granules should provide control with a 

 minimum interval between application and harvest as ensilage, stover or grain. DDT 

 or toxaphene granules can be used if the corn is to be used only as grain. We empha- 

 size the use of granules if the worms are moderately deep in the whorl, since the 

 granules may penetrate the whorls better than a spray. If the worms are high in the 

 whorls, then sprays will give adequate control. 



Corn hybrid seed producers especially should be concerned about this fall 

 armyworm. It is the worm that often attacks seed corn just before harvest and scars 

 the top of the kernels. (However, mice and earworms will do the same thing.) To 

 avoid damage, look for the gray scaly egg masses of the fall armyworm. Examine the 

 plants and be ready to apply carbaryl or DDT as a spray in mid- to late August (do 

 not use DDT on dairy farms). We cannot at this time provide any better timing infor- 

 mation. 



Corn leaf aphids are decreasing in the southern half of the state, particu- 

 larly in the earlier maturing corn. The sticky honey-dew secretions and the white 

 cast-off skins of the aphids are present, but aphid populations in these fields are 

 low. Infestations may develop in some of the later maturing fields. 



In the northern half of the state, aphid infestations are increasing rapidly 

 In some fields, 100 percent of the whorls or tassels are infested. 



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