J- <u 7 



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/US. DEPARTMENT OF AGRICULTURE COOPERATING 



- 



FOR IMMEDIATE RELEASE 



No. 16, July 6, 1973 



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

 plant disease situation (fruit and commercial vegetables excepted) , along with sug- 

 gested, abbreviated, control measures. Each individual should check his own fields 

 to determine local conditions. 



INSECTS 



CORN INSECTS 



Fall arm/worms , corn earworms , and common stalk borers can all be found in occasional 

 spots in cornfields about this time of year, and 1973 is no exception- -although corn 

 earworms have not as yet been reported. 



The feeding most commonly occurs on the leaves as they are rolled up in the whorl. 

 When they emerge, the plant appears ragged. Fall armyworms are just now appearing, 

 but some of the common stalk borers , present for two or three weeks , have been leav- 

 ing the whorls now and are boring into the lower parts of the stalks, killing the 

 plant. 



In conventionally tilled corn, common stalk borers attack a few plants in the outside 

 crop rows next to the f encerows , ditch banks, grass waterways, and similar areas. The 

 ones you see now are all there will be. They may kill a few more plants, but they 

 won't be increasing in number, and there is only one generation a year. The moths lay 

 eggs in weedy spots in August. These eggs hatch the following spring. The control 

 measure for next year is to cut the weeds by August 1. In zero-tillage corn these 

 pests may be more common over the entire field. Control presents problems, and we are 

 working on this . 



An occasional corn earworm sometimes can be found in the whorl of a plant here and 

 there. A corn earworm moth has laid a single egg in the whorl. Usually only one 

 plant in a place is affected. With field corn, this type of infestation is not a 

 problem. Ear infestations in late corn this fall could create difficulties . 



Fall armyworms are brown, slick-skinned worms that appear in late-developing corn, 

 either in spots of replanted areas or over the entire field if the corn is uniformly 

 late and the infestation is severe. With mild infestations, several plants- -perhaps 

 15 or 20 - -will be affected in small areas within a field. Although control is dif- 

 ficult and usually unneeded, carbaryl (Sevin) , diazinon, Gardona, or toxaphene gran- 

 ules may reach the worms deep in the whorls . 



Corn leaf aphids have appeared on some sorghum in southern Illinois. Their impor- 

 tance in sorghum production is debatable. Damage to corn can be severe if these aphids 

 appear during a stress period (pollination and silk production) , particularly if the 

 plants are in need of moisture. 



