Ss. / 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URB ANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



JSECT. WEED & PL A NT DISEASE SURVEY BULLETIN 



rE/COUNTY/LOCAL GROUPS/US. DEPARTMEMT OF AGRICULTURE COOPERATING 



• HIT OF eras 



~: 



FOR IMMEDIATE RELEASE 



LIBRARY 



No. 16, July 11, 1969 



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 



CORN INSECTS 



Fall armyworms are damaging late-maturing com, particularly in the southern sections 

 of the state. These dark -brown to dull-green, smooth-skinned worms feed in the whorl, 

 giving plants a ragged appearance as the leaves emerge. A series of plants in a row 

 will show damage, and these patches of infested plants will usually be over the entire 

 field. The adult moths deposit a cluster of eggs on one plant; after hatching, the 

 worms move to adjacent plants. You will find only one worm per plant since they eat 

 one another. 



In general, infestations are light and control is not needed. Treatment is justified 

 in fields having 20 percent or more of the plants infested. Before applying insecti- 

 cides, be sure the worms are still present, and that most of them are not more than 

 1-1/4 inches long. IVhen they reach about 1-1/2 inches, they are mature; at that size, 

 they stop feeding, drop to the ground, enter the soil, and pupate. 



For control, use granules of either carbaryl (Sevin) or toxaphene at 1-1/2 pounds of 

 actual chemical per acre. Sprays provide erratic results, so the granular form is 

 preferred. Do not feed toxaphene -treated forage to dairy cattle. Do not feed toxaphene- 

 treated corn as silage to livestock fattening for slaughter. Corn treated with toxa- 

 phene granules may be fed as stover to livestock to within 28 days of slaughter. 



First-generation European corn borers are pupating in the southern sections, and second- 

 generation moths will begin to emerge this week (July 13). Check late-maturing corn for 

 whorl damage --the last week of July and early August. 



In the central section, the borers are just beginning to enter the stalk, and it will 

 soon be too late (end of the week of July 13) for effective control. Occasional small 

 borers can still be found, along with those about half grown. Between 10 and 50 per- 

 cent of the plants are infested with borers in the more-mature fields in this area, 

 representing about 0.5- to 2-percent yield loss in these fields. Occasional fields 

 have 70 to 80 percent of the plants infested. These can be profitably treated, if it 

 is done immediately. 



In the northern section, populations appear to be lower. The more-mature fields have 

 between 5 and 30 percent of the plants infested. The borers are still small and have 

 not yet tunnelled into the stalks. 



