./Hs 



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/US. DEPARTMEMT OF AGRICULTURE COOPEHAflNQ 





FOR IMMEDIATE RELEASE 



No. 17, July 18, 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 can still be found in some medium -maturing fields and in most late- 

 maturing cornfields. Occasional fields have 20 to 50 percent infested plants, but 

 in most fields the range is between 5 and 15 percent infested plants. 



In the southern section, many of the larvae have already matured, stopped feeding, 

 and pupated. Additional generations could still present further problems in late- 

 maturing fields. After corn has tasseled, fall armyworms will attack the developing 

 ears (like corn earworms) , and some larvae will be present in ears until frost. 



In the central and northern sections, the larvae were about half grown to nearly 

 full grown this week, and pupation will now progress rapidly. 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. When 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 corn as forage to dairy cattle. Do not 

 feed toxaphene- treated corn as silage to livestock fattening for slaughter. Corn 

 treated with toxaphene granules may be fed as stover to livestock to within 28 days 

 of slaughter. There are no restrictions for carbaryl. 



Corn rootworm larval populations continue to increase as hatch of overwintering eggs 

 reaches its peak, particularly in the northern section. As eggs continue to hatch, 

 the number of larvae is expected to increase or hold about the same for the next 

 2 weeks. Pupation of larvae is progressing rapidly in many fields, and a few adults 

 have emerged in the western and central sections. Pupation reached 4 percent this 

 week in northern sections, but will progress rapidly from now on. 



Damage to roots is becoming more evident, and goosenecking of plants as a result of 

 larval feeding is now evident in a few fields. This will become increasingly evident 

 in the weeks ahead, especially if strong winds or rains accompanied by strong winds 

 occur. Thus far the insecticides recommended for resistant rootworms as planting- 

 time and as basal treatments off the cultivator have generally provided good to ex- 

 cellent control of larvae in spite of the heavy rainfall in some areas. 



