-2- 



If rootworm beetles are numerous, they can reduce pollination. Medium to late-maturing 

 fields will likely be most seriously affected, since beetle numbers are likely to be 

 higher in these fields during the critical pollinating period. Treatment is justified 

 if there are 5 or more beetles per plant and if not over 50 percent of the plants have 

 silked. Sprays of carbaryl (Sevin) , malathion, or diazinon at 1 pound of actual chemica 

 per acre, or 1/4 pound of actual methyl parathion per acre are effective. Methyl para- 

 thion should be used by experienced applicators only . Allow 5 days between treatment 

 and harvest for malathion, 10 days for diazinon, and 12 days for methyl parathion. 

 Carbaryl has no waiting period. 



If you want to estimate the prospects of rootworm problems for next year, make a check 

 on the number of rootworm beetles and rootworm damage during the next week or two. If 

 you find lots of beetles (5 or more per plant) , or if the roots are moderately to severe 

 damaged, then there may be enough rootworms in the field to cause economic losses in 197 

 if the field is planted to corn again. 



Notify your county extension adviser if you have had failures with one of the organic 

 phosphate or carbamate insecticides used for the control of resistant rootworms. Also 

 report any fields of first-year corn that have been damaged by rootworms. 



Corn leaf aphids are increasing slowly but populations are still not alarming. In most 

 fields aphid infestations on plants ranged from 5 to 10 percent this week. One field 

 was reported to have up to 30 percent of the plants lightly infested. Aphids multiply 

 fastest when corn is in pre-tassel or late-whorl to brown silk stage. Since most of our 

 com is now, or soon will be, beyond this susceptible stage, and since aphid populations 

 are low, we do not anticipate a generally severe problem. Continue to examine late corn 

 particularly in the drier areas of Illinois. Aphid populations may still increase and 

 damage these fields. Treatment is warranted when corn is in the late-whorl to early 

 tassel stage and when 50 percent or more of the plants have a light to moderate number o 

 aphids. At the latest, treatment should be made prior to brown silks. 



Spray treatments by ground or air, with 1 pound of malathion or diazinon or 1/4 pound of 

 methyl parathion per acre, are effective. Allow 5 days for malathion, 10 days for diazi 

 and 12 days for methyl parathion between treatment and harvest for grain, ensilage, or' 

 stover. Methyl parathion should be applied by experienced applicators only . If corn is 

 in the late-whorl stage, seed producers may prefer to use 1 pound per acre of either 

 diazinon or phorate (Thimet) as granules. To avoid potential hazards to detasselers, 

 use phorate only on male-sterile corn. 



Second -generation European corn borer moth emergence is well under way in southern sec- 

 tions, and eggs are being laid. Moth emergence is just beginning in the central section 

 Pupation reached about 20 percent in the northern section. Now is the time to check 

 late-maturing fields for egg masses or whorl feeding in the southern section. Wait abou 

 a week in the central section and about 2 weeks in the northern section. Treat whorl - 

 stage corn if 75 percent or more of the plants show recent whorl feeding. Apply 

 carbaryl (Sevin) or diazinon as granules. Treat tasselled corn if the egg mass per plan 

 averages one or more. Apply an insecticide after a few eggs have hatched. 



Commercial applicators may prefer to use parathion at 1/2 pound per acre. Sprays by air 



or with high -clearance ground equipment are effective on tasselled corn. Allow 10 days 



between treatment and harvest when using diazinon and 12 days for parathion. Carbaryl 

 has no waiting period. 



