Our next concern will be the green, yellow, or striped rootworm beetles that feed on 

 silks. If they are abundant in fields less than 50 percent silked, damage to pollina- 

 tion will be measurable. 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 chemical per acre or 1/4 pound of actual 

 methyl parathion per acre are effective. Methyl parathion 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. 



Corn leaf aphids are more plentiful than last week, but the situation is not alarming. 

 In most fields infestations ranged from to 6 percent this week. In one field we found 

 15 percent of the plants infested. Infestations are much lower than in 1966 and 1968. 



Aphids multiply fastest when corn is in the pretassel or late-whorl to brown-silk stage. 

 Since most of our corn is now beyond this susceptible stage or rapidly approaching the 

 nonsusceptible stage and aphid populations are low, we do not anticipate a severe general 

 problem. However, examine late corn, particularly in the drier areas of Illinois. Aphid 

 populations may still increase and damage these fields severely. 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 of 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 diazinon, 

 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. 



European corn borers are in between broods except in extreme southern Illinois, where 

 second-generation borers were found this week. In northern Illinois expect second- 

 generation moth flight to begin about August 5 to 10; in central Illinois, August 1 to 

 10. Moths will be present in southern Illinois from now on. 



Insecticide applications may be justified to control second -generation borers in late 

 corn this year. In southern Illinois check late fields now. 



Second-generation infestations in late -maturing fields can be handled in the same way as 

 the first-generation problems. If 75 percent or more of the plants have whorl-leaf feed- 

 ing, apply carbaryl (Sevin) or diazinon granules. If the corn has tasseled, look for egg 

 masses. If the average is 1 or more per plant, 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 tasseled corn. Allow 10 days 

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

 no waiting period. 



Southwestern corn borers are present in late corn in extreme southern Illinois. Late 

 fields averaged 21 percent stalk infestation in fields in the southern tip of Illinois 

 this week. Examine these late plantings for this spotted worm. Carbaryl or diazinon 

 granules may be helpful in control if you find 25 percent or more of the plants infested. 



