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week in the southern and central sections and next week in the northern sections 

 to determine whether treatments are needed. If there is an average of one or more 

 egg masses per plant, apply an insecticide after a few eggs have hatched. If the 

 corn is in the whorl stage and if 75 percent or more of the plants are showing re- 

 cent whorl feeding, apply carbaryl (Sevin) or diazinon as granules or sprays. Aerial 

 sprays on tasseled corn are effective; but on whorl-stage corn, aerial applications 

 should be granules and not sprays. Direct ground- applied sprays into the whorl of 

 whorl-stage corn, and from the ear zone upward in tasseled corn. Use 1.5 pounds of 

 carbaryl or 1 pound of diazinon per acre. Wait ten days after applying diazinon be- 

 fore ensiling the corn. No waiting period is required for carbaiyl. 



In late-maturing sweet corn, apply an insecticide every three to five days if there 

 are 20 or more unhatched egg masses per 100 plants and the corn has a tassel ratio of 

 30 or more. For corn in silk, spray at the ear zone every three to five days to pro- 

 tect against both corn borer and corn earworm. The addition of 0.5 to 0.75 pound of 

 parathion to 1.5 pounds of carbaryl applied per acre improves earworm control. Allow 

 12 days between the last application of parathion and harvest. Parathion should only 

 be applied by experienced applicators. 



Fall armyworms are still numerous in very late-planted fields over the entire 

 state. Numbers have decreased in older fields that were infested earlier. These 

 worms not only feed in the whorl of the corn plant, but occasionally will cut into 

 the stalk. They often feed on the ear, as an earworm does. 



Corn leaf aphid colonies continue to show up in some fields over the northern half 

 of the state. There are fields that have tasseled and the aphid population has de- 

 creased, leaving behind white skins shed by the aphids plus a sticky secretion on 

 leaves and tassel called "honeydew." Parasites and predators are commonly found 

 among the aphid colonies. Swollen brown aphids, each with a tiny hole in the back, 

 have been parasitized by a wasp. Lady beetles and syrphid flies are the common pre- 

 dators feeding on aphids now. In many other fields, the aphid population has not 

 decreased. 



The white skins you see on the plants are the cast skins of the aphids. All insects 

 grow by shedding their external skeletons, leaving the remains. As noted, the sticky 

 material on the plants is honeydew, an exudate from the aphids. When this is exces- 

 sive, the plant becomes shiny. Sooty mold will soon develop on the honeydew, and 

 the plant will look sooty-black. 



When faced with a decision about treatment, you should estimate (1) the aphid popula- 

 tion, (2) the time needed for the corn to reach the dry silk stage, (3) the number 

 of natural enemies, and (4) the susceptibility or resistance of the hybrid. If you 

 decide that treatment is required, 1 pound of malathion or diazinon will provide ad- 

 equate control. Our rule of thumb is to treat if the corn leaf aphids are present 

 in moderate numbers on 50 percent of the corn plants when the field is in the pre- 

 tassel to early silk stages. 



HOMEOWNER INSECTS 



Fall webworms are defoliating certain trees- -especially birch, ash, and elm. These 

 pale-green or yellow worms (with a dark stripe down the back and a yellow stripe 

 along each side) spin a web over the ends of the branches and skeletonize the leaves 

 inside. They continue to extend the web to take in fresh foliage. The damaged 

 leaves curl, turn brown, and dry up. 



A spray of carbaryl (Sevin), using 2 tablespoons of the 50-percent wettable powder 

 per gallon of water, is effective. 



