-2- 



per day. Within 2 to 5 days after birth, an aphid may be mature and giving birth to 

 young. One aphid today can be 1,400 in two weeks. 



The white skins you will see on the plants during the next two weeks will be the cast 

 skins of the aphids. All insects grow by shedding their external skeletons, leaving 

 the shed skeleton remains. 



- 



The sticky material on the plants is honeydew, an exudate from the aphids. When this 

 is excessive, the plant becomes shiny. Sooty mold will soon develop on the honeydew, 

 and the plant will look sooty-black. 



All of these facts about corn leaf aphids are not meant to panic anybody. But you may 

 need this information during the next four weeks. This week's observations leave us 

 undecided about aphid possibilities. 



When faced with a decision about treatment, you should estimate the aphid population, 

 length of time for the corn to reach the dry silk stage, the number of natural en- 

 emies, weather predictions (dry is bad), and the susceptibility or resistance of the 

 hybrid. If you decide that treatment is required, 1 pound of malathion or diazinon 

 will provide adequate control. 



Our rule of thumb is to treat if corn leaf aphids are present in moderate numbers on 

 50 percent of the corn plants when the field is in the pretassel to early silk stages 

 and is in need of rain. 



Fall armyworms are quite common in the southern half of Illinois. This is a grey to 

 greasy brown worm with a distinct, inverty "Y" on the head. They can be found in a 

 wide range of fields, but most commonly in corn that is knee- to head-high. A corn I 

 whorl usually ends up with only one worm- -they are cannibalistic. The worm feeds in 

 the whorl; and as the leaves emerge from the whorl, they are ragged. It is common to 

 find damage and no worms, since many worms have matured already and have entered 

 the soil to pupate. The corn will grow out of this damage. 



The moths deposit clusters of eggs and cover them with their gray body scales, giving 

 the egg mass a feathery or cottony appearance. Since dozens of eggs are deposited in 

 one cluster, infestations are concentrated in patches within a field involving sever- 

 al plants. In severe cases, all of the plants in large areas in a field may be infested. 



Severe infestations can certainly depress corn yield, but the losses from considerable 

 feeding by this insect are usually hard to measure. We may have some late fields severe- 

 ly infested by the next generation. From now on, watch closely fields that were planted 

 late. If this pest continues to increase, it could present a problem in some fields. 



The white capsules attached to the skin right behind the head of the fall armyworm are 

 the eggs of a fly. These eggs will hatch and the tiny grubs will enter the insect's 

 body- -causing eventual death, often after the damage has been done. But once this build- 

 up of parasites occurs, future infestations of fall armyworms may be prevented or at 

 least minimized. 



Although control is difficult and usually unneeded,carbaryl (Sevin), diazinon, Gardona, 

 or toxaphene granules may reach the worms deep in the whorls. 



European corn borer first-generation populations are generally low, but are great ( 

 enough in a few exceptionally early fields to be slightly damaging. This includes both 

 field and sweet corn. Whether or not sufficient moths will be produced to cause a 



