Various studies have shown that partial defoliation at this stage can have a marked 

 effect on yields. Therefore, examine carefully and critically those fields between 

 the stages of early blossom and mid pod-fill. This year, we probably should say that 

 a 25- to 30-percent defoliation will result in economic loss and that treatment 

 should be applied when the loss of foliage is 15 to 25 percent. Most soybean grow- 

 ers have encouraged us to be less conservative this year on our damage statements. 



Yield losses commence when 25 to 30 percent of the foliage is removed at the full- 

 bloom stage. If that foliage loss is greater, so are yield losses. These losses be- 

 come even greater when such defoliation occurs from early pod set to mid-pod- fill . 

 By full-pod-fill, yield losses moderate. [This statement is courtesy of W.O. Scott, 

 Professor of Agronomy. ] 



If your field warrants the use of an insecticide, we suggest carbaryl (Sevin)or 

 malathion. Bees do not frequent soybean blossoms to any great extent, but if you 

 see honey bees, wait until late in the day to spray. Toxaphene would be safer for 

 use around bees, but farmers complained about erratic results in our last outbreak 

 several years ago. 



Leafhoppers are also present in soybean fields. You will find these green, wedge- 

 shaped insects on the ground after you shake the plants as you count green clover- 

 worms. Many of them are winged and some fly away, but a number of them are bright 

 yellow-green to yellow and wingless. These are the young or nymphal leafhoppers. We 

 do not know what damage they do to Illinois varieties, but we usually cannot measure 

 an effect on yield. Any smooth-leaved variety will be damaged. NOTE: if you do 

 treat for green cloverworms, the leafhoppers will also be killed. 



Bean leaf beetles are yellow, green, or red. They have a black line all the way 

 around the wings. There are usually two to four square, black spots on their backs. 

 These beetles can also defoliate beans. We have not seen them in great quantity yet, 

 but they may appear in a few weeks. Again, the insecticides for green cloverworms 

 will control bean leaf beetles. 



CORN INSECTS 



Corn leaf aphid populations have not materialized, except in an occasional field. 

 Generally, most of the corn crop will escape damage. But we did see one field in 

 northern Illinois and one in west-central Illinois this week in which treatment 

 might be warranted. 



Rains have generally helped reduce the numbers of aphids. But if you are in one of 

 those narrow areas where moisture is a problem, continue to watch for this pest in 

 later-maturing corn. 



European corn borer populations in the southern part of Illinois appear to be low 

 generally, but there may be one area in southeastern and possibly one in west- 

 southwestern Illinois where corn borers will increase this year- -particularly if 

 we should have a third generation of them. Moths are flying in southern Illinois. 

 A few were observed in central Illinois this past week. We also found a few egg 

 masses in pretassel corn in southern Illinois. Except for these two areas, we be- 

 lieve that the second generation will not be serious in the southern part of Illi- 

 nois, but a third generation could create a problem in late corn fields. 



Pupation of first-generation corn borers is quite high in the northern half of the 

 state. Some emergence was recorded, so eggs will begin to appear soon. Peak moth 



