-6- 



The major sign of injury during the past week has been " onion- leafing ." Although 

 the total number of fields actually affected may still be relatively low, some 

 fields have shown rather severe, tight rolling of the leaves. 



This rolling has occurred in many areas of the state on many different hybrids 

 and apparently with many different 2,4-D formulations. Although some injury has 

 shown up after both early and late spraying, most of the injury seems to have oc- 

 curred where corn was sprayed early, when it was only a few inches tall. 



Our best guess is that with the cool, moist stress conditions present during the 

 last part of May, the 2,4-D affected the plants when most of the leaves were in 

 the very early stages of formation- -surrounding the growing point and hardly 

 recognizable as leaves. Then, with the subsequent moist and hot weather and 

 pattern of extremely rapid growth, these early effects later became visible as 

 the onion- leafing. 



An occasional tendency toward onion- leafing has been reported this year even in 

 fields not sprayed with 2,4-D. This is most likely related to the very rapid 

 growing conditions, possibly to certain genetic lines of corn. 



Usually in previous years, only a very small percentage of the plants in a field 

 where extensive onion- leafing has appeared have been seriously affected. Leaves 

 have usually unrolled soon enough for tassels to emerge. Pollination was nearly 

 normal, and there was little effect on ears. This year, however, where some of 

 the leaves seem to be very tightly rolled, there may be a greater- than-usual ef- 

 fect on tassel emergence. It's difficult to predict what the result may be on 

 ears; but with a smaller leaf area exposed for normal photosynthesis, ear devel- 

 opment may be affected. 



There seems to be an increase in smut in some fields. Where the corn was brittle, 

 cracking opened the way for more smut. The seriousness of the situation will have 

 to be assessed in individual fields, using common sense and good judgment. Hope- 

 fully, some fields may outgrow the injury fairly well. 



This problem would tend to make one cautious about applying 2,4-D during the next 

 few weeks. However, the symptoms we see now do not necessarily mean that severe 

 problems will develop with later spraying. 



Do not spray injured fields a second time with 2,4-D. Avoid spraying on hot, 

 humid days. Be sure the correct rates are carefully applied. 



There is little that can be done now about the injured fields, except to hope 

 that a high percentage of the plants will outgrow most of the injury. 



Pond Weeds 



Chara vulgaris , commonly known as mushgrass, becomes abundant in many bodies of 

 water in Illinois. At this time of year, other vegetative problems may have 

 matured or responded to applications of herbicides. 



In general, chara resembles other aquatic vegetation. But since it is an algal 

 species, it is not susceptible to commonly used herbicides, such as endothal or 

 2,4-D. Stands of chara can be eliminated by applications of crystals of copper 

 sulfate directly to it. This is the cheapest and most -effective method for con- 

 trol. Chara has a pungent odor, and this can be imparted to the water and fish. 



