SOYBEAN INJURY 



Some soybeans were planted too deep; others, too shallow. Some soybean seedlings may 

 nave an enlarged hypocotyl (the part of the stem below the cotyledons) . Although this 

 :ondition may sometimes be associated with herbicide injury, you will sometimes find 

 'swollen" hypocotyls on soybeans that have not been treated with herbicides. 



Ireflan can cause soj"? stunting of soybean seedlings and some pruning of roots. 



t/ernam may cause nouiceable crinkling of leaves and stunted plants. 



Lorox can cause a browning and dying-back of the leaves which is sometimes difficult 

 to distinguish from the effect of atrazine residue. If weather has been dry, Lorox 

 that remains on the surface may later be splashed up by rain onto emerged soybeans 

 :ausing brown speckling on the leaves and discoloration of the leaf veins. The leaf- 

 trein discoloration is less than when Lorox or atrazine move from the root out to the 

 leaves . 



Amiben may cause a little stunting of soybeans, but since there is little change in 

 color or shape of leaves and the effect is usually quite uniform, it may not be no- 

 ticed. Occasionally Amiben that moved to seed depth very soon after planting and was 

 taken up by the swelling seed may cause more significant injury. Roots may show mal- 

 formation and proliferation. 



Lasso can cause a "drawstring effect." The leaf midrib is shortened at the tip and 

 the leaf margins at the tip are pulled downward toward the shortened midrib. Only 

 some of the first leaves are affected and this is of little or no significance. 



With warm, moist weather, good physical soil condition, and appropriate planting depth, 

 soybeans usually have the ability to outgrow a little early injury quite well. But if 

 several factors such as disease, cool wet conditions, or deep planting also put the soy- 

 bean seedlings under stress, injury can be more severe. 



We have noticed considerable varietal differences in vigor and ability to tolerate her- 

 bicides in some of our plots this year. In general, some of the more vigorous vari- 

 eties also tolerate herbicides best. 



Atrazine residue injury to soybeans doesn't seem to be a serious problem, but, as usu- 

 al, such injury does appear in spots that have overdoses of the material . To help 

 avoid problems next year, do not use atrazine postemergence in corn after June 10 on 

 fields where you plan to plant crops other than corn or sorghum next year. 



Oats injury from atrazine residue has appeared in northern Illinois this year. Dry 

 weather, excessive applications, and perhaps the period of hot weather during May might 

 have affected availability uptake, and rate of decomposition in soil and plants. Oats 

 and small -seeded legumes and grasses should not be seeded the year following atrazine 

 application. 



We do not mean to overemphasize herbicide injury. The actual acreage seriously affect- 

 ed is usually relatively minor. The benefits of weed control usually far outweigh 

 risks and losses even within individual fields. 



(With many herbicides the margin of selectivity- -the ability to kill the bad and leave 

 the good plants- -is narrow. Growers and applicators should be fully aware of the risks. 



