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1 



areas of the state. Seedlings infected with the bacterium may appear wilted on hot 

 dry days and when the base of the plant is cut lengthwise it may reveal a dark brown, 

 wet rot of the crown area. Symptoms on older plants are long pale- green to brown 

 streaks that originate from corn-flea beetle feeding wounds. Controls include grow- 

 ing resistant varieties and controlling beetles. Many sweet corn varieties are avail- 

 able that resist this disease after the third-, fourth-, or fifth-leaf stage and dent 

 corn is generally much more resistant than sweet corn. Resistance to Stewart's dis- 

 ease has been correlated with resistance to northern corn leaf blight. 



Beetles can be controlled by spraying or dusting plants with recommended insecticide. 

 More information is available in Report on Plant Diseases No. 201, Stewart's Leaf 

 Blight of Corn, available from the Department of Plant Pathology, University of Illi- 

 nois, 218 Mumford Hall, Urbana 61801. 



WEEDS 



HERBICIDE INJURY 



When diagnosing possible herbicide injury, be sure to get all the facts before jumping 

 to conclusions. We have had several inquiries about symptoms of herbicide injury, 

 but we have also had several cases of injury caused by crusting or by corn leafing- 

 out under the soil surface. 



It's difficult to generalize about herbicide injury, but here are some of the prob- 

 lems that have occurred: 



Several soybean samples that show yellowing of the lower leaves have been received. 

 The symptoms of all photosynthetic- inhibitors, such as AAtrex (atrazine), Lorox (lin- 

 uron) , Maloran or Bromex (chlorbromuron) , and Sencor (metribuzin) , are the same wheth- 

 er the cause is atrazine carryover from last year or a current season application of 

 a soybean herbicide. Marginal carryover plus marginal crop tolerance may combine to 

 cause serious injury. 



We have also received some calls on drift injury resulting from aerial application 

 of herbicides. Drift is a function of particle size, height of fall, and wind speed. 

 Particle size is smaller and height of fall is greater with aerial application and 

 drift is often more serious than with ground application. 



Span sprayers (low-volume air-propellant sprayers) have been promoted in some areas 

 for herbicide application. These sprayers tend to produce a small particle size and 

 may poorly distribute the particle behind the applicator. We do not think that span 

 sprayers should be used to apply herbicides. 



SORGHUM NEED CONTROL 



Delayed corn planting in some flooded areas and a demand for feed grains have raised 

 questions about growing grain sorghum and grain- sorghum weed control. Corn herbicides 

 that are also cleared for use on sorghum are Ramrod, Ramrod/atrazine, Ramrod plus 

 Mtrex, AAtrex, and 2,4-D. AAtrex and 2,4-D are cleared for use only as postemergence 

 treatments on sorghum. Lorox plus Ramrod can also be tank-mixed and used preemergence 

 on grain sorghum. Milogard (propazine) , Herban 21A (norea plus atrazine) , and Herban 

 21P (norea plus propazine) are labeled only for sorghum and are not generally avail- 

 able in Illinois because of limited sorghum production. Milogard can also be tank- 

 mixed with Ramrod for sorghum weed control . 



