Banvel is also registered now for use on grass pastures. This herbicide is more ef- 

 fective on some persistent perennial weeds than 2,4-D, MCPA, or 2,4,5-T. The recom- 

 mended rates of application vary from a half a pint per acre upward, depending on the | 

 prevalent weed species. The rates and corresponding grazing restrictions are given 



on the label. 



Other herbicides such as Amino triazole and Tordon are particularly effective in 

 controlling many broadleaf weeds, but are not registered for use on pastures. 



All of the herbicide treatments listed will injure forage legumes, as well as control 

 broadleaf weeds. Use these treatments only on straight grass pastures or where in- 

 jury to the legume is permissible. 



PLANT DISEASES 



SOYBEAN DISEASES 



Phyllosticta leaf spot . As expected, Phyllosticta leaf spot (caused by P. sojicola) 

 is now hard to find in soybean fields. The disease affects only the first and pos- 

 sibly the second set of leaflets on the soybean plants. Dead areas turn papery and 

 break off easily from infected plants, leaving a ragged hole that may resemble hail 

 injury on the primary and on first or second leaves. There are no resistant varie- 

 ties to this disease. 



Phytophthora root rot . The plant disease clinic recently received samples of Beeson 

 soybeans that appeared to be infected with Phytophthora megaspevma var sojae. Iso- 

 lations from the samples by USDA Soybean Pathologist Dr. L. Gray proved that Beeson 

 remains resistant to Phytophthora and that no new strain of the fungus is yet present 

 in Illinois. The pathogen isolated from Beeson was Rhizootonia solani, and not Phy- 

 tophthora. 



Phytophthora can infect susceptible soybeans throughout the season. The advancing 

 margin of infection may be found above the soil line, especially in poorly drained 

 soil that is subject to prolonged wet conditions. 



Brown spot . Several samples containing Brown spot have been received at the disease 

 clinic. This disease appears on primary leaves as angular, reddish-brown spots that 

 are up to one- fifth of an inch wide. As the plants grow, fungus spores produced on 

 the primary leaves spread to the trifoliate leaves, stems, and pods. Heavily in- 

 fected leaves gradually turn yellow and fall prematurely. Fruiting bodies (pyenidia) 

 of Septoria glycines are required for positive diagnosis. Fortunately, this disease 

 has not reached major proportions in Illinois. At least a one-year rotation pro- 

 gram is necessary to prevent the buildup of this fungus. No soybean varieties grown 

 in Illinois are resistant to this disease. 



Bacterial blight . Cool, wet weather has favored the occurrence of common bacterial 

 blight caused by Pseucbmonas glycinea. The bacteria are splashed from soil or dis- 

 eased plants onto the primary or higher leaves of the plant. Characteristic symptoms 

 are small, water-soaked, angular spots on the leaves. These spots are brown at first, 

 but then turn yellow. Heavily infected leaves generally have a ragged appearance as 

 the diseased tissue drops off. All soybean varieties are susceptible. 



For more information about soybean diseases, see Illinois Circular 676, Diseases of 

 Soybeans in Illinois. Copies are available from the Department of Plant Pathology, 

 218 Mumford Hall or the Office of Agricultural Publications, 123 Mumford Hall, Ur- 

 bana 61801. 



