-6- 



As winter plants mature, the near-microscopic mites migrate to nearby volunteer wheat, 

 grasses, and corn. Several corn fields in south-central Illinois showed typical wheat- 

 streak mosaic symptoms in 1972. During the late summer and early fall, the wheat-streak 

 virus is transmitted to volunteer wheat and to wheat planted in the fall. 



No hard or soft wheats currently grown in Illinois are resistant to wheat-streak mosaic. 

 Chemical control of wheat-curl mites has not been successful. Request Report on Plant 

 Diseases Number 120 for more details. 



Soil -Borne Wheat Mosaic . Infection by this disease has been favored by this spring's 

 wet soils and cool weather. The virus that causes this disease is transmitted through 

 infections of wheat -seedling roots by a soil-borne fungus. Soil-borne mosaic appears 

 in wheat fields when growth begins in the early spring, and it will persist until tem- 

 peratures average about 75° F. At that time, the symptoms become masked. Parker, Tri- 

 umph, and Centurk, are susceptible wheat varieties. Wheat throughout the state is now 

 outgrowing the symptoms of soil -borne mosaic. 



SOYBEAN DISEASES 



Soybean Seed Treatment . There is little scientific evidence to indicate that treating 

 high-quality soybean seed significantly increases yields. In blotter or field tests, 

 treatment may increase the germination rate and the emergence of poor-quality seed by 

 as much as 25 percent. Satisfactory yields have been obtained by treating poor-quality 

 beans that have a germination rate of not less than 60 to 70 percent. However, treat- 

 ing high-quality seed (above 80-percent germination) produced little increase in ger- 

 mination, emergence, or yield in studies at several of the state experiment stations. 



Inoculating soybean seed with Rhizobiwn bacteria is not generally needed in Illinois- - 

 especially where soybeans have been grown previously. If a grower needs both treatment 

 and inoculation, the seed should be treated first and then inoculated within two hours 

 after being planted in the field. 



The recommended seed treatments are Captan (Orthocide) and Thiram (Arasan) --either 

 alone or in combination. Thorough coverage of the seed is essential. Treated seed 

 CANNOT be used for food, feed, or oil purposes --even if stored for a year after treat- 

 ment. More information about treating soybeans is available in Report on Plant Dis- 

 ease Number 506. 



Copies of the Reports on Plant Disease, are available from the Department of Plant Pa- 

 thology, 218 Mumford Hall, University of Illinois at Urbana- Champaign, Urbana, Illinois 

 61801. 



READ THE LABEL AND FOLLOW ALL PRECAUTIONS 



This weekly report was prepared as follows: 



INSECTS: H.B. Petty, Steve Moore, Roscoe Randell , Don Kuhlman, and Tim Cooley , College 

 of Agriculture, University of Illinois at Urbana-Champaign , and the Illinois Natural 

 History Survey. 



WEEDS: Ellery Knake and Marshall McGlamery , Department of Agronomy , and A.J. Turgeon, 

 Department of Horticulture. 



PLANT DISEASES: M.C. Shurtleff , Ed Burns, and Tim Bowyer , Department of Plant Pathology. 



