and many ornamentals. As the caterpillars defoliate limbs, they spin webs in the 

 crotches of the limbs. If control is necessary, apply a spray containing carbaryl 

 (Sevin) or malathion. For carbaryl, mix 2 tablespoons of the 50-percent wettable 

 powder per gallon of water. For malathion, mix 2 teaspoons of the 50- to 75-per- 

 cent liquid concentrate per gallon of water. For the present, however, we inter- 

 pret the current law to mean that tank mixes are not legal unless the label of each 

 material involved is cleared for such use. The responsibility for personal or 

 crop injury and for residues above the tolerance level permitted is the responsi- 

 bility of the individual user. 



PLANT DISEASES 



SMALL GRAIN DISEASES 



Soil -borne wheat mosaic is now appearing in some wheat varieties ordinarily listed 

 as "resistant or tolerant." However, with the return of more seasonal and sunny 

 weather, these varieties should recover with little or no yield loss. 



Soil -borne wheat mosaic symptoms are present in many winter wheat fields in south- 

 ern and central Illinois. Plants usually appear light-green to bronze-yellow or 

 light purple in color, depending on the variety and growing conditions. Other symp- 

 toms include leaf mottling, resetting, or stunted leaves and tillers. 



The disease is most prevalent in low, wet areas or during years when fall precipi- 

 tation is above normal. Wet field conditions and dark, overcast weather during 

 the early spring also favor the development of this disease. 



Soil -borne mosaic is caused by a virus that is transmitted by the fungus polymyxa 

 graminis. Swimming spores produced by the fungus carry the virus through the soil 

 to the roots and crowns of healthy wheat seedlings. These spores then penetrate and 

 infect the healthy plants. The virus is not transmitted through the seed or by in- 

 sects. 



A more detailed description of the symptoms and control of this disease is available 

 in Report on Plant Diseases No. 102, "Soil-Borne Wheat Mosaic." 



Septoria, or speckled- leaf spot , causes the greatest damage if it attacks wheat dur- 

 ing the fall and early spring. Cool, moist weather in the fall and spring will fa- 

 vor the infection of wheat seedlings. In an extremely bad year, leaf spot may kill 

 most of the rosetted leaves and up to 50 percent of the tiller leaves. By harvest 

 time, 90 percent of the leaves may be infected; 14 percent, dead. 



Check wheat fields during the early spring for the appearance of light-green to 

 yellow lesions between the veins of the wheat leaf blade. Severely infected 

 leaves will turn yellow, wither, and die prematurely. 



Last fall, infections developed from spores produced on wheat stubble or in nearby, 

 volunteer wheat plants. The fungus overwinters in live wheat seedlings or on dead 

 plant refuse. 



In the spring, the lesions elongate, turn light-brown to reddish-brown, and are 

 often surrounded by a yellowish band. As the lesions age, small dark-brown to 

 black specks form in the lighter-colored centers of the lesions. These black 

 specks are the spore -producing . bodies of the fungus. During cool, wet spring 

 weather, the fungus begins to grow and to produce spores again. 



