streaks with wavy margins --are most noticeable on plants that are less than two feet 

 tall. Several streaks on a leaf will cause it to shrivel, die, and appear to be frost- 

 ed or suffering from lack of water. The streaks are parallel to the leaf margins, and 

 are generally associated with injury caused by flea-beetle feeding. Sweet corn is usu- 

 ally more susceptible to leaf blight than field corn, but field corn and even resist- 

 ant sweet corn can be infected in the seedling stage. 



The bacteria that cause Stewart's disease overwinter almost exclusively within the bod- 

 ies of adult corn- flea beetles. In areas where wilt was severe the previous summer, 

 about 20 percent of the beetles that come out of hibernation the following spring are 

 contaminated with the silt-causing bacteria. 



Sweet -corn producers should plant resistant sweet -corn varieties and follow Extension 

 Entomologists' suggestions to control the corn-flea beetles. Write for Report on Plant 

 Diseases, Numbers 201 and 907. They describe Stewart's wilt and leaf blight in more 

 detail. Resistant sweet-corn varieties are listed in RPD Number 907. 



Corn Genetic Abnormalities . Corn samples occasionally show long white streaks that can 

 be mistaken for Stewart's leaf blight. These plants usually occur singly and are not 

 common in the field. The streaks result from mutated cells within the plant that are 

 not able to synthesize chlorophyll. All cells derived from the mutated (genetically 

 abnormal) cells lack this ability; therefore, long streaks with SMOOTH margins are ob- 

 served- -all derived from common cells in the growing embryonic tissue of the seedling. 

 The survival of abnormal plants depends on the extent of chlorosis (absence of green 

 chlorophyll) . 



SMALL GRAIN DISEASES 



Septoria Leaf Blotch of Wheat . Septoria tritioi continues to exist on wheat. However, 

 warm and dry weather slews down the progress of the disease. A normal year's loss in 

 yield due to leaf blotch is about 5 percent, especially on early maturing varieties. 



Dark-brown to black specks called "pyenidia" (spore -producing bodies) form in the dead 

 lower leaves. Severely infected leaves turn yellow, wither, and die prematurely. Pye- 

 nidia can be observed readily with a hand lens . 



Septoria Glume Blotch of Wheat . Glume blotch, caused by Septoria nodorvm, infects the 

 chaff (glumes) of wheat heads, as well as the culms (leaf sheaths) and leaves. Unlike 

 Septoria leaf blotch, glume blotch is a disease associated with warm, moist weather. 

 Glume blotch causes the highest losses when excessive rainfall occurs between flower- 

 ing and grain harvest. 



Small, irregular, grayish or brownish spots or blotches appear on the chaff, usually- 

 near the top third of the glume. As the blotches age, pyenidia appear in the chocolate- 

 brown to tan areas. 



The fungi that cause leaf blotch and glume blotch survive on volunteer wheat and on 

 stubble left over from previous seasons . None of the wheat varieties adapted and rec- 

 ommended for Illinois are resistant to Septoria leaf blotch or to glume blotch. Early 

 maturing varieties are generally more susceptible than late-maturing ones. Write for 

 Report on Riant Diseases Number 105 for more details on Septoria disease of wheat. 



Wheat Streak Mosaic on Corn . Wheat plants that become infected with wheat-streak mo- 

 saic in the early spring develop leaf symptoms, but yield losses are usually slight. 

 The virus that causes the disease is spread only by the feeding of tiny, white, cigar- 

 shaped, wheat-curl mites. 



