-5- 



(2,4-dichlorophenoxy-butyric acid). 2,4-D is the acetic acid form (2,4- 

 dichlorophencocy-acetic acid). You can use 2,4-DB on legumes, but not 2,4-D 

 butyl ester. 



PLANT DISEASES' 



FIRST SOUTHERN CORN LEAF BLIGHT FOUND 



The first positive case of southern corn leaf blight in Illinois was identified 

 in the Plant Disease Clinic at the University of Illinois on May 19. The com 

 sample came from a St. Clair County field, planted to a blend. The infected corn 

 grows next to a grain bin where corn was shelled-out just before a rainy period. 



The disease has not spread in the field, and new leaves that have emerged since 

 May 14 appear to be healthy. Because the known diseased area is small, patholo- 

 gists suggested plowing-down the infected corn and replanting the area to re- 

 sistant corn or soybeans. 



Southern corn leaf blight appears as small, oval or round spots on the leaves with 

 a reddish-brown border . A yellowish halo may surround the border of some spots. 



The Plant Disease Clinic is receiving many corn specimens that show weather damage- 

 mostly cold, hail, and wind-whipping. Yellowish spots, blotches, or streaks ap- 

 pear in the leaves and later develop whitish or translucent centers. The tissue 

 may also be torn on some spots. Scorched leaf tips are also common, sometimes 

 associated with grayish areas in the leaf caused by the separation of the upper 

 cuticle . 



SCLB spots can be distinguished from "weather spots" by the appearance of the def- 

 inite, reddish-brown border. 



POWDERY MILDEW AND SEPTORIA LEAF BLOTCH OF WHEAT 



Powdery mildew and septoria leaf blotch are now showing up in small amounts where 

 wheat stands are thick and the nitrogen fertilization rate is high. Mildew ap- 

 pears as a whitish mold on the leaves, which may later turn "mealy" and brownish 

 and in which black specks are formed (overwintering or oversummering fruiting 

 bodies of the mildew fungus) . Septoria shows up as tan- to-brownish, oval-to- 

 irregular blotches on the leaves. Later, the centers are sprinkled with black 

 specks (fruiting bodies of the septoria fungus) . These diseases cause little 

 damage and yield loss. In most years, powdery mildew and septoria can be found 

 six to eight weeks earlier. Dry weather has held these diseases in check up to now. 



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 Illi- 

 nois Natural History Survey. 



WEEDS: Ellery Knake and Marshal McGlamery , Department of Agronomy . 



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



AG COMMUNICATIONS: Ray Woodis . 



The information for this report was gathered by these people, staff members, 

 county Extension advisers, and others, in cooperation with the USDA Agricultural 

 Research Service, Plant Pest Control Branch. 



