The lesions are usually round to elliptical spots, which may range from small dots 

 to spots half an inch in diameter. When infected areas overlap, the spots can be 

 irregularly shaped. The spots are first dark-green and watersoaked. Later, they 

 become dry and are tan to white in color. Occasionally the spots will have a dark, 

 reddish border. In locations where sun scald occurs simultaneously, the spots may 

 be surrounded by scald halos . Dry weather checks Holcus spot in mid- season, so it 

 is generally thought of as a minor disease. [See pages 19 and 20 in the North-Central 

 Regional Bulletin 21, Diseases of, Corn in the Midwest, also numbered as Illinois 

 Circular 967.] 



"ONION-LEAFING" OR "CRAZY TOP" IN CORN 



A non-parasitic disease of corn was observed in the Springfield area where the leaves 

 of corn plants remained tightly wrapped in the whorl. In the past, this condition 

 has been called "buggy-whip" or "onion- leafing." It is thought to develop when the 

 emergence and vertical elongation of the leaves occurs faster than opening or unroll- 

 ing. 



Onion- leafing appears suddenly when very favorable growing conditions arise after an 

 unfavorable growing period. Corn varieties respond differently to the rapidly chang- 

 ing environmental conditions, presumably because of differences in genetic background. 

 Onion- leafing can sometimes be associated with 2,4-D injury, which may affect the tis- 

 sue around the growing point. The results can be delayed for several weeks making di- 

 agnosis difficult. Onion- leafing is often found in fields where no herbicides have 

 been applied. 



Corn "crazy top" may appear in late-planted corn that was flooded by heavy rains. The 

 downy mildew fungus, Solerospora maarospora, overwinters in the soil. The infection 

 develops only where the soil has been flooded or waterlogged sometime between seed 

 germination and when the seedlings reach 6 to 10 inches high (four- to five-leaf stage) 

 The early symptoms of corn downy mildew are similar to those of onion- leafing. See 

 Report on Plant Diseases No. 207, "Crazy Top of Corn"; also, NCR Bulletin No. 21, Dis- 

 eases of Corn in the Midwest (111. Circular 967) for further details. 



ALFALFA 



Common and Stemphylium leaf spots as well as spring black stem are all causing leaf- 

 lets to turn yellow and drop off, particularly in areas of the state that have re- 

 ceived more than their share of rain during the past couple of weeks. The only con- 

 trol we can suggest now is to cut severely infected stands early, before heavy leaf 

 drop occurs. This will help reduce forage losses in future cuttings. 



Douny mildew has also appeared, following the unusually cool and wet weather of a week 

 or so ago. This mildew will disappear with warm, dry weather. Look for pale-green to 

 yellowish -green areas on the upper leaf surfaces. The leaves may roll and twist down- 

 ward. A delicate, violet-gray mold may be evident on the undersides of such leaflets 

 in cool, wet weather. 



Control measures are not necessary. A change in the weather will check the spread 

 of the disease. Additional details are provided in Report on Plant Diseases No. 301, 

 "Leaf and Stem Diseases of Alfalfa." 



SOYBEANS 



Phyllosticta leaf blight, a very sporadic disease that has not been this prevalent in 

 many years, can now be found in almost every Illinois soybean field. Phyllosticta 



