PLANT diseases 



WINTER INJURY TO ALFALFA AND CLOVER 





Several alfalfa and red clover samples received by the Extension Plant Pathologists 

 in the Department of Plant Pathology show crowns that are soft (easily broken) and 

 usually dark to reddish-brown when split apart. The center of the primary root may 

 also appear discolored and hollow, and the walls of the hollowed root may appear 

 "honeycombed." These symptoms indicate winter injury followed by attack by one or 

 more crown and root-rotting fungi. 



Four types of winter injury are commonly recognized: 



1. Heaving- -Alternate freezing and thawing, especially where fields were wet dur- 

 ing the winter, can lift the plant from the soil and separate it from the side 

 roots. 



2. Low- temperature injury --This kind of injury usually occurs when unadapted va- 

 rieties are planted. Application of fertilizers, especially nitrogen, and cut- 

 ting or grazing in late fall may aggravate the problem. 



5. Frost injury - -Frosts that occur after plants have started vigorous spring 

 growth can leave fields brown. However, unless complications develop, plants 

 should recover rapidly in warm weather. 



4. Ice sheets --Ice sheets cause the most serious type of winter injury. Entire 

 stands can be lost to ice-sheet formations caused by sleet storms or water 

 from rain or melting snow that has frozen. Varieties that are resistant to 

 cold injury are generally most resistant to ice -sheet injury. 



Winter injury often leaves plant tissue with deep cracks or other wounds that act 

 as entry points for plant -pathogenic fungi and bacteria. 



Controls include: 



1. Sow seed of adapted varieties that are certified disease- free and high yield- 

 ing. 



2. Practice balanced soil fertility. Avoid overfertilization as well as late- 

 summer or fall application of fertilizer. 



3. Avoid overgrazing and "short clipping." These practices cut down food re- 

 serves and lessen the chances for winter survival. 



Further information can be obtained from your county Extension adviser or by 

 writing to the University of Illinois Department of Plant Pathology, Urbana, Il- 

 linois 61801. Ask for Report on Plant Diseases, No. 302, "Roof and Crown Dis- 

 eases of Alfalfa," or RPD No. 304, "Root and Crown Diseases of Clover." 



LEAF-SPOTTING DISEASES OF ALFALFA 



Leaf spotting of alfalfa can cause loss of vigor and reduction in hay quality and 

 yield. Wet spring weather increases the chances of 1 leaf spotting. 



1. Common leaf spot --Symptoms of this disease are small, circular, dark-brown 

 spots about 1/16 inch in diameter on alfalfa leaflets. First-year plants may 



