Unit 7: Alfalfa Diseases

 Bacterial Wilt Occurs when conditions are right for rapid, vigorous growth Symptoms  Reduced stand  Dwarfing of infected plants  Bunch-growth caused by shortened stems  Small, yellow, curled leaves Wilting during hot weather

Unit 7: Alfalfa Diseases Spread by:  Mowers  Drainage water  Irrigation water Diseased plants susceptible to water injury Infection enters through plant wounds Most infected plants die in 2 nd year

Unit 7: Alfalfa Diseases Prevention  Plant resistant varieties Most all varieties have some resistance  Anthracnose Symptoms  Diamond shaped lesions on the stem Center is straw colored  Death at the top of the plant Top of plant curls over  “Shepherd’s crook”

Unit 7: Alfalfa Diseases Fungus overwinters on plant debris  New inoculum for the spring Warm, wet weather is ideal Spreads by spores  Rain  Wind  Machinery Control  Plant resistant varieties

Unit 7: Alfalfa Diseases  Verticillium Wilt Symptoms  V-shaped yellowing of leaf tips  Rolling along leaf margin  All leaves eventually roll and die  Stem remains green Spores carried by wind, insects, harvesting equipment More common problem on older alfalfa stands

Unit 7: Alfalfa Diseases  Fusarium Wilt Reddish brown discoloration inside the root Stunting of the plant More prevalent in older stands Can be more destructive in conjunction with another disease

Unit 7: Alfalfa Diseases  Phytophthora Root Rot Interior of the roots rot Stunted and dead plants Common in wet areas of the field Use resistant varieties and improve drainage  Crown & Root Rots Rot in crown and roots Similar symptoms to phytophthora

Unit 7: Alfalfa Diseases  Leaf Diseases Leaf Spot  Most common fungal disease  Most prevalent in wet, humid regions  Small circular brown spots on leaves Causes early leaf drop Yellow Leaf Blotch  Long yellow streaks on leaves In either case, cut alfalfa as soon as fungal infection becomes serious