Unit 7: Alfalfa Diseases

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 2nd 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