Download Unit 7: Alfalfa Diseases

Unit 7: Alfalfa Diseases
Unit 7: Alfalfa Diseases
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Bacterial Wilt
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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
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Wilting during hot weather
Unit 7: Alfalfa Diseases
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Spread by:
Mowers
 Drainage water
 Irrigation water
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Diseased plants susceptible to water
injury
Infection enters through plant wounds
Most infected plants die in 2nd year
Unit 7: Alfalfa Diseases
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Prevention
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Plant resistant varieties
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Most all varieties have some resistance
Anthracnose
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Symptoms
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Diamond shaped lesions on the stem
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Center is straw colored
Death at the top of the plant
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Top of plant curls over
 “Shepherd’s crook”
Unit 7: Alfalfa Diseases
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Fungus overwinters on plant debris
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New inoculum for the spring
Warm, wet weather is ideal
Spreads by spores
Rain
 Wind
 Machinery
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Control
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Plant resistant varieties
Unit 7: Alfalfa Diseases
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Verticillium Wilt
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Symptoms
V-shaped yellowing of leaf tips
 Rolling along leaf margin
 All leaves eventually roll and die
 Stem remains green
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Spores carried by wind, insects,
harvesting equipment
More common problem on older alfalfa
stands
Unit 7: Alfalfa Diseases
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Fusarium Wilt
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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
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Phytophthora Root Rot
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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
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Rot in crown and roots
Similar symptoms to phytophthora
Unit 7: Alfalfa Diseases
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Leaf Diseases
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Leaf Spot
Most common fungal disease
 Most prevalent in wet, humid regions
 Small circular brown spots on leaves
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Yellow Leaf Blotch
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Causes early leaf drop
Long yellow streaks on leaves
In either case, cut alfalfa as soon as
fungal infection becomes serious