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Knowledge Nuggets
A brief description of the disease, where it is mainly a problem, and control measures are listed below.
- Anthranose – mainly a disease of southern and eastern United States
- Aphanomyces root rot (ARR) – mainly a disease of eastern and western United States, in wet soils. Symptoms similar to nitrogen deficiency.
- Bacterial wilt (BW) – in the south and central prairies. Cause serious stand losses in 3-5 yr stands. Plants start out yellow-green and advance to stunted with spindly stems.
- Common leaf spot (CLS) – in the south and central prairies. Occurs in 1st and 2nd cuttings and in fall regrowth. Causes reduced yield and lower forage quality.
- Crown bud rot (CBR) – common in irrigated or moist soils. Progressive decline in stand and yield. Control – delay spring harvest, leave 25 cm on plant after the last harvest.
- Fusarium wilt (FW) - in the south and central prairies. Causes gradual stand thinning. Symptoms are similar to bacterial wilt, but plants are not stunted. Control – control pea aphids and potato leafhoppers.
- Lepto spot (LS) - mostly in central Alberta and southern Manitoba. Attacks young regrowth and yield and quality are reduced. There are no resistant cultivars available.
- Phytopthera root rot (PRR) – a problem in the south and central prairies, in wet or slowly drained soils. Plants have reduced root mass and growth rate, and can die rapidly. Control – crop rotation is not effective, avoid untimely cutting (plants stressed, before a heavy rain), control leaf-feeding insects, use tillage and land-leveling.
- Root lesion nematodes – moderate problem in eastern Canada and along the southwest coast of B.C.
- Sclerotinia – moderate problem in eastern Canada.
- Spring black stem - in the south and central prairies. Causes leaf drop, stem girdling and infection of the crown and roots resulting in death. Reduces yield and quality.
- Summer black stem – mainly a disease of the eastern and western United States.
- Verticillium Wilt – a problem in pockets of south central B.C., and southern Alberta and Manitoba. Leaves yellow, leaving a green stem. Crown infection results in death. Yield can be reduced up to 50%. Control – harvest non-infected fields first.
- Winter crown rot or snow mold (WCR) – dark brown rot of crown. Control – plant winter hardy cultivars
There are five common control methods that can be used to keep these diseases in check as listed below.
- Resistant Varieties – CBR, ARR, BW, CLS, FW, PRR, SBS, VW
- Crop Rotation – CBR, VW
- Maintain Stand Vigor – WCR, CBR
- Maintain Good Fertility – CBR, FW, PRR
- Harvest Early – CLS, SBS
Fact Sheets
Alfalfa Analyst
Alfalfa Anthracnose - available in PDF format only
Alfalfa Anthracnose - Ohio State University Extension
Alfalfa Crown and Root Rots and Stand Longevity - available in PDF format only
Alfalfa Disease Management - available in PDF format only
Alfalfa Disease Resistance Ratings
Alfalfa Diseases in Missouri
Alfalfa Snout Beetle
Alfalfa: Weeds, Diseases and Insects
Alfalfa Weevil
Aphanomyces root rot
Bacterial wilt of Alfalfa
Common Leaf Spot and Leptosphaerulina (Lepto) Leaf Spot
Diseases in Alfalfa
Lepto leaf spot
Nutrient Deficiencies in Alfalfa for Forage
Phytophthora Root Rot of Alfalfa
Rhizoctonia Root, Stem and Crown Rot of Alfalfa
Root and Crown Troubles of Alfalfa - available in PDF format only
Root lesion nematodes
Spring Black Stem of Alfalfa
Verticillium Wilt on Alfalfa
Verticillium Wilt on Alfalfa - Ohio State University Extension
Research Papers
A novel source of resistance to verticillium wilt in alfalfa
Assessing resistance to spring black stem and leaf spot of alfalfa caused by Phoma spp. - available in PDF format |
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