Transcript Alfalfa Diseases

Crown rot symptoms in alfalfa
Verticillium, Fusarium,
Rhizoctonia, Phytophthora,
Pythium, Phoma,
Mycoleptodiscus, Stagonospora,
and Macrophomina
Crown rot control
• Variety selection
• Promote vigorous growth with proper fertility and
irrigation practices.
• Control foliar diseases and insect problems.
• Avoid cutting hay when soils are wet.
• Avoid heavy grazing.
• Control weeds with herbicides and avoid cultivation
practices which damage crowns.
• Avoid field sites with heavy or poorly-drained soils.
• Rotate out of alfalfa for 2-3 years.
• Heavy watering in the fall will delay dormancy
– Stop watering end of September
Stem nematode in alfalfa
• Ditylenchus dipsaci
White flagging
Swollen nodes
Stunted plants, shortened internodes
Crinkled leaves (between veins)
Stem nematode on alfalfa
• Spread by surface water runoff, irrigation,
wind-blown crop debris, infested hay, soil and
crop debris clinging to equipment, humans and
livestock, and with seed
• Prevent introduction of nematodes into a field
• Rotate with a non-host (not alfalfa or sainfoin)
and control alfalfa volunteers 2-4 years
• Some resistant lines (not completely resistant)
• Cut infected fields slightly higher and when dry
to reduce spread
Boron deficiency in alfalfa
• Can result in hollow, corky stems; bushy
plant; yellow/reddish leaves
• Test soil; apply fertilizer containing
boron
Alfalfa mosaic virus
• Vectored by aphids
• Symptoms masked by heat
• Wide host range: most legumes, many
weeds, potatoes
• Transmitted mechanically and in seed
• Makes plants more susceptible to
winterkill
Brown root rot of alfalfa
• Phoma sclerotioides
• Most active in late winter and early
spring
• Very broad host range, including
grasses
2006 Survey
BRR survey
• About 250 crowns collected from MT
• PCR analysis of crown lesions
• Zero positive so far (may have been too
warm when collected?)
• Will test DNA for other crown rot
pathogens
– Stemphylium botryosum
– Phytophtora medicaginis
– Aphanomyces euteiches