Crown rot symptoms in alfalfa

1
Crown rot symptoms in alfalfa
Verticillium, Fusarium, Rhizoctonia,
Phytophthora, Pythium, Phoma, Mycoleptodiscus,
Stagonospora, and Macrophomina
2
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

3
Stem nematode in alfalfa

• Ditylenchus dipsaci

White flagging Stunted plants, shortened
internodes Swollen nodes Crinkled leaves
(between veins)
4
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

5
Boron deficiency in alfalfa

• Can result in hollow, corky stems bushy plant
  yellow/reddish leaves
• Test soil apply fertilizer containing boron

6
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

7
Brown root rot of alfalfa

• Phoma sclerotioides
• Most active in late winter and early spring
• Very broad host range, including grasses

8
2006 Survey
9
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