Alfalfa Stem Nematode
Symptoms:
This nematode has not been reported in Illinois, but is a serious pest of alfalfa in parts of the western U.S.
- Stems, stem nodes, and crown buds of plants infected with stem nematodes are swollen.
- Infected stems are shorter than healthy stems due to decreased internodal length
- Heavily infected plants may have curled and distorted leaves, stems may become white and blackened and die, and the entire plant may be killed.
- Severe infections can also reduce stem numbers and predispose plants to winterkill and other diseases such as bacterial wilt and Fusarium wilt.
Pathogen Involved:
- Ditylenchus dipsaci
- More than 20 races of D. dispaci attack more than 300 plant species.
- The alfalfa race reproduces on alfalfa and sainfoin only
Time of Occurrence:
- All season
- In irrigated areas, the stem nematode is usually a problem only in the first cutting.
Conditions Favoring Disease:
- Moderate temperatures favor infection and reproduction. Infection and reproduction can occur at temperatures from 5-30° C.
- It is common in parts of the western US, and is most serious in fields with heavy soils and heavy rainfall or irrigation.
- The stem nematode is spread by irrigation water, rain, alfalfa debris, and harvesting equipment.
Disease Management:
- Plant alfalfa cultivars resistant to stem nematodes. Cultivars with resistance slow nematode reproduction and/or are more tolerant of their feeding.
- Two or three year rotations out of alfalfa to a non-host crop such as corn, small grains or beans can reduce populations to low levels.
- Fields can be quickly infested, so efforts should be made to avoid contamination of fields with irrigation water, soil, contaminated seed, and plant debris.