HPIPM:Onion Stem Bulb Nematode

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Nematoda
Class	Chromodorea
Order	Tylenchida
Family	Anguinidae
Genus	Ditylenchus

Scientific Name

Ditylenchus dipsaci

Common Name

alfalfa stem nematode

Author: Howard F. Schwartz, David H. Gent, and Michael E. Bartolo

Identification and Life Cycle

The stem or bulb nematode, Ditylenchus dipsaci, can attack over 400 plant species including alfalfa, onion, dry bean, soybean, potato and many common weeds. It has generally been a minor problem on onion in western regions.

Nematodes survive on seeds, onion debris, weeds and in infected transplants. The pathogen is favored by free moisture and an optimum soil temperature of 70°F. Its life cycle is completed within 23 days at 60°F with four molts and four juvenile stages; and adults live up to 73 days. Damage occurs in many crops at infestation levels as low as 10 nematodes per 500 grams of soil.

Plant Response and Damage

Stem nematode-injured plants are dwarfed, twisted and abnormally white with swollen split areas of the bulbs. Plant stands may be erratic. In older onion bulbs, tissue softens near the top of the bulb and at the base of leaves of stunted plants. Older plants often crack or produce doubles. Secondary breakdown by bacteria and fungi is common. Nematode losses generally small, but precise yield loss estimates in the High Plains production regions are not available.

Biological Control

Incorporation of green manure crops such as sudangrass, sesame, rapeseed, white mustard, or perennial ryegrass the season before potatoes are planted can reduce some nematode populations.

Cultural Control

Select high quality transplants produced in fields fumigated before planting. Practice a four-year or longer rotation. Avoid aggravating plant stresses such as soil compaction, root pruning during cultivation, and moisture extremes. Avoid reuse of irrigation water, as nematodes are readily moved in water. Thoroughly wash equipment to prevent moving contaminated soil into new fields.

Chemical Control

Nematicides and soil fumigation are effective, but very expensive and probably not cost effective in most fields unless high populations of the Fusarium basal plate rot and pink root fungi are present.

Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.