HPIPM: Nematodes

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Nematoda
Class	Chromodorea
Order	Tylenchida
Family	Heteroderidae

Scientific Name

Meloidogyne

Common Name

root-knot nematode

Nematodes (Scientific name)

Author: Howard F. Schwartz, David H. Gent, Martha Mikkelson, and Jack Riesselman

• Source1
• Source2
• Source3

Cause

Various nematodes can attack pea, including the pea cyst nematode (Heterodera goettingiana), root-knot nematode (Meloidogyne incognita), and root-lesion nematode (Pratylenchus penetrans).

Symptoms

Above ground symptoms of nematode injury appear as patches of stunted or dying plants. When roots are examined they appear pruned, but some nematodes (such as the cyst nematode) can cause a proliferation of lateral feeder roots. Other nematodes can cause a round to spindle-shaped galls on roots (root-knot) and reddish-orange to brown lesions (lesion).

Impact of Disease

Infected plants may wilt when stressed by high temperature or moisture stress. Nematode damage to pea has not been investigated thoroughly in the High Plains.

Life Cycle of the Pathogen

The life cycle of different nematode species vary, and may include feeding on the outside of roots or penetration and development within roots. The cyst nematode is one of the most damaging nematode pests of pea. Cysts are the dead bodies of females and may contain up to 300 eggs. Cysts are very persistent in the soil, surviving more than 12 years, and can be spread by moving contaminated soil on plant parts, equipment, and irrigation water. Cool soil temperatures promote root invasion. Nematodes survive between susceptible crops by feeding on other crops and weeds, and, sometimes, as dormant cysts.

Cyst nematode symptoms include yellowing of foliage that spreads rapidly from the bottom of the plant to the top. Affected plants lack fibrous roots and nitrogen-fixing nodules. Tiny (less than 0.02 inches) cream-colored, lemon-shaped cysts can be found embedded in root tissue, but once cysts mature and turn dark brown, they detach easily from root systems and are difficult to detect.

Management Approaches

Biological Control

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

Cultural Management Practices

Prevent the introduction of nematodes in clean fields by thoroughly cleaning equipment between fields. Plant peas when soil temperatures are warm, but be aware of other production problems associated with late pea plantings. Avoid the reuse of irrigation water. Provide adequate fertilizer and irrigation for crop development to reduce the impact of nematode feeding. Sprinkler irrigation tends to be more effective than furrow irrigation for supplying even water to nematode-damaged plants. Practice a five-year or longer crop rotation to non-hosts such as small grains; avoid vegetable crops, faba bean, and vetch in rotations. Control weeds that may serve as alternate hosts of nematodes. Promptly incorporate crop residues after harvest to limit nematode reproduction.

Chemical Management Program

No nematicides are registered for pea.

Consult pesticide labels for additional rate, application, and safety information. Additional information and current labels can be found at http://www.greenbook.net or http://www.cdms.net.

References

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.