Root lesion nematode
Beginner
Scientific Name
Pratylenchus penetrans
Identification
At crop emergence, heavy infestations of root lesion nematodes cause areas of poor growth with stunted, yellowish, wilted, weak plants. Plants do not recover and eventually die.
In infected plant roots, nematode feeding damage cause brown lesions. These lesions grow together and turn black.
Often Confused With
Crop stress
Period of Activity
Throughout the season
Scouting Notes
Scouting should start at crop emergence. Fields should be monitored at least twice a week.
When walking fields, stop at many sites as possible and check plants at random. If you find wilted plants, check the root system and look for brown to black lesions of feeder roots.
Take soil samples from areas where infected plants are found. Soil analysis is a useful method to detect the level of root lesion nematode infestation in the soil.
Threshold
2000 root lesion nematodes per kg of soil. For very susceptible varieties such as Superior, the threshold should be reduced to 1000 root lesion nematodes per kg of soil.
Advanced
Scientific Name
Pratylenchus penetrans
Identification
At crop emergence, heavy infestations of root lesion nematodes cause areas of poor growth with stunted, yellowish, wilted, weak plants. Plants do not recover and eventually die.
In infected plant roots, nematode feeding damage cause brown lesions. These lesions grow together and turn black.
Often Confused With
Crop stress
Biology
The root lesion nematode is a tiny, threadlike worm about 0.5 mm long when mature. It feeds on roots causing lesions that interfere with nutrient absorption. Initial symptoms are detected shortly after crop emergence. If root lesion nematode populations are above threshold levels, yield losses are severe. This nematode affects potato yields directly by reducing the size and weight of tubers and also indirectly by weakening the plants and making them more susceptible to Verticillium wilt.
High populations cause extensive damage to young feeder roots, which are then invaded and damaged by other soil microorganisms.
Higher infestations of the root lesion nematode are usually found in sandy fields with short rotations out of potatoes.
Period of Activity
Throughout the season
Scouting Notes
Scouting should start at crop emergence. Fields should be monitored at least twice a week.
When walking fields, stop at many sites as possible and check plants at random. If you find wilted plants, check the root system and look for brown to black lesions of feeder roots.
Take soil samples from areas where infected plants are found. Soil analysis is a useful method to detect the level of root lesion nematode infestation in the soil.
Threshold
2000 root lesion nematodes per kg of soil. For very susceptible varieties such as Superior, the threshold should be reduced to 1000 root lesion nematodes per kg of soil.
Management Notes
Avoid planting rotational crops that are good hosts for root lesion nematodes in the year prior to planting potatoes. Soybeans and red clover are both good hosts for nematodes, while annual ryegrass is less so.
Root lesion nematode populations may be reduced by growing cover crops such as oilseed radish, and mustards when incorporated as green manure. Poultry litter compost has been reported to reduce root lesion nematode populations.
Soil fumigation reduces nematode populations in soil, but these chemicals are expensive and not necessarily cost-effective.
