Symptoms of Sweet Potato Root Knot Nematodes
Root knot nematodes of sweet potatoes are white to yellow and live amongst the storage roots. Although tiny, these nematodes can be seen without a magnifying glass. They overwinter as eggs in the soil and complete their life cycle in about 30 days. Since a single female can lay up to 3,000 eggs, a severe infestation of root knot nematodes in sweet potatoes can seriously damage a crop. Root knot nematodes are most abundant in sandy soils. Signs of root knot nematodes include stunted vines and yellowing. The symptoms often mimic those of a plant with a nutrient deficiency. Roots will be distorted and cracked with a tough texture. If they infest the plants early in the growing season, small galls may be seen; if they attack later in the season, they can be found in the larger storage roots. For a sure diagnosis, split the small roots lengthwise and look for a swollen female nematode embedded in the root. Usually, the area surrounding the nematode is dark and the nematode itself looks a bit like a pearl nestled into the flesh of the root.
Management of Sweet Potatoes with Nematodes
Commercial growers may resort to the use of nematicides. However, there are no nematicides suitable for use in the home garden. The home gardener must then use other management methods to control the nematodes. To control root knot nematodes, use disease resistant stock. Evangeline and Bienville are commercially available sweet potato varieties with resistance to root knot nematodes. Practice crop rotation. Following a sweet potato crop, a different vegetable should be planted for the next two years, although that being said, most vegetables are susceptible to root knot nematodes. Some varieties of tomato or southern pea are resistant.
