Carrot Root Knot
Root knot of carrot is caused by the soil dwelling nematode, Meloidogyne hapla, which has a wide host range among vegetable crops.
Nematodes are attracted by root and seed secretions and penetrate the root tips, position themselves in the vascular system, and induce plants to form giant cells on which they feed. Activity of the nematodes result in changes in root morphology by hypertrophy an hyperplasia. M. hapla reproduce quickly and high populations (500-2000 nematodes per gram of root) occur by mid-season.
When soil populations of M. hapla are high symptoms include stunted plants, uneven stands, premature leaf death, and branches and swellings on both lateral and tap roots. Marketable yield is reduced by deformities, size reduction, branches, and knobs.
The damage threshold for carrots and parsnips is very low at 1-5 nematodes/gram root. Before planting highly susceptible crops, have soil tested for nematode populations.
- Monitor soils for nematode populations before planting highly susceptible crops.
- Rotate with non-hosts such as cereals.
- Soil solarization or field fumigation in the fall may reduce nematode populations. Biofumigation with brassica crops as green manure has shown promise in reducing nematode populations.
For Current information on disease recommendations ins specific crops including information on chemical control & pesticide management, please visit the New England Vegetable Management Guide website.
Diseases
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