Effects of green manures on nematode population densities in an organic tomato field
S. L. MEYER (1), K. L. Everts (2), B. B. McSpadden Gardener (3)
(1) USDA ARS, Beltsville, MD, U.S.A.; (2) University of Maryland and University of Delaware, Salisbury, MD, U.S.A.; (3) The Ohio State University - OARDC, Wooster, OH, U.S.A.
Phytopathology 101:S120

An increased demand for organic foods has resulted in a greater need for pest management strategies in organic vegetable production systems. To this end, cover crops incorporated as green manures in an organic tomato field were studied for effects on nematode population densities. Treatments were: 1) mixed species hay (Festuca arundinacea, tall fescue; Dactylis glomerata, orchard grass; Phleum pretense, timothy; Trifolium pretense, red clover; Medicago sativa, alfalfa); 2) Vicia villosa (hairy vetch); 3) V. villosa plus Secale cereale (rye); 4) V. villosa plus Raphanus sativus (forage radish); and 5) a bare ground control, six plots/treatment. Cover crops were incorporated with a chisel plow in April 2010. Plots were sampled before incorporation, <2 weeks later, midseason and harvest. Meloidogyne was found in only 3 plots, at the second sampling time. Total plant-parasitic nematode numbers/100 cc soil at that time were 21.3, 2.5, 33.8, 26.3, and 8.3 (means for treatments 1-5, respectively), and at harvest were 26.9, 40.8, 46.7, 43.8, and 40.8. No significant differences were found among treatments or dates, and no root galling was observed. Marketable tomato yield means ranged from 2.6 lbs (on two selected plants/plot) for hairy vetch+rye to 5.9 pounds for hairy vetch; no significant differences were found among treatments. The results indicate that under low nematode pressure, the cover crops did not result in any change in nematode populations.