Suppression of Pratylenchus penetrans and Tylenchorhynchus dubius by Trichoderma viride.

Trichoderma spp. are common soil fungi which influence tile development of plant-pathogenic fungi in the soil (1, 8). Yang et al. (9) found that T. harzianum influenced the severity of Fusarium wilt of cotton in the presence of Meloidogyne incognita. We report herein that the survival of two other plant-parasitic nematodes also was influenced by addit ion of cornminuted cultures of Trichoderrna viride to soil. Trichoderma viride isolated from roots of apple (Malus sylvestris Mill.) was grown in 8% casamino acid l iquid medium (2) [25 ml/125-ml Erlenlneyer flask on a rotary shaker (10 rpm/min ) at room temperature (ca 22C)]. After 7 days, the contents of the flasks were comminuted in a blender for 3 rain and then 125 ml of this mixture were diluted with an equal volume of water. Sixty ml of this mixture were mixed with 250 gm of a fine sandy loam natural ly infested with 83 Pratylenchus penetrans and 21 Tylenchorhynchus dubius/lO0 grn of soil. T h e 250 gm of soil were placed in a 340-ml styrofoam cup and mixed by shaking. A sterile medium or deionized water was added to infested soil in a similar manner to provide controIs. For comparison, the nematicide oxamyl and the fungicide benomyl were used in soil with and without mycelial suspensions at the rate of 10 t'g (a.i.)/gm of soil. T h e cups of soil were randomized in 4 blocks on a laboratory bench, watered as needed, and incubated for 3 weeks at 22C. After 3 weeks, 2 samples (100 grn each) were taken from each replicate. Nematodes were extracted by the paper-filter method (4). Thus only live, motile nematodes were counted. In the first exper iment with infested soil, counts of P. penetrans and T.