EFFECTS OF 3 MICROBIAL BROTH CULTURES AND AN ORGANIC AMENDMENT ON GROWTH AND POPULATIONS OF FREE-LIVING AND PLANT-PARASITIC NEMATODES ON BANANA

The effect of 24 treatment combinations of cultures of Streptomyces co staricanus sp. nov. (ATCC55274), Bacillus thuringiensis (ATCC55273) an d a strain of Paecilomyces marquandii, nematicide (cadusaphos), and/or wheat mash on growth and response of potted banana plants (Musa AAA) and populations of Radopholus similis, Helicotylenchus multicinctus an d free living nematodes were studied in Rio Frio, Costa Rica. The best plant responses (height, leaf numbers, healthy root weight), lowest n umbers of plant parasitic nematodes and highest numbers of free living nematodes were observed for treatments containing wheat as a componen t. Two treatments, viz. wheat + Streptomyces costaricanus (200-ml cult ure) and wheat + FI marquandii (200-ml culture), gave the overall best results. Numbers of free living nematodes increased up to 1500-fold o nly for treatments containing wheat. Significant positive correlations existed between numbers of free living nematodes and shoot weight, he althy root biomass, plant height, and leaf numbers. Non-wheat treatmen ts, including nematicide only, gave the poorest responses in general. Observations of nematodes sampled 50 days following planting in wheat- containing treatments showed most of the free-living nematodes (approx imate to 90%) to be infected by nematophagous fungi (species not recor ded). The results show that an organic amendment to soil, with or with out a microbial component, can be an effective inducer of processes th at regulate plant-parasitic nematode populations in soil.