VIEW ARTICLE

Disease Control and Pest Management

Biological Control Effects of a New Isolate of Trichoderma harzianum on Pythium aphanidermatum. A. Sivan, Research assistant, Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel; Y. Elad(2), and I. Chet(3). (2)(3)Research assistant, and professor, respectively, Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel. Phytopathology 74:498-501. Accepted for publication 7 December 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-498.

A wheat-bran plus peat mixture (1:1, v/v) was the most efficient of the raw plant material substrates (which included several agricultural plant wastes) found suitable for growing a new isolate of Trichoderma harzianum (T-315). The bran/peat preparation of T. harzianum, applied to either soil or rooting mixture, efficiently controlled damping-off induced by Pythium aphanidermatum in peas, cucumbers, tomatoes, peppers, and gypsophila. Disease reduction of up to 85% was obtained in tomatoes. T. harzianum applied in a seed coating mixture containing 5 × 10⁹ conidia per milliliter was as effective in sandy soil as the broadcast application of wheat bran/peat preparation. However, the broadcast application was superior to seed coating for protecting tomato seedlings in an infested peat/vermiculite rooting mixture. When germinated at low temperature (22 C) pea seeds coated with conidia of T. hamatum were better protected from P. aphanidermatum than seeds coated with T. harzianum, but this was not the case at 30 C. Extracellular filtrate from cultures of T. harzianum, added to a synthetic medium, inhibited linear growth of P. aphanidermatum by 83% compared with 8% inhibition by a culture filtrate of T. hamatum. Substances excreted by P. aphanidermatum into the growth medium enhanced the linear growth of T. harzianum by 34%, but not that of T. hamatum.