VIEW ARTICLE

Disease Control and Pest Management

Biodegradation of Metalaxyl in Avocado Soils. Ana Maria Bailey, Research associate, Department of Plant Pathology, University of California, Riverside 92521; Michael D. Coffey, professor, Department of Plant Pathology, University of California, Riverside 92521. Phytopathology 75:135-137. Accepted for publication 1 August 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-135.

Using a sensitive bioassay involving Phytophthora boehmeriae as the test organism, biodegradation of metalaxyl was detected in three of five avocado soils that had received repeated applications of the fungicide over a period of 2- 5 yr. The average half-life of metalaxyl in these soils was 28 days, and in the most active soils the half-life was 14 days. The composition and levels of the microbial populations (bacteria, fungi, and actinomycetes) of similar soils, either active or inactive in the breakdown of metalaxyl, did not differ. Active microbial populations were recovered both from soils with a history of prior metalaxyl treatment and from similar untreated soils with no ability to degrade the fungicide. Fungal and bacterial microflora were recovered from these two soils by using either selective media or filtration techniques and were capable of degrading metalaxyl over a 45-day period. One soil capable of degrading metalaxyl (50% over 14 days) did not promote degradation of either the acylanilide fungicides RE 26745 and oxadixyl, or the chemically related herbicide metolachlor.