THE SOIL AS A RESERVOIR FOR NATURAL ENEMIES OF PEST INSECTS AND MITES WITH EMPHASIS ON FUNGI AND NEMATODES

Abstract

Fungi are notorious for losing virulence and changing their morphology when successively subcultured on artificial media. Various terms have been used to describe this phenomenon including phenotypic degeneration, phenotypic instability, phenotypic deterioration, dual phenomenon, saltation and attenuation (Butt, 2002; Kawakami, 1960; Nagaich, 1973; Ibrahim et al., 2002; Ryan et al., 2001). Morphological changes include a change in colour, and growth form as well as reduced sporulation. In this article, the term degenerate is used to cover both attenuation of virulence and phenotypic degeneration. Degenerate cultures are a major concern to manufacturers of fungal biocontrol agents (BCAs) since batches that are inconsistent in spore yield or virulence will make the product commercially unviable. Growers naturally would be reluctant to use any product, which was potentially unstable.