Tolerance of Trichoderma isolates to forestry agrichemicals

Abstract

Two Trichoderma isolate mixtures PR6 and PR3a show promise to enhance tree growth and suppress foliar disease in New Zealand’s most important forest species, radiata pine. Availability of one or both mixtures may lead to increased productivity, sustainability, and economic gain in the New Zealand forest industry. The successful integration of these biocontrol organisms into radiata pine production systems requires knowledge of their compatibility with commonly used pesticides and other products. The sensitivity of the eight isolates that comprise the PR6 and PR3a mixtures was determined in the presence of fifty-one agrichemicals (14 fungicides, 2 fumigants, 14 herbicides, 6 insecticides, 4 fertilisers, 5 adjuvants, 2 adherents, 3 biostimulants and 1 bird repellent) commonly used in New Zealand forestry. Sensitivity of these isolates to agrichemicals was determined by in-vitro laboratory studies (spore germination, colony mycelial growth and sporulation) and in-vivo greenhouse studies using containerised radiata pine seedlings. Agrichemicals had a range of effects on isolate development in laboratory studies (Table 1). However, the sensitivity of Trichoderma PR6 established in radiata pine roots, to the single application of agrichemicals at recommended rates, was minimal or nil (Table 1). In some experiments, root colonisation in seedlings was enhanced in the first month of growth when resident competitive fungal species may have been suppressed allowing the applied Trichoderma to dominate.