Epsilon Open Archive

Abstract

Grey mould, caused by Botrytis cinerea Pers.:Fr., is a severe problem in conifer seedling production in Swedish forest nurseries. The overall aim of the study was to investigate the possibility of biological control and to find naturally occurring needle fungi with biosuppressive activity against grey mould on conifer seedlings in Swedish forest nurseries. The potential of biological control was demonstrated by means of the microbial products Binab, GlioMix and Mycostop. These products reduced B. cinerea infections in Scots pine seedlings by 16 to 57% in a field trial at a Swedish forest nursery, and by 51 to 94% in growth room assays under controlled climatic conditions. The effect of BinabÒ and GlioMixÒ was of the same level as the fungicide tolylfluanid. A novel microcosm bioassay was developed to evaluate microorganisms for biocontrol of B. cinerea in co-inoculation tests on three-week-old Scots pine (Pinus sylvestris L.) seedlings. Pre-inoculation treatment by incubation at 40 °C for five hours predisposed seedlings to infection by B. cinerea. Different isolates of needle fungi were low to highly effective in suppression of B. cinerea. One of these isolates was identified as a Fusarium sp. strain F31 and was shown to secrete a spectrum of enniatins in liquid medium. Two new enniatins, J2 and J3, were co-isolated. Inhibitory activity to spore germination of B. cinerea was shown for the enniatins B, B1, B4 and K1. Based on the screening tests, nine fungal isolates were selected and evaluated for their efficacy to suppress spontaneous infections by B. cinerea in first-year Scots pine seedlings in a small-scale field experiment. Two isolates of Trichoderma sp. and the fungicide tolylfluanid showed some degree of control. The impact of the tested control agents on the community structure of needle-inhabiting fungi was analysed. This thesis describes the first steps in the development of biological control of grey mould in forest nurseries. Further investigations are needed in the search for an efficient biocontrol method that can replace or complement chemical control.