Spectral filters for the control of Botrytis cinerea

Experiments performed in vitro examined the sporulation of Botrytis cinerea (grey mould) under different spectral distributions. Eighty-three isolates , taken from plants of primula (Primula vulgaris) at different locations th roughout the UK, were incubated in the dark, with visible light only and vi sible plus near-ultraviolet (nUV) light. On average, compared to isolates n ot exposed to nUV, sporulation was increased 54-fold following illumination with nUV light. No isolates showed complete insensitivity to near ultravio let. New polyethylene materials with different optical properties were then tested on two typical isolates. A film which removed nUV up to 405 nm, com pared to a film with nUV absorption up to 384 nm, resulted in the lowest pr oduction of conidia (by 5-fold). The former film was used to clad horticult ural polyethylene tunnels in which crops of P. vulgaris and strawberry were grown for two seasons and the incidence of B. cinerea assessed throughout the growth of the crops. The incidence of infection on the P. vulgaris and strawberries was reduced by c. 50% and c. 26% respectively with the nUV blo cking film compared to a standard film. The results are discussed in terms of the potential of spectral filters as a novel means of grey mould control in greenhouse-produced crops.