Grey mould is a severe and frequent disease in the greenhouse. The pathogen, Botrytis cinerea Pers., is a polyphagous fungus that attacks ornamental and vegetable crops. Control of this disease is difficult because both the microclimate and the cropping methods in greenhouse production are conducive to its development (Jarvis, 1992). No resistant commercial varieties are presently available. Hence, traditional chemical methods continue to be the principal means of control even though it is complicated by resistance to fungicides and the small number of registered products for greenhouse crops (Nicot and Baille, 1996).