Biological control of grape grey mould by Trichoderma harzianum Yigal Elad Department of Plant Pathology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel Biological and chemical control of grey mould was tested in vineyards of table and wine grapes. Treatments with Trichoderma harzianum (OS-1 .O g I-‘), dicarboximide fungicides (vinclozolin or iprodione) (0.5 g I-‘) or diethofencarb plus carbendazim (0.25 g I-‘) resulted in up to 78% disease reduction. A tank mix of the biocontrol agent with a dicarboximide fungicide was not superior to either treatment alone. It is suggested that alternate sprays of the biocontrol preparation with a fungicide should be employed in vineyards in order to reduce the use of chemicals. Populations of Trichoderma on grapes treated with the biocontrol agent were 4.5 X lo5 per berry compared with 40@-2000 per berry on untreated bunches. The application of T. harzianum in the vineyard did not interfere with processes involved in wine production from the grapes. T. harzianum and iprodione applied alone in the vineyard reduced the postharvest rot of grapes in one of two experiments. Alternation of T. harzianum with diethofencarb plus carbendazim, or its mixture with iprodione in the vineyard, resulted in a 64-68% reduction in postharvest rot caused by Botrytis cinerea. Keywords: Biological control; Botrytis cinerea; Trichoderma harzianum; iprodione; vinclozolin; dicarboximide; diethofencarb; carbendazim; Vitis vinifera; integrated pest management Grape grey mould (Botrytis bunch rot) caused by Botrytis cinerea Pers.; Fr. can be a serious disease in vineyards in many places around the world (McClellan and Hewitt, 1973; Pearson and Riegel, 1983; Gessler and Jermini, 1985; Gubler, Marois and Bledsoe, 1987; Bulit and Dubos, 1988), including Israel (Elad, Shabi and Katan, 1988). For the control of grey mould, in table or wine cultivars, growers rely heavily on fungi- cides, mainly benzimidazoles and dicarboximides. How- ever, the spread of B. cinerea strains resistant to either or both groups of fungicides has greatly reduced their effectiveness. Thus, control of grey mould continues to be a challenge (Pommer and Lorenz, 1982; Gullino and Garibaldi, 1986; Elad et al., 1988). Several attempts have been made to reduce grey mould in vineyards by means of biological control. Successful experiments were conducted with isolates of Trichoderma spp. (Dubos, Jailloux and Bulit, 1982; Bisiach et al., Gullino, Mezzalama and Garibaldi, 1985; Gullino and Garibaldi, 1988). However, commercial preparations have not yet been developed with the aim of biological control of grey mould (Lynch, 1988; Elad, 1990). It has been suggested that one of the reasons for the delay in development of biological control of foliar pathogens, including the important grey mould disease, is the availability of effective and cheap fungicides (Elad, 1990). The development of a formulated preparation of Trichoderma harzianum aimed at the control of grape grey mould under field conditions is reported here. Materials and methods Experiments in commercial vineyards Experiments were carried out in commercial vineyards, on random blocks with five replicates. Each plot consisted of ten treated vines (Vitis vinifera). The fungicides sprayed were iprodione (Rovral 50 WP, Rhone-Poulenc, Lyon, France), vinclozolin (Ronilan 50 WP, BASF AG, Ludwigshafen, Germany), Folpet (Folpan 50 WP, Makhteshim Chemical Works Ltd, Be’er Sheva, Israel) and a factory-prepared mixture of diethofencarb (25%) and carbendazim (25%) (Reset WP, Sumitomo Chemical Co., Osaka, Japan). An isolate of T. harzianum obtained from cucumber fruit, grown and formulated by Makhteshim Chemical Works (Trichodex, 25 WP T. harzianum), was used throughout this work. As soon as symptoms were observed on berries (one focus per ten vines) in the vineyards, treatments against grey mould were started. The grape bunches were sprayed until runoff with a knapsack motor sprayer (Echo SHR 200 E, Kiorizo Corp., Japan) at a calculated volume of 1000 1 ha-‘. The spray nozzle type used was a Conjet DX6. All experiments were terminated 4-10 days before harvest. Typical symptoms of grey mould on the berries were regarded as infection foci and counted on the sampling dates. Experiment 1 was conducted in central Israel with table grapes cv. Barlinka in summer 1987. Sprays were applied on 17 August, and 2, 16 and 27 September. 0261-2 194/94/01 lOO35-04 @ 1994 Butterworth-Heinemann Ltd Crop Protection 1994 Volume 13 Number 1 35