3.1.13
CONTROL OF BOTRYTIS CINEREA AND OTHER FOLIAR PATHOGENS IN GREENHOUSE VEGETABLE CROPS BY TRICHODERMA HARZIANUM T39 ALTERNATED WITH CHEMICAL FUNGICIDES ACCORDING TO THE GREENMAN DECISION SUPPORT SYSTEM

Y ELAD and D SHTIENBERG

Department of Plant Pathology, The Volcani Center, Bet Dagan 50250, Israel

Background and objectives
Botrytis cinerea (grey mould) is a ubiquitous pathogen which causes severe losses in many fruit, vegetable and ornamental crops and which can be especially important in greenhouse production. The pathogen infects the leaves, stems, flowers and fruits in greenhouse vegetables. Sclerotinia sclerotiorum (white mould) and Fulvia fulva (leaf mould) are also common in non-heated greenhouses. Trichoderma harzianum T39 (as TRICHODEX 20P, Makhteshim Ltd, Be'er Sheva, Israel) effectively controls Botrytis diseases under a wide range of conditions in greenhouse crops [1] as well as leaf mould on tomato and white mould. A new approach based on a decision-support system named BOTMAN was developed [2] for the control of B. cinerea and was later widened in order to take care of other greenhouse diseases. The outcome is a system named GREENMAN. This approach was tested for tomatoes and cucumbers. The aim of GREENMAN is the right timing of applications of the biocontrol agent and chemical fungicides so that the latter will be applied only when necessary and the former will be used on all other occasions during the period when epidemics develop in greenhouses.

Materials and methods
Experiments were carried out in polyethylene-covered greenhouses during the winters of 1994-98. Decisions on whether to apply the biocontrol agent TRICHODEX or chemical fungicides were taken according to GREENMAN instructions before each spray. The factors taken into consideration were weather forecast (rain amount and duration, temperatures minima and maxima and cloudiness), the type of the greenhouse (height, ventilation, partial heating, cover) and crop (age, density), the resistance of the pathogen towards fungicides, the potential efficacy of the biological or chemical control agents, the effect of microclimate conditions on the efficacy of the biocontrol agent and the stage of development of each disease [1,2]. Sprays with chemical fungicides were limited to occasions when GREENMAN indicated a high potential for epidemic development, and on other occasions the biocontrol agent was applied.

Results and conclusions
Out of an average of 11 sprays with either chemical or biological agents to greenhouse crops, 60% of the sprays in programs managed according to GREENMAN were carried out with the biocontrol preparation TRICHODEX. In plots treated according to GREENMAN instructions, the degree of grey mould control on tomato leaves and stems or on cucumber fruits and stems and of plant mortality was 60-90%. Similar control of leaf mould on tomato leaves and of white mould on cucumber fruits and stems was obtained. Disease suppression was at least as efficient as in plots treated only with fungicides on a weekly basis.

Management of greenhouse diseases according to GREENMAN by means of the biocontrol agent TRICHODEX and chemical fungicides results in effective control of the diseases. It also results in a reduction in the number of chemical fungicide sprays, and limits of the pressure towards development of pathogen populations resistant to chemical fungicides.

References
1. O'Neill TM, Niv A, Elad Y, Shtienberg D, 1996. European Journal of Plant Pathology 102, 635-43.
2. Shtienberg D, Elad Y, 1997. Phytopathology 87, 332-40.