CONTROL OF GRAPEVINE GREY MOLD WITH TRICHODERMA-HARZIANUM T39

The efficacy of a formulation of Trichoderma harzianum T39 for control of grey mould (Botrytis cinerea) on grapevine was examined in 133 exp eriments conducted under diverse commercial conditions. The experiment s were carried out between 1988 and 1994 in 19 countries and on 34 var ieties. The average disease incidence in the untreated plots of all ex periments was 42 +/- 2.3% (mean +/- standard error). In general, the r eduction of disease achieved by T. harzianum application was lower tha n that obtained by chemical fungicides: 36.3 +/- 2.7% disease reductio n in biocontrol treatments and 52.3 +/- 2.6% in the exclusively chemic al treatments. Control efficacy declined when the interval between app lication and assessment dates increased to 5 weeks. The experiments al so included treatments in which T. harzianum was integrated with chemi cal fungicides, the two being applied alternately and a reduced chemic al treatment in which only chemicals were applied, and only at the tim es when chemicals were applied in the integrated treatment The mean co ntrol efficacy in these treatments was 55.8 +/- 3.2% and 44.2 +/- 4.9% respectively. The roles of the integration of biological and chemical compounds in reducing pesticide residues in fruit at harvest and lowe ring the pressure towards development of fungicide-resistance populati ons of B. cinerea are discussed.