Grey Mould disease caused by Botrytis cinerea is genrally the most severe decay during the ripening of grapes and costs Australian grape growers around $30 million each year including $8 million on control measures. The disease infects flowers to establish latent infections which later become active decays as the fruit ripen. B. cinerea has conventionally been managed using chemical fungicides, but over use has resulted in resistance to many chemical groups, and most effective chemicals cannot be applied after berries are the size of a pea, due to restrictions on chemical residues in export wine markets.
The environment of the ripening grapes is a challenging “ infection court” for biological control with a rich diversity of microbes, abundant natural yeasts and increasing phyllosphere sugar levels. Studies by the author have suggested that the microbial diversity increases as the season progresses and natural antagonists of B. cinerea are not common in the grape flowers or the developing fruit, but small populations of fungi such as Trichoderma spp. begin to appear in the canopy at about the time of veraison.
A variety of Trichoderma spp. collected from vineyard environments were screened for the ability to suppress B. cinerea in culture and in vivo assays. Two isolates, Trichoderma koningii (race Td67) and Trichoderma harzianum (race Td81b) were collected which stood out for reducing infection. The T. koningii Td67 race has affinity for colonisation of the grape stigma and pollen receptacle and reducing latent flower infection by B. cinerea. The T. harzianum Td81b race is specifically selected for ability to grow and cause lysis of B. cinerea on the ripening fruit. The two have potential to be used as an integrated spray program and in trials provide reductions in the order of 80% relative to untreated controls.