Constraints to the development of biofungicides: The example of “AQ10”, a new product for controlling powdery mildews

Abstract

Over recent years, the company ECOGEN Inc. has been successfully developing a biofungicide known under the trade name ‘AQ10’ in the USA where it has been authorized in 1994 for controlling powdery mildews on various host plants. This new product is based on the use ofAmpelomyces quisqualis, an hyperparasitic fungal species infesting representatives ofErysiphaceae (powdery mildews) only. The production process now allows for the hyperparasite to be mass-cultured and formulated into an easily water-dispersed, dry powder which preserves spore viability at room temperature for a period in excess of 12 months. Upon spraying, the conidia germinate rapidly to effectively attack any developing powdery mildew colonies. Efforts are now concentrating on experimental application schedules in vineyards aimed at defining an optimal positioning of the biofungicide within existing disease control programmes. The pilot trials are being conducted over a large number of wine-producing areas under a Mediterranean climate around the world where powdery mildew represents the major pest problem. Results obtained so far show that in order to achieve an optimal, cost-effective, consistent disease control, the biofungicide has to be applied before the incidence of powdery mildew has reached high levels, and at any of the three most susceptible growth stages of grapevine,i.e. bud break, between flowering and bunch closure, and just before veraison. The biofungicide may therefore be used as a curative to slightly preventative control agent likely to fit into any IPM strategies. The various technical problems associated with the development and industrial production of this new biofungicide are largely solved. Constraints relating to designing comprehensive, user-friendly IPM programmes which include ‘AQ10’ still require adjustments in terms of defining spraying dates and intervals according to a range of agricultural practices, climatic changes likely to occur during the season, and compatibility for tank-mixing with other pesticides. A number of additional constraints relate to official registration in various countries, distributors’ and farmers’ acceptance of a new, ‘living’ product: these are still more difficult to address because they claim for a profound change in the users’ general attitude towards controlling diseases of cultivated plants.