A REVIEW OF THE BIOLOGY AND CONTROL OF THE VINE WEEVIL, OTIORHYNCHUS-SULCATUS (COLEOPTERA, CURCULIONIDAE)

At the turn of the century, damage by Otiorhynchus sulcatus was sporad ic and limited to small areas. Increasing horticultural intensificatio n and the adoption of husbandry techniques favourable to the weevil, s uch as the use of polythene mulches, increased its pest status. The de velopment of the early inorganic pesticides reduced the number of seri ous outbreaks of this pest and weevil control was further improved by the development of the persistent organochlorine insecticides in the 1 940's. The banning of a number of the more persistent insecticides ove r recent years has now left the horticultural industry in a very vulne rable position. O. sulcatus is now a pest on a range of horticultural crops throughout the temperate regions of the world. Infestations are most common in Europe (where it originated) and the USA, and nearly 15 0 plants species have been identified as potential hosts to O. sulcatu s. Damage is most frequently caused by the root feeding larval stage. Populations as low as one larva plant-1 can kill sensitive species suc h as Cyclamen. Severe damage by the leaf feeding adults is less common , although low levels of damage or contamination by adults may be unac ceptable in certain situations. There is one generation a year. Ovipos ition by the flightless parthenogenetic females occurs over the summer months with oviposition rates of c. 500 and 1200 eggs adult-1 for out door and laboratory populations, respectively. O. sulcatus mainly over winters as larvae, although significant numbers of adults may survive in areas where winter temperatures are not too severe. A number of nat ural enemies, such as hedgehogs, frogs and predatory beetles, help to maintain O. sulcatus populations at a low level in natural environment s, but they are less successful in intensive horticultural systems whe re persistent chemicals have been heavily relied on to maintain the po pulation below the economic threshold level. Increasing environmental concern is now forcing growers to consider new pest control strategies . Controlled release formulations of non-persistent products, such as fonofos and chlorpyrifos, have shown potential as control agents for O . sulcatus larvae. Biological control agents, such as insect parasitic nematodes, have been developed commercially and new microbial control agents are in the process of development. Most of the new control pro ducts are directed towards control of O. sulcatus larvae. Adult vine w eevils are nocturnal and a much more difficult target for the new cont rol agents. It is likely that an integrated approach to pest control w ill be required to maintain O. sulcatus populations below their econom ic threshold level.