A technique for continuous mass rearing of the black vine weevil, Otiorhynchus sulcatus

Abstract

The black vine weevil, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae) is a univoltine, polyphagous insect that is a nocuous pest of field and container grown ornamentals as well as small fruit crops world-wide (Moorhouse et al., 1992). In the USA, the environmental horticulture industry (floriculture and nursery crops) is the third largest value crop behind corn and soybeans (USDA fact sheets 2001, http://www.nass.usda.gov). Otiorhynchus sulcatus is thought to have a northern European origin and was first recorded in North America in 1835 (Smith, 1932). Oviposition occurs at night with eggs being either dropped on the soil surface or inserted into crevices on plants (Smith, 1932). Early instars begin by feeding on small roots while the later instars feed on larger roots, especially on the phloem and cambium tissues near the soil surface (La Lone & Clarke, 1981). Adults are nocturnal and mainly cause aesthetic damage to plants by notching the leaves. Adults are parthenogenic, so a single individual left unchecked can result in the infestation of an entire nursery. Because of the biology of O. sulcatus , the collection of larvae and adults from the field is very tedious and often requires countless hours of digging through field soil, container-grown plants or searching for adults after dark. Indeed, many chemical and biological control companies developing products for O. sulcatus larval control still rely on searching through infested plant material in order to gather the needed larvae for efficacy studies. Although an artificial diet initially developed by Shorey & Hale (1965) as modified by Shanks & Finnigan (1973) and Shanks (1980) (hereafter referred to as the ‘standard diet’) sustains larvae and is commercially available, there has been no documented technique for continuous mass rearing of O. sulcatus . Studies of weevil biology as well as the development of control strategies require a large, uniform, and predictable supply of insects of all life stages throughout the year. When considering field or potted plants for use in control efficacy or host plant resistant studies, other researchers have often found it useful to store insect eggs for several weeks for subsequent use; many thousands to millions of eggs were needed. The stockpiling of eggs for future use has been necessary with other reared species of Coleoptera (Branson, 1978; Fisher & Edwards, 2002). The egg hatch and viability of the strawberry root weevil, Otiorhynchus ovatus L. were not significantly reduced when it was stored for up to 4 weeks at 4 ° C (Fisher & Edwards, 2002). We have developed a technique for continuous mass rearing of O. sulcatus in the laboratory using a meridic diet. Since small changes in diet composition can often lead to dramatic changes in larval survival and growth, experiments were also performed to determine if O. sulcatus larval survival and development were increased on the improved diet described here, compared to the standard diet. Additionally, we determined if O. sulcatus eggs could be stored for up to 4 weeks at 4 ° C without significant reductions in larval survival and development.