Control of Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae) Larvae on a Range of Hardy Ornamental Nursery Stock Species Using the Entomogenous Fungus Metarhizium anisopliae

Abstract

The potential of the entomogenous fungus Metarhizium anisopliae as a microbial control agent for vine weevil (Otiorhynchus sulcatus) larvae was examined on a range of outdoor hardy nursery stock species. A curative application of M. anisopliae conidia (5× 10⁸ conidia l^‐1compost) reduced larval numbers by 62% on Skimmia japonica ’Rubella’ and by up to 43% on Viburnum plicatum ’Mariesii’. Four M. anisopliae isolates were examined and all reduced the larval populations on both species. However, the reductions were only significant with strains 159–83 and 100–82 on S. japonica ’Rubella’ and 100–82 on V. plicatum ’Mariesii’. Larval development on two other species (Hydrangea macrophylla ’Blue Wave’ and Thuja plicata ’Zebrina') which had been treated with 0.05% Triton X‐100 (the control treatment) was very poor and therefore it was not possible to determine whether or not the fungal drench had any effect. The experiment was repeated in the following year at two different sites, East Mailing and Littlehampton, using a prophylactic drench of two M. anisopliae isolates on a greater number of plant species. Strain 275–86 was more effective than 159–83 on all species at East Mailing, with the exception of V. davidii. The difference was less pronounced at Littlehampton and the results from the two isolates were similar. Larval control was highly variable and species dependent with a reduction in larval numbers ranging from zero to 96% and zero to 90% at East Mailing and Littlehampton respectively. The larval populations in pots treated with Triton X‐100 were also highly variable, ranging from zero (Chaemaecyparis lawsoniana ’Stardust’ Dianthus ’Maria’ Escallonia ’Crimson Spire’ and Pittosporum tenuifolium ’Gamettii') to 17.8 larvae per pot (Ribes nigrum ’Baldwin ‘). The results indicate the potential of M. anisopliae and demonstrate the complexity of plant‐weevil‐fungus interactions.

Keywords:

• entomogenous fungus
• Metarhizium anisopliae
• vine weevil
• Otiorhynchus sulcatus
• biological control
• hardy ornamental nursery stock

Notes

Microbiology & Crop Protection Department, Horticulture Research International, Worthing Road, Littlehampton, West Sussex BN17 6LP, UK

Horticultural Development Council, 18 Lavant Street, Petersfield, Hants GU32 2EW, UK.

Horticulture Research International, East Mailing, West Mailing, Kent ME19 6BJ, UK.

Chr. Hansen Biosystems A/S., DK 2970, H⊘rsholm, Denmark.

School of Biological Sciences, University of Bath, Bath BA2 7AY, UK.