APPLICATION OF METARHIZIUM-ANISOPLIAE (METSCH) SOR CONIDIA TO CONTROLOTIORHYNCHUS-SULCATUS (F) (COLEOPTERA, CURCULIONIDAE) LARVAE ON GLASSHOUSE POT PLANTS

The efficacy of the entomogenous fungus Metarhizium anisopliae was ass essed against vine weevil (Otiorhynchus sulcatus) larvae in the glassh ouse. Prophylactic application of M. anisopliae conidia to begonia res ulted in total larval control, but curative applications were less eff ective with only 65% control when conidial application was delayed unt il 8 weeks after egg infestation. Prophylactic applications also provi ded effective larval control on begonia plants which received multiple egg applications over a six week period. Larval mortality was monitor ed on cyclamen plants which had received a prophylactic drench of M. a nisopliae conidia. The population was reduced by 78% within 5 weeks of egg application and control rose to 90% after 17 weeks, although the increase was not significant. Prophylactic conidial drenches were comp ared with a similar number of compost incorporated conidia on cyclamen , but there was no significant difference between the two spore applic ation strategies. Application of M. anisopliae conidia to impatiens mo dules before potting-on resulted in over 89% larval control compared t o over 97% control when a similar number of conidia were applied to th e plants after potting. Larval control was further reduced to 79% when the module drenches were reduced to one quarter of the highest dose ( 5 x 10(7) compared to 2 x 10(8) conidia per module). The persistence o f three M. anisopliae strains was examined over a 20 week period on im patiens. There was no overall decline in efficacy over this period, al though there was variability in the performance of the different strai ns and it was suggested that this was linked to temperature. The resul ts of these experiments suggest that M. anisopliae has considerable po tential as a microbial control agent for O. sulcatus on glasshouse orn amentals.