A ‘little and often’ system for application of entomopathogenic nematodes for vine weevil control in hardy ornamental nursery stock

Abstract: Various species of entomopathogenic nematodes are available for biological control of vine weevil and these can provide effective control. However, unlike growers of soft fruit crops who apply nematodes through drip irrigation for vine weevil control, most growers of hardy nursery stock (HNS) do not use drip irrigation and apply the nematodes as high volume drenches, which are labour intensive and therefore more expensive. An experiment completed in 2016 evaluated a novel method for applying nematodes in a ‘little and often’ approach using the overhead irrigation system. Steinernema kraussei was applied to replicated plots of potted Fuchsia plants infested with vine weevil eggs in a research polythene tunnel. The nematodes were applied at the recommended rate in September and October either as a drench comparable with the industry standard or through the overhead irrigation system, or at reduced rates (20% and 40% of recommended rate) applied through the overhead irrigation system every month between June and October. Water control treatments were applied either as a drench or through the overhead irrigation system. All the nematode treatments were equally effective in significantly reducing numbers of vine weevil larvae per pot compared with the water controls. The results showed that reduced rates of nematodes applied as a ‘little and often’ system through overhead irrigation were as effective as the full rate applied as a drench and could offer a less labour-intensive and more cost-effective application system than using high volume drenches.