Applying nematode treatments for the control of vine weevil in hardy nursery stock at reduced rates through overhead irrigation systems over a period of time, rather than targeted high volume drenches, is as reliable, and potentially more cost-effective, latest research finds.
Most nursery stock growers apply nematodes to control vine weevil larvae via high volume drenches to individual containers, which can be labour intensive and, therefore, make the treatment expensive. Many soft fruit growers have already adapted the practice of a ‘little and often’ approach to application, splitting the nematode dose and applying it monthly via drip irrigation between May and September, instead of applying the full recommended rate in August or September.
Strawberry growers have reported that this method has given better control of vine weevil larvae, but at no extra cost for the nematodes, so AHDB Horticulture has been funding trials to test whether this alternate application method can also be effective for hardy nursery stock growers.
In trials, five applications were made at reduced rates (20% and 40% of the recommended rate) from July through to October and compared with full-rate drenches. Significantly, for hardy nursery stock growers, the ‘little and often’ treatments were just as effective as the full-rate drenches in reducing the number of vine weevil larvae and the level of severely damaged root systems. This method could, therefore, offer growers a less labour intensive and more cost-effective way of using nematodes compared to the current method of using high volume drenches applied to individual plants.
Vine weevil control remains a top priority for hardy nursery stock growers, largely because of a reduction in the number of long-term chemical control measures for larvae. Control has to be very effective as even one vine weevil larva within the root ball of a plant can lead buyers to reject crops.
Wayne Brough, knowledge exchange manager at AHDB Horticulture said, “Vine weevil control is a critical issue for all growers of hardy nursery stock, and the research we are funding is designed to integrate the available current control measures into robust control programmes which businesses can adopt. Sharing knowledge and learning from across horticulture sectors has played a crucial role in identifying solutions to this challenge.”
Image (C) Harper Adams University