Most nursery stock growers apply nematodes to control vine weevil larvae via high-volume drenches to individual containers. This can be labour-intensive and therefore make the treatment expensive. Many soft-fruit growers have already adapted a "little-and-often" approach to application, splitting the nematode dose and applying it monthly via drip irrigation instead of applying the full recommended rate.
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 alternative 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. 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.
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 and even one vine weevil larva within the root ball of a plant can lead buyers to reject crops.
A fact sheet based on AHDB Horticulture-funded research work on vine weevil will be available soon.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk.