Western flower thrips (WFT) is a serious pest of protected strawberries and recent experiences have suggested that existing biocontrol agents do not always provide complete control. WFT feeding on the flowers and developing berries leads to bronzing of the fruit, rendering it unmarketable.
AHDB funded this research project (SF 146) to identify alternative predators that are not currently being exploited for WFT control but could be incorporated into a biocontrol programme to replace or supplement Neoseiulus cucumeris on protected strawberry crops.
The trials focused on evaluating Neoseiulus cucumeris, Neoseiulus californicus and the predatory substrate dwelling mites Stratiolaelaps scimitus (formerly Hypoaspis miles) and Macrocheles robustulus.
N. californicus was shown to offer similar control of WFT to N. cucumeris and there was found to be no interspecific competition between the adult mites. However, N. californicus is known to prey on two-spotted spider mite in glasshouse crops, and should such alternative prey be present, control of WFT may be compromised.
Growers need to determine which Neoseiulus predator they have in their crops — the two species can only be differentiated by trained entomologists.
The substrate predatory mites S. scimitus and M. robustulus were found to prey on WFT pupae in soil-less substrates, and when combined with the use of predatory nematodes (Steinernema feltiae) the level of control was improved, but control was not twice the level of that achieved by the predatory mite alone.
For details on all AHDB Horticulture activity, see horticulture.ahdb.org.uk