Investigating foliar fertiliser effects on the incidence of clover flea (Sminthurus viridis) damage on white clover.

Clover flea (Sminthurus viridis (L.) is a sporadic and at times serious pest of white clover in New Zealand. Clover flea feeding is reduced in the laboratory by application of foliar fertilisers. The possibility that this was related to potassium status was tested in outdoor conditions using potted clover plants sprayed with two general purpose fertilisers, NitrosolR and ThriveR, potash, the insecticide diazinon and water. In one experiment, sprayed plants were placed in a paddock where clover flea were active while in the second, treated plants were surrounded by a barrier and clover flea released into the enclosure. Three treatments significantly reduced the incidence of feeding damage 7-9 days after treatment compared to the water treatment, with diazinon (42-57% reduction in the incidence of damage) more effective than NitrosolR (26-44%) and potash (38%). There was no evidence the effect was related to potassium. Only ThriveR increased the amount of foliage.