Use of the plant growth regulator chlormequat chloride to control the aphid Hyperomyzus lactucae on black currants

A single application of chlormequat chloride at 2500 ppm reduced the density of Hyperomyzus lactucae on black currants below that at which damage was caused. This treatment had no short-term effects on the aphid predators present, but did affect interactions between the aphids, their host and the predators. There were no effects on yield in the year of the experiment, but in the following year bushes which had been treated gave considerably higher yields. This increase was attributed both to direct action of the chlormequat chloride and to indirect effects through the reduction of aphid density. Prospects for the use of plant growth regulators as dual-function compounds in integrated control programmes are discussed.