TEMPORAL SYNERGISM

Temporal synergism is a concept invented by Graham Moores and Robin Gunning. Patents for the technology are held by Rothamsted Research and NSW DPI. Temporal synergism works on the principle that to be most effective, synergists need to have completely inhibited the defence enzymes of a pest before exposure to pesticide. The pest is then often in a hypersensitive state, and concentrations of pesticide that kill susceptible pests will usually kill even very resistant pests. Furthermore, susceptible pests will be killed by a concentration less than the standard dose.

When a synergist, e.g. PBO is applied to an insect, it often takes several hours to cross the cuticle and inhibit the esterases and oxidases. The pesticide will usually cross the cuticle faster than this, so will still be detoxified by the enzymes. However, if the synergist is applied first, allowed time to inhibit the enzymes prior to pesticide application, then the synergism factors can be extreme.

The figure (above left) shows that it takes around 5 hours for PBO to inhibit esterase activity in Helicoverpa armigera (cotton bollworm). it also shows that mortality is increased if application of insecticide is delayed by the same 5 hours after addition of PBO. The figure (above right) demonstrates the vast synergism facors that can be obtained using this process. In this example, 1000-fold less pirimicarb was required to kill resistant peach-potato aphids (Myzus persicae).

Clearly 2 applications of chemicals (synergist followed by pesticide hours later) is not feasible for most practical situations, so bespoke encapsulated formulations are used that give a burst-release of synergist followed a pre-determined time later by a release of pesticide.

This method allows control of resistant pests, or the use of less pesticide for controlling susceptible pests, with all the concomitant advantages that such a strategy brings to the environment.