The history of the use of pyrethrum formulations to control Antestiopsis spp. on arabica coffee in Kenya is reviewed.

The material with which the present work was done comprised three distinct forms of Antestiopsis of doubtful taxonomic status; these were not observed to differ in their response to the insecticidal treatments used.

Laboratory experiments showed that Antestiopsis was highly susceptible to pyrethrum and that the addition of piperonyl butoxide, a pyrethrum synergist, did not affect this response.

Preliminary field experiments showed that concentrations of pyrethrins higher than those found effective in the laboratory were required. A hypothesis is advanced and established that this was due to a variable proportion of insects becoming paralysed and falling off the tree before acquiring a lethal dose.

These observations and experiments suggested a two-phase method of control, using pyrethrum as a non-persistent foliage spray at an economical but effective concentration of 0·005–0·006 per cent, pyrethrins, coupled with a 5 per cent. DDT or 0·5 per cent, dieldrin dust applied to the bole of the tree to form a persistent toxic barrier. The spray removed the bugs from the tree whilst the dust prevented the return of or killed those that had only received a sub-lethal dose of pyrethrum. It seemed unlikely that such a localised application of the persistent insecticide would have any appreciable effect on beneficial insects.

This two-phase treatment has been used successfully both in trials and in commercial practice for the control of Antestiopsis. When the initial population is in excess of 20 per tree, two spray applications and one dusting are necessary to effect control.