Observations on the effect of DDT formulations on the yellow tea mite, Hemitarsonemus latus (Banks), in Uganda

Abstract

The effect of DDT applied to cotton plants four times at 10-day intervals at a rate of 1 lb. active ingredient per acre per application against Hemitarsonemus latus Banks was studied at Serere Eesearch Station, Uganda. DDT applied as a 10 per cent, dust, or in a spray from a 50 per cent, wettable powder increased the damage caused by the mite, while DDT applied in a spray from a 25 per cent. miscible liquid decreased it.Another trial using a DDT miscible-liquid spray applied at intervals of 10, 15 and 20 days at 1 lb. active ingredient per acre per application demonstrated partial control of the mite. However, when spraying ceased, tea-mite damage increased. At the final count all spray intervals showed significantly less damage than the control and there was an over-all significant difference between spray treatments and the control. In both trials the number of mite-infested plants increased in an exponential manner with time.It is not considered that the present recommended practice of applying DDT four times, at 15-day intervals, in a spray from 25 per cent, miscible liquid at 1 lb. active ingredient per acre will cause an increase of the mite on peasant-grown cotton in Uganda, although it will only partially control any infestation of it that is present.