Possible alternatives to DDT for control of plague thrips in apples

Abstract

Seven insecticides were tested as possible alternatives to DDT for control of plague thrips, Thrips imaginis, in Granny Smith apples in a field trial at Bathurst Agricultural Research Station in October 1971. Thrips were moderately plentiful but the infestation was insufficient to impose severe pressure on the treatments. None of the treatments was as effective as the standard 0.1 per cent a.i. DDT. However, 0.1 per cent a.i. TDE, 0.066 per cent a.i. endosulfan, 0.06 per cent a.i. maldison, 0.2 per cent a.i. methoxychlor and 0.1 per cent a.i. tetrachlorvinphos were sufficiently effective to be considered as possible alternatives. Chlorcam 0.1 5 per cent a.i. and phosalone 0.06 per cent a.i. were less effective in reducing thrips numbers but phosalone was as effective as some other treatments in reducing damage to styles. In a separate sub-trial, using Granny Smith, Democrat and Jonathan varieties, maldison, endosulfan and methoxychlor were less repellent to bees than was the standard DDT treatment. TDE and tetrachlorvinphos were not significantly less repellent than DDT. The only significant tree injury was a severe browning and premature drop of petals on all three varieties when TDE and methoxychlor were sprayed at full bloom.