Injury to young cashew plants, Anacardium occidentale L., by the red-banded thrips Selenothrips rubrocinctus Giard (Thysanoptera: Thripidae)

Abstract

The damage caused to young cashew plants, — Anacardium occidentale L. — by the red-banded thrips, Selenothrips rubrocinctus Giard was studied with the objective of establishing the economic injury threshold of this insect on the crop to effect a timely control. Six infestation levels (0, 40, 80, 160, 240 and 320) of adult thrips were used on 6-week-old cashew seedlings in a randomized complete block design of five replicates. The results showed that the mean leaf number and shoot weight bore significant linear relationships ( P<0.001) (without detectable higher power components) to increased number of thrips. Damage by up to 160 adult thrips on 6-week-old cashew plants did not differ significantly from the control at P<0.05. On the other hand, infestation rates of 240 thrips and above caused significant defoliation and shoot weight loss when compared with the control. The need to spray chemical insecticides to control thrips on the basis of pest numbers as against spraying to a schedule is discussed.