Immediate and delayed mortality of the pine processionary moth treated by Bacillus thuringiensis var. kurstaki 3a 3b in the sub-Saharian pine reforestations

Abstract

In the reforestations of Pinus halepensis, situated in the Algerian sub-Saharian region, 1 500 hectares were treated by an aerial application against the third and fourth larval stage of the pine processionary moth. The microbiological insecticide used contained Bacillus thuringiensis var. kurstaki 3a 3b. The immediate mortality was evaluated by sampling colonies of caterpillars 7 and 14 days after the application of the treatment, and the delayed mortality was determined firstly for caterpillars after 80 and 100 days in the field and secondly for pupae by collecting and rearing surviving caterpillars to Btk at the end of the larval cycle during the nomadic period. The mortality rate of the caterpillars increased between 7 and 100 days and averaged 93 % in the treated zone. The caterpillars exposed to the treatment were more contaminated by Beauveria bassiana and infested by the larval-pupal parasitoïds Erigorgus femorator Aub. (Hym, Ichneumonidae) and Phryxe caudata Rond. (Dip., Tachninidae). The sex ratio of surviving moths was 1.7 in favour of males which suggests that female caterpillars are more vulnerable to Btk.

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