EFFECT OF BACTERIA ON THE BIOLOGY OF DIAMONDBACK MOTH (Plutella xylostella) ON CABBAGE (Brassica oleraceae VAR. capitata) CV. MIDORI

Abstract

The diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae)is the most important cabbage pest in Brazil. Its control includes the use ofchemicals and Bacillus thuringiensis, individually or combined in an integratedpest management program. Plant growth-promoting rhizobacteria (PGPR)may be an important and new alternative in biological control of P. xylostella.This work aimed to study the effects of PGPR on the biology of DBM oncabbage through two different periods May to July 2000 (raining season) andFebruary to May 2001 (dry season). Cabbage seeds cv. Midori were immersedfor 30 min in a A580 = 0.52 or 108 CFU/ml bacterial suspensions, driedovernight, planted in polystyrene trays and transplanted field to three plots ina randomized design. At different days after transplanting (DAT) leavescollected randomly were brought to the laboratory and 8cm Ø-discs wereplaced in a Petri dish over filter paper. Ten 1st instar DBM larvae grown inlaboratory conditions were placed to feed on each leaf disc. Beginning onthe third day, leaf disks were changed daily until pupation. It was analyzedlarval mortality (LM) and pupal viability (PV), larval (LD) and pupal (LP)duration. In both experiments LM and PV were significantly increased andreduced by strains ENF14 (Enterobacter cloacae), EN5 (Alcaligenes piechaudii)and EN4 (Kluyvera ascorbata). Values for LM reached 60% compared with1.7% in control. In the raining season the protection was observed from 63to 74 DAT. In the dry season the effect was reduced and anticipated to theperiod from 45 to 60 DAT.