Evidence for Resistance toBacillus thuringiensis(Bt) subsp.kurstakiHD-1,Btsubsp.aizawaiand Abamectin in Field Populations ofPlutella xylostellafrom Malaysia

Abstract

BBSRC IACR Rothamsted, Harpenden, Hertfordshire AL5 254, UK Abstract: The efficacy of Bacillus thuringiensis (Bt) subsp. kurstaki HD-1 ('Dipel'@; Btk; CryIA & CryII) and Bt. subsp. aizawai('Florbac'@; Bta; CryIA & CryIC) was assessed against larvae from various field populations of Plutellu xylostella (F2 generation) collected in the Cameron Highlands, Malaysia in April 1994 and a lowland population (SERD 2; F10 generation) collected in December 1993. Evidence of resistance to Btk and to a lesser extent Bta is reported in these populations (LC,, Toxicity Ratios [TR] = 3-14 and 2-8 respectively), most notably in SERD 2. The first recorded evidence of resistance to abamectin (TR = 17-195-fold) in field populations of P. xylostellu is also reported. In an unselected sub-population of SERD 2, the TR values for Btk, Bta and abamectin declined 2-to 3-fold ( P < 0.01) over six generations in the laboratory (F10-F16) while in sub-populations of SERD 2 selected with these products there was a significant ( P < 0.01) increase in the TR (15-, 3-and 2.5-fold respectively) when compared with the F10 generation. This suggests the presence of marked resistance to Btk and some resistance to Bta and abamectin. There is also evidence of slight cross-resistance to Btk in the Bta-selected sub-population but no evidence for the reverse selection of resistance or for cross-resistance between Btk and abamectin. Concurrent selection studies (Fll-Fl5) with another sub-population of SERD 2 demonstrated resistance to the acylurea insect growth regulator, teflubenzuron ('Nomolt'@) (29-fold increase in TR). Based on the selection experiments with SERD 2, estimates of realised heritability (h2) of resistance gave very high values for teflubenzuron and Btk (c.0.7) and moderate values for abamectin and Bta (c.0.3). The results are discussed in relation to integrated pest management (IPM) and insecticide resistance management (IRM) strategies for P. xylostella.

Genetic and Biochemical Approach for Characterization of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Field Population of the Diamondback Moth, Plutella xylostella

“…kurstaki-SEL subpopulation showed moderate (Ͼ100-fold) resistance to B. thuringiensis subsp. kurstaki which is comparable to that of other Malaysian strains of P. xylostella (23,40). The B. thuringiensis subsp.…”

“…The B. thuringiensis subsp. aizawai-SEL population showed a level of resistance (26-fold) similar to that of a Cameron Highland population collected in 1993 (23,58).…”

“…To date, reports of field resistance to B. thuringiensis subspp. kurstaki and aizawai (23,36,40,44,58) have been limited to the diamondback moth, Plutella xylostella.…”

Classificação de cultivares de brássicas com relação à resistência à traça-das-crucíferas e à presença de glucosinolatos

“…No Brasil, a resistência de P. xylostella a inseticidas foi relatada por Castelo Branco & Gatehouse (1997), em relação aos diferentes princípios ativos comumente utilizados em seu controle. Recentemente, Castelo Branco & Melo (2002) estudaram a resistência apresentada por populações de traça-das-crucíferas a abamectin, com base nos trabalhos de Zhang et al (2001) e Iqbal et al (1996), que haviam observado resistência dessa praga àquele inseticida, na China e Malásia, respectivamente.…”

Insecticide resistance in populations of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), from the state of Pernambuco, Brazil

“…In China (Zhang et al 2001, Pu et al 2010 and Malaysia (Iqbal et al 1996), where abamectin is registered for P. xylostella control, cases of ield resistance have already been reported. In Brazil, resistance to this insecticide has been identi ied in populations of P. xylostella from both the Distrito Federal and Pernambuco State (Castelo Branco & Melo 2002, Oliveira et al 2011.…”