Susceptibility of Grapholita molesta (Busck, 1916) to formulations of Bacillus thuringiensis, individual toxins and their mixtures

Abstract

The Oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide, such as peach and apple. Bacillus thuringiensis has been shown to be an efficient alternative to synthetic insecticides in the control of many agricultural pests. The objective of this study was to evaluate the effectiveness of B. thuringiensis individual toxins and their mixtures for the control of G. molesta. Bioassays were performed with Cry1Aa, Cry1Ac, Cry1Ca, Vip3Aa, Vip3Af and Vip3Ca, as well as with the commercial products DiPel® and XenTari®. The most active proteins were Vip3Aa and Cry1Aa, with LC values of 1.8 and 7.5ng/cm, respectively. Vip3Ca was nontoxic to this insect species. Among the commercial products, DiPel® was slightly, but significantly, more toxic than XenTari®, with LC values of 13 and 33ng commercial product/cm, respectively. Since Vip3A and Cry1 proteins are expressed together in some insect-resistant crops, we evaluated possible synergistic or antagonistic interactions among them. The results showed moderate to high antagonism in the combinations of Vip3Aa with Cry1Aa and Cry1Ca.

Isolation and molecular characterization of Bacillus thuringiensis subsp. kurstaki toxic to lepidopteran pests Spodoptera spp. and Plutella xylostella

“…Different types of Cry toxins may interact synergistically to increase the mortality of target insects, and there have been attempts to evaluate the synergistic effect among the combinations of Bt insecticidal proteins. [53][54][55][56] To evaluate the synergistic effects between the Cry toxins, insecticidal activity tests against lepidopteran pests were performed with recombinant Bt strains by two different methods. One is cell pellet dry weight-based assay and the other is the Cry toxin concentration-based method (Fig.…”

Characterization of Bacillus thuringiensis isolates by their insecticidal activity and their production of Cry and Vip3 proteins

“…The toxicity of the affinity-purified Vip3Aa65 protein was tested against five important lepidopteran pests. For the sake of comparison, we included Vip3Aa16 as a reference protein which has been used in previous studies [ 22 , 23 , 41 , 42 ], which differs from Vip3Aa65 by 9 amino acid residues ( Table 7 ). Although both proteins were similarly toxic to G .…”

Spodoptera albula susceptibility to Bacillus thuringiensis-based biopesticides

“…Bt-based biopesticides can be a useful tool against pest outbreaks as reported by Broza et al (1991) and Polanczyk et al (2017) to S. exigua and Helicoverpa armigera, respectively. Furthermore, other virulence factors, such as spores and Vip toxins, can increase the Bt toxicity and delay the insect resistance development (Burges et al, 1976;Estruch et al, 1996;Crickmore, 2006;Raymond et al, 2013;Jakka et al, 2014;Ricietto et al, 2016). The results of our study emphasize the possibility of using Bt-based biopesticides against S. albula; however, the formulation must be carefully chosen.…”