Amelia Tudoran1,2, Göran Nordlander1, Anna Karlberg3, Adriana Puentes1. 1. Department of Ecology, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden. 2. Department of Plant Protection, University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca (USAMV Cluj Napoca), Cluj-Napoca, Romania. 3. SweTree Technologies AB, Umeå, Sweden.
Abstract
BACKGROUND: The pine weevil (Hylobius abietis) is a major forest regeneration pest causing high levels of seedling mortality and economic losses. Current management relies on silviculture, stem coatings and insecticides. Here we evaluated for the first time the effects of Bacillus thuringiensis (Bt) strains on H. abietis adults: two producing the Coleoptera-targeted toxins Cry3Aa (Bt tenebrionis NB-176) and Cry8Da (Bt galleriae SDS-502), and one producing the Diptera-targeted Cry10A (Bt israelensis AM65-52). Choice and nonchoice assays using individual and mixtures of Bt formulations, containing these strains respectively, were conducted. RESULTS: We found that Bt had toxic and lethal effects on H. abietis, but effects varied with strain and formulation concentration. The Diptera-targeted Bt israelensis had the most negative effects on weevil weight, feeding and mortality (70-82% feeding reduction, 65-82% greater mortality than control), whereas the effect was lower for the Coleoptera-specific Bt tenebrionis (38-42%; 37-42%) and Bt galleriae (11-30%; 15-32%). Reduced weevil feeding was observed after 3 days, and the highest mortality occurred 7-14 days following Bt exposure. However, we found no synergistic toxic effects, and no formulation combination was better than Bt israelensis alone at reducing consumption and survival. Also, pine weevils were not deterred by Bt, feeding equally on Bt-treated and non-Bt treated food. CONCLUSION: There is potential to develop forest pest management measures against H. abietis that include Bt, but only the Diptera-targeted Bt israelensis would provide effective seedling protection. Its Diptera-specificity may need reconsideration, and evaluation of other Bt strains/toxins against H. abietis would be of interest.
BACKGROUND: The pine weevil (Hylobius abietis) is a major forest regeneration pest causing high levels of seedling mortality and economic losses. Current management relies on silviculture, stem coatings and insecticides. Here we evaluated for the first time the effects of Bacillus thuringiensis (Bt) strains on H. abietis adults: two producing the Coleoptera-targeted toxins Cry3Aa (Bttenebrionis NB-176) and Cry8Da (BtgalleriaeSDS-502), and one producing the Diptera-targeted Cry10A (Btisraelensis AM65-52). Choice and nonchoice assays using individual and mixtures of Bt formulations, containing these strains respectively, were conducted. RESULTS: We found that Bt had toxic and lethal effects on H. abietis, but effects varied with strain and formulation concentration. The Diptera-targeted Btisraelensis had the most negative effects on weevil weight, feeding and mortality (70-82% feeding reduction, 65-82% greater mortality than control), whereas the effect was lower for the Coleoptera-specific Bttenebrionis (38-42%; 37-42%) and Btgalleriae (11-30%; 15-32%). Reduced weevil feeding was observed after 3 days, and the highest mortality occurred 7-14 days following Bt exposure. However, we found no synergistic toxic effects, and no formulation combination was better than Btisraelensis alone at reducing consumption and survival. Also, pine weevils were not deterred by Bt, feeding equally on Bt-treated and non-Bt treated food. CONCLUSION: There is potential to develop forest pest management measures against H. abietis that include Bt, but only the Diptera-targeted Btisraelensis would provide effective seedling protection. Its Diptera-specificity may need reconsideration, and evaluation of other Bt strains/toxins against H. abietis would be of interest.
Authors: Juraj Galko; Michal Lalík; Slavomír Rell; Christo Nikolov; Marek Barta; Ján Pittner; Silvia Hyblerová; Milan Zúbrik; Andrej Kunca; Jozef Vakula; Andrej Gubka; Jaroslav Holuša Journal: Sci Rep Date: 2022-06-11 Impact factor: 4.996