Effects of biochar on ambrosia beetle attacks on redbud and pecan container trees

Abstract

Abstract Mitigating tree stress can be a valuable strategy to combat ambrosia beetles, such as the granulate ambrosia beetle, Xylosandrus crassiusculus (Motschulsky; Coleoptera: Curculionidae, Scolytinae) under nursery conditions. Biochar and kaolin clay are known for their stress-relieving properties but their indirect effects on ambrosia beetle in ornamental or pecan (Carya spp.) trees have not been determined. Although entomopathogenic fungi, Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) and Trichoderma spp. (Hypocreales: Hypocreaceae) have shown effectiveness against adult ambrosia beetles, their role in reducing tree attacks is unclear. Thus, the objective was to determine the effects of biochar, kaolin clay, permethrin (industry standard), and entomopathogenic fungi on reducing ambrosia beetle attacks on young redbud (Cercis canadensis L.; Fabaceae) and pecan trees. The treatments were biochar, kaolin clay, permethrin, biochar + permethrin, kaolin clay + permethrin, B. bassiana, Trichoderma spp., and a nontreated control. Compared to the nontreated trees, biochar and biochar + permethrin treatments significantly reduced ambrosia beetle attacks on redbud trees. Kaolin clay, permethrin, B. bassiana, and Trichoderma spp. did not significantly reduce the number of ambrosia beetle attack holes when compared with the nontreated trees. This suggests that biochar can reduce ambrosia beetle attacks on ornamental trees and should be further evaluated for longer-term effects for multiple seasons.