Bacterial metabolites as alternative pest management agents in pecan

Pecan growers face increasing difficulty in pest management due to limitations of existing strategies. Some key pests, such as the black pecan aphid (Melanocallis caryaefoliae), have developed resistance to synthetic insecticides, and numerous old-class chemicals are restricted to use because of environmental concerns. Entomopathogenic nematodes of the families Heterorhabditidae and Steinernematidae, carrying the symbiotic bacteria Photorhabdus spp. and Xenorhabdus spp., respectively, can be utilized for biocontrol, but their efficacy depends on environmental conditions. Previously, culture broths of Photorhabdus luminescens and Xenorhabdus bovienii were shown to be lethal towards M. caryaefoliae as well as the blackmargined aphid (Monellia caryella). However, the carrier used for bacterial culture also showed lethal effects. The goal of this study is to test the insect toxicity of bacterial metabolites separated from bacterial cells and the carrier against various pecan pests. The four target pests will include M. caryaefoliae, the brown stink bug (Euschistus servus), Phylloxera spp., and the hickory shuckworm (Cydia caryana). Pests will be treated with various concentrations of metabolites from both bacteria, and their mortality will be evaluated after seven days. The bacterial metabolites are expected to cause high pest mortality, varying with pest species and bacterial strains, and serve as viable alternatives to synthetic insecticides in managing pecan pests.