Effects of permethrin on ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) in ornamental nurseries.

Exotic ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), such as Xylosandrus crassiusculus (Motschulsky), Xylosandrus germanus (Blandford), and Xylosandrus compactus (Eichoff) are serious pests in southeastern ornamental nurseries. Preventative pyrethroid trunk sprays effectively reduce boring damage. However, it is unclear how pyrethroids such as permethrin prevent attack. Thus, the objective was to determine how permethrin-treated bolts interact with invading ambrosia beetles. In 2022, a study with 2 independent trials was conducted in a nursery on red maple (Acer rubrum L.), bolts during March and April, respectively. The treatments were (i) nonbaited, nontreated bolt, (ii) ethanol baited bolt, (iii) nonbaited bolt + glue [painted on bolt], (iv) ethanol baited bolt + glue, (v) ethanol baited bolt + glue + permethrin, (vi) ethanol baited bolt + glue + permethrin + verbenone, and (vii) ethanol baited bolt + glue + verbenone. Ambrosia beetles trapped on glue, beetles which fell into the pail with soap solution under the bolts, and entry holes on bolts were quantified. Permethrin prevented beetle attacks but did not reduce the number of ambrosia beetles landing on the treated bolts. Verbenone reduced ambrosia beetles from landing on the bolts but did not prevent boring into bolts. The numbers of ambrosia beetles in soapy water were not significantly different among treatments. Ambrosia beetles are landing on permethrin-treated bolts but not boring into the bolts, implying that fresh permethrin residues may not be necessary for ambrosia beetle management.

Exploring risk factors for insect borer attack in Georgia's (USA) urban landscapes.

Urban trees are at risk of stress due to heat island effects and the increased proportion of impervious areas surrounding them. Among pests of trees, insect borers such as bark beetles (Coleoptera: Curculionidae) and flatheaded borers (Coleoptera: Buprestidae) are some of the most devastating, frequently colonizing stressed trees. The objective of this study was to explore the effects of biotic and abiotic risk factors on borer attacks on trees in urban areas. In the summer of 2021 and 2022, this study was conducted in 50 urban sites in Atlanta and Augusta, Georgia (USA). Specific factors explored include overall tree health, differentially warmer maximum and minimum temperatures of sites compared to surrounding areas, tree species, and the percentage of impervious surface surrounding trees. Generalized linear models and zero-inflated models explored how these factors were related to damage from these borers. The number of borer attacks on trees increased with higher percentage impervious area. As the two most commonly encountered trees, Acer rubrum was found to be significantly more susceptible to attack from borers than Ulmus parvifolia. Unhealthy trees were more likely to experience more frequent and more severe borer attack. Trees with increased impervious cover around them as well as those with differentially warmer daily maximum and minimum temperatures relative to surrounding were more likely to be attacked.