Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are destructive wood-boring insects of horticultural trees. We evaluated long-lasting insecticide netting for protecting stems against ambrosia beetles. Container-grown eastern redbud, Cercis canadensis, trees were flood-stressed to induce ambrosia beetle attacks, and deltamethrin-treated netting was wrapped from the base of the stem vertically to the branch junction. Trees were deployed under field conditions in Ohio, Virginia, Tennessee, and Mississippi with the following treatments: (1) flooded tree; (2) flooded tree with untreated netting; (3) flooded tree with treated ‘standard mesh’ netting of 24 holes/cm²; (4) flooded tree with treated ‘fine mesh’ netting of 28 holes/cm²; and/or (5) non-flooded tree. Treated netting reduced attacks compared to untreated netting and/or unprotected trees in Mississippi in 2017, Ohio and Tennessee in 2018, and Virginia in 2017–2018. Inconsistent effects occurred in Mississippi in 2018. Fewer Anisandrus maiche, Xylosandrus germanus, and Xyleborinus saxesenii were dissected from trees deployed in Ohio protected with treated netting compared to untreated netting; trees deployed in other locations were not dissected. These results indicate long-lasting insecticide netting can provide some protection of trees from ambrosia beetle attacks.

Dormancy accrual is an important process in mitigating the abiotic stressors of overwintering trees at ornamental nurseries, with frost-injured tree crops at heightened risk of ensuing biotic insect and disease attack. As mean global temperatures rise, overwintering nursery crops may lose dormancy earlier. Using potted eastern redbud (Cercis canadensis L.) trees placed under two types of shade cloth, under full sun, or in walk-in coolers, we measured stem, air and root zone temperatures, accrual of chill hours and mean time to bud break at two sites. While there was no significant difference between the two shade treatments, shade cloths did moderate both high and low temperatures to which trees were exposed. Differences in mean time to first bud break were observed from shaded trees versus those in full sun at each site. It may be useful to alter our shading design to continue protection from overnight lows while preventing excess warming from daytime highs, and thus promoting dormancy and preventing frost exposure in some regions, but further tests will be required. Species used in this study: eastern redbud (Cercis canadensis L.).