Some exotic ambrosia beetles are damaging pests in ornamental nurseries. Xylosandrus germanus (Blandford) is the most problematic ambrosia beetle in Ohio nurseries. Movement of X . germanus in nurseries has not been characterized, and knowledge is lacking on whether infestations originate from within nurseries or surrounding habitats. Flight activity of X . germanus was monitored in nurseries and adjacent wooded areas to determine the source of beetles infesting nurseries, and characterize their movement within nurseries. Ethanol-baited bottle traps were positioned within wooded areas adjacent to commercial nurseries and within nurseries at various distances from the nursery woodlot interface. Flight activity of overwintered X . germanus occurred in wooded areas adjacent to nurseries before occurrence within nurseries. There was a direct relationship between degree-days and the distance from woodlots when X . germanus were first found in traps in spring, with earlier captures closest to wooded areas and latest ones furthest away into the nursery. X. germanus appeared to move into nurseries from adjacent wooded areas, with numbers trapped within nurseries decreasing with distance away from wooded areas. Trees in the interior of nurseries would appear to be subjected to less attack pressure than trees near the nursery border. Intercepting beetles as they move into nurseries might be an effective strategy to reduce attack pressure on valuable trees.

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.

Beauveria bassiana (Balsamo) Vuillemin infects a wide variety of insects, including the green peach aphid, Myzus persicae (Sulzer). Volatiles emitted from B. bassiana can act as semiochemical attractants or repellents, with most responses reported to date resulting in insects avoiding B. bassiana. Since insects can detect ‘enemy-specific volatile compounds’, we hypothesized the preference behavior of M. persicae would be influenced by volatile emissions from B. bassiana. We conducted Petri dish and Y-tube olfactometer bioassays to characterize the preference of M. persicae to B. bassiana strain GHA. During Petri dish bioassays, more apterous and alate M. persicae were recorded in the vicinity of agar colonized by B. bassiana compared to agar, or Fusarium proliferatum (Matsushima) Nirenberg and Ambrosiella grosmanniae Mayers, McNew, & Harrington as representatives of nonentomopathogenic fungi. Petri dish bioassays also determined that apterous and alate M. persicae preferred filter paper saturated with 1 × 10⁷, 1 × 10⁶, and 1 × 10⁵ B. bassiana conidia/ml compared to Tween 80. Y-tube bioassays documented that more apterous and alate M. persicae oriented upwind to volatiles from B. bassiana mycelia compared to agar. Apterous and alate Myzus persicae were also preferentially attracted to 1 × 10⁷ and 1 × 10⁶ B. bassiana conidia/ml compared to Tween-80 during Y-tube bioassays. These results complement a previous finding that the mosquito Anopheles stephensi (Diptera: Culicidae) Liston is attracted to volatiles from B. bassiana. Future studies aimed at characterizing the olfactory mechanism leading to the attraction of M. persicae to B. bassiana could aid in optimizing lure-and-kill strategies.

The ambrosia beetles Xylosandrus germanus (Blandford) and Xylosandrus crassiusculus (Motschulsky) bore into flood-stressed trees to establish colonies, but the influence of flooding duration on colonization is unknown. This relationship was examined by flooding trees for various time periods and evaluating colonization. In one experiment, X. germanus bored into 20 dogwood (Cornus florida L.) trees during a 3-d flood treatment. Ten trees dissected that season had no offspring present in tunnels; the remaining trees appeared healthy and bloomed the following spring. In another experiment, dogwood trees were flooded for 3 or 7 d and then dissected to assess colonization. The incidence of superficial (short unbranched) and healed (callus tissue in entrance) tunnels was greater in the 3-d trees, while the incidence of tunnels with X. germanus or offspring was greater in the 7-d trees. Four experiments (three in Ohio and one in Virginia) had flood treatments of 0 (nonflooded), 3, 5, 7, and 10 d. Numbers of tunnel entrances, tunnels with X. germanus, and incidence of tunnels with offspring or live foundresses tended to increase as flood duration increased on apple (Malus × domestica Borkh.), dogwood, and redbud (Cercis canadensis L.) in Ohio and redbud in Virginia. Nonflooded trees in Ohio had no boring activity, but ambrosia beetles bored into three nonflooded trees in Virginia. Indicators of unsuccessful colonization, such as superficial tunnels and healing, decreased as flood duration increased. These results suggest tree crops may recover from boring by ambrosia beetles following short-duration flood events, and not necessarily require culling.