Invasive species' facilitation, or benefiting, of native species is rarely considered in biological invasion literature but could have serious economic consequences should a non-native herbivore facilitate injury by a native pest of high-value crops. Japanese beetle (JB), Popillia japonica, a polyphagous scarab, facilitates feeding by the obligate fruit-feeding native green June beetle (GJB), Cotinis nitida, by biting into intact grape berries that GJB, which has blunt spatulate mandibles, is otherwise unable to exploit. Here, we show JB further facilitates GJB by contaminating fruits with yeasts, and by creating infection courts for yeasts associated with GJB, that elicit volatiles exploited as aggregation kairomones by GJB. Traps baited with combinations of grapes and beetles were used to show that fruits injured by JB alone, or in combination with GJB, become highly attractive to both sexes of GJB. Such grapes emit high amounts of fermentation compounds compared with intact grapes. Beetle feeding on grape mash induced the same volatiles as addition of winemaker's yeast, and similar attraction of GJB in the field. Eight yeast species were isolated and identified from JB collected from grapevine foliage. Establishment and spread of JB throughout fruit-growing regions of the United States is likely to elevate the pest status of GJB and other pests of ripening fruits in vineyards and orchards.Cotinis nitida ͉ facilitation ͉ invasive species ͉ Popillia japonica ͉ tritrophic interaction

Adult activity of native green June beetles, Cotinis nitida L., and invasive Japanese beetles, Popillia japonica Newman, peaked in late July in Kentucky coincident with later stages of veraison in early- and midseason ripening grape (Vitis spp.) cultivars. Most C. nitida feeding aggregations sampled on clusters of early-ripening grapes in the research vineyard also contained Japanese beetles. Assays showed C. nitida generally are unable to bite into intact ripe grape berries, whereas Japanese beetles readily do so. The beetles' disparate biting ability is likely because of differences in their mandibles, which are sharply pointed and opposable in P. japonica compared with C. nitida mandibles that are bluntly spatulate, do not meet at their tips, and seemingly are only suited for feeding on fruit pulp or other soft food. Japanese beetles were shown to facilitate C. nitida feeding by biting through the skin and providing access to the soft berry pulp. Juice from early- and midseason ripening grape cultivars with relatively high sugar content elicited the greatest feeding by P. japonica. A scenario is suggested wherein Japanese beetles open wound sites and contaminate fruits with yeasts that induce fermentation volatiles that attract C. nitida. Japanese beetles had difficulty biting berries of Sunbelt, a late-ripening cultivar. Phenological resistance, i.e., planting cultivars that ripen after peak flight, could be an effective management strategy. Establishment of P. japonica in grape-growing regions of the southeastern United States will likely elevate the pest status of C. nitida in vineyards.

Adult activity of native green June beetles, Cotinis nitida L., and invasive Japanese beetles, Popillia japonica Newman, peaked in late July in Kentucky coincident with later stages of veraison in early- and midseason ripening grape (Vitis spp.) cultivars. Most C. nitida feeding aggregations sampled on clusters of early-ripening grapes in the research vineyard also contained Japanese beetles. Assays showed C. nitida generally are unable to bite into intact ripe grape berries, whereas Japanese beetles readily do so. The beetles' disparate biting ability is likely because of differences in their mandibles, which are sharply pointed and opposable in P. japonica compared with C. nitida mandibles that are bluntly spatulate, do not meet at their tips, and seemingly are only suited for feeding on fruit pulp or other soft food. Japanese beetles were shown to facilitate C. nitida feeding by biting through the skin and providing access to the soft berry pulp. Juice from early- and midseason ripening grape cultivars with relatively high sugar content elicited the greatest feeding by P. japonica. A scenario is suggested wherein Japanese beetles open wound sites and contaminate fruits with yeasts that induce fermentation volatiles that attract C. nitida. Japanese beetles had difficulty biting berries of Sunbelt, a late-ripening cultivar. Phenological resistance, i.e., planting cultivars that ripen after peak flight, could be an effective management strategy. Establishment of P. japonica in grape-growing regions of the southeastern United States will likely elevate the pest status of C. nitida in vineyards.

Foliar loss from JB feeding can set back establishment and productivity of young grapevines. Nevertheless, many growers can reduce spray frequency without compromising the benefits of JB management. Even susceptible cultivars can tolerate low to moderate (<20%) levels of defoliation, and some are resistant enough to be grown without treating for JB.

Changes in fruit characteristics associated with ripening increase the vulnerability of crops to insect depredation, making it difficult for growers to protect cultivated fruits from pest injury close to harvest. This study evaluated phenological resistance, the use of cultivars that ripen before or after peak pest activity, for reducing injury to grapes (Vitis spp.) by the green June beetle (GJB) (Cotinis nitida), an obligate feeder on soft, ripe fruits. Accumulation of sugars, softening of berry skins and recruitment of GJB feeding aggregations were monitored on replicated vines of early‐, mid‐ and late‐season ripening cultivars that require from 85 to 125 growing days from bloom to harvest. GJB flight peaked in late July and early August coinciding with later stages of veraison of early‐season ripening cultivars which recruited numerous GJB feeding aggregations resulting in >95% crop loss. Small (1–2 weeks) phenological differences between mid‐season ripening cultivars and peak GJB flight translated to marked differences in injury, whereas cultivars that ripened in mid‐August or later, after GJB flight had waned, sustained little or no damage. Trapping experiments confirmed that the tougher berries and low sugar content of less‐ripe fruit clusters inhibited beetle feeding and induction of yeast‐mediated volatiles responsible for GJB host‐location. Implications of these findings for sustainable or organic management of GJB and other near‐harvest fruit pests are discussed.