Xylosandrus crassiusculus

This beetle is native to Asia, and has spread to other parts of the world as an invasive species in Africa, the Americas, Europe and Oceania.^[5] It was first reported in the southeastern United States in 1974, had reached Costa Rica by 1996, Panama by 2003, and Guatemala and northern Brazil by 2008. It appeared in Argentina in 2001, nearly a decade before it was detected in southern Brazil and Uruguay; as the latter two countries were vigilant, with long-term trapping programmes, the Argentine collection may represent a direct introduction from a non-American source, with the insects later spreading northwards up the coast.^[6]

Females mate with their siblings before leaving the galleries. Although males are flightless, females can fly and disperse to other potential host trees. Here they excavate tunnels and lay eggs. The larvae develop and enlarge the galleries and the female stays with the brood, overwintering there.^[5]

Although the larvae of ambrosia beetles develop in cavities in wood, the food of both adults and larvae is exclusively a symbiotic fungus which the female beetle introduces into the tunnels and galleries she excavates. In the case of Xylosandrus crassiusculus, the fungus has been identified as Ambrosiella roeperi. It has been shown that the beetle is attracted to the smell of this fungus, which may concentrate attacks on specific trees. The beetle can infest branches as small as 1.5 cm (0.6 in) across and trunks 2.5 to 6 cm (1.0 to 2.4 in) in diameter.^[5]

This beetle is polyphagous, infesting many species of host trees.^[7] It is usually restricted to stressed young trees and nursery stock, but sometimes attacks apparently healthy young trees. It additionally infests stacked timber, where it causes economic damage.^[6] In the United States, trees and shrubs infested include oak, cherry and crape myrtle, as well as pecan, peach, plum, persimmon, elm, sweet gum, magnolia, fig, buckeye and sweet potato.^[8] In Europe its host is the carob (Ceratonia siliqua), while in Israel, where the carob grows, its only known host is the Palestine oak (Quercus calliprinos).^[5]