The host shift of Bactrocera dorsalis: early warning of the risk of damage to the fruit industry in northern China

Agricultural ecosystems are extremely vulnerable to invasions by various pestiferous organisms. Bactrocera dorsalis is one of the invasive insect pests on fruits and vegetables in southern China, gradually spreading northward in past decades. To clarify its risk to damage to the northern fruits, the performance and fitness of the first and third reared generations of B. dorsalis were studied with two-sex life table on northern fruits (apples and peaches as dominant fruits) and southern fruit (oranges as appropriate host). Furthermore, the preference of host and oviposition selection were also conducted in laboratory experiments. Also, the CLIMEX model was used to comprehensively assess its potential risk in northern orchards. It was found that B. dorsalis had high fitness on peaches and good-performance on apples within first and third generations. This implies that peaches and apples are liable to become one of its most favorable hosts in northern orchards. The simulation based on CLIMEX model showed B. dorsalis had a high population growth potential in summer and autumn in some regions of northern China, where the life cycle can be completed and two simulated occurrence peaks last two to three months from early June to late July and from mid-late August to early September, long enough to cause serious harm. Projection for its distribution by 2080 indicated that the suitable area for B. dorsalis would further expand northward. Innate ability of B. dorsalis in flight, adaptability and wide range of hosts is conducive to its diffusion into new habitats, and external causes including harm concealment within fruits, frequent transportation were also discussed. Therefore, monitoring of B. dorsalis occurrence in northern orchards is necessary, combined with strict quarantine and control efforts, to avoid its further expansion and the consequent economic losses.