Abstract:

Objective: Paracarophenax alternatus is a newly found miniature phoretic mite that has parasitic and lethal effects on the eggs of Monochamus alternatus, a main vector of pine wood nematode in China. This study aims to further understand the mite's habitat adaptability by investigating its phoretic characteristics by M. alternatus adults, and to evaluate its application potential in order to provide an important basis for establishing scientific filed application technique. Method: The indoor breeding, behavior observation, simulation experiment and field trapping investigation were conducted to study the distribution of the mites on the body surface of M. alternatus adults, the transmitting law during M. alternatus adults feeding, oviposition and co-breeding, and the amount of the mites carried by the M. alternatus adults trapped in the field. Result: The female adult mites were taken as phoretic state, P. alternatus actively transferred and aggregated in the ventral grooves of M. alternatus adults, and the number of mites carried by both male and female M. alternatus adults on the metathorax was the most. During the feeding process, each female and male M. alternatus adult transmitted an average of 3.0 and 2.9 P. alternatus to the pine branches in 1 hour, respectively. During the process of ovipositon, an average of 6.5 P. alternatus were able to be transmitted to the egg-laying site per egg laid. The mites were able to be transmitted from one to another of M. alternatus adult. An average 39.3 P. alternatus individuals were transmitted from mites-carrying M. alternatus to non mites-carrying M. alternatus, and after 2 days of co-breeding, the transmitted percentage was 8.1%. After 10 days of co-breeding, the transmitted number and percentage increased to 192.2 and 38.5%, respectively. In different feeding combinations, the transmitted number and percentage were the highest in the M. alternatus gender combination from mites-carrying M. alternatus males to non mites-carrying M. alternatus females. In the inhabited forest of P. alternatus, the mites-carrying percentage of M. alternatus adults is 55.0%, of which 39.2% were male and 61.6% were female, and the latter was significantly higher than the former. A single M. alternatus male adult carried an average of 247.3 mites, and a single female adult carried an average of 291.4 mites. There was no significant difference between these two. Conclusion: P. alternatus can actively aggregate on the M. alternatus adults, be transferred among different individuals, and then accelerate diffusion and expansion of populations through feeding, oviposition and other living activities of M. alternatus adults. The phoresy characteristics of the mite do not only reflect P. alternatus' population habitat adaptability, but also show its strong a bio-control potential. In the future field practices, it is recommended to release high-density P. alternatus population in the activity area of M. alternatus adults or eggs, using its phoresy characteristics to exert its biological control effect.

Key words: Paracarophenax alternatus, Monochamus alternatus, phoresy, Bursaphelenchus xylophilus