关键词: 松天牛小首螨, 松褐天牛, 松材线虫病, 生物学特性

Abstract:

Objective: Paracarophenax alternatus is a newly found parasitic mite species that can feed on and kill the eggs of Monochamus alternatus, the main vector of pine wilt disease in China. Clarification of its biological characteristics can provide a basis for the applications of this mite to control M. alternatus. Method: The behavioral habits, parasitism rate, development duration, fecundity and longevity of P. alternatus were investigated through indoor breeding and microscopic observation under controlled conditions. Result: P. alternatus is a phoretic mite and the adults usually attached on the thorax and abdomen of the adult of M. alternatus. Phoretic mites crawled into the oviposition grooves and then parasitized to kill the eggs of M. alternatus. P. alternatus reproduced as gamogenesis and viviparism mode. After parasitizing the egg, the abdomen of female adult mite gradually expanded into physogastry. The nymphs grew in the physogastry, and the adults crawled out from the physogastry one by one. The male adult mites crawled out first and then stayed aside the physogastry waiting for mating. The mating process lasted for 3-6 s commonly. Usually, a female mite reproduced only 1 to 2 male mites, and the rest were all females.The parasitism rate of P. alternatus to M. alternatus egg reached 80.85%, and all parasitized eggs became shriveled and died. Temperature played a significant role on the developmental duration, longevity and the physogastry volume of P. alternatus. With the increase of temperature, both development duration and longevity of P. alternatus significantly shortened. Averagely, the development duration was 6.9 d at 17 ℃ and then decreased to 2.2 d at 33 ℃. Its developmental threshold temperature was (10.44 ± 0.09) ℃, and the effective accumulated temperature was (46.28 ± 0.28) d·℃. The adult female mites could survive 70.3 d at 15 ℃ and 10.7 d at 30 ℃. The volume of the physogastry was 1.54 mm³ at 21 ℃, however, decreased to 0.72 mm³ at 17 ℃. P.alternatus showed a high fecundity, and each female adult reproduced averagely 71.2 offspring at 25 ℃, with a minimum of 14 and a maximum of 139. Its fecundity exhibited significantly positive correlation with the volume of its physogastry. The physogastry with the volume less than 1.0 mm³ was able to just reproduce averagely 32.2 offspring, however, the physogastry with the volume more than 3.0 mm³ could reproduce averagely 110.9 offspring. Conclusion: P. alternatus is an important biological factor for controlling M. alternatus, due to its high parasitic and lethal rate on M. alternatus eggs, short developmental cycle, high fecundity and easy propagation and spread.

Key words: Paracarophenax alternatus, Monochamus alternatus, Bursaphelenchus xylophilus, biological characteristics