| Pine wilt disease (PWD), which is caused by Bursaphelenehus xylophilus, is one ofthe worldwide quarantined diseases. In China, the first record of PWN was in Nanjing in1982. Since then, it was spread to Anhui, Guangdong, Zhejiang, Shandong, Hongkong,Taiwan and several other provinces, killing a large number of pine trees with hugeeconomic losses, and threatening the forest production and ecological safety seriously. Inthis present paper, we selected emamectin benzoate, avermectin, milbemectin andthiacloprid, and compared their stressing effects on the reproduction and development ofB.xylophilus. The population development, egg-laying capability, egg hatchability,individual development progress, sexual ratio and body size of B. xylophilus wereinvestigated after being applied with sublethal doses of LC20in laboratory. In addition,mating behavior of B. xylophilus was investigated and, further more, the effect of chemicalstress from emamectin benzoate on the mating behavior of B. xylophilus was analyzed. Theresults are as followings:1. Among the four tested chemicals, emamectin benzoate was the most effective oneto depress the population increase of B. xylophilus. Compared to control, populationquantity, fecundity and egg hatchability of B. xylophilus decreased sharply from20850to411,24.33to3.50and84.03%to49.63%respectively with significantly difference inemamectin benzoate treatment. Moreover, the development progress was inhibited and thebody size was shortened significantly by emamectin benzoate.2. Avermectin and milbemectin also displayed nice sublethal effects by depressing thepopulation increase and inhibiting the development progress of B. xylophilus. But numberof eggs laid per female and egg hatchability were not affected by neither milbemectin noravermectin.3. Compared to others, however, thiacloprid had almost no stress on populationincrease, number of eggs laid per female, egg hatchability and body size of B. xylophilus,except slowing down its development progress.4. By observation with eyes and long-time microscope videos, we investigated anddescribed the mating behavior of B. xylophilus qualitatively. In addition, the behavioralfeatures of B. xylophilus in the mating process were analyzed quantitatively. About85.24%individuals could complete mating successfully for one time, and33.33%,16.67%and4.16%for two, three and four times respectively. Time length of copulation were9.52± 1.46,8.17±1.63,8.41±1.25and7.98±1.36min for four different times from the first tothe fourth respectively with no obvious difference.5. Compared to1♀+1♂treatment, times of mating behavior decreased from1.37±0.34to0.72±0.08and0.62±0.10and the mating successreduced from85.24%±6.75%to64.32%±5.91%and55.31%±4.23%respectively with significant differences for1♀+3♂and3♀+1♂treatments. In contrast, however, their time length of copulation wassignificantly prolonged. For the treatments of1♀+3♂,3♀+1♂and3♀+3♂, obviousintra-sexual competition and disturbance were observed during the mating process. Whenone male was copulating with one female, others would try to disturb them, like swingingbody violently to crash the mating male or female, even dragging one of them by trappingits body.6. After being treated with emamectin benzoate at the sublethal dosage of LC20, i.e.0.0461mg/L, mating quality of B. xylophilus was significantly compromised, indicated bythe shortened copulation time from9.21±1.3to5.63±0.62and, the increase of matingtimes from1.37±0.34to1.82±0.47with significant difference. In addition, theejaculation of male and egg-laying behavior of female were obviously depressed under thestress of emamectin benzoate, though there is no obvious change in mating success. |
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