Characteristics of the emergence of Monochamus alternatus, the vector of Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae), from Pinus thunbergii logs in Nanjing, China, and of the transmission of the nematodes through feeding wounds

Abstract

AbstractThe pine wood nematode (PWN), Bursaphelenchus xylophilus, which in China and East Asia is vectored by Monochamus alternatus, is the causal agent of pine wilt disease of Japanese black pine, Pinus thunbergii. The vector emergence and the transmission of nematodes through vector feeding on pine twigs were monitored during 2004 and 2005 in Nanjing, China. The emergence started from late April to the end of June and peaked from late May to early June. There were 438 and 927 adults collected in 2004 and 2005, respectively, and approximately 70% of the beetles emerged during the peak period. Visual estimation of the nematode burden on vectors by observation of the atrium of the first abdominal spiracle gave unreliable information. The percentage of beetles carrying PWN of the total number of emerged beetles was between 20 and 30%. Seventy percent of the nematodes were released from beetle cadavers after 3 days of extraction. The sex and longevity of the beetle had no significant relationship with the number of nematodes that remained in cadavers. Transmission of nematodes into pine twigs through beetle feeding started 10 days after emergence of the vector. The period of nematode transmission could last for up to 79 days after beetle emergence. Two types of nematode-transmission curve were found by measuring the number of nematodes transmitted into pine twigs per day. The unimodal pattern peaked between 3 and 6 weeks after adult emergence; the bimodal pattern had two transmission peaks: one between 2 and 3 weeks, and another between 5 to 7 weeks after beetle emergence.