Occurrence and Survival of the Dispersal Forms of Pine Wood Nematode, Bursaphelenchus lignicolus MAMIYA and KIYOHARA : Ecological significance of dormancy in plant parasitic nematodes. V.

Abstract

The dispersal 3rd-stage larvae (LIIIs) of B. lignicolus began to occur after 3 to 5 months on the fungal mat of Botrytis cinerea without being subcultured and constituted almost 100% of the surviving nematodes after 10 months. However, extended monoxenic culturing of the nematodes brought about a decrease in the survivability under the starvation and consequently decreased the production of the LIIIs. Addition of fatty extracts from larvae and pupae of a cerambycid beetle. Monochamus alternatus, gave rise to an increase in surviving nematodes and in the LIIIs after being left without subculture. The molting of the LIIIs in water to the dispersal 4th-stage larvae (LIVs) was positively correlated to the developmental stages of the beetle at the collection time of worms. However, most of LIIIs, which had been left in the pupal chambers for 20 days after the removal of the insects, molted into the prpagative 4th-stage larvae (L4s), irrespective of the pupation of the insect. LIIIs and LIVs were both still viable after 100 days under starvation. The live LIVs were recovered from dried cadavers of adult beetles after 6 months. The LIIIs seem to be relatively better able to surive under starvation, whilst the LIVs under dryness.