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 (L_IIIs) 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 L_IIIs. 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 L_IIIs after being left without subculture. The molting of the L_IIIs in water to the dispersal 4th-stage larvae (L_IVs) was positively correlated to the developmental stages of the beetle at the collection time of worms. However, most of L_IIIs, 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. L_IIIs and L_IVs were both still viable after 100 days under starvation. The live L_IVs were recovered from dried cadavers of adult beetles after 6 months. The L_IIIs seem to be relatively better able to surive under starvation, whilst the L_IVs under dryness.