ECOLOGICAL SIGNIFICANCE OF DORMANCY IN PLANT PARASITIC NEMATODES .5. OCCURRENCE AND SURVIVAL OF DISPERSAL FORMS OF PINE WOOD NEMATODE, BURSAPHELENCHUS-LIGNICOLUS

The dispersal 3rd-stage larvae (L3) of B. lignicolus began after 3-5 mo. on fungal mats of Botrytis cinerea without being subcultured and constituted almost 100% of the surviving nematodes after 10 mo. Extended monoxenic culturing of the nematodes brought about a decrease in the survival under starvation and consequently decreased the production of the L3. 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 L3 after being left without subculture. The molting of L3 in water to the dispersal 4th-stage larvae (L4) was positively correlated to the developmental stages of the beetle at the collection time of worms. Most L3 left in the pupal chambers for 20 days after the removal of the insects molted into the propagative L4, irrespective of pupation. L3 and L4 were both still viable after 100 days starvation. Live L4 were recovered from dried cadavers of adult beetles after 6 mo. The L3 seemed relatively better able to survive under starvation, and the L4 under dryness.