Re-establishment and resurgence of plant-parasitic nematodes in fumigated pineapple fields at different elevations and irrigation regimes in Hawaii

Introduced or remnant populations of Meloidogyne javanica, Rotylenchulus reniformis, Helicotylenchus dihystera and Paratylenchus spp. in Hawaiian pineapple fields located at three elevations or subjected to two irrigation regimes were monitored following soil fumigation. Introduced populations of M. javanica established more readily at high-elevation than lower-elevation sites, and resident populations of Helicotylenchus, Rotylenchulus and Paratylenchus resurged readily at lower- but not at high-elevation sites. Despite variations in number of M. javanica introduced initially, resident as well as introduced nematodes multiplied subsequently to various specific levels at different localities. Generally, population densities of M. javanica and resident nematodes at a particular site were higher at time of ratoon- than plant-crop harvest, and In irrigated than non-irrigated plots. Fruit yields of the ratoon-crop were equal to or lower than the plant-crop, and were more affected in irrigated than in non-irrigated plots. Site location, irrigation and time of crop harvest were important factors influencing the rate as well as the final level of a nematode population build-up. The feasibility of exploiting these factors for nematode control should be further studied.