POPULATION FLUCTUATIONS OF ROTYLENCHULUS-RENIFORMIS IN PINEAPPLE FIELDS AND THE EFFECT OF THE NEMATODE ON FRUIT YIELD

Population fluctuations of Rotylenchulus reniformis were studied in th ree pineapple fields on the island of Oahu. Hawaii, in nematicide-trea ted and untreated plots. Soil population densities of the nematode rem ained low (<200/250 cm(3) of soil) for 6-9 mo after planting in all fi elds regardless of treatment. Nematode populations reached the carryin g capacity in each pineapple field within 12 mo after planting. Number s of R. reniformis decreased after newer induction but quickly resurge d. Nematodes negatively affected yield. A single preplant application of 1,3-dichloropropene (337 L/ha) increased fruit yield in the first h arvest over the untreated controls in all three fields. Postplant appl ication of fenamiphos (1.1 kg a.i./ha) resulted in highest yields by t he second harvest (8% more in one field and 25% more in another field) . Nematode control remains imperative for economical pineapple product ion in Hawaii, yet the long lag phase in nematode population developme nt that follows a new planting of pineapple perhaps could be exploited to enhance long-term control.