INFLUENCE OF ROOT-KNOT NEMATODES ON THE DECLINE IN VIGOR OF THE RED SPANISH VARIETY OF PINEAPPLE IN PUERTO RICO

Abstract

1. Pineapple plants planted in nematocide-treated soil, showed greener, stockier, and more vigorous growth than those growing in plots not so treated. The mean yield obtained from pineapple plants cultivated on the nematocide-treated soil was from 10.78 to 15.92 tons of fruit per acre. The Checks produced a mean yield of 6.24 tons per acre. 2. The results of the soil treatments indicated that Dowfume W-85 was superior to all other nematocides, irrespective of spray treatments. The Dowfume W-85 soil treatment combined with iron sulfate sprays produced the heaviest yields, 17.92 tons per acre. 3. The mean number of slips produced per acre obtained with the different soil treatments varied from 22,974 to 47,432, in contrast with 11,939 produced in the Check plots. The highest yield of 47,432 slips per acre corresponds to treatment with Dowfume W-85. 4. The mean number of suckers produced per acre, obtained with the nematocide-treated plots ranged from 9,357 to 13,339, in contrast with a mean yield of 4,517 produced in the Check plots. Dowfume W-85 was best with a mean yield of 13,337 suckers per acre. This treatment produced 15,701 suckers per acre when combined with iron sulfate sprays, and the percentage of larger fruits (sizes 12 to 36) was 74 (see table 9) as compared with the Check at 40. 5. The percentage of large fruits was higher in all plots treated with nematocides.