Plant-parasitic nematodes associated with pomegranate (Punica granatum L.) in Jordan and an attempt to chemical control

Abstract

In an irrigated pomegranate (Punica granatum L.) orchard at Wadi Dhulail, Jordan, several of the trees showed symptoms of severe decline. These included stuntin£", poor vegetative growth, desiccation and defoliation of branches and yellowing of leaves (often with brown necrotic tips). Soil samples from this orchard contained large numbers of Helicotylenchus pseudorobustus (Steiner) Golden (up to 3,400 nematodes/100 ml of soil); Tylenchorhynchus clams Allen, Longidorus sp. and larvae of Meloidogyne spp. were also present, but were usually less numerous. Roots of some trees had galls and were sometimes distorted and necrotic; examination of root samples immersed in boiling lactophenol/cotton blue (3 mins) and then differentiated in clear lactophenol showed H. pseudorobustus, M. incognita (Kofoid et White) Chitw. and M. javanica (Treub) Chitw. in their feeding positions. Sampling in various districts in northwest Jordan revealed the presence of several plant-parasitic nematodes in the rhizosphere of pomegranate (Table I). A simple experiment with 16 trees at the Wadi Dhulail orchard was initiated in May, 1982 to assess the efficacy of Carbofuran for the control of soil populations of nematodes. Eight of the trees were treated with the chemical, at the rate of 2 g a.i. per tree applied as granules in a 15 em deep furrow around each tree; eight trees were left untreated as controls. The orchard was irrigated two days after treatment. Nematodes were extracted from soil samples taken from the rhizosphere of each tree immediately prior to and two months after treatment. During this period, population levels of H. pseudorobustus decreased by approximately 65 % around both treated and untreated trees and the treatment had no discernible effect on decline symptoms.