Impact of Nematode pest management strategies on Nematode communities in tomato production systems in Zimbabwe

Abstract

An analysis of soil nematode communities can be a useful tool for assessing the quality of soils and for the development of biological monitoring systems due to their intimate relationship of nematodes with their surrounding environment. In this study, soil sampling surveys were carried out in Chinamhora Communal Lands in Goromonzi District, the Botanic Gardens in Harare, and Henderson Research Station in Mazowe District at 0 – 15 and 15 – 30 cm depth to explore the effects of the land management systems and recommended tomato cropping sequences on the soil nematode communities. Glasshouse and field experiments, laid in randomized complete block design also were conducted in the 200/72008 and 2008/2009 seasons to examine the effects of chicken manure, Tagetes spp., nematicides and inorganic fertilizers on nematode communities in soils planted to tomato (Solanum lycopersicum L.). Soil from the treatments were extracted using Baermann and wet-sieving techniques and nematodes from each sub-sample were identified into trophic groups i.e. bacterivores, fungivores, predators, plant-parasites and omnivores and then identified to genus and in the case of Meloidogyne spp. nematodes to species level. High abundance of nematode communities was recovered between 0 – 15 cm soil depth because it is the area of high biological activities. Soils at Henderson station had higher soil bulk density values that are not favourable for free-living nematodes. Predators and omnivores were more abundant in soils from the Botanic Gardens. Organic amendments were less consistent in the management of plant parasitic nematodes and they stimulated more populations of free living nematodes. Fenamiphos had long term negative effects on the abundances of fungivorous and omnivorous nematodes. Soybean cake showed higher reproduction factor for free-living nematodes and most plant parasitic nematodes reproduced more in the NPK fertilizer treatment. High structural SI and maturity MI index values were observed in less disturbed soils implying that the soils are fertile and well structured. Soil nematode communities responded to changes in agricultural management. This implies that nematodes and the indices derived from the analysis of their community structures have demonstrated that changes in soil management are either beneficial or deleterious to the soil ecology and are well suited to the role of bioindicators for soil health in agroecosystems.