Nematode Management in Polyhouse Cultivation

Abstract

Globally, the area under protected cultivation is 4.05 lakh hectares, while in India it is close to 110,000 hectares after the National Horticulture Mission enacted the promotion of polyhouse and greenhouses. Though the cultivation of crops in polyhouses enhances the yield per unit area, there is a build-up of soil-borne pests and pathogens, especially nematodes. The plant-parasitic root-knot (Meloidogyne incognita) and reniform (Rotylenchulus reniformis) nematodes, once introduced in a polyhouse, multiply to high densities due to the availability of optimum moisture around the root zone, favourable temperatures and uninterrupted food from long duration varieties, enabling the completion of several life cycles. The number of infective juveniles in the soil increases tremendously, from 1‒3 J2/cc soil at pre-plant to up to 80 J2/cc soil at crop maturity. Multiple root galls that gradually increase in number and size are predisposed to fungal pathogens like Rhizoctonia solani, Fusarium oxysporum, Macrophomina etc.; sometimes followed by mortality of plants. M. incognita and M. javanica are serious constraints to polyhouse vegetables, especially tomato and cucumber causing yield losses of 25‒100 per cent. Chemical nematicides like metham sodium and Velum prime (fluopyram) are effective in nematode management. However, they result in an initial decline in nematode densities for 3‒4 months and later the residual nematode population in the soil builds-up exponentially. With an increasing awareness of environmental protection and food safety, there is a need to exploit environment-friendly methods of nematode management. Besides the phytosanitary measures which are most important, deep tillage of the soil, use of soil solarization, biocontrol agents, trap crops, organic amendments and grafted cultivars can reduce the pest population below economic threshold levels. The various options have their merits and demerits and therefore managing the nematode pests in polyhouses is challenging and requires awareness, monitoring and regulation.