Potential Of Combining Host Plant Resistance And Intercropping In The Management Of Root-knot Nematodes And Insect Pests In The Indigenous Leafy Vegetables
Indigenous leafy vegetables (ILVs) play an important role as income and food security crops in many rural and urban households in Kenya, yet their potential in alleviating poverty and ensuring household food and nutrition security has not been exploited. Diversification of diets through increased utilization and consumption of these vegetables would go along way in alleviating the hidden hunger and malnutrition. The objective of this study was to, assess the reaction of ILVs to root knot nematodes, identify the insect pests and plant parasitic nematodes (PPNs) associated with them, and evaluate the effective cultural management strategies for sustainable production of ILVs. A greenhouse experiment was carried out where six indigenous leafy vegetables namely spider plant (Cleome gynandra), amaranth (Amaranth hybridus), black night shade (Solanum nigrum), cowpea (Vigna unguiculata), jute mallow (Corchorus spp) and sun hemp (Crotalaria juncea) were assessed. The seeds were planted in six pots and half of the pots were infested with 2000 second stage juveniles of root knot nematodes. On termination data on plant height, fresh and dry shoot weight, galling index, egg mass index and the second stage juvenile count was recorded and analyzed. The field experiments were established in Kahatia in Murang’a County for two seasons to evaluate the effect of insect pests and plant parasitic nematodes on the indigenous leafy vegetables. Black nightshade, sun hemp and spider plant were selected for intercropping. Experiments were laid out in a randomized complete block design replicated three times. Treatments consisted of same row intercropping, same hill row intercropping, single and two rows intercropping, alternate row intercropping, border cropping and control plots which consisted of black night shade only. Insect pests that infested the indigenous leafy vegetables were identified through visual leaf inspection. Shoot damage, fresh and dry shoot weight of the plants and change in the second stage juvenile numbers in the soil were collected to assess root knot nematodes and insect pests. These plants were rated using galling index on a scale of 1-10, where 1=resistant and 10=most susceptible. Spider plant, sun hemp and amaranth were rated as resistant while jute mallow, cow pea and black night shade were susceptible. Black aphids (Aphis fabae), flea beetles (Chrysomelidae spp), leaf miners (Lyriomyza spp), red spider mites (Tetranchus spp), cutworms (Agrotis spp), diamond back moth (Plutella xylostella), African bollworm (Helicoverpa armigera), thrips (Thrips tabaci), whiteflies (Bemisa spp) and root knot nematodes (Meloidogyne spp) infested the ILVs. Same hill and same row arrangement pattern for the intercrop were the most effective and significant (P≤0.05) in reducing the effect of plant parasitic nematodes and insect pests infestation. The identified resistant varieties can be used as intercrops in agricultural production systems as a component of root knot nematode suppression in the soil. Intercropping resistant and susceptible vegetables can be integrated with other control methods for effective management of plant parasitic nematodes and insect pests. It is a practice that can easily be adapted by farmers with low external inputs.