Effect of soil fertilization on population build up of spider mite (Tetranychus turkestani Ugarov and Nikolskii) in Cowpea

Investigations were undertaken to study the response of spider mite Tetranychus turkestani Ugarov and Nikolskii to chemical fertilizers applied in different combinations on cowpea. Six combinations of N, P, K and S were tried during Kharif season 2003. Mite population was significantly high (12.65 to 50.09 leaf⁻¹) in plots treated with chemical fertilizers in comparison to untreated control (7.58 motile mites leaf⁻¹). Treatment combination of N₃₀P₈₀S₁₀ harboured greater mites (50.09 leaf⁻¹), followed by K-treated plots (12.65 to 31.70 mites leaf⁻¹). The treatments containing N, P and S carried high mite population on the crop than K-treated plots. Mite population (7.58 leaf⁻¹) and egg number (16.06 leaf⁻¹) was less in untreated cowpea plots as compared to fertilizer treated plots (12.65–50.09 mite leaf ⁻¹ and 19.34–55.09 eggs leaf⁻¹). A direct relationship between fertilizer application to the cowpea and population of T. turkestani was noticed.