Effect of nitrogen, phosphorus and potash on population dynamics of European red mite, Panonychus ulmi (Koch) on apple

European red mite, Panonychus ulmi (Koch) has assumed a status of major pest in recent years in Himachal Pradesh, India. It is essential that a fresh approach to mite control be undertaken especially studying its population fluctuation in relation to host plant nutrition. The effect of three levels of NPK combination each at recommended dose (N₁P₁K₁), 25% above (N₂P₂K₂) and 25% below the recommended dose (N₃P₃K₃) including untreated control (N₀P₀Ko) was studied on build up of P. ulmi population on potted plants of Delicious cultivars of apple at RHRS, Mashobra, Shimla. Combinations of N, P and K exhibited significant effect on the population levels of P. ulmi. Among ten treatments including nine combinations of N, P and K and a control, the least population of all stages of mite was recorded in NaP₂K₂ (25% less dose of N and 25% higher dose of P and K than recommended dose) with respective mean population of 21.85, 29.22 and 103.20 adults, immatures and eggs/leaf as against 40.00 adults, 44.33 immatures and 166.30 eggs in the control. Treatment combination N₂P₃K₃ (25% higher dose of N and 25% less dose of P& K than recommended dose) supported maximum population of 74.78 adults, 91.81 immatures and 320.90 eggs per leaf, significantly different from the remaining treatments. The population level in the other treatment combinations remained at intermediate level. These results clearly suggest that slight manipulation in the recommended doses of NPK fertilizers can contribute substantially in regulating the abundance of P. ulmi population on apple trees.