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Aim of the study: To develop a method to optimize the pesticide dose considering the combined influence of plant, pest, pesticide, and spray equipment on bioefficacy. Area of study: Agricultural Engineering College and Research Institute, Tamil Nadu Agricultural University, Coimbatore, India. Material and methods: A controlled droplet applicator generated droplets from 200 to 50 μm. The target leaf's deposition density of a preset droplet size can be controlled by timing the spray. A sequence of bioassays was performed at various droplet densities at each pesticide (imidachloprid 17.8% SL) dose and droplet size to determine the mortality of cotton aphids (Aphis gossypii) and jassids (Amrasca biguttula) feeding on immature cotton plants. Calculating the number of droplets per target area needed to cause 50% and 90% mortality (LN50 and LN90) yielded a series of model curves. Field tests were done on the computed optimal doses of the pesticide for a spray apparatus (electrostatically charged spray) to assess the spray's bioefficacy against A. gossypii and A. biguttula. Main results: In comparison to uncharged mist blower spray, which had a bioefficacy of 91% for an LN90 dose of 110 g a.i. L-1, the spray had an 89% bioefficacy on A. gossypii. Using the electrostatic spray, it was 91% effective against A. biguttula and 98% effective against an uncharged mist blower at a dose of 110 g a.i. L-1 of LN90. Research highlights: This generalized method of modelling could effectively compute the optimal pesticide dose for any plant, pest, pesticide, and spray equipment combination.