Aqueous extracts and oil of neem combined with neonicotinoid insecticides against Bemisia tabaci biotype B in melon

This research was aimed at evaluating nymph population density of whitefly (Bemisia tabaci biotype B) in melon plants after treatment with neem-dry-leaf aqueous extracts and neem-oil ( A. Juss.) applied alternately with neonicotinoid insecticides under field conditions. The experimental design was a randomized block, with 6 treatments and 4 replications. The treatments were control (only water); neem-dry-leaf extract at 5% (neem-dry-leaf powder 50g L-1 of water); neem oil (5.0mL L-1 water); chemicals insecticides imidacloprid (30g 25L-1 of water) and acetamiprid (5g 20L-1 of water); neem-dry-leaf extract at 5% weekly alternated with imidacloprid (30g 25L-1 of water) and acetamiprid (5g 20L-1 of water); neem oil (5.0mL L-1 of water) weekly alternated with imidacloprid (30g 25L-1 of water) and acetamiprid (5g20 L-1 of water). The efficiency of treatments was compared through of the number of nymphs recorded in leaves of melon with 35, and 50 days after planting. The less number of nymphs was registered when the neem oil was applied alternatively with the chemical treatment with efficiency of 28.58 and 7.85% in the first and second evaluations, respectively. However, the nymphs incidence was higher when the neem oil and the chemical treatment were applied separately.