Effectiveness of imidacloprid in combination with a root nitrogen fertilizer applied to tomato seedlings against Bemisia tabaci (Hemiptera: Aleyrodidae)

•Sub-irrigation of imidacloprid in combination with a root fertilizer Root Feed to tomato at the seeding stage is cost-effective for managing Bemisia tabaci.•The effectiveness of 12 ml seeding−1 imidacloprid against B. tabaci lasted up to 50 days.•0.02 or 0.04 ml seeding−1 Root Feed positively interacted with imidacloprid after treatment.•In greenhouse, 12 ml seedling−1 imidacloprid alone or combined with the fertilizer was effective against B. tabaci.

The whitefly Bemisia tabaci (biotype B) is a worldwide pest of vegetables and field crops. We tested the efficacy of imidacloprid (IM) with a root fertilizer ‘Root Feed (RF)’ (9% N, 7% Ca, 1.5% Mg and 0.1% B) sub-irrigated in the growing medium against the whitefly on tomato. Tomato seedlings (3–4 true leaves) were treated with 0, 3, 6 or 12 mg active ingredient (a.i.) seedling−1 of IM and with RF (0, 0.02, 0.04 or 0.08 ml seedling−1). The efficacy of 12 mg IM seedling−1 was further evaluated in the greenhouse for 60 days. The survival of B. tabaci adults, nymphs, and egg production were negatively affected by the treatments in a dosage-dependent manner. Treatment of 12 mg IM seedling−1 caused >60% adult and nymph mortality 50 days after treatment (DAT). The active ingredient of IM in tomato leaves also increased with the increase of IM dosage. The RF exhibited a limited effect on B. tabaci. However, the mortality of whitefly adults and nymphs treated with RF (0.02 or 0.04 ml seedling−1) positively interacted with IM, and was greater than IM alone. In the greenhouse, 12 mg IM seedling−1 greatly reduced the number of whitefly adults and increased the dry weight of the tomato plants at 30 DAT. In conclusion, application of 12 mg IM seedling−1 on tomato seedlings before transplanting effectively controled B. tabaci for up to 50 days, and the efficacy of IM combined with 0.02 ml RF seedling−1 performed even better. This could be a cost-effective method for managing B. tabaci on tomato and other vegetables.