Successful single-truss cropping cultivation of healthy tomato seedlings raised in an electrostatically guarded nursery cabinet with non-chemical control of whiteflies

Koji Kakutani Yoshinori Matsu

Abstract

The present study presented an efficient non-chemical method of controlling insecticide-resistant whiteflies in a single-truss cropping system for hydroponic tomatoes. For this purpose, we used two kinds of electrostatic apparatus: an electrostatically guarded nursery cabinet (EGNC) to create a pestfree space by preventing the entry of whiteflies, and an electrostatic insect sweeper (EIS) to directly trap whiteflies colonising tomato plants. The EGNC was newly devised in this study. It had two layers of insulated conductor iron wires (ICWs) in parallel arrays and two electrostatic direct current voltage generators that supplied negative or positive voltages to the ICWs. Within each layer, the ICWs were placed parallel at 5-mm intervals and connected to each other and to a negative or positive voltage generator. The negatively and positively charged ICWs are represented as ICW(–)s and ICW(+)s, respectively. Two IC Wlayers were placed parallel at a 2-mm interval and the ICWs in the layers were offset relative to each other. Adult whiteflies were blown into the space between the ICWs to identify the voltage range that would capture all of the test insects. The results showed that at ≥4.0 kV, the force was strong enough that the ICWs captured all of the whiteflies, despite a wind speed of 3 m/s. The EGNC was practically applicable to a greenhouse that suffered from frequent invasion by numerous viruliferous whiteflies; we found that seedlings grew normally inside the EGNC during a40-day cultivation period. The EIS was also effective in protecting tomato plants subsequently transplanted to a non-guarded greenhouse. The EIS was handy and easy to operate on-site in a greenhouse, and it was used to trap whiteflies residing on tomato plants during daily plant care. Through this daily elimination of whiteflies, the whitefly population in a greenhouse was controlled to negligible levels during the experimental period (40 days), and nearly all tomato plants were able to produce normal fruit. Thus, the present study demonstrated that single-truss cultivation of greenhouse tomatoes could be performed with the aid of two electrostatic apparatuses to control insecticide-resistant whiteflies.