ABSTRACT
The sweetpotato whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is challenging to control using chemical pesticides owing to its resistance to many insecticides. Thus, there has been an increasing demand for alternative control measures. Thus, this study evaluated the efficacy of a newly designed pest suction machine to manage whiteflies on tomato plants (Solanum lycopersicum L.) (Solanales: Solanaceae) in greenhouses over 2 seasons. The suction machine comprised a battery-powered cart with a mounted suction unit, an ultrasonic device, and green lights. Ultrasonic irradiation provided non-contact vibration, facilitating the movement of adult whiteflies away from the plants, and green lights attracted them to the suction device. This combination effectively captured whitefly adults, even with a weak suction force, saving electricity consumption. The efficacy of suction machine was further evaluated by measuring the number of whitefly adults caught by the machine and the number of adults and nymphs remaining on the tomato leaves. The whitefly population was considerably lower in the treated blocks than in the non-treated blocks in the autumn trial. The machine reduced the density of whitefly adults without using chemical pesticides. Although a lot of optimizations would be required, suction control is an additional and alternative strategy that may be incorporated in the integrated pest management of whiteflies on greenhouse tomato plants.
ABSTRACT
Monitoring resistance allele frequency at the early stage of resistance development is important for the successful acaricide resistance management. Etoxazole is a mite growth inhibitor to which resistance is conferred by an amino acid substitution in the chitin synthase 1 (CHS1; I1017F) in T. urticae. If the susceptible allele can be specifically digested by restriction endonuclease, the ΔΔCt method using real-time PCR for genomic DNA (RED-ΔΔCt method) may be available for monitoring the resistance allele frequency. We tested whether the etoxazole resistance allele frequency in a pooled sample was accurately measured by the RED-ΔΔCt method and validated whether the resistance variant frequency was correlated with etoxazole resistance phenotype in a bioassay. Finally, we performed a pilot test using field populations. Strong linearity of the measures by the RED-ΔΔCt method with practical resistance allele frequencies; resistance allele frequency in the range between 0.5% to at least 0.75% was strictly represented. The strong linear relationship between hatchability of haploid male eggs after the etoxazole treatments (phenotype) and resistance allele frequencies in their mothers provided direct evidence that I1017F is a primary resistance factor to etoxazole in the strains used for experiments. The pilot test revealed a significant correlation between egg hatchability (including both diploid female eggs and haploid male eggs) and estimators in field populations. Consequently, we concluded that the RED-ΔΔCt method is a powerful tool for monitoring a resistance allele in a pooled sample.
