Abstract
Hemipteran insects, such as whiteflies, aphids and planthoppers, resemble one of the most important pest groups threating food security. While many insecticides have been used to control these pests, many issues such as insecticide resistance have been found, highlighting the urgent need to develop novel insecticides. Here, we first observed that a commercial tetramycin solution was highly effective in killing whitefly. The major bioactive constituents were identified to be isothiazolinones, a group of biocides. We then tested the toxicity of several isothiazolinones to five hemipteran insects. The results show that Kathon, a widely used biocide against microorganisms, and its two constituents, chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT), can cause considerable levels of mortality to whiteflies and aphids when applied at concentrations close to, or lower than, the upper limit of these chemicals permitted in cosmetic products. The results also indicate that two other isothiazolinones, benzisothiazolinone (BIT) and octylisothiazolinone (OIT) can cause considerable levels of mortality to whitefly and aphids but are less toxic than Kathon. Further, we show that Kathon marginally affects whitefly endosymbionts, suggesting its insecticidal activity is independent of its biocidal activity. These results suggest that some isothiazolinones are promising candidates for the development of a new class of insecticides for the control of hemipteran pests.
Highlights
As the global population will continue to grow to roughly nine billion by the middle of this century, sustaining crop production is vital, which entails, among others, efficient crop protection against insect pests [1,2]
Since no insecticidal activity of tetramycin has been reported, but has been used in the field for many years, we speculated some other components in the formulated tetramycin solution may be responsible for killing whiteflies
In the process of tracing the insecticidal components in the tetramycin solution, we identified two isothiazoline biocides that exhibited insecticidal activity against whitefly
Summary
As the global population will continue to grow to roughly nine billion by the middle of this century, sustaining crop production is vital, which entails, among others, efficient crop protection against insect pests [1,2]. Hemipterans such as whiteflies, aphids and planthoppers, are one of the most significant groups threating food security as they damage crops directly by feeding and indirectly by transmitting plant diseases [3,4]. Feeding on crops may result in reduced plant vigor and physiological perturbation; more importantly, whiteflies can transmit many plant viruses belonging to the genera. Aphids represent a serious challenge for the sustainable production of many important cereal and vegetable crops; they can remove plant sap, secret phytotoxic salivary components and transmit viruses such as potyviruses [10]. Planthoppers are economically important pests of many cereals such as rice; they feed directly or serve as vectors of pathogenic microorganisms including viruses, resulting in significant crop damage and yield losses [11]
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