Abstract
Mineral-based products represent a valid alternative to synthetic pesticides in integrated pest management. We investigated the effects of a novel granite dust product as an agent for controlling two-spotted spider mites, Tetranychus urticae Koch (Acari: Tetranychidae), on tomato plants (Solanum lycopersicum L.). Two-choice tests for repellency and repulsiveness, and no-choice bioassays with different type of applications (soil, foliar, and soil–foliar) were used in order to evaluate performance and action of the product. Evaluation of epidermal micromorphology and mesophyll structure of treated plants and elemental analyses of leaves were performed. In repulsiveness experiments, almost all dust treatments significantly inhibited mites from migrating to and/or settling on the treated leaf. In repellency experiments, foliar and soil dust treatments were not significantly different from control. Significant mortality was observed for all dust treatments in two-choice and in no-choice bioassays, suggesting mites are susceptible to rock dust by contact, and by indirect interaction through the feeding on plants subjected to soil application of rock dust. Leaf epidermal micromorphology and mesophyll structure of treated plants showed structural variation due to mineral accumulation, which was also confirmed by elemental analyses of leaves. These results demonstrate for the first time that granite rock dust interacts with two-spotted spider mites by modifying pest behavior and via acaricidal action, providing more insights in understanding the mechanism of this novel natural product as pest management tool.
Highlights
Mineral-based products represent a valid alternative to synthetic pesticides in integrated pest management
The application of rock dust material via foliar and/or soil application resulted in acaricidal and repellent activity towards Two-spotted spider mite (TSSM)
In repulsiveness experiments, the dust treatment significantly repelled mites from migration towards the treated disc and/or to settling on the treated disc (Fig. 1a)
Summary
Mineral-based products represent a valid alternative to synthetic pesticides in integrated pest management. Leaf epidermal micromorphology and mesophyll structure of treated plants showed structural variation due to mineral accumulation, which was confirmed by elemental analyses of leaves These results demonstrate for the first time that granite rock dust interacts with two-spotted spider mites by modifying pest behavior and via acaricidal action, providing more insights in understanding the mechanism of this novel natural product as pest management tool. In terms of the mode of action, it remains unclear precisely how granite dust affects herbivores leading to a reduction in insect performance and plant damage In this context, we want to evaluate: (a) the effect of granite dust in controlling cell disrupting herbivores; (b) potential pest control differences within the application via the roots (as soil amendment) and/or as a leaf surface (foliar) application; (c) the defence mechanism involved (mode of action). As host for our study, we selected tomato plants (Solanum lycopersicum L.) as representative crop for main greenhouse vegetable industry in Canada significantly affected by TSSM, and because the exposure to rock dust in preliminary studies induced changes on plant fitness and fruit quality (personal observation)
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