Abrasive und hydrophil/lipophile Effekte unterschiedlicher inerter Stäube im Einsatz gegen Schadinsekten am Beispiel des Kornkäfers Sitophilus granarius L. |
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| Authors: | Christian Ulrichs S Entenmann A Goswami Inga Mewis |
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| Institution: | 1. Institute für Gartenbauwissenschaften, Fachgebiet Urbaner Gartenbau, Humboldt-Universit?t zu Berlin, Lentzeallee 55–57, 14195, Berlin, Germany
2. Bio Science Division, Indian Statistical Institute, Indian Statistical Institute, 203 B.T. Road, 700 108, Calcutta, India
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| Abstract: | Modern research on the insecticidal effects of inert dusts as a stored-grain protectant and for plant protection purposes began in the 1920s. The main advantage of inert dusts is their low-mammalian toxicity. One group of inert dusts used for pest control is diatomaceous earth (DE). DE has been tested as a whole and evaluated as a Group 3 carcinogen by the International Agency for Research on Cancer (IARC). A Group 3 listing indicates that DE is not classifiable as to its carcinogenicity to humans, since definitive conclusions cannot be drawn from the research conducted to date. DE is a form of naturally occurring amorphous silica that can kill insects by ab/adsorbing the lipids such as waxes and triglycerides of the outer cuticle layer by direct contact. When the thin, waterproof layer is lost, the insect looses water and dies. Desiccation follows Ficks law of diffusion into the surrounding atmosphere. In addition to its desiccant action the theory that DE works abrasively to rupture insect cuticles has been proposed. To evaluate the abrasive effects of DE we have tested 27 inert dusts with different surface properties. Materials were compared based on the time needed to kill 50% (LT50) of Sitophilus granarius weevils in laboratory experiments. Substances with hydrophilic and/or hydrophobe properties were significantly more effective against S.?granarius than substances which are mainly abrasive. There is a strong correlation between LT50 and weight loss (=?water loss) of insects (p?=?0.014). Particle size played only a secondary role (p?=?0.077). Commercial DE formulations and activated charcoal (Carbopal MB4) were the most effective hydrophilic substances tested. The most abrasive substances were corundum and silica sand with small particle sizes. It is concluded, that those materials were effective because of a good coverage of the insects outer cuticle and existing shear stress. All results presented are discussed in context of the insecticidal mode of action of inert dusts and possible registration of silica based formulations as biocide. |
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