Abstract
Laboratory bioassays were conducted to evaluate the insecticidal efficacy of a diatomaceous earth deposit from Greece, for a wide range of stored product insects. In this context, populations of five different insect species, Tribolium confusum Jacquelin DuVal, the confused flour beetle; Sitophilus oryzae (L.), the rice weevil; Rhyzopertha dominica (F.), the lesser grain borer; Oryzaephilus surinamensis (L.), the sawtoothed grain beetle; Cryptolestes ferrugineus (Stephens), the rusty grain beetle, which cover a major spectrum of insects species of stored products worldwide, were used in the bioassays. The different treatment of diatomaceous earth (DE) rocks (grinding, diatomaceous enrichment, powder granulometry) led to the creation of five types of formulations (namely DE1, DE2, DE3, DE5 and DE6) that exhibited significant fluctuations in their insecticidal efficacy when applied on wheat. In general, some of the modified formulations were found to be very effective against species such as R. dominica and T. confusum that may be difficult to control at the current labeled doses of commercial DE formulations. Overall, our data clearly indicate that this specific Greek deposit has considerable insecticidal properties, which can be further utilized in designing commercial formulations for insect control at the postharvest stages of durable agricultural commodities, provided that the deposit will be modified at specific enrichment and granulometry levels.
Highlights
In 1703, a man looking with his simple microscope a pond-weed’s root observed many pretty structures to be attached in the roots
Our data clearly indicate that this specific Greek deposit has considerable insecticidal properties, which can be further utilized in designing commercial formulations for insect control at the postharvest stages of durable agricultural commodities, provided that the deposit will be modified at specific enrichment and granulometry levels
It was found that diatomaceous earths (DE) formulations originated from Elassona, Greece, had large particles (45–150 μm) that were in some cases more effective than smaller ones in other tested
Summary
In 1703, a man looking with his simple microscope a pond-weed’s root observed many pretty structures to be attached in the roots. His descriptions and diagrams are the first certain records of a diatom—a unicellular aquatic plant related to the algae [1] Fossils of such organisms, which contain high percentages (80–93%) of silicon dioxide (SiO2 ), an ingredient with insecticidal properties, formed along with other elements such as clay minerals, organic matter, quartz, calcium and magnesium carbonate [2]—the so-called diatomaceous earths (DE). The mode of action of DE is generally accepted to have a desiccating effect on the insects, as diatoms have the ability to absorb the epicuticular lipids of the insect cuticle [4] This indicates that DE toxicity primarily depends on its physical properties and much less on its chemical composition [5]. DE is safe to use with an extremely low mammalian toxicity, does not react with other substances in the environment, does not affect grain end-use quality, provides long-term protection and is comparable in cost to other methods
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