# Acaricidal Efficacy of Diatomaceous Earths on Different Life Stages of Acarus siro L. and Tyrophagus putrescentiae (Schrank)

## TL;DR

This study shows that diatomaceous earths InsectoSec and Fossil Shield effectively kill different life stages of two mite species that infest stored wheat.

## Contribution

The study compares the acaricidal efficacy of two diatomaceous earths against multiple life stages of two mite species on wheat.

## Key findings

- InsectoSec and Fossil Shield showed dose- and exposure-dependent efficacy against all life stages of A. siro and T. putrescentiae.
- Larvae and nymphs were more susceptible to diatomaceous earths than adults.
- InsectoSec was more toxic than Fossil Shield, especially at higher doses.

## Abstract

The acaricidal efficacy of two diatomaceous earths (DEs), InsectoSec and Fossil Shield, was investigated against various developmental stages of Acarus siro L. and Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) on wheat at two dose rates. Both DEs demonstrated dose- and exposure-dependent efficacy against A. siro and T. putrescentiae at all developmental stages. Additionally, the immature stages of both species (i.e., larvae and nymphs) were more susceptible to DEs than adults. Tyrophagus putrescentiae was more sensitive to both DEs than A. siro. InsectoSec was more toxic compared to Fossil Shield.

Acarus siro L. and Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae) are cosmopolitan mite species in food storage and processing environments, infesting a wide variety of commodities. In the current study, the diatomaceous earths (DEs) InsectoSec and Fossil Shield were evaluated for wheat protection against adults, larvae, and nymphs of A. siro and T. putrescentiae. Both DEs were examined at 200 and 500 ppm at 1, 2, and 5 days post-exposure. The efficacy of both formulations against A. siro and T. putrescentiae life stages depended on dose and exposure. Mortality of A. siro reached 100% in larvae, 99.3% in nymphs, and 95.6% in adults by day 5 at 500 ppm of InsectoSec. Similarly, Fossil Shield achieved almost complete larval mortality (99.3%) of A. siro at 500 ppm. For T. putrescentiae, 100% mortality was observed for larvae at both doses of InsectoSec and for adults or nymphs at 500 ppm by the fifth day. Fossil Shield caused a similar mortality to larvae, reaching 97.0% and 100%, at 200 and 500 ppm, respectively, after 5 days. Our findings indicate that InsectoSec and Fossil Shield can be used as sustainable management tools against A. siro and T. putrescentiae.