# Influence of the Physicochemical and Microstructural Properties on the Insecticidal Efficacy of Diatomaceous Earth on the Poultry Pest Alphitobius diaperinus

## TL;DR

This study shows that the insecticidal effectiveness of diatomaceous earth against a poultry pest depends on its physical and structural properties.

## Contribution

The study identifies crystallinity as the key factor influencing the insecticidal activity of diatomaceous earth.

## Key findings

- DE4 showed the highest insecticidal efficacy with 98% and 88% mortality for larvae and adults, respectively.
- Higher crystallinity in DE samples reduced their insecticidal activity, causing mortality rates of around 10–20% in adult insects.
- Calcined treatment increased crystallinity and particle size but reduced adsorption/absorption capacity and insecticidal effectiveness.

## Abstract

Different diatomaceous earth (DE) samples were studied
to evaluate
the influence of physicochemical and microstructural characteristics
on insecticidal activity against Alphitobius diaperinus. The insecticidal efficacy study showed that DE4 was more effective
for larvae and adults (98% and 88% mortality, respectively), contrasting
with DE1, which presented similar results to the control (49% and
6% mortality for larvae and adults, respectively). DE2 and DE3, in
turn, exhibited promising insecticidal results. X-ray diffraction
analyses showed a predominantly crystalline profile for DE1, while
an amorphous profile was found for DE4. Laser diffraction analysis
and scanning electron microscopy showed that DE1 had a larger average
particle size (∼45 μm) than DE2, DE3, and DE4 (∼28,
26, and 25 μm, respectively). In addition, DE1 showed poor powder
adherence to the adult insects and reduced adsorption/absorption capacity
compared with the other samples (p < 0.05). The
calcined treatment promoted significant microstructural changes in
DE samples. An increase in the crystallinity of the samples is perceived,
accompanied by an increase in particle size and a reduction in their
adsorption/absorption capacity. These changes significantly impact
the insecticidal activity of DE samples against adult insects, resulting
in mortality rates of around ∼10–20%. In summary, the
results showed that increasing the degree of crystallinity of DE samples
negatively affects their insecticidal activity against A. diaperinus and seems to be the DE characteristic
that most influences insecticidal activity.