The effects of metaldehyde on non-target aquatic macroinvertebrates: Integrating field and laboratory-based evidence

Assessing the combined toxic effects of metaldehyde mollucide

The excessive use of metaldehyde in agriculture to combat mollusks endangers both the environment and non-target organisms. The aim of this study is to investigate the toxicity caused by metaldehyde in Allium cepa with the help of physiological, cytogenetic, biochemical and anatomical parameters. Also, DNA fragmentation caused by metaldehyde in root tip cells was measured by the "Comet Assay" method. The control group was germinated with tap water and the application groups were germinated with 20 mg/L metaldehyde, 40 mg/L metaldehyde, 100 mg/L metaldehyde and 200 mg/L metaldehyde for 72 h. The results of the physiological parameters showed that metaldehyde had a growth-limiting effect in A. cepa, depending on the application dose. According to root elongation levels, the EC₅₀ (effective concentration) value for metaldehyde was 60.6 mg/L in A. cepa. As the treatment dose increased, the incidence of micronucleus and chromosomal aberrations gradually increased while mitotic index decreased. Metaldehyde exposure induced damages such as sticky chromosome, fragment, unequal distribution of chromatin, reverse polarization, bridge, and multipolar anaphase. In addition, metaldehyde caused cell damage in epidermis and cortex, thickening of the cortex cell wall and flattened cell nucleus in root meristem. Increasing doses of metaldehyde application also increased malondialdehyde levels, superoxide dismutase and catalase activities. As a result, it has been determined that the toxicity of metaldehyde in plants is versatile and the A. cepa test material is a suitable biological indicator to determine this toxicity.

The Fate of Deroceras reticulatum Following Metaldehyde Poisoning

Simple Summary

The grey field slug, Deroceras reticulatum (Müller, 1774) (Agriolimacidae), is one of the most economically important crop pests and is a particular threat to oil seed rape and winter wheat. Without effective slug control, it is estimated that the loss of yield due to slug damage could equate to over £100 million annually for the UK agricultural sector. The molluscicide metaldehyde is one of the most common active ingredients used in slug pellets across the globe; however, its application presents a high risk of surface water pollution and threatens non-target wildlife. The control of slugs by metaldehyde relies on slugs consuming or being in contact with a pellet long enough to receive a lethal dose; otherwise, a slug may recover from the dehydrating and paralysing effects of the molluscicide. This research explores the effect of different concentrations of metaldehyde on slug survival, paralysis and recovery after contact with metaldehyde, and highlights the prospect of slug paralysis being a major contributing factor to successful slug control.

Abstract

The concentration of a pesticide used in agriculture not only has implications for effectiveness of pest control but may also have significant wider environmental consequences. This research explores the acceptability of metaldehyde slug pellets at different concentrations by Deroceras reticulatum (Müller, 1774) (Agriolimacidae), and the changes in the health status of the slug when allowed to recover. The highest metaldehyde concentration (5%) yielded the highest slug mortality; however, it also produced the highest proportion of unpoisoned slugs, suggesting the highest level of pellet rejection. Pellets with 1% metaldehyde were as effective as 3% pellets in paralysing a significant proportion of the population after initial pellet exposure; however, more slugs were able to recover from metaldehyde poisoning at 1% metaldehyde compared with 3%. There was no statistically significant difference between the mortality rate of slugs regardless of metaldehyde concentration, suggesting that a lower concentration of metaldehyde may be as effective as a higher concentration.

Control of the number of field slugs Deroceras agreste L. in the plantations of garden strawberry

Slugs cause serious harm to nurseries and young plantations of fruit and berry crops in the Krasnodar region. On garden strawberries, the most common species is the field slug Deroceras agreste L., whose larvae damage ripe fruits and leaves, as well as contaminate them with their secretions and mucus, which leads to a decrease in the quality of seedlings and contributes to damage by secondary pests. In modern protection systems, the most commonly used pest control systems are molluscicides containing methaldehyde. The aim of our research was to assess the biological effectiveness of the molluscicides Sliznyakoff, G (60 g/kg methaldehyde) and Slizneed, G (60 g/kg methaldehyde) in controlling the abundance of field slugs in strawberry agrocenoses on the Clery variety. It was found that with an average number of phytophage larvae in the control variant (12.5-16.0 individuals / 10 m2), a single use of molluscicides causes 95.3 % mortality of D. agreste L. on the 7th day.