Understanding mechanisms behind the toxicity of ethanedinitrile, an alternative fumigant to methyl bromide : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Entomology (Plant Sciences) at Massey University, Manawatū, New Zealand
Loading...
Date
2021
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Ethanedinitrile (EDN, syn. cyanogen, EDN Fumigas®) has the potential to replace methyl bromide for the phytosanitary treatment of export timber and logs. Previous studies have shown that the toxicity of EDN differs between insect species and their life stages. For example, adults of the golden-haired bark beetle, Hylurgus ligniperda (Fabricius) (Coleoptera: Curculionidae) are highly tolerant to EDN, while those of the burnt pine longhorn beetle, Arhopalus ferus (Mulsant) (Coleoptera: Cerambycidae) are highly susceptible, implying that the mode of action might be species-specific. To understand the mechanisms behind the toxicity of the fumigant to insects, I examined the anatomy of the cuticle and spiracles of adults of both beetles. I found that
H. ligniperda possessed smaller total spiracle area, suggesting the possibility of less EDN uptake; and more cuticle layers, suggesting the possibility of delayed penetration of the fumigant. These morphological features might limit the uptake of EDN and the related toxic effect. Further studies have shown that the main route of entry for EDN into the insect body was through the spiracles for A. ferus, and through the cuticle for H. ligniperda. The fumigant caused a reduction in walking activity, narcosis, and paralysis in both species. Reductions in walking activities and narcosis occurred earlier in H. ligniperda, suggesting that this species may be able to quickly decrease metabolism and respiration rates in response to EDN, which could minimize uptake and toxic effect of the fumigant. Using attenuated total reflection - fourier transformed infrared (ATR - FTIR) spectroscopy, I identified higher cyanide (CN-) peaks in the insect ganglia in adult A. ferus, confirming the higher susceptibility of this species to EDN. This study has contributed to the knowledge of mechanisms behind the variable toxicity of EDN to adult A. ferus and H. ligniperda. The findings will provide a platform for future studies of the mode of action of EDN against insect pests.
Description
Keywords
Cyanogen compounds, Fumigants, Toxicology, New Zealand, Cerambycidae, Hylurgus ligniperda