Review A Review of the Mechanisms Involved in the Action of Phosphine as an Insecticide and Phosphine Resistance in Stored‐Product Insects

Abstract

: Phosphine gas has been used world-wide for more than four decades as an ideal fumigant for disinfestation of stored grains and other commodities. Its use as a safe fumigant of stored products has become even more important with recent restrictions on the production of the only alternative, methyl bromide. Widespread resistance to phosphine has emerged in several species of storedproduct insects in many countries, which in some instances may have caused control failures.Chemically, phosphine is a strong reducing agent and biological redox systems, especially the components of the mitochondrial electron transport chain, are probably the site of its action in insects. The oxidation of phosphine could produce reactive phosphorylating species and interactions of phosphine with biological redox systems have been reported to cause generation of highly reactive oxyradicals. This appears to be the basis of phosphine toxicity to insects, which di †ers from that of respiratory inhibitors such as hydrogen cyanide.Phosphine-resistant strains of several species of stored-product insects have been reported to absorb very small amounts of the compound compared to their susceptible counterparts. This reduced uptake in resistant insects appears to result from respiratory exclusion of phosphine. The overall mechanism of resistance also involves a detoxiÐcation process. Despite the likely involvement of oxyradicals in the insecticidal action of phosphine, the level of anti-oxidant enzymes in resistant insects is apparently not higher than that in their susceptible counterparts. The reduced uptake of the compound might be due either to the presence of a phosphine insensitive target site or to a membrane-based efflux system that excludes phosphine gas in resistant insects. Studies have indicated the oxygen uptake in mitochondrial preparations from susceptible and resistant insects to be equally sensitive to inhibition by phosphine in vitro. The nature of the phosphine-exclusion system in resistant insects has not been fully elucidated.The possibilities of controlling resistant insects with phosphine and prospects for developing new alternative fumigants are also discussed.

Effect of different phosphine gas concentrations against Frankliniella occidentalis (Pergande, 1895) (Thysanoptera: Thripidae) on tomato and green pepper fruit, and determination of fruit quality after application under low-temperature storage conditions

“…Therefore, it is thought that the differences in the mortality rates of the green pepper and tomato were caused by this. Eggs and pupae of several species are reported as the most phosphine tolerant stages (Chaudhry, 1997). Shorter fumigation period with lower phosphine gas level would also help prevent injury to vegetables.…”

Activity of oxalic and citric acids on the mite Varroa destructor in laboratory assays

“…Resistance to low molecular weight substances has been repeatedly reported. Widespread resistance to phosphine, PH 3 , in stored-product insects is a well known example (Chaudhry, 1997) and slight increases in tolerance were observed even with extremely unspecific biocides such as methyl bromide (Rajendran, 1992).…”

Spread of phosphine resistance among brazilian populations of three species of stored product insects

“…In addition, the lack of airtight conditions for fumigation in most storage units increases the frequency of control failures and consequently increases the frequency of applications (Tyler et al 1983, Chaudhry 2000, Benhalima et al 2004. This results in an increased selection pressure for phosphine resistance (Chaudhry 1997(Chaudhry , 2000.…”