Chlorpyrifos-induced hormesis in insecticide-resistant and -susceptible Plutella xylostella under normal and high temperatures

Abstract

Hormesis induced by insecticides at the dosage lower than what ostensibly directly causes death on insects was studied. This paper reports the effects of the in vivo application of varied concentrations of chlorpyrifos (CPF) on Plutella xylostella (DBM). The insecticide concentrations applied included 0.000025-2.5 mg l-1, which are far lower than LC1 (7.2 mg l-1), for the CPF-susceptable (Si) DBM, and 250 mg l-1 which is far below LC1 (1286 mg l-1), for the CPF-resistant (Rc) DBM, as well as LC10- and LC50-doses for both strains. Significant hormesis was found with the 'hermetic-CPFs', i.e., 0.0025 mg l-1 for Si DBM and 2.5 mg l-1 for Rc DBM, at the normal or high temperature either in a 24 h or under a long-term treatment. These doses of CPF significantly stimulated the development and increased the fecundity of Si and Rc DBM at 25°C with approximately 23.5-29.8% activity increase on acetylcholinesterase (AChE) and 30.5-91.3% increase on glutathione S-transferases (GSTs) at 25 or 38°C in 4-24 h. The enzymatic activities were significantly reduced by LC50-CPF at 25°C in vivo, but the inhibition was relieved significantly, if the insects were first subjected to a hormetic-CPF pretreatment. It was remarkable that the average rates of enzymatic activity increase were 67.5-76.6% for AChE and 366-546% for GSTs. Consequently, it was concluded that the hormesis on Si and Rc DBM could be induced by CPF doses far below LC1 at normal or high temperature in short- or long-term treatment. These findings might help to improve the current insect control practices in the field.

Sublethal pesticide exposure improves resistance to infection in the Asian corn borer

“…The botanical insecticide azadirachtin significantly reduced the number of haemocytes in the reduviid, Rhodnius prolixus (Azambuja et al, 1991). fenvalerate and methomyl (Sota et al, 1998), and the phosphorothioate insecticides chlorpyrifos (Deng et al, 2016). Our experiment, however, revealed an opposite trend, which enhanced the insect immune function, and may be a concurrent hormesis.…”

“…A few studies in recent years have demonstrated that some organophosphate, botanical and IGR pesticides have been shown to reduce the effects on insect immunity through affecting either the PO activity or the haemocyte activity (George & Ambrose, 2004;Ma et al, 2008;Nasr et al, 2010). In the diamond moth (Plutella xylostella), a sublethal dose of chlorpyrifos was found substantially to increase the activity of several enzymes, such as acetylcholinesterase and glutathione S-transferases (Deng et al, 2016). Hormesis is a dose-response phenomenon, which is the most fundamental dose response in the biomedical and toxicological sciences, characterised by a low-dose stimulation and high-dose inhibition (Calabrese & Baldwin, 2003).…”

“…The hormesis phenomenon was found to occur over a wide range of insecticides, e.g. fenvalerate and methomyl (Sota et al, 1998), and the phosphorothioate insecticides chlorpyrifos (Deng et al, 2016). In the diamond moth (Plutella xylostella), a sublethal dose of chlorpyrifos was found substantially to increase the activity of several enzymes, such as acetylcholinesterase and glutathione S-transferases (Deng et al, 2016).…”

Sublethal effects of chronic exposure to chlorpyrifos or imidacloprid insecticides or their binary mixtures on Culex pipiens mosquitoes

“…This might be because of the effect of sublethal concentrations and/or interaction of chlorpyrifos and imidacloprid. Several studies report adaptive responses subsequent to exposure to sublethal concentrations of chemical pesticides (Zanuncio et al, 2005;Deng et al, 2016).…”

Susceptibilities of Candidatus Liberibacter asiaticus‐infected and noninfected Diaphorina citri to entomopathogenic fungi and their detoxification enzyme activities under different temperatures

“…Although previous studies have been conducted to show the effect of temperature on synthetic insecticides susceptibility, the alteration in entomopathogenic fungi pathogenicity due to changes in temperature was not understood (Deng, Zhang, Wu, Yu, & Wu, ; Garcia et al., ; Lasa, Williams, & Caballero, ; Zhang et al., ). However, susceptibility to entomopathogenic fungi was increased in Las‐infected as compared to uninfected D. citri , but Las infection did not affect the correlation coefficients between temperature and psyllids mortality.…”