Toxicity of Thiamethoxam and Mixtures of Chlorantraniliprole Plus Acetamiprid, Esfenvalerate, or Thiamethoxam to Neonates of Oriental Fruit Moth (Lepidoptera: Tortricidae)

Abstract

To assess the toxicity ofthiamethoxam and three mixtures of insecticides to oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), we added the insecticides to diet and fed it to neonates of two laboratory colonies; mortality was assessed after 96 h. Thiamethoxam was much less toxic than insecticides previously tested. Five of six analyses of the joint action of chlorantraniliprole plus acetamiprid, esfenvalerate, or thiamethoxam indicated that toxicity was not independent and not correlated. For chlorantraniliprole plus acetamiprid, mortality was slightly lower than expected at low concentrations and greater than expected at high concentrations. For chlorantraniliprole plus esfenvalerate, mortality was less than expected at nearly all concentrations, suggesting antagonism despite the two compounds' different modes of action. For chlorantraniliprole plus thiamethoxam, observed mortality exceeded expected mortality at low concentrations, but this trend did not continue at higher concentrations. Although the null hypothesis of independent and uncorrelated toxicity was rejected for chlorantraniliprole plus acetamiprid and chlorantraniliprole plus thiamethoxam in three of four analyses, differences between observed and expected mortality were minor and inconsistent over the range of concentrations tested. We do not expect these mixtures to exhibit significant synergism or antagonism in the field. Apparent antagonism between chlorantraniliprole and esfenvalerate is particularly relevant because these insecticides (or chlorantraniliprole plus a different pyrethroid) may be used together in apples or peaches for control of oriental fruit moth and hemipteran pests. The effectiveness of each insecticide against oriental fruit moth might be reduced in such applications.

Degradation of Thiamethoxam in aqueous solution by ozonation: Influencing factors, intermediates, degradation mechanism and toxicity assessment

“…Since the discovery in 1991, Thiamethoxam (THIA), one of the most profitable neonicotinoids, has quickly become the best-selling insecticide because of its unique biological and chemical properties: flexible application methods, favorable safety profile, low use rate, long-lasting residual activity and excellent efficacy for modern integrated pest management programmes (Maienfisch et al, 2001), and plays an active role in the control of numerous sucking and biting insect pests (Misra and Senapati, 2003;Sharma and Lal, 2002). However, THIA is toxic (Jones et al, 2012), bio-accumulative (Maienfisch et al, 2001) and difficult to mineralize (Pena et al, 2011;Myresiotis et al, 2012), undoubtedly threatening humans (Banks et al, 2005) and ecological health because of its ability to harm liver, kidney, and testes (Dong et al, 2011). It threatens the surface and underground water because of its low soil sorption, high leaching capability and high solubility in water .…”

Thiamethoxam induces oxidative stress and antioxidant response in zebrafish (DanioRerio) livers

“…Thiamethoxam is stable to hydrolysis under acidic or neutral pH condition (Morrissey et al, ). Furthermore, the compound is toxic (Cavusoglu et al, ; Jones et al, ), bioaccumulative (Guillen and Bielza ), and difficult to mineralize (Pena et al, ). In addition, thiamethoxam also shows significant risk to aquatic ecosystems and human health due to their resistance to biological treatment (Yang et al, ).…”

Pesticide contamination of milkweeds across the agricultural, urban, and open spaces of low elevation Northern California

“…This does not mean that the low concentration of many compounds is not important, as they could act synergistically, which cannot be quantified with the current data. There are far fewer studies on interactions of multiple compounds, however synergistic effects have been identified in Lepidoptera for thiamethoxam, chlorantraniliprole, imidacloprid, and methoxyfenozide (Jones et al, 2012b; Liu et al, 2018b; Chen et al, 2019), all of which we detected. These findings suggest possible negative effects on lepidopterans; however, it is clear that more research is needed to understand the synergistic effects of field-relevant concentrations on non-target insects.…”

“…While individual pesticides can have lethal and sub-lethal effects (Pisa et al, 2014), plants sampled in agricultural landscapes often contain multiple compounds (Krupke et al, 2012; Olaya-Arenas and Kaplan, 2019). The literature on the additive or synergistic effects of pesticide combinations on non-target organisms is sparse, however particular combinations have been shown to behave synergistically in insects broadly (Zhu et al, 2014; Morrissey et al, 2015) and pest Lepidoptera specifically (Jones et al, 2012a; Liu et al, 2018a; Chen et al, 2019). By focusing on one or a few select pesticides or even a single class of pesticides, the realized risk of these chemicals on non-target insects is likely being underestimated.…”