Evaluation of systemic neonicotinoid insecticides for the management of the Asian citrus psyllid Diaphorina citri on containerized citrus

Abstract

If the time needed to achieve effective thresholds of a systemic neonicotinoid is known, treatments at production facilities could be scheduled that would minimize unnecessary post-treatment holding periods and ensure maximum retention of effective concentrations after the plants have shipped to retail outlets. The rapid uptake of the insecticides and retention at effective concentrations in containerized citrus suggest that the current 30 day post-treatment shipping restriction from production facilities to retail outlets outside of quarantine could be shortened to 14 days. Thiamethoxam should be added to the list of approved nursery treatments. © 2016 Society of Chemical Industry.

Influence of Tree Size and Application Rate on Expression of Thiamethoxam in Citrus and Its Efficacy Against Diaphorina citri (Hemiptera: Liviidae)

“…Thiamethoxam is a neonicotinoid precursor to clothianidin ( Nauen et al 2003 ) and clothianidin is known to metabolize into TZNG and TZMU ( Kim et al 2012 ). While clothianidin is effective against D. citri , little is known about the influence of specific dosage on D. citri feeding behavior or mortality ( Byrne et al 2017 ). Langdon and Rogers (2017) found that the LC 50 of thiamethoxam and clothianidin to the LS population by ingestion was 0.11 and 0.09 ppm, respectively, while the LC 90 was 4.94 and 9.35 ppm, respectively.…”

“…Consequently, we cannot determine how any one metabolite, including clothianidin, affects D. citri mortality in this study. While understanding the role of each metabolite is beyond the scope of this investigation, it is possible that the combination of multiple metabolites has an additive effect on D. citri mortality as suggested by Byrne et al (2017) . Byrne et al (2017) demonstrated a strong correlation between thiamethoxam and the metabolite, clothianidin, but were unable to determine whether mortality was the result of either thiamethoxam or clothianidin, or a combination of the two.…”

“…While understanding the role of each metabolite is beyond the scope of this investigation, it is possible that the combination of multiple metabolites has an additive effect on D. citri mortality as suggested by Byrne et al (2017) . Byrne et al (2017) demonstrated a strong correlation between thiamethoxam and the metabolite, clothianidin, but were unable to determine whether mortality was the result of either thiamethoxam or clothianidin, or a combination of the two. Although earlier studies used ELISA to quantify expression of neonicotinoids ( Castle et al 2005 , Garlapati 2009 , Sétamou et al 2010 ), they did not quantify metabolites of thiamethoxam nor manipulate tree size or application rate to study effects on thiamethoxam titer.…”

“…Residual activity of insecticides applied to the soil are likely influenced by factors such as soil type, application volume, irrigation, tree age and size, and environmental conditions such as rainfall. Moreover, neonicotinoid insecticides metabolize into various analytes, though the effect of any one resulting metabolite on D. citri mortality is unknown ( Byrne et al 2017 ). For example, thiamethoxam metabolizes into clothianidin ( Nauen et al 2003 ) and clothianidin further metabolizes into TZNG ( N -(2-chlorothiazol-5-ylmethyl)- N -nitroguanidine) and TZMU ( N -(2-chlorothiazol- 5-ylmethyl)- N -methylurea) ( Kim et al 2012 ).…”

“…Previous insecticide trials evaluating soil-applied neonicotinoids used percent control relative to the untreated check or mean number of D. citri per sample size to assess efficacy ( Qureshi and Stansly 2007 , Qureshi and Stansly 2009 , Ichinose et al 2010 , Sétamou et al 2010 , Byrne et al 2012 , Rogers 2012 ). Additional studies specifically quantified the concentration of neonicotinoids in leaf tissue following soil application using enzyme-linked immunosorbent assay (ELISA) ( Castle et al 2005 , Garlapati 2009 , Sétamou et al 2010 , Byrne et al 2017 ). However, only one attempted to compare percent control with chemical titer within citrus leaf tissues.…”