Long‐term persistence and efficacy of spinosad against Rhyzopertha dominica (Coleoptera: Bostrychidae) in wheat

Abstract

A laboratory study was undertaken to determine the persistence and efficacy of spinosad against Rhyzopertha dominica (F.) in wheat stored for 9 months at 30 degrees C and 55 and 70% relative humidity. The aim was to investigate the potential of spinosad for protecting wheat from R. dominica during long-term storage in warm climates. Wheat was treated with spinosad at 0.1, 0.5 and 1 mg kg(-1) grain and sampled after 0, 1.5, 3, 4.5, 6, 7.5 and 9 months of storage for bioassays and residue analyses. Residues were estimated to have declined by 30% during 9 months of storage at 30 degrees C and there was no effect of relative humidity. Spinosad applied at 0.5 or 1 mg kg(-1) was completely effective for 9 months, with 100% adult mortality after 14 days of exposure and no live F1 adults produced. Adult mortality was <100% in some samples of wheat treated with 0.1 mg kg(-1) of spinosad, and live progeny were produced in all samples treated at this level. The results show that spinosad is likely to be an effective grain protectant against R. dominica in wheat stored in warm climates.

Bioactivities of Cocos nucifera L. (Arecales: Arecaceae) and Terminalia catappa L. (Myrtales: Combretaceae) leaf extracts as post-harvest grain protectants against four major stored product pests

“…It is highly advantageous if a plant product is active for longer durations and protects or prevents the grain from further infestation. Previously, several compounds have been shown to be highly effective as long-term grain protectants having residual toxicity against most of the major stored product pests (Athanassiou et al 2004(Athanassiou et al , 2005Vayias et al 2006;Daglish and Nayak 2006;Stathers et al 2008). Arthur (1996) pointed out that the use of residual insecticides remains controversial because of the demand for the residue-free food.…”

Effects of Short Exposures to Spinosad-Treated Wheat or Maize on Four Stored-Grain Insects

“…Before this, spinosad has already been proved very effective against a range of stored-grain insect species, even at lower rates than the application rate, in both laboratory (Fang et al 2002a, Toews and Subramanyam 2003, Nayak et al 2005, Daglish and Nayak 2006 and Þeld tests (Maier et al 2006, Subramanyam et al 2007, Daglish et al 2008. Due to the above-mentioned characteristics and its low mammalian toxicity, spinosad is a desirable alternative to the use of traditional grain protectants, especially organophosphorous insecticides (OPs), which often are very toxic to mammals.…”

Effect of temperature and relative humidity on the efficacy of spinetoram for the control of three stored product beetle species

“…progeny production counts, R. dominica was highly susceptible to spinetoram-treated wheat. This efficacy of spinosyns against R. dominica has been extensively examined for spinosad, the first commercially available spinosyn-based insecticide (Nayak et al, 2005;Daglish and Nayak, 2006;Athanassiou et al, 2011;Hertlein et al, 2011). Also, newer studies testing spinetoram against stored product pests, concluded that R. dominica is highly susceptible to this compound .…”