Study of spinetoram nano suspension for environmentally friendly control of Plutella xylostella L. (Lepidoptera: Plutellidae)

Abstract

Diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) is the main pest for brassicas and can potentially cause 90% yield losses. Currently the most effective control method is the use of insecticides, with spinetoram Suspension Concentrate (SC) formulation as one of the newest insecticide generations against this pest. However, there are some limitations in current SC formulations, including run-off issues owing to poor wettability, which may cause low efficacy and severe environmental contamination. Nano formulations that involve very small particles of an insecticide active ingredient could be promising candidates to solve this issue. Therefore, this study aims to prepare spinetoram nano suspension formulations using two modifications milling techniques NS1 and NS2, with various sized ZrO2 beads and evaluated their toxicity against 3rd larvae instars of P. xylostella. The PSA and SEM confirmed that NS1 and NS2 produced nano-sized particles pre-milled (2299.44 nm) to smaller than 100 nm. NS1 and NS2 improved the attachment and penetration of spinetoram into the leaf surface as provided a lower contact angle NS1 (56.98°), NS2 (55.82°), SC (80.03°). The LC50 of NS1 and NS2 with the wetting agent test improved the toxicity by 33% (NS1: 0.0061) and 7% (NS2: 0.0085) compared with SC (0.0091). Without the inclusion of the wetting agent, the spinetoram samples were 46% (NS1: 0.0138) and 41% (NS2: 0.0181) more toxic than SC (0.0256). This result was concluded that spinetoram nano suspension formulations can be administered at low doses as indicating their greater safety, and environmental friendliness than basic SC.