Toxicity to Diaphania hyalinata, selectivity to non-target species and phytotoxicity of furanones and phthalide analogues.

Background: Despite being of great importance to crop protection, the disadvantages of intensive and inappropriate use of pesticides have stimulated the search for more selective and less harmful agrochemicals. Thus, we have evaluated the effectiveness of 16 synthetic molecules (phthalides and precursors) to control the melonworm Diaphania hyalinata, a key pest in cucurbit crops of economic importance in Brazil. The selectivity to beneficial organisms Solenopsis saevissima and Tetragonisca angustula and the phytotoxicity to Cucumis sativus of the promising insecticides were also assessed.

Results: In the screening assay, compounds 1 and 6 provided 91 and 88% mortality of the melonworm. Compound 1 presented higher toxicity (median lethal dose LD50 = 15.99 µmol g(-1) ) and higher speed on pest control (median survival time LT50 = 420 min) than compound 6 (LD50 = 44.51 µmol g(-1) and LT50 = 840 min). Both compounds inhibited less than 11% of host-plant growth and caused ≤36 and ≥93% mortality of predator and pollinator respectively.

Conclusion: Among the tested compounds, only compounds 1 and 6 were effective in melonworm control. Both compounds presented no considerable phytotoxicity and were selective to predator but non-selective to pollinator, which enables their application for pest control if the exposure of the bees is minimised. © 2015 Society of Chemical Industry.