Effective concentrations of garlic distillate (Allium sativum) for the control of Tetranychus urticae (Tetranychidae)

The two‐spotted spider mite, Tetranychus urticae Koch, is a worldwide pest that feeds on a large variety of plant families. Because its resistance to acaricides is spreading rapidly, the development of new biological control tactics for population management is crucial. Plant extracts, such as garlic extract (Allium sativum Linn.), may represent viable alternatives, because they are currently considered to be minimum‐risk pesticides. Although garlic is known for its acaricidal properties, the extract concentration that provides the most efficient control has not yet been precisely determined. In this study, we conducted a series of laboratory experiments to determine the susceptibility of adult females to different concentrations of garlic extract. Fresh garlic cloves were steam‐distilled and sprayed using a Potter spray tower. Mortality and fecundity were measured upon treatment with garlic extract concentrations ranging from 0.46 to 14.4 mg/l. Female mortality increased with concentration, with LD₅₀ and LD₉₀ values of 7.49 and 13.5 mg/l, respectively. Reduced fecundity was previously observed at concentrations of 0.36 and 0.74 mg/l. The chemical composition of the Allium sativum distillate was characterized by reversed‐phase high‐performance liquid chromatography coupled with photodiode array detection, GC/MS and Fast GC‐FID against an authentic standard (Standard, Bioextract).Vinyl dithiin, diallyl disulphide, diallyl trisulphide and methyl allyl trisulphide were identified based on their mass spectra. Sesquiterpenoids were identified by their retention index.