Bioactivity of Indigenous Medicinal Plants against the Two-Spotted Spider Mite, Tetranychus urticae

Forty two methanol extracts and 12 aqueous extracts of 29 indigenous medicinal plant species were tested for their acaricidal bioactivity against the two spotted spider mite, Tetranychus urticae adults at the laboratory. Fourteen methanol plant extracts caused significant mortality in mites. This is the first report for the potential effect on survival of mites for 27 tested endemic plant species. Methanol whole plant extracts (WPEs) of Lotus carmeli, Alchemilla diademata, Eryngium deserlorum and aqueous fruit extracts (FrEs) of Melia azedarach caused toxic effects against the adult mites in the range of 41-46% mortality. The methanol WPE of L. carmeli and the aqueous FrE of M. azedarach (1-5) caused the highest mite mortality of 43.55% and 45.55%, respectively and each was used as reference sample for potential acaricidal activity in the methanol and aqueous treatment groups. The latter extract was not significantly different in its effect from aqueous extracts of M. azedarach leaf extract (LE) and Achillea damascena WPE. Methanol extracts of Salvia rubifolia flowers and Calendula palestina FrE were found to be more active against the adult mite than their extracts of other plant parts as leaves and flowers, respectively. The former two extracts, flower extracts of Anthemis scariosa, Echinops gaillardoti, Nepeta curviflora, and Ranunculus cuneatus, leaves and stems extract of An. scariosa and WPEs of Melissa inodora, Ranunuculus myosuroides, Origanum libanoticum and Ac. damascena were found to be comparable in their acaricidal activity to that of the whole plant extract of L. carmeli. Thus, these bioactive extracts of some local plant species can cause toxicity to adult T. urticae mites and consequently could be an alternative control for mite pests.