Abstract
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.
Highlights
The two spotted spider mite Tetranychus urticae Koch has been recorded from more than 900 different plant species and its polyphagous nature has been documented worldwide on at least 150 economical crops (Fasulo & Denmark, 2009)
Results of our current study have shown efficacy in decreasing number of live adult mites in some treatments with plant extracts of these medicinal plants, under laboratory conditions
The 5th treatment group including the 3 remaining extracts, 2 fruit extracts and one stem extract, are discussed in a comparative manner related to different plant parts of the same plant species collected from one location; the latter group included 13 extracts of Sa. rubifolia, An. scariosa, N. curviflora and Ca. palestina
Summary
The two spotted spider mite Tetranychus urticae Koch has been recorded from more than 900 different plant species and its polyphagous nature has been documented worldwide on at least 150 economical crops (Fasulo & Denmark, 2009). The degree of resistance to many established acaricides has resulted in a demand for new acaricides as plant derived materials with novel modes of action (Khater, 2012; George et al, 2014). These problems have established the need for alternative pest management control measures that include the search for new classes of pesticides and the reassessment and use of pest control agents of botanical origin. Many plants develop intrinsically secondary compounds as chemical defenses in their eco-habitat These plants might be origin of biodegradable pesticides (Farombi, 2003). These plants might be used further locally as insecticides, acaricides, or rodenticides (Mishra et al, 2013)
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