Insecticidal and acaricidal effect of three Lamiaceae plant essential oils against Tetranychus urticae Koch and Bemisia tabaci Genn.

Abstract

Tetranychus urticae Koch (Acari: Tetranychidae) and Bemisia tabaci Genn. (Homoptera: Aleyrodidae) are two economically important pests of greenhouse vegetables and ornamentals. The management is commonly done based on repetitive applications of chemicals, resulting in environmental pollution and resistance in pest population.

In the present study, essential oil vapours from Micromeria fruticosa L., Nepeta racemosa L. and Origanum vulgare L. (Lamiaceae) were tested for toxicities against the nymphs and/or adults of T. urticae and the adults of B. tabaci. Amounts of the essential oils applied were 2, 4, 6 and 8 μl in each of the desiccators with 4 l capacity, corresponding to 0.5, 1, 1.5 and 2 μl/l air. The essential oil vapours of all three plant species caused the highest mortality in 2 μl/l air doses and at 120 h of exposure in both of two pests’ species. In general, higher mortality was observed as the doses of essential oils and exposure period increased. T. urticae was more tolerant than B. tabaci at all doses of essential oils in all times. The data may suggest that essential oils of all three plants have potential to be used for management of T. urticae and B. tabaci pests in greenhouse conditions.

Introduction

Tetranychus urticae Koch (Acari: Tetranychidae) and the white fly, Bemisia tabaci Genn. (Homoptera: Aleyrodidae) are the major pests of greenhouse plants in the world including Turkey. These pests are commonly controlled by applications of the synthetic insecticides and acaricides (Choi et al., 2004). However, it is difficult to manage both of these pests in greenhouse and/or fields by chemical applications due to resistance. In addition, the use of different synthetic insecticides and acaricides as a pest control method, in order to increase yields and protect stored products, may involve serious health hazards for Mammalia. These insecticides and acaricides are often associated with residuals that are dangerous for the consumer and the environment (Lamiri et al., 2001). In addition, the risk of developing insect resistance and the high cost–benefit ratio of synthetic pesticides pushed research towards investigating alternative insecticides. The number of confirmed resistant insect and mite species to synthetic pesticides has continued to rise, apart from risks associated with the use of these chemicals (Campos et al., 1995, White, 1995). Therefore, in the current scenario, there is an urgent need to develop safer, environmentally friendlier and efficient alternatives that have potential to replace synthetic pesticides and are convenient to use. In the search for alternatives to conventional pesticides, essential oils extracted from aromatic plants have been widely investigated. Their toxicities, arresting and repellent effects to stored-product insects and greenhouse pests have been of special interest during the last decade (Huang et al., 1997, Ho et al., 1997, Obeng-Ofori and Reichmuth, 1997, Tunc and Sahinkaya, 1998, Landolt et al., 1999, Tunç et al., 2000, Tripathi et al., 2000, Choi et al., 2003, Choi et al., 2004, Aslan et al., 2004).

In Turkey, aromatic plants widely separated and there are a very rich and diversified flora, are famous for their nutritional and medicinal characteristic. They are used in various industries such as cosmetics, perfumes, detergents, as well as in pharmacology and food flavoring. In the world, to these rapidly evolving traditional sectors, a new industrial development could be added in the plant protection field.

Micromeria, Origanum and Nepeta are well known genera in the Lamiaceae family, and are typical Mediterranean plants. These genera are generally used as traditional remedy to treat various ailments such as a spasmodic, antimicrobial, insecticides, repellents, expectorant carminative and aromatic for whooping and convulsive coughs, digestive disorders and menstrual problems sedative, anesthetic, antiseptic, abortifacient, antirheumatic, CNS stimulant in addition to the treatment of heart disorders and colds (Ietswaart, 1980, Wollenweber, 1982, Kishore and Dwivedi, 1992, Hallahan et al., 1998, Guner et al., 2000, Tabanca et al., 2001, Aligiannis et al., 2001, Lamiri et al., 2001, Şahin et al., 2004).

Nepeta racemosa, Origanum vulgare and Micromeria fruticosa are three wild medicinal plants distributed mainly in the eastern Anatolia region of Turkey. In previous studies, it has been determined the chemical compositions of essential oils from many medicinal plants species including M. fruticosa, N. racemosa and O. vulgare plants collected from the eastern Anatolia region of Turkey (Bourrel et al., 1993, Güllüce et al., 2004, Şahin et al., 2004). In addition, some other biological activities of these plants species such as antimicrobial and antioxidant properties have been studied up to now (Lamiri et al., 2001, Şahin et al., 2004, Güllüce et al., 2004). However, there have been no attempts to study the toxicity of essential oils from these plants species on economically important pests in the greenhouses or open field conditions.

The objective of this study was to assess in more details the potential of essential oils to control pests of greenhouse crops. Greenhouses, like storehouses and beehives, are closed spaces where essential oil vapours can be applied as fumigants. The toxicity of essential oil vapours obtained from three plant species, M. fruticosa, N. racemosa and O. vulgare to T. urticae and B. tabaci was investigated.