Sabrine Attia

A review of the major biological approaches to control the worldwide pest Tetranychus urticae (Acari: Tetranychidae) with special reference to natural pesticides

The two-spotted spider mite, Tetranychus urticae Koch, is a phytophagous pest that can cause significant yield losses in many agricultural crops, including fruits, cotton, vegetables, and ornamentals. To date, 3877 host species have been reported around the world in both outdoor crops and greenhouses. In this paper, we present the common methods to control this pest including chemical and biological practices. While synthetic acaricides have been widely used to manage T. urticae, in recent years, interest in pesticides derived from plants has increased considerably as a result of environmental concerns and pest population resistance to conventional pesticides. Some botanical pesticides can be easily produced, are relatively efficient against pests, and with few exceptions, their mammalian toxicity and persistence in the environment is low. Thus, the use of plant extracts appears to be a promising alternative strategy for pest management. The present paper reviews studies on the biocidal activities of plant extracts, including essential oils, against T. urticae, a plant-feeding mite found worldwide and a serious agricultural and home garden pest.

Acaricidal activity of 31 essential oils extracted from plants collected in Tunisia

The two-spotted spider mite Tetranychus urticae Koch is a worldwide pest, feeding on a large variety of plant families. As its resistance to acaricides spreads rapidly, it is crucial to develop new biological control tactics to manage its populations. In this respect, essential oils may be a good alternative, as they are currently considered minimum-risk pesticides. In this paper, we conducted a series of laboratory experiments to determine the susceptibility of adult females to 31 essential oils extracted from plants collected from Tunisia and compare it with the results obtained with two synthetic acaricides (spirodiclofen and fenbutatin oxide). Details of the essential oil yield of these plants were also recorded. A maximum yield of 0.5% was obtained. Laboratory bioassay indicated that the development of the tetranychid mite population was significantly affected by the use of Deverra scoparia, Haplophyllum tuberculatum, Chrysanthemum coronarium and Mentha pulegium plant extracts that killed 97%, 93%, 93% and 91% of T. urticae, respectively. The chemical composition of the most effective extracts were characterized by gas chromatography–mass spectrometry (GC–MS) and fast GC–flame ionization detector (FID). The evaluation of the potential of biologically active plant volatiles against T. urticae might provide a new approach to the development of natural acaricides to be used both in biological and integrated pest management strategies for controlling two-spotted spider mites.

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.

Chemical Composition and Acaricidal Properties of Deverra scoparia Essential Oil (Araliales: Apiaceae) and Blends of Its Major Constituents Against Tetranychus urticae (Acari: Tetranychidae)

ABSTRACT The essential oil of Deverra scoparia Coss. & Durieu was investigated for its acaricidal activity against the worldwide pest twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The essential oil was analyzed by fast gas chromatography (GC) and GC-mass spectrometry. The activities of its individual and blended constituents were determined. Our study showed that female mortality increased with increasing D. scoparia oil concentrations, with LD50 and LD90 values at 1.79 and 3.2 mg liter-1, respectively. A reduction in fecundity had already been observed for concentrations of 0.064, 0.08, and 0.26 mg liter-1 D. scoparia essential oil. Ten major components, comprising 98.52% of the total weight, were identified; &agr;-pinene was the most abundant constituent (31.95%) followed by sabinene (17.24%) and &Dgr;3-carene (16.85%). The 10 major constituents of D. scoparia oil were individually tested against T. urticae females. The most potent toxicity was found with a-pinene, &Dgr;3-carene, and terpinen-4-ol. The presence of all constituents together in the artificial mixture caused a significant decrease in the number of eggs laid by females, at 0.26 mg liter-1 (11 eggs), compared with the control (50 eggs). The toxicity of blends of selected constituents indicated that the presence of all constituents was necessary to reproduce the toxicity level of the natural oil.

Acaricidal activities of Santolina africana and Hertia cheirifolia essential oils against the two-spotted spider mite (Tetranychus urticae)

BACKGROUND Many plant essential oils show a broad spectrum of activity against pests. This study investigated the effects of two essential oils on Tetranychus urticae, one of the most serious pests in the world. RESULTS The chemical composition of the two oils was characterised by GC-MS. The most abundant component in the Santolina africana (Jord. & Fourr) oil was terpinen-4-ol (54.96%), while thymol (61%) was prevalent in the Hertia cheirifolia (L.) oil. Mortality and fecundity were measured upon treatment with oil concentrations ranging from 0.07 to 6.75 mg L(-1) with a Potter spray tower. Mite mortality increased with oil concentration, with LC(50) values of 2.35 mg L(-1) for S. africana and 3.43 mg L(-1) for H. cheirifolia respectively. For both oils, a reduction in fecundity was observed at concentrations of 0.07, 0.09 and 0.29 mg L(-1) . Artificial blends of constituents of oils were also prepared and tested with individual constituents missing from the mixture. The results showed that the presence of all constituents was necessary to equal the toxicity of the two natural oils. CONCLUSION S. africana and H. cheirifolia oils can provide valuable acaricide activity with significantly lower LC(50) values. Thus, these oils cause important mortality and reduce the number of eggs laid by females.