Abstract
The present study was carried out to investigate the effect of five plant extracts, Limoniastrum guyonianum Del., Zygophyllum album L., Calotropis procera (Ait.), Thymelaea hirsuta (L.) Endl and Dodonaea viscosa L. at the concentrations 0.01 and 0.005 %. The toxic effect of these concentrations was tested against adult females of the Two-spottedd spider mite Tetranychus urticae Koch (TSSM) 24, 48 and 72 h after treatment under laboratory conditions. The results showed that, after 72 h, the highest mortality 93.33% was recorded by treatment with seeds of C. procera followed by leaves of D. viscosa 86.67% at the concentration of 0.01%. At the concentration 0.005%, the highest mortality was 66.67% by C. procera (seed extract). Under greenhouse conditions, after 72 h at 0.01 % and 0.005 % concentrations were giving a highly percent reduction of hatchability for eggs at C. procera (seeds extract) with an average 95 % and 79.49 % respectively. Also, of larva stages was recorded highly percent mortality at 0.01% and 0.005 % concentration of C. procera (seeds extract) 91.67 % and 70% respectively. In nymphs, the highest mortality percentage with C. procera (seeds) at the same concentrations after 72 h were recorded 93.75% and 71.43 % respectively. In adult females was found the highest mortality percentage in C. procera (seeds extract) at 0.01% and 0.005 % concentration after 72 h was recorded 91.67% and 76.92 %. Analytical studies proved that major amounts of phenolic compounds were detected in T. hirsuta catechin, gallic and chlorogenic acids at the concentrations 1609.24, 1066.78 and 839.67 µg/g., respectively. In C. procera (seeds extract) it was found that phenolic compounds were lower than T. hirsuta, while coumaric acid has been only identified in C. procera seeds (21.08 µg/ g. plant). In D. viscosa, phenolic compounds were represented by chlorogenic acid (267.41 µg/ g plant) and gallic acid (84.43 µg/ g plant), while catechin was not detected. The highest mortality percentage of T. urticae treated with seeds extracts may be due to the appearance of coumaric acid, which was found in seeds more than other extracts.
Highlights
Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most polyphagous spider mite species and is a major pest in many cropping systems worldwide (Nauen et al 2001)
Rearing of the Two-Spotted Spider Mite (TSSM): 1.Source of T. urticae: The Two-spotted spider mite was collected from infested cucumber, tomato, and pepper plants are grown at Faculty of Agricultural, Ain Shams University, Egypt. 2.Mite Colony: One newly matted adult mite female was transferred by a fine camel hair brush to a sweet potato leaf (1mm), kept on a moist cotton wool pad in Petri dish and left for laying eggs
According to the results showed in Table (1) and Figures (1&2) it can be stated that the highest mortality percentage after 24 h was 73.33% at C. procera seeds extract and D. viscosa at concentration 0.01%, but there were no significant differences between them were noticed
Summary
Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most polyphagous spider mite species and is a major pest in many cropping systems worldwide (Nauen et al 2001). Plant phenolic compounds act as antioxidants, structural polymers (lignin), attractants (flavonoids and carotenoids), UV screens (flavonoids), signal compounds (salicylic acid and flavonoids) but they are defense response chemicals (tannins and chlorogenic acid). These substances are produced by plants that act as agents protecting the plant from pathogens and pests, we must first consider whether the compounds are present prior to the time of infection or whether they are synthesized in response to damage
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