Repellence and Toxicity Effect of Crude Plant Extracts on the Two-Spotted Spider Mite Tetranychus urticae on Roses

Tetranychus urticae Koch is a major pest of cut rose flowers and causes high losses if not controlled effectively on time. Laboratory trials were conducted to evaluate and validate the repellent and toxic properties of three local plants Cleome gynandra (Capparaceae), Urtica dioica (Urticaceae) and Capsicum frutescence (Solanaceae) against the two-spotted spider mite Tetranychus urticae Koch (Tetranychidae; Acari) on rose flowers leaves grown under greenhouse. 100 g of each plant extracts was constituted in methanol and distilled water separately and rose leaves at 3-leaflet stage were immersed in it. Ten T. urticae mites were introduced onto the treated leaves and observations on repellence and mortality of mites was recorded. The experiment was laid out in a Completely Randomized Design (CRD) with nine treatments replicated three times. Methanol was found to be the most effective solvent and Cleome gynandra, Urtica dioica and Capsicum frutescence methanoic extracts identified and recommended for further evaluation in the field trials for repellence and efficacy effects on the yield and quality of cut rose flowers. Results showed that these extracts from methanol were effective against T. urticae with the number of mites repelled significantly at p <= 0.05. Cleome gynandra methanol extract, Capsicum frutescence methanol extract and Urtica dioica methanol extract were the most effective repellents in descending order. Significance of the treatments was more evident with exposure time. The crude extracts on the first day had moderate repellance in the second hour and higher repellence was found on the third and fourth hours. However, the observations also showed that plant extracts have a slow toxicity effect on the two-spotted spider mites over the 6 day period and direct contact toxicity compared to Polytrin miticide which attained approximately 70% kill on the 1st-6th day. The powders were slow acting achieving up to 80% kill on the 6th day as observed in Cleome gynandra methanol extract. The three test plants have repellence and toxicity effects which may be used as there is considerable acaricidal activity of C. gynandra, C. frutescence and U. dioica on T. urticae as repellents and acaricides. Their use against the two-spotted spider mites significantly reduced the population of mites on rose leaves within a period of 6 days. However, the level of toxicity and repellence was dependent upon the period of exposure to the crude plant extracts. The potential benefits of methanoic plant volatile extraction in the control of mites in rose grown for export markets is evident.