Effect of stinging nettle, African Spider plant and chilli extracts on two spotted spider mite (tetranychus urticae koch) population and damage on roses

Abstract

Tetranychus urricae 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 fiwrescence (solanaceae) against the two spotted spider mite T erranychus urticae Koch (Acari; T erranychidae) on rose flowers grown under greenhouse. 100g of each plant extracts was constituted in methanol and distilled water separately and rose leaves at 3 leaflet stage were immersed in it. Ten TI 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 with nine treatments replicated three times. Methanol was found to be the most effective solvent and Cleome gynandra, Urtica dioica and Capsicum frutercence methanoic extracts identified and recommended for further evaluation in the field trials for repellence and eflicacy efiects on the yield and quality of out rose flowers. Results showed that these extracts from methanol were effective against T. urticae with the number of mites repelled significantly higher at P5005. 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 after exposure. However, the observations also showed that plant extracts have a slow mortality effect on the two spotted spider mites over the six days period compared to Polytrin miticide which attained approximately 70% kill on the first day to sixth 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 mortality effects which may be used as there is considerable acaricidal activity of C. gynandra, C. frutescence and U. dioica on T. urticae. Their use against the two spotted spider mites significantly reduced the population of mites on rose leaves within a period of six days. However, the level of mortality 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