Impact of Climatic Factors on the Population Density of Spider Mites (Acari: Tetranychidae) Infesting Hedge Bamboos

Bambusa multiplex (Lour. ) Raeusch. ex Schult.& Schult. f. is an easy to maintain, hedge bamboo, as well as being very hardy, clumping variety, it is by far the best bamboo for growing potted indoors. A study on the seasonal fluctuation in the population density of spider mites (Schizotetranychus spp. ) on this bamboo was carried out in the Calicut University Campus from November, 2012 to October, 2013 in the Malappuram district of Kerala. Results of the study indicated that spider mites live on the undersides of leaves in colonies, being protected by silken webs and inducing damage by puncturing the leaf tissue and sucking the plant sap resulting in chlorosis of the infested leaves thereby decreasing the vigour of the plants. The population density of these mites was generally showing an increasing trend up to May and then due to the onset of rainfall it was decreased drastically. The average number of spider mites present per leaf of B. multiplex was 5.02. The effects of temperature, relative humidity and rainfall on the population density of these mites were discussed in the paper. Temperature showed a positive correlation (r = 0.77) with the population of spider mites whereas relative humidity showed a least negative correlation (r = -0.18). Rainfall exerted a tremendous negative impact on the population density of spider mites (r = 0.46).