Studies on population dynamics of the scarlet mite, Brevipalpus phoenicis, a pest of tea in Indonesia

Tea is the national drink of Indonesia. The habitual consumption prevents intestinal infections; the production provides many Indonesians with a living. The production is affected by scarlet mites (Brevipalpus phoenicis GEIJSKES), an important pest of tropical and subtropical crops. It is one of the main pests of tea in Indonesia and inhabits virtually all tea bushes. The factors restricting the development of this mite on tea in West Java were studied by observations and experiments in the laboratory and the tea gardens of the Research Institute for Tea and Cinchona.Scarlet mites multiply fast under favourable conditions. The intrinsic rate of increase (r m = 0.0610) however is far less than that of some spider mites. The scarlet mite populations develop continuously in the field, without synchronization. The mites stay on the undersurface of the tea maintenance leaves and are rather sedentary. A deteriorating leaf quality triggers off migration with a positive phototactic orientation, i.e. towards younger leaves of the bush.Different tea clones and seedlings sustain significantly different mite densities as a consequence of differences in host plant resistance. Tea bushes are pruned once in four years in West Java. This strongly reduces the abundance of scarlet mites. The populations build up slowly and exponentially to a mean equilibrium level which is attained around two years after pruning. Most populations have a low and rather stable density during the second two years of the pruning cycle; some populations have high and fluctuating densities. Generally speaking, the populations especially increase during the dry seasons and decrease during the transitory periods. Maxima are reached usually at the end of the dry season. The fluctuations are not directly related to the average minimum or maximum temperature, average minimum relative humidity or the total rainfall. Application of copper fungicides (copperoxychloride) increases the average mite densities and esp