Sustainable control stategies of the two-spotted mite Tetranychus urticae Koch (Prostigmata: Tetranychidae) in citrus

Abstract: The two spotted mite is a key pest in Mediterranean citrus crops. This citrus
agrosystem harbors a rich and abundant community of native predators that feed on
Tetranychus urticae. The groundcover vegetations also plays an important role in the
population regulation. However, recurrent outbreaks during summer lead to repetitive sprays to control its populations. During two consecutive years, a T. urticae control strategy based on conservation biological control and the use of paraffin oils was implemented in a commercial grove of Citrus clementina cv., Clementina de Nules grafted on Citrange Carrizo rootstock, located in southern Catalonia (Spain). No synthetic acaricides nor insecticides were sprayed during that period. A permanent groundcover was maintained and mowed regularly. The population dynamics of T. urticae and natural enemies in the tree canopies was monitored. The number of symptomatic or spotted leaves, T. urticae individuals per leaf, and the presence of natural enemies were recorded. From August onwards T. urticae population on fruits was also monitored. When the economic threshold was reached, paraffin oil was used to keep it under control. Two sprays during the first season and three during the second were conducted. At harvest, the symptoms caused by T. urticae on fruits were assessed. During the first season, only 1 % of the fruits showed severe scarring and 12 % showed small scars on the fruit rind. At harvest of the second season no fruits with severe scarring were recorded, showing the efficacy of the strategy followed.