Survival and population dynamics of the red palm mite, Raoiella indica Hirst (Acari:Tenuipalpidae), in dry and wet experimental conditions

We conducted greenhouse and laboratory experiments to determine the survival rates and dynamics of RPM populations exposed to different water conditions. RPM’s infested coconut palms grown in pots were distributed in two treatments, ten replicates. In the first treatment plants received water from an overhead spray system (9 mm of water, three times per week) simulating rainfall of 1,300mm per year. For the second treatment irrigation was applied directly to the base of the palms. Petri dishes with water were placed under the palm canopies to trap falling mites. The leaf area projected over the Petri dish was counted for mites. In addition, mites were counted on the second youngest expanded leaf. Finally, double-sided tape was placed at the base of the palm trunk to trap mites. Mites were counted monthly for four months. Plant chlorophyll, leaf area, and stomatal conductance were measured during the experiment. In the first treatment (‘rain’) the number of mites was more than 60% higher at the second month than the dry treatment. In laboratory, fifty female mite adults were placed in 1.5mL tubes (five replicates/treatment) and subjected to one of two treatments. In the wet treatment, 1 mL of water was added to the tube. In the dry treatment, no water was added. The control was coconut leaf arenas placed in Petri dishes. The survival of mites was determined for 1 to 22 days at 26C. The mite survival at 10 days was 88% in the leaf arena, 49% in the tubes with water and zero in the dry treatment.