Geostatistical characterization of the spatial distribution of Xylella fastidiosa sharpshooter vectors on citrus
The spatial distribution of the three principal species of sharpshooter (Dilobopterus costalimai Young Acrogonia sp. c Oncometopia facialis Signoret), vectors of Xylella fastidiosa causal agent of Citrus Variegated Chlorosis, was studied by using geostatistics. The evaluations were carried out in a commercial 'Pera' sweet orange (Citrus sinensis [L] Osb.) grove budded on Rangpur lime (Citrus limonia Osb.) located at Bebedouro, Sao Paulo state, aiming to establish better means for vector and disease control. The sharpshooters were monitored using with 50 uniformly distributed 3" x 5" yellow sticky traps hanging down in branches at 1.5 m up to the ground, which were replaced monthly. Acrogonia sp. was the prevalent species sampled. The results were used to adjust population models to semivariograms of the spatial distribution of the three sharpshooters species in the grove. During the three consecutive years of sampling, the population of Acrogonia sp., D. costalimai and O. Jacialis showed an aggregated distribution only during summer, winter and spring, respectively, showing that intensive monitoring of these vectors is necessary to control their population in periods favorable to their development. The aggregation area of the sharpshooters within the orange grove was determined using geostatistic parameters. Acrogonia sp. showed a mean aggregation area of 15,760 m(2), whereas for O.facialis and D. costalimai, the corresponding areas were 11,555 m(2) and 10,980 m(2), respectively. Therefore, in order to obtain a reliable estimate of sharpshooter populations, at least one trap should be used per hectare.