Spatial distribution pattern of Diaphorina citri Kuwayama (Hem.: Liviidae) on Lime (Citrus aurantifolia) and Orange (Citrus sinensis) in citrus orchards of Iran

The spatial distribution Pattern of Asian citrus psyllid (ACP), Diaphorina citri, nymphs on Lime and Orange was studied in Jiroft-Bluk section (Kerman Province, Iran) during 2014. The distribution pattern was analyzed using six methods: the indices of variance/mean relationship, coefficient of Green, Lloyd's mean crowding, K index, Iwao's patchiness regression and Taylor’s Power Law. The s2/X (ranging from 1.98 to 4.89 for lime, and 3.50 to 5.49 for orange); Lloyd’s index of patchiness were greater than unity; The Green's index was greater than 0; The K index, in all cases was greater than 0. The slopes of Taylor's power law and Iwao's patchiness regression methods were 1.89
and 1.31 for Lime and 1.45 and 1.30 for Orange, respectively. These slopes had significant difference from one. Based on various mathematical indices of dispersion and regression models, the field dispersion patterns of ACP nymphs were aggregated. Densities of psyllid nymphs were significantly higher on Lime. The population of psyllid nymphs on the tree quadrants did not differ significantly on Lime, however, on orange, psyllid nymphs was also significantly in lower numbers in south quadrant of trees. Densities of psyllid nymphs in the upper half of the canopy were significantly higher than the lower half.

Key words: Spatial distribution, Population density, Taylor’s Power Law, Iwao's patchiness regression

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