Examining the spatial distribution pattern and optimum sample size for monitoring of the white mango scale insect, Aulacaspis tubercularis (Newstead) (Hemiptera: Diaspididae) on certain mango cultivars

Abstract

The white mango scale insect, Aulacaspis tubercularis (Newstead) (Hemiptera: Diaspididae) is one of the most destructive pests of mango trees in Egypt. The main objective of the present work is to estimate the spatial distribution pattern and minimum sample size for monitoring populations of A. tubercularis on six different cultivars of mango through the two successive years of 2017/2018 and 2018/2019 at Esna district, Luxor Governorate, Egypt. Data on the indices of distribution and Taylor’s and Iwao’s regression analyses indicate significant aggregation behaviour during each year in all the tested cultivars of mango trees, that may be caused by environmental heterogeneity. The regression models of Taylor’s power law (b) and Iwao’s patchiness (β) were both significantly >1, indicating that A. tubercularis had an aggregation distribution with a negative binomial distribution during each year in all the tested mango cultivars. The Iwao regression coefficients were used to determine the optimum sample size required to estimate populations at three fixed precision levels. The optimum size decreased with increased density in all levels of precision (5, 10 and 15%) in all tested mango cultivars. These can be deployed to develop a sampling plan to estimate the population density accurately. Results suggesting that the optimum sample size was flexible and the precision levels of 5 and 10% were suitable for ecological or insect behavioral studies of A. tubercularis where a higher level of precision is required, whereas, for pest management programs, a 15% level would be acceptable. Furthermore, the distribution, different mango cultivars, and sampling protocol presented here could be used as a tool for future research on pest management methods for this pest.