Population fluctuation of Diastocera trifasciata (Fabricius, 1775) (Coleoptera: Cerambycidae), cashew branches girdler in the Brobo locality (Central Côte d'Ivoire)

Abstract

Diastocera trifasciata (Coleoptera: Cerambycidae), formerly known as the Analeptes trifasciata, is a fearful girdler of cashew branches in Cote d'Ivoire. The lack of effective means of control and data on the dynamics of this species motivated the present work which aims to study the fluctuations of its population. Specifically, the aim is to determine the period of occurrence of the species, to study the interactions between abiotic and biotic factors and the population of D. trifasciata. Study was conducted from October 2015 to September 2017 in three orchards located in three villages. Manual captures were made on 150 cashew trees per orchard every two weeks during the two years of study. Temperature, relative humidity and rainfall of the area were recorded. Results revealed that there is a significant positive correlation between rainfall and D. trifasciata population. During the two years of study, adults were observed from May after the first rains and persist until January of the following year with a peak in October. No adults were observed from February to April, a period corresponding to the dry season. Mean temperature revealed a significant negative correlation, in contrast to the mean relative humidity being positively correlated with the pest population. Peaks of individuals were recorded when the trees were in the pre-floral vegetative flush phase. All this information guides the choice of the method and the moments of intervention for an efficient fight.