The variation of abundance and fruit damage of Bactrocera dorsalis on two commercial varieties of Mangifera indica in main Bio-climatic Zones of Sri Lanka

Abstract

Bactrocera dorsalis Hendel, (Diptera: Tephritidae) is one of the serious fruit pests in South Asia. In Sri Lanka, there are dearth of past studies on the abundance and infestations of B. dorsalis on commercially important fruit varieties. Hence, the present study aimed to investigate the abundance of B. dorsalis adults and their infestation levels on Willard (Wld) and Karthakolomban (Kc) mango varieties grown in main bio-climatic zones of Sri Lanka. The study was conducted from September 2020 to February 2021 in eight study sites of four main bio-climatic zones. In every month, flies were collected from field traps. Infested fruits were also collected from study sites and fruit fly infestation levels and adult emergence were studied in the laboratory. The highest percentage of average infestation (Wld: P>0.05; Kc, P<0.05) and the highest mean value for the adult emergence for both mango varieties were recorded in the intermediate zone. The adult emergence for Kc was higher than the Wld in all study sites and it was significantly different between two mango varieties (P<0.05). The highest number of B. dorsalis were collected from traps in the intermediate zone (Wld: P<0.05; Kc, P>0.05). The infestation percentages, adult emergence, and the abundance of caught flies increased significantly during the study period for both Wld and Kc (P<0.05). The abundance of trapped flies was significantly varied between mango varieties (P<0.05) and positively correlated with the fruit infestation (Wld: r= 0.69; P<0.05 and Kc: r= 0.61; P<0.05). Trap collections for Kc in the intermediate zone showed a significant positive correlation with the rainfall (r= -0.90; P<0.05). The result of the present study can provide baseline information for the B. dorsalis infestation on two commercial mango varieties and the knowledge on their abundance in different bio climatic zones will be helpful to refurbish current pest management strategies.