Studies on the Trypetids and their natural enemies in West Pakistan. III. Dacus (Strumeta) zonatus (Saunders).
Syed R. A., Ghani M. A., Murtaza M.
Author Affiliation: Pakistan Station, Commonwealth Institute of Biological Control, Rawalpindi.
Technical Bulletin, Commonwealth Institute of Biological Control : 1-16
Abstract : In this third part of a series [cf. RAE/A 52, p. 401], information is given on the food-plants, seasonal history in various areas, seasonal activity and geographic distribution in relation to temperature, bionomics, and natural enemies of Dacus zonatus (Saund.), which is a major pest of mango and guava over all Pakistan except the north-west and also attacks the fruits of many other trees and plants, especially plum. It is active throughout the year in coastal areas and inactive for 1-3 months towards the north in winter. In observations in 1962-64, it was active at mean monthly temperatures of 62-97 deg F and occurred in areas with mean annual temperatures of 74-80 deg F. Mean temperatures of below 50 deg F, even for a month, had marked adverse effects on a population. The egg, larval and pupal stages lasted about 43 h, 8 days and 10 days, respectively; pairing occurred about 15 days after adult emergence and oviposition began about 6 days later. The adults usually entered fruit orchards for oviposition only, and rested and fed on plants that were either in flower or coated with honeydew from aphid infestations. Parasitism was very low. A species of Opius (possibly O. longicaudatus (Ashm.)) occurred over almost the whole distribution area of D. zonatus but afforded negligible control; it appeared to have two strains, of which the southern one attacked only D. zonatus and the northern one both D. zonatus and D. dorsalis Hend. The difficulties are discussed of control by introduced parasites, chemical sprays and the sterile-male technique against a pest present throughout most of the year in widely scattered orchards. The most promising method would appear to be to prevent the year-round development of D. zonatus by prohibiting the cultivation of two or more of its major food-plants, with different phenologies, in a single area.