REDUCED ATTACK OF KEORA (<em>SONNERATIA</em> <em>APETALA</em>) BY STEM BORER IN MIXED-SPECIES PLANTATIONS IN COASTAL BANGLADESH

Abstract

A survey was conducted in 1990-1992 on attack by the stem borer, Zeuzera conferta, in mixed-species and monoculture plantations of keora (Sonneratia apetala) in four Coastal Afforestation Divisions and natural stands in the Sundarbans, Bangladesh. In monoculture stands., 51 % of the keora trees were attacked by stem borers, whereas 32% sustained attack in mixed-species stands. In the latter stands, infested trees comprised only 10.6% of the total stems. Infestation levels were similar in plantations and natural stands. Infestation frequency increased from the West coast to the East, with the least infestation in the Sundarbans. There was a significant negative relationship (r = -0.98) between the numbers of kankra (Bru'guiera conjugata) trees and the intensity of infestation in the mixed-species stands in all the coastal divisions. Soil salinity levels in the Sundarbans did not show any correlation (r = 0.12) with infestation. We recommend that in the future keora should be planted with kankra in mixed culture in coastal areas of Bangladesh.