Managing shoot borers by using acacia auriculiformis as a nurse crop for establishing mahogany seedlings
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Date
2000-12-16
Authors
Mahroof, R. M.
Edirisinghe, J. P.
Hauxwell, C
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
TIle main factor. which has limited cultivation of mahogany. Swietenia macrophylla, King (Meliaceae: Swietenoideae) is damage by shoot borers (Hypsipvlo spp.). Attack results in destruction of the apical shoot, causing branching of the tree. and significantly reducing the economic value of the timber. Although shoot borers have been intensively investigated no consistently effective control methods currently exist. However, some observations suggested that overhead shade provided by a nurse crop during early growing phase of mahogany seedlings might reduce the attack. Yet much of the information available is anecdotal. Although shade reduces attack by shoot borer. mahogany being a light demander. shade also may reduce the growth of seedlings. Hence a study was designed to assess the effect of different light availability on survival, growth and attack by shoot borers under different light conditions. This study was done from 1997-99 at three sites. two from Rambukkana and one from Mirigama under a nurse crop .-Icacia auriculiformis A. Cunn. Ex Benth. (Miruosaceae). Each site composed of three plots with different canopy openings of high. medium and low shade obtained by pruning of Acacia trees. Within pruned area (5 m x 5 m), 18 mahogany seedlings of similar origin. age and height were planted.
TIle Photosynthetically Active Radiation (PAR) reaching each plot was measured using a data logger with a PAR sensor. Pattern of flushing and growth of mahogany seedlings were recorded monthly. Number of shoot borer attacks per plant was recorded l~ months after planting. Relative PAR values in the three sites varied from 21.6 ± U % in the higher shade gap to 93.1 ± 3.3 % in tlle lower shade gap. Seedling survival a year after planting did not show significant differences between light regimes. Under low shade. seedling height was 57.~ % greater than under high shade. and was highly significant in ANOYA (d.f.=2. P=0.00(1). TIle root collar diameter under low shade was U ± 0.09 em, while that under high shade was 0.8 ± 0.04 cm (d.f=2, P=O.OOUI).Seasonal variation in shoot phenology showed a similar trend in all shade regimes. with increased flushing observed during the rainy period, but shoot remained dormant during the dry spell. Number of attacks per plant in low shade plot was 112 times higher than under high shade (d.f=2. P=O.OOOI).Observations of this study show that high shade (20-30 % PAR) reduces growth of mahogany even though it might reduce attack by shoot borer and the best rapprochement to manage shoot borer problem while achieving reasonably good growth would be medium shade conditions (~5-50 % PAR).
Description
Keywords
Ecology , Accacia , Nurse crop , Mahagony
Citation
Proceedings and Abstract of the Annual Research Sessions, December 16, 2000, University of Peradeniya, Sri Lanka pp 143-154