VARIATION IN INFESTATION AND FACTORS AFFECTING OVIPOSITION OF MANGO PULP WEEVIL, Sternochetus frigidus (Fabr.) (Coleoptera:Curculionidae) ON MANGO Mangifera indica IN NORTHERN PENINSULAR MALAYSIA
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Date
2014-08
Authors
MOHD SOBRI, NOR SHAZUANI
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Abstract
Potential threat of Mango Pulp Weevil (MPW) to Malaysian mango industry was investigated by examining infested fruits from various orchards and scattered trees in residential areas in selected places in the northern peninsular Malaysia. Higher infestation of MPW was recorded in Kedah (65%) followed by Penang (60%) and Perlis (45%) and 22% from these states suffered severe infestation. Sternochetus frigidus preferred mango cultivars Gajah (mean weevil per fruit = 6.4±5.86) better than Siku Raja (3.6±0.93), Chok Anan (3.0±0.98), Sala (2.8±0.60) and Siam (2.7±0.47). Fruit parameters such as weight, perimeter, length, width and thickness of flesh influenced MPW infestations (all p<0.05) on fruits of Chok Anan and India. Other factors such as age of trees, land use in the surrounding area and landcape elevation had no influence on weevil infestation. Oviposition of MPW in different phenological stages of mango fruits (Chok Anan and Sala) was studied in mango field. The majority of female MPW oviposit on the medium part of small size mango fruits (4 – 6 cm) and had highly preference towards Chok Anan compare to Sala cultivar (all p<0.05). The selectivity of ovipositing females give a high chances for larval development completion. Suitable environmental factors; temperature, rainfall, wind speed and relative humidity also affected oviposition activity of MPW. The result from this study suggest the best timing period to prevent this pest from infesting mango fruits best before Chok Anan fruit sizze reach 4 cm while Sala 6 cm (3 - 4 weeks after fruiting). This study also discovered the compositions of volatile compounds in both Chok Anan and Sala mango cultivars as oviposition attractants to female of MPW. Result from Gass chromatography-mass spectometry (GC-MS) for Chok Anan and Sala mango cultivar fruits (pulp and peel) showed that 18 and 19 compounds were found in Chok Anan mango pulp and peel while 12 and 25 compounds were found in Sala pulp and peel. Terpinolene, limonene, pinene <alpha->, myrcene, phellandrene <alpha->, cymene <para->, linalool and caryophyllene <(E)-> were identified as oviposition attractant. Terpinolene was highly found in Chok Anan (27.201%– pulp and 25.041 % – peel) cultivar compare to Sala (0.055% - peel). Thus, these eigth compounds were the key contributors to the aroma of MPW oviposition attractant in both cultivars and it found that MPW highly prefer ovipositing on Chok Anan (5.0±0.82) compare to Sala (0.15±0.04).
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Keywords
VARIATION IN INFESTATION , FACTORS AFFECTING OVIPOSITION