Browsing by Author "de Silva, P.H.P.R."

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    Advances in research on biological control of the coconut mite, Aceria Guerreronis Keifer in Sri Lanka
    (2009) Aratchige, N.S.; Fernando, L.C.P.; Kumara, A.D.N.T.; Suwandharathne, N.I.; Perera, K.F.G.; Hapuarachchi, D.C.L.; de Silva, P.H.P.R.
    Biological control is considered as the most economical, sustainable and environment-friendly approach for the control of coconut mite, Aceria Guerreronis Keifer. In Sri. Lanka, several research have been done on the local predatory mite, Neoseiulus baraki Athias-Henriot and the entomopathogenic fungus, Hirsutella thompsonii Fisher to evaluate their effectiveness against the coconut mite in an augmentative biological control approach. This paper reports the development in research on N. baraki and H, thompsonii in Sri Lanka as potential biological control agents of the coconut mite. Two technologies, "dry culture" arena method and the "sachet" method were developed for mass rearing of N. baraki. The effect of a single augmentative release of N. baraki in the field to reduce the coconut mite populations was not consistently significant. Release of N. baraki at the rate of 5000 mites/ palm in two-months intervals increases the number of nuts with discontinued damage scars and reduces the number of nuts that are sold at half-price in the harvest. H. thompsonii isolate IMI 391722 showed the highest efficacy in reducing the coconut mite populations. Single application of//. thompsonii in the field is effective only for a short duration. Application of the fungus both at 2- and 3-month intervals caused similar mortality levels of the coconut mites. Perspectives of these findings in the biological control of coconut mite are discussed.
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    Rearing of coconut mite Aceria guerreronis and the predatory mite Neoseiulus baraki in the laboratory
    (Springer Science, 2008) de Silva, P.H.P.R.; Fernando, L.C.P.
    A method was developed for the rearing of coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), and its predatory mite Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae) on embryo culture seedlings of coconut (Cocos nucifera) in the laboratory. Seedlings in the ages of <2, 2–4 and 4–6 months were infested with 75 Weld- collected coconut mites and the population growth was determined up to six weeks after introduction. The populations of coconut mites increased exponentially up to Wve weeks after introduction and declined thereafter on seedlings of all ages with signiWcant diVer- ences among the three groups of seedlings occurring over time. At week 5, a signiWcantly higher mean number (§SE) of coconut mites (20,098 § 3,465) was bred on 4–6-month-old seedlings than on smaller seedlings, and on the largest seedlings the numbers were highest at all time intervals, except at week 2. Neoseiulus baraki was reared on embryo culture seedlings of the three age groups infested with coconut mites, by introduction of Wve female deutonymphs and one male, three weeks after introducing coconut mites. Predator numbers progressed signiWcantly over time, but the size of seedlings did not signiWcantly inXuence the numbers. On all groups of seedlings, the mean number of N. baraki increased up to two weeks after introduction on to seedlings and then declined. Many coconut mites were successfully reared in the laboratory for a longer period by this method and it could also be used as an alternative method to rear N. baraki. Development of this method may contribute to the progress of studies on the biology and ecology of coconut mite and its interactions with natural enemies.