Browsing by Author "Wegiriya, H. C. E."

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Diversity, abundance, and activity patterns of bee pollinators in Cajanus cajan (pigeon pea) in Hambantota district, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Bandara, H. M. N. N.; De Silva, H. S. D. R.; Siriwardhana, B. M. K. T.; Wijekoon, W. M. C. D.; Wegiriya, H. C. E.
The pigeon pea (Cajanus cajan (L.)) is often a cross-pollinated, perennial legume grown in different agroclimatic regions. The study was carried out to investigate the Pigeon pea flower-visiting bee diversity, their relative abundance and their active time at Bata Atha Agro Technology and Tourism Park, Hambantota District in Sri Lanka, from April to June 2024. Three sampling plots (1 m2 each) were identified in the sampling location and the study was conducted twice monthly on sunny days. The abundance of bees was recorded by visual observations and the sweep net (40 cm diameter) method was used to collect bees for identification. The observations were carried out from 0700–1700h to study the active time of bees. The study revealed that Xylocopa aestuans, Ceratina beata, Ceratina smaragdula, Amegilla cingulata, Apis cerana, Megachile lanata, Megachile disjuncta were the key bee pollinators of pigeon pea at study site. The most abundant bee species was Ceratina beata and their relative abundance is 26.31% (n = 10) and the less abundant species was Amegilla cingulate (7.8%, n = 3) from total bee pollinators in the sampling site. Xylocopa aestuans, Ceratina smaragdula, Amegilla cingulata, Apis cerana, Megachile lanata, Megachile disjuncta relative abundance were 10.53% (n = 4), 18.42% (n = 7), 13.16% (n = 5), 10.53% (n = 4), 7.8% (n = 3), 13.16% (n = 5) respectively. The activity of bee pollinators starts at 0900–1000h time of the day and the peak of the active time of the bees for pigeon pea flowers was identified as from 1100-1300h of the day. The activity tends to be reduced after 1600–1700h. The findings suggest that pigeon pea plantations in the Southern Province could benefit from the presence of these diverse bee species, which are effective pollinators. Promoting pigeon pea cultivation could potentially enhance agricultural productivity in the region, given the effective natural pollination by local bee species. This study emphasizes the importance of preserving and promoting bee populations, as they play a crucial role in the pollination of crops, directly impacting agricultural yields and sustainability.
Infestation and emergence of Bactrocera dorsalis (Diptera: Tephritidae) on two varieties of Mangifera indica from selected locations in the wet and dry zones of Sri Lanka
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Wijekoon, W. M. C. D.; Ganehiarachchi, G. A. S. M.; Wegiriya, H. C. E.; Vidanage, S. P.
Bactrocera dorsalis Hendel, (Diptera: Tephritidae) is one of the most serious fruit pests in Sri Lanka. There has been a dearth of documented records of infestation and damages of fruit flies on commercially important fruit varieties in the country. Hence, the present study aims to estimate the percentages of infestations and emergence of B. dorsalis on two commercially important mango varieties grown in the wet zone and dry zone in Sri Lanka. The study was conducted from September 2020 to February 2021 in Ratnapura and Embilipitiya. Ratnapura was selected as the study site in the wet zone and Embilipitiya was selected as the study site in the dry zone. In each site, two sub sampling sites were selected. Twenty ripened fruits (per variety) of Willard (Wld) and Karutha kolomban (Kc) were collected randomly from selected trees. Sampling was done once a month and fruits which have already fallen to the ground were collected. Collected fruits were observed for signs of fruit fly infestations by examining fresh oviposition marks visually using a hand lens. Fruits with confirmed infestations were placed in plastic containers with pre- sterilized sand and muslin cloth cover (storing four fruits; same variety, ≈ weight, temperature: 250 C, RH: 75-85 %) until the emergence of adults. After fifteen days, the average number of adults that emerged per fruit per location was calculated. Two indices; percentage infestations and adult fly emergence were calculated. Mean weight (g) (mean ± SE) of mango fruits used for the study were (127.47 ± 9.05) g and (203.65 ± 9.5) g for Wld and Kc respectively. The percentages of average infestation were 35% for Wld in dry zone and 30% in wet zone, and for Kc, 24% in dry zone and 20% in wet zone. For both varieties, comparatively high percentage infestations recorded from the dry zone site than that of the wet zone site (p> 0.05). The slightly high infestations for both Wld and Kc observed from dry zone site were in October 2020 and February in 2021 (during the season). The average number of adults that emerged per variety was (3.33 ±0.73) for Wld and (3.83 ±0.93) for Kc. The average adult emergence significantly varied between dry zone (4.25± 1.0) and wet zone (2.92±0.57) sites (p< 0.05). This study provides baseline information of infestation and emergence of B. dorsalis adults on two commercially important mango varieties in Sri Lanka.
Oviposition Preference and Performance of Bactrocera dorsalis Hendel, (Diptera: Tephritidae) on Four Colour Types of Willard mango (Mangifera indica L)
(Egyptian Academic Journal of Biological Sciences. A, Entomology, 2022) Wijekoon, W. M.C.D.; Ganehiarachchi, G. A.S.M.; Wegiriya, H. C. E.; idanage, S. P.
Bactrocera dorsalis Hendel is the most widespread serious fruit pest in Asia and the knowledge on oviposition behaviour of B. dorsalis on different fruit varieties are vital for effective management of the pest. Hence, the present study investigated the preference and oviposition behaviour of B. dorsalis on different colour types of Willard mango variety. A series of choice and non-choice laboratory experiments for testing the oviposition preference were conducted and tested fruits were incubated until pupation and the emergence of adults. The results revealed that female B. dorsalis showed a significantly high preference to visit and oviposit in yellow colour Willard mangoes (p < /em><0.05) over red, orange and green colours. The number of pupae and number of adult flies that emerged was also significantly high in yellow colour mangoes under choice condition (p < /em><0.05). In both choice and non-choice tests, green colour Willard was less prominently used by female flies for their visiting and ovipositing (p < /em><0.05). The number of visits and visit duration of fruits was positively correlated with oviposition attempts of female flies in choice conditions. In both tests, the number of oviposition attempts was significantly correlated with the number of pupae and adults who emerged. There was no influence of the colour on the percentage of adult emergence from the pupae in non-choice trials. The study findings could be incorporated to plan and implement the control measures to avoid infestations of commercial mango varieties by fruit flies at the field and at the market level.
Seasonal forecasting of Bactrocera dorsalis Hendel, 1912 (Diptera: Tephritidae) in bioclimatic zones of Sri Lanka using the SARIMA model
(CABI Agriculture and Bioscience, 2024) Wijekoon, W. M. C. D.; Ganehiarachchi, G. A. S. M.; Wegiriya, H. C. E.; Vidanage, S. P.
Bactrocera dorsalis Hendel is a severe fruit pest that causes significant economic losses globally. Despite B. dorsalis having been distributed mostly across Asia, studies on its current and future density variation in Sri Lanka are sparse to date. The present study was thus carried out to assess the contemporary density variation (2020–2022) and future density fluctuation (2023–2025) of B. dorsalis in bioclimatic zones of Sri Lanka. The density was assessed using the monthly-based fruit fly trap collection method from randomly selected 40 locations in all bioclimatic zones (wet, intermediate, dry, and arid). The SARIMA modelling technique was applied for delineating the best-fit model and for density forecasting in each bioclimatic zone. The density variations were depicted for the year and for the bioclimatic zone (2020–2025) by colour intensity maps using QGIS. According to the findings, B. dorsalis shows a seasonal component to its year-round density variation and an ascending trend in its density from 2020 to 2025. Density forecasting records a 20%, 30%, 26%, and 37% density increase in the wet, intermediate, dry, and arid zones, respectively, in 2025. In 2025, the highest predicted B. dorsalis density from the arid zone and the lowest predicted density from the wet zone were recorded. This study contains the first forecasting attempt for B. dorsalis density using the SARIMA approach as well as the application of colour-intensity depiction for its density variation in Sri Lanka, which leads decision makers and stakeholders in economic agriculture to plan the scientific management of B. dorsalis to avoid its current and potential future threat to the country’s fruit industry.
A taxonomic survey of fireflies (Coleoptera: Lampyridae) in selected sites of Rammale Forest Reserve, Southern, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) De Silva, D. R.; Wijekoon, W. M. C. D.; Madushanka, A. D. T. I.; Wegiriya, H. C. E.
Fireflies are a group of charismatic insects, and they are important for the sake of tourism and biodiversity. Information on fireflies associating with forest ecosystems in Sri Lanka is still scarce. Hence, the present study was aimed for investigating the firefly fauna in Rammale Forest Reserve (RFR), southern, intermediate zone, Sri Lanka. The study was conducted from December 2022 to May 2023. Six visual encounter surveys were conducted once per month using 10 randomly selected sampling points (radius = 3 m) in the RFR. Six sampling points in terrestrial areas and four points in freshwater-associated areas were selected. Fireflies at selected sampling points were observed from 17.30 to 22.00 in each survey. In the study, 13 species of fireflies among 10 genera, namely Abscondita (Abs. perplexa and Abs. promelaena), Luciola (L. candezei and L. nicolleri), Diaphanes (D. lutescens), Pygoluciola (sp1 and sp2), and one from the genus Asymmetriacta (A. humeralis), Curtos (C. costipennis), Lamprigera (L. tenebrosus), Sclerotia (Scl. substriata), Harmatelia (H. bilinia), and Eugeusis (E. palpator), were recorded. Among them, H. bilinia, and E. palpator are endemic to Sri Lanka. Pygoluciola sp1 (n = 78, 19.5%), Abs. perplexa (n = 76, 19%), Abs. promelaena (n = 64, 16%), Pygoluciola sp2 (n = 53, 13.2%) and A. humeralis (n = 45, 11%) were common species in RFR, while the rest of the 8 species were recorded as less abundant fireflies in the forest. Three species, Scl. substriata, Pygoluciola sp1 and sp2, were recorded from water-associated areas, and the other 11 species were recorded from terrestrial areas. Terrestrial habitats consisted with moderate canopy of intermediate trees and water associated habitats mainly contained ferns and other riparian vegetation. Both types of habitats are free of human-induced disturbance. This baseline survey is vital as the first taxonomic survey of fireflies in RFR, and its findings will crucially support enhancing the information on firefly biodiversity in Sri Lanka.