Browsing by Author "Ganehiarachchi, G.A.S.M."

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Acute Toxicity and Sub-lethal Effects of Chlorpyrifos to Three Larvivorous Fish, Poecilia eticulate Aplocheilus dayi, and Rasbora daniconius
(University of Kelaniya, 2012) Ganehiarachchi, G.A.S.M.; Amarasinghe, L.D.; Weerasinghe, T.
The insecticide belonging to the organophosphate group, chlorpyrifos 40 % EC, is reported to be highly toxic on fish and it is under restricted usage globally. This chemical is used by Dry Zone chena cultivators and hence, there is a possibility of contaminating the bordering water sources rich with larvivorous fish by tracer amounts of this chemical. Two naturally occurring fish species, Aplocheilus dayi (nalahandaya) and Rasbora daniconius (dandiya) and introduced fish species, Poecilia reticulata (wild guppy) are among the potential larvivorous fish in Sri Lanka. The present study was carried out to find out; acute toxicity of chlorpyrifos 40% EC (commando™), to Aplocheilus dayi, Rasbora daniconius and Poecilia reticulata, effects of sub-lethal concentrations of chlorpyrifos on offspring production and on histological alterations in the gill structure. The exposure media contained a series of concentrations (50, 5, 0.5 and 0 μg/l) of chlorpyrifos 40 EC in glass aquaria. Based on the mortality data, LC50 (24 hr) value of chlorpyrifos 40 EC for Aplocheilus dayi, Rasbora daniconius and Poeceilia reticulata was estimated as 0.514μg/l, 0.472 μg/l and 0.882μg/l respectively. It was also revealed that chlorpyrifos 0.5 μg/l of sub-lethal level to P. reticulata has induced production of hatchlings (mean number of 15 hatchings per female per day) whereas no production of hatchings was observed in other treatments during the exposure period. Histopathological study of the gills exposed to 5 and 50 μg/l of chlopyrifos for 48 hr showed hypertrophy of gill arches, lifting and degeneration of lamella epithelium, degeneration of gill filaments and vasodialation in the lamella axis of both Rasbora daniconius and Poecilia reticulata. This study concludes that LC50 values vary for three fish species tested and Poecilia reticulata is more resistant than the other two species. The sub-lethal levels of contaminants of chlorpyrifos 40EC cause histological and physiological aberration in freshwater fish.
Biology and population dynamics of the sugarcane planthopper purilla perpusilla walker IHomoptera : Lophopidate)
(1998) Ganehiarachchi, G.A.S.M.
Bionomics and Intergrated Control of the Sunflower Seed Maggot (Neotephritis finalis) and the Sunflower Bud Moth (Suleima helianthana) in the Nothern Plains Sunflower Production Region. 2009 Results.
(National Sunflower Association Research Forum, 2010) Knodel, J.J.; Ganehiarachchi, G.A.S.M.; Charlet, L.D.; Beauzay, P.
In the past several years, sunflower producers, field scouts and seed companies have expressed concern about the injury to sunflower resulting in deformed and misshapen areas in the head. The head damage was unlike that caused by sunflower midge and was attributed to feeding injury caused by the sunflower seed maggot, Neotephritis finalis (Loew) (Fig. 1) and/or sunflower bud moth, Suleima helianthana (Riley) (Fig. 2). Although reported from a number of sources, the exact extent and economic loss from these insect pests are not known. Although sunflower seed maggot and sunflower bud moth have been reported in the literature as insect pests of sunflower, a better understanding of their economic impact and potentially useful pest management strategies is needed. This research determined the biology of sunflower seed maggot in North Dakota, and examined two different pest management strategies for control of sunflower seed maggot and sunflower bud moth in North Dakota: 1) Planting dates, and 2) Insecticide timing and insecticide mode of action. Biology of Sunflower Seed Maggot: The bionomics of sunflower seed maggot was determined and findings are summarized in this report. Planting Dates: Late planting date (early to mid-June) was effective in reducing the damage ratings and percentage of damaged heads for sunflower seed maggot at three of the five locations examined in 2009 in North Dakota. Overall, population densities of sunflower seed maggots were low in 2009 and decreased from previous years (source NSA Sunflower Survey) making damage assessments between early (early to late May) and late (early to mid-June) planting dates difficult. For sunflower seed maggot, the late planting date had a lower percentage of damaged heads than the early planting date at three of the five research sites examined. For sunflower bud moth, the late planting date also had a lower percentage of damage heads than the early planting date at two of the five research sites examined. However, sunflower bud moth also had very low population levels and was reported only in sporadic ‘hot spots’ in 2009. Yield differences were attributed to other agronomic factors or bird damage, and not due to head damage caused by sunflower seed maggot or sunflower bud moth. Efficacy of Insecticide Timing and Mode of Action: Neither insecticide timing nor mode of action had any significant effect on the sunflower seed maggot damage ratings, nor the percentage of heads damaged from sunflower seed maggot or sunflower bud moth at any location. The lack of differences could be due to low population densities of adults or missed application timing. Therefore, future plans include the addition of insecticide applications at the R1 growth stage in addition to the R3 and R5 stages. For insecticide mode of action, the pyrethroid insecticide (Asana) and the organophosphate + pyrethroid insecticide (Cobalt) typically had higher yields than the organophosphate insecticide (Lorsban) alone. This is probably due to organophosphate insecticide having a shorter residual effect than pyrethroids. Given that the lowest yields were those treatments with insecticides applied at R3, yield differences are probably due to later (R5.1) infestations of other insect pests, like banded sunflower moth and/or red sunflower seed weevil. In conclusion, it was difficult to assess the insecticide efficacy and mode of action due to low population densities of adult insects. 2009 results indicate that there is no insecticide treatment correlation to damage assessment for sunflower seed maggot and sunflower bud moth and yield. Additional research is necessary to determine viable pest management strategies for control of sunflower seed maggot and sunflower bud moth.
Comparison of larvicidal and repellent efficacy of Ocimum basilicum (L.); “Maduruthala”, leaves and pods, against dengue vector, Aedes aegypti (L.)
(Institute of Biology, Sri Lanka, 2015) Abhayawickrama, W.L.B.P.; Ganehiarachchi, G.A.S.M.; Paranagama, P.A.
Courtship behaviour of Smith’s tiger spider Poecilotheria smithi (Arachnida:Theraphosidae) in the wild
(Faculty of Graduate Studies, University of Kelaniya, 2015) Nanayakkara, R.P.; Ganehiarachchi, G.A.S.M.; Vishvanath, N.; Kusuminda, T.G.T.
The reproductive behaviour of Mygalomorph spiders in the wild is scarce, due to their nocturnal and cryptic habits. The current study describes and interprets the courtship behaviour exhibited by Smith‘s tiger spider Poecilotheria smithi in the wild. Behavioural observations were conducted in the area of Ranamure (GPS coordinates are 7°24'0" N and 80°48'0" E) in the Knuckles region of Sri Lanka. Observations began at 19.45 hours and continued until the behaviour was over. The same mating couple was observed throughout the observation period, which lasted for four consecutive days from 10th November 2013 to 14th November 2013. We selected scan sampling as the sampling rule and instantaneous sampling as the recording rule, mating behaviour was observed following Martin and Bateson 1993. Behavioural transitions were calculated in one of the two ways depending on whether the transition occurred only once during the reproduction. An ethogram of 20 behavioural acts was complied. The courtship behaviour (pedipalp drumming, leg drumming, push-up and shaking) was divided into three distinct patterns; orientation, persuasion and copulation. Adult males perform courtship movements, when they locate a female‘s burrow probably in order to avoid female aggression. Females displayed typical behaviour of a burrowing tarantula, making rapid bouts of tapping vigorously with the first pair of legs and palps. The mating position observed was typical of mygalomorphs, in which the female raises her body up and opens her fangs, while the male uses the legs to hold the female up and finally begin a series of attempts at palpal insertion. The dorsal flexion was observed during mating and the number of successful matings in open arenas suggests that copulation would take place outside the burrow. Males appear to use chemical and/or tactile cues from the females silk around the burrow during short-range searching behaviour. We did not observe sexual cannibalism during the courtship behaviour of these spiders.
Current Distribution of Tiger Spiders (Genus: Poecilotheria), in Selected Sites in Sri Lanka
(University of Kelaniya, 2012) Nanayakkara, R.P.; Ganehiarachchi, G.A.S.M.; Vishvanath, N.; Kusuminda, T.G.T.
Six species of Poecilotheria are currently recorded in Sri Lanka: Poecilotheria fasciata, Poecilotheria ornata, Poecilotheria subfusca, Poecilotheria uniformis, Poecilotheria smithi and Poecilotheria pederseni, the genus is widely distributed covering all geo climatic zones of the island. It has been found that, each species is restricted to a specific locality, no overlap with that of others being observed, a unique feature amongst this genus. The objective of the survey was to map the distribution of the genus Poecilotheria in selected study sites in Sri Lanka. The study was initiated in 2009 and continues to date. The capture and release method was used to identify Poecilotheria spp. distinguished by the ventral markings on leg I and leg IV. So far seventy-one sites covering all ecological zones have been surveyed. In three of the sites no species of Poecilotheria was recorded. Of the other 69 sites, in the Northwest, Southern, Eastern, Northern and Central Provinces, 112 sighting of Poecilotheria (P. fasciata - (61), P. ornata (18), P. subfusca (9), P. smithi (2), P. pederseni (7), P. cf regalis (10), P. cf hanumavilasumica (3)) were recorded. The survey recorded two poecilotherians which have not been described previously. They are likely to be new species. Most species were found in their specific microhabitats, such as bark peels, hollows in trees, etc. The most preferred trees being Drypetes sepiaria, Chloroxylon swietenia, Manilkara hexandra, in the Dry Zone, Cocos nucifera, Thespesia populnea, Ficus sp, Areca catechu in the Wet and Intermediate Zones, while distinct preference was observed for abandoned sheds, cracks in walls, crevices amongst rocks, in the Highland eco-zone.
Development of an alternative low-cost larval diet for mass rearing of Aedes aegypti mosquitoes
(Hindawi Publishing, 2020) Senevirathna, U.; Udayanga, L.; Ganehiarachchi, G.A.S.M.; Hapugoda, M.; Ranathunge, T.; Gunawardene, N.S.
BACKGROUND: Aedes aegypti is a major vector of arboviruses that may be controlled on an area-wide basis, using novel approaches such as Sterile Insect Technique (SIT) and Incompatible Insect Technique (IIT). Larval diet is a critical factor to be considered in mass rearing of Aedes mosquitoes for SIT and IIT programs. Therefore, the current study is aimed at evaluating the effects of two novel diets developed from dry fish powder on the growth and development of immature stages and adult fitness-related characteristics of Ae. aegypti in Sri Lanka. METHOD: Three batches of the first instar Ae. aegypti larva, each containing 250 larvae, were exposed to three different larval diets as standard dry fish powder (D1), dry fish powder meal and brewer’s yeast (D2), and International Atomic Energy Agency- (IAEA-) recommended diet (D3), separately. Morphometric and developmental parameters of the 4th instar larvae, pupae, and adult mosquitoes reared under different dietary treatments were measured. The entire experimental setup was replicated thrice. A General Linear Model (GLM) in the form of two-way ANOVA was used for the statistical analysis. RESULTS: Significant diet-based variations were observed in the head length, head width, thoracic length, thoracic width, abdominal length, abdominal width, and total length (; ) of Ae. aegypti larvae. The highest pupation success and the larval size were observed from the larvae fed the D2 diet, while the lowest was reported from D1. All adult morphometric parameters of adult male and female Ae. aegypti mosquitoes also denoted significant dietary variations, reporting the best-sized adults from the D2 diet (; ). Further, significantly higher fecundity and male longevity were also shown by the adult Ae. aegypti (; ) mosquitoes reared under diet D2. CONCLUSION: Based on all the growth and developmental parameters, the D2 diet tends to perform similar to the IAEA-recommended diet in mass rearing of Ae. aegypti mosquitoes, while being more inexpensive. Therefore, larval diet D2 could be suggested as the ideal diet for mass rearing of Ae. aegypti for IIT and SIT-based vector control in Sri Lanka.
The effect of chemical exudates of three larvivorous fish species on oviposition preference of Aedes aegypti and Aedes albopictus (Diptera: Culicidae)
(Med Vet Entomol, 2021) Rathnayaka, R.M.G.S.; Jayatunga, D.P.W.; Ganehiarachchi, G.A.S.M.
Mosquito species Aedes aegypti and Aedes albopictus are vectors of dengue worldwide. Mosquito vector control through maintaining larvivorous fish in water bodies is generally suggested, however, its underlying role towards oviposition preference of these dengue vectors is unknown in the Sri Lankan context. The current study investigated the effect of chemical exudates from larvivorous fish species Poecilia reticulata, Rasbora daniconius and Applocheilus dayi on the oviposition preference of Aedes mosquitoes. The number of eggs laid by each mosquito species was determined using ovitraps that contained water conditioned by the fish species both separately and in combination. The ovitraps were placed inside insect cages containing engorged gravid Aedes females. Both the mosquito species had the least preference of oviposition in water conditioned by A. dayi followed by R. daniconius. The highest preference of oviposition was shown for water conditioned by P. reticulata. The current study indicated that oviposition site selection in Ae. aegypti and Ae. albopictus was reduced by A. dayi and R. daniconius, however, it was not influenced by the fish combinations used. Further studies are warranted to understand the chemical cues associated with larvivorous fish towards the oviposition preference in Aedes mosquitoes.
Effect of predatory fish chemical exudates on oviposition preference of two Aedes mosquito species; Aedes aegypti and Aedes albopictus
(Sri Lanka Association for Fisheries and Aquatic Resources, 2016) Rathnayaka, R.M.G.H.; Ganehiarachchi, G.A.S.M.
Effect of The Domestic Characteristic on Colonization of Phlebotomine Sand Flies: A Case Study in Anuradhapura District, Sri Lanka
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Ganehiarachchi, G.A.S.M.; Rajapakse, R.P.V.J.; Jayanetti, S.R.
Cutaneous Leishmaniasis (CL)is an endemic vector-borne disease in Sri Lanka.It is caused by protozoan parasite Leishmania species and transmitted via infective bite of female Phlebotomine sand flies (Diptera: Psychodidae). The public health importance of this disease is positively increasing due to inadequate knowledge of vector biology. The current study is an attempt to uncover the vector biological aspects, focusing on the successful vector control interventions. This study was carried out in Anuradhapura district, Sri Lanka; a district with high disease prevalence of CL. Three sampling localities were selected; Thalawa, Padawiya and Wijayapura. A questioner and field studies were carried out in the sampling areas among CL patients to assess the effect of domestic environment characteristics on colonization of phlebotomine sand flies. Presence of decaying garbage, termite hills, manna grass (Glyceria sp.), water streams, unclear areas, wet soil areas, scrub jungles and gardening areas are the concerned characteristics for the present study. Field studies were conducted every month for seven months continuously. In every visit, Phlebotomine sand fly samples were collected from the study sites mentioned above using yellow sticky trap method. Increment of the mean number of sand fly population alongwith the increment of the number of domestic characteristics was tested with the regression analysis.With the increment of supportive environmental characteristics, sand fly populations were increased linearly (P = 0.000) in each site. This relationship revealed that the maximum sand fly populations were recorded in the places with all the tested characteristics stated above. Accordingly, the surrounding characteristics of the domestic environment have a significant effect on the colonization of sand fly populations. Domestic characteristics such as decaying organic matter, wet soil, unclear areas and water streams around the living environment show higher contribution to the colonization of sand flies. In conclusion, characteristics of the domestic environments have effect on the colonization of sand flies. Increment of the supportive domestic characters intensifies the colonization of sand flies.
Environmental impacts of gem mining in Nivithigala area
(Department of Zoology and Environmental Management, University of Kelaniya, 2015) Ishara, N.N.; Wijesinghe, D.C.M.; Mazahir, E.M.; Niroja, K.; Ganehiarachchi, G.A.S.M.
Gape size of wild guppy (Poecilia reticulata): Does it matter in mosquito larval control?
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Weerakoon, S.N.; Ganehiarachchi, G.A.S.M.
Larvivorous fish is very important tool in controlling disease transmitting vector mosquitoes in many parts of the world. However, there is a lacuna of knowledge about the vector control potency in relation to the gape size of these fish. Since the wild guppy, Poecilia reticulata; is a topmost larvivorous fish, the current study was performed to study the effect of gape size of guppy in controlling mosquito larvae. For the current study, wild guppies were collected from their own natural habitats located around the Kelaniya area. In the laboratory, measurements of total length (TL) and Gape Size (GS) of individual specimens were obtained. These fish were then grouped in to ten length classes of 0.2 cm intervals ranging from 0.8 to 2.8 cm. For each length class of fish, 5L capacity glass tank was assigned. Accordingly, there were 10 experimental tanks for 10 size classes of fish, and for each tank assigned for a particular size class, 10 fishes were introduced. After acclimatization, fish were kept without food for 24 hours. In the meantime, laboratory reared mosquito larvae were collected and separated according to their instar level. Four instar stages of larval and the pupal stage were used for investigating of prey selection by P. reticulata. The rationale used here was that all the immature stages of mosquitoes were separately exposed to each length class of fish to determine the mosquito larval/pupal mortalities. Ten mosquito larvae/pupa form a particular instar were introduced to a fish tank at a time. Subsequently, the mortality rates of mosquito larvae/pupa in each tank were determined after 24 hours. All the fish were kept under 24 hour fasting period prior to each experimental cycle. In the next experimental cycle, ten mosquito larvae/pupa form a particular instar were introduced to another fish tank. This procedure was continued until all the instar/pupal stages expose to all the fish tanks. Relationship between TL and GS was tested with a Pearson correlation and with linear regression analysis. One way – ANOVA was performed to analyse the significance of the mortality of different instars along in different length classes. The results revealed that the relationship between TL and GS is best fitted for liner regression model (R2 = 0.80) with the equation; GS = 0.1 TL – 0.02. The 24 hour percentage mortality of different mosquito instars indicated that the 1st and 2nd mosquito larval instars were vulnerable to all the length classes tested for these instars (GS range = 0.06 – 0.26 cm). Fishes of 0.8 – 1.0 cm length class (GS range = 0.06 – 0.08 cm) were unable to consume 3rd instar mosquito larvae. Fishes of 0.8 – 1.2 cm length range (GS range = 0.06 – 0.1 cm) were unable to consume 4th instar larvae. Pupae were consumed by the fishes whose length range was 1.4 – 2.8 cm (GS range = 0.12 – 0.26 cm). Hence, the gape size of the guppy fish has a significant effect on the mosquito larval controlling and the fishes with GS > 0.12 cm (TL > 1.4 cm) are excellent in controlling the pupae and all the instars of mosquito larvae.
Impact of Planting Dates on a seed Maggot, Neotephritis finalis (Diptera: Tephritidae), and Sunflower Bud Moth (Lepidoptera: Tortricidae) Damage in cultivated sunflower
(Journal of Economic Entomology, 2011) Knodel, J.J.; Ganehiarachchi, G.A.S.M.; Beauzay, P.B.; Chirumamilla, A.; Charlet, L.D.
Neotephritis finalis (Loew) (Diptera: Tephritidae), and sunflower bud moth, Suleima helianthana (Riley) (Lepidoptera: Tortricidae) are major head-infesting insect pests of cultivated sunflower (Helianthus annuus L.). Planting date was evaluated as a cultural pest management strategy for control of N. finalis and S. helianthana in several production regions of North Dakota during 2009 and 2010. Results of the nine site-year study revealed that late planting date (early to mid-June) reduced damage ratings and percentage of damaged heads for N. finalis compared with early planting dates (mid- to late May). Visual observations of adult N. finalis found that the majority of flies were found in the early planted sunflower (78.2%) compared with the late planted sunflower (21.8%). Late planting date also reduced the percentage of S. helianthana damaged heads compared with early planting dates. Yield losses were reduced with late planting date when populations of N. finalis and S. helianthana were high enough to cause damage. Results of this study showed that delayed planting is an effective integrated pest management strategy that can reduce head damage caused by N. finalis and S. helianthana and mitigate yield losses.
Influence of humidity and temperature variation of natural breeding sites on abundance of Leishmaniasis vector Phlebotomus argentipes population in Anuradhapura District
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Nayakarathna, N.M.N.G.; Ganehiarachchi, G.A.S.M.; Rajapakse, R.P.V.J.; Jayanetti, S.R.
Cutaneous leishmaniasis (CL) is an endemic public health problem in Sri Lanka. Leishmania donovani is the suspected causative agent of the disease and this parasite is transmitted by a dipteran fly species; Phlebotomus argentipes. Studies on vector behavioral and ecological aspects, although important for better understanding of disease transmission, are still limited. The present study is an attempt to uncover the vector ecological aspects focusing on the successful vector control interventions. This study is being carried out in Anuradhapura district, Sri Lanka; where there is a high disease prevalence of CL. Three sampling sites; Thalawa, Wijayapura and Padawiya were selected. Adult sand flies were collected monthly over a six months duration using CDC light traps (5) and yellow sticky traps (30). In the meantime, relative humidity and air temperature were measured using hygrometer and thermometer in each site. The collected sand flies were identified up to the species level using standard keys. Percentage composition of each of the species was calculated. Temporal variations of primary vector, Phlebotomus argentipes along with the dynamics of temperature and relative humidity was determined using regression analysis. Phlebotomus argentipes was the dominant sand fly species found in the study sites. The percentage composition of the primary vector exhibited a variation during the study period and maximum percentage composition was recorded during May and June, 2016. The relationship between percentage composition of Ph.argentipes versus mean temperature was significant (P = 0.000, R2 = 97.7%) and elevated percentage composition were recorded under lower temperature. Further, percentage composition of Ph.argentipes exhibited an increasing trend with higher humidity levels (P = 0.000, R2= 98.4%). In conclusion, the primary vector populations of leishmaniasis are increased with lower temperature and higher humidity. As such, this relationship will helpful to predict the variation of vector population with the changes of ecological parameters and finally a successful vector management strategy can be implemented with the thorough knowledge of its life history parameters and behavioral pattern.
Influence of Vertebrate Excreta on Attraction, Oviposition and Development of the Asian Tiger Mosquito, Aedes albopictus (Diptera: Culicidae)
(MDPI, 2021) Rajapaksha, R.D.T.; Jayatunga, D.P.W; Ganehiarachchi, G.A.S.M.
Aedes albopictus is an important vector of dengue worldwide. Eliminating dengue in Sri Lanka depends entirely on controlling the vector and human-vector contact. Thus, studying the bionomics and behavior of Ae. albopictus is paramount. The objective of this study was to evaluate the effect of the excreta of cow, goat and pig on the attraction, oviposition and development of Ae. albopictus. Bioassay chambers determined the mosquito stimulatory response. Ovitraps determined Ae. albopictus oviposition preference to excreta singly, in combination and on fermentation. The excreta effect on larval development was also determined. The results revealed that Ae. albopictus gravid females were significantly attracted to goat excreta but were repelled by pig excreta. The oviposition preference was highest for cow excreta and lowest for pig excreta. For excreta combinations, the Cow+Goat combination increased the oviposition while the Pig+Goat combination reduced the oviposition. The oviposition preference of Ae. albopictus increased with the rate of fermentation. The pig excreta increased the Ae. albopictus larval mortality, larval and pupal duration and reduced adult fecundity, whereas the cow excreta positively affected all these aspects. Our findings additionally suggest that a high abundance of Ae. albopictus in rural areas of Sri Lanka may be due to its oviposition attraction and growth performance for vertebrate excreta.
Investigation of oviposition responses of container breeding mosquitoes to different colored containers and to the location using tap water, hay infusion and ariconut infusion
(Institute of Biology, Sri Lanka, 2013) Fernando, H.M.S.N.; Ganehiarachchi, G.A.S.M.
Lesson 22: Identify the types of insect pests and their damage
(Research Services Centre, Faculty of Science, University of Kelaniya, 2015) Amarasinghe, L.D.; Ganehiarachchi, G.A.S.M.
Lesson 28: Study and calibration of knapsack sprayer
(Research Services Centre, Faculty of Science, University of Kelaniya, 2015) Ganehiarachchi, G.A.S.M.
Phytoplankton and Zooplankton Community Dynamics and Aspects of Food of Two Fish Species in Two Streams and Two Lakes in Presence and Absence of Anophelese Mosquito Larvae in Mahaoya, Sri Lanka
(University of Kelaniya, 2012) Amarasinghe, L.D.; Ganehiarachchi, G.A.S.M.; Ruchirani, C.; Weerasinghe, T.
Plankton samples were collected using plankton nets to examine the phytoplankton and zooplankton community dynamics in two streams: namely, Mahaoya, and Panajjawa Oya and two lakes: namely, Bubula Lake and Wagaspitiya Lake in Mahaoya, Ampara district, Sri Lanka. The samples were collected in two consecutive periods in May and August 2011. Aplocheilus dayi and Rasbora daniconius, two naturally occurring fish species were collected (n=50) using cast nets to examine their food aspects in absence of Anopheles mosquito larvae in May 2011 and in their presence in August 2011. Of the total plankton community, only about 28% (14 species) represented zooplanktons while 72% (55 species) were phytoplanktons. Total 14 zooplankton species belonged to; Class Branchiopoda (5 species); Class Lobosa (1 species); Class Maxillopoda (4 species); and Class Monogononta (4 species), and 55 species of phytoplankton population belonged to Class; Chlorophyta (24 species); Class Cyanophyta (11 species); Class Bacillariaphyta (10 species); Class Ochrophyta (4 species); Class Euglenophyta (4 species); Class Heterokontophyta (2 species). The zooplankton population of two streams was dominated by Chromogaster spp. (40 - 80 /ml) while that of two lakes, Bubula and Wagaspitiya were dominated by Eucyclops spp.(120/ml) and Cyclops spp. (80/ml) respectively. The phytoplankton population in all the four water bodies was dominated by Closterium spp. (200-400/ml). The above data reveals that the phytoplankton diversity in two lakes is greater (total of 26 species/taxa) than that of two streams (total number of 14 species/taxa) but, there was no difference in zooplankton diversity between the two habitats. Density and diversity of both phytoplankton and zooplankton in each site between two consecutive sampling occasions (soon after heavy rains in absence of mosquito larvae and during the dry spell in presence of mosquito larvae) did not vary significantly. Gut analysis of two naturally occurring fish species, Aplocheilus dayi and Rasbora daniconius revealed that both of their diets mainly composed of crustaceans 40%, insects 35% and algae, detritus, diatoms and plant parts 25% by number, in presence of mosquito larvae in the habitats in August 2011.
Records of fruit files(Diptera: Tephritidae: Dacinae: Dacini) in a selected mango (Mangifera indica L.)(Kautha Kollomban) cultivation in Ambalanthota, Sri Lanka.
(Proceedings of the lnternational Symposium on Agriculture and Environment 2022,University of Ruhunu, Sri Lanka., 2022) Wijekoon, W.M.C.D.; Ganehiarachchi, G.A.S.M.; Wegiriya, H.C.E.; Vidanage, S.P.
Fn1lr flies are one of the widely dlstrlbuted Insect pests and rhey mostly damage economically Important fruits and vegetables In the tropical region. However. there are no recently published reports of fruit fly assemblages associated with conunerclal fruit plantations In Srt Lanka. Hence. the present study aimed to investigate the abundance and d.lversll)' of fruit files arcracted to the methyl-eugenol tleld rraps In a selected mango cultivation ("Kan11ha kollomban· vartecy) In Ambalanthota Srt Lanka. Six fruit fly traps (5 cm diameter. 10 cm height two cirrnlar openinglmm radius and a methyl-eugenol coated sponge) were bun: (1.5· 4 m above the ground level and 20111 inter-trap dlsrance) In six mango trees which were located In die middle of each randomly selected slx sampling plots (400111') in die cultivation (0.54 ha). Trapped flies were collected twice a month from October to December 2021 (during the fruiting season) replacing new traps In each sampling round. Collected samples were ldentlfled using s tandard taxonomic keys by observing wider the light microscope (Nlkon-ECLIPSE-ElOO) ( 10•4). Two Indices: Simpson Population Dominance lnde.~ and the Abundance Index were calatlated The variation or species abw1dance was compared using one-way ANOVA test. Seven fruit fly species: Baccrocera dorsalls (Hendel). R kandlansts (Drew and Hancock). B. correaa (Be-zzl). B. /arlfrons (Hendel), B. cubercr,lara (Bezzl), B, ntgrofemoralts (White and Tsuruta) and B. cacumfnaca (Hering) were recorded In this smdy. Out or the total 803 specimens examined, B. dorsalis had a slgnltlcanrly higher abundance ( 412, 51.31 %) (P<0.05) dian other species, and B. cacumlnaca had the lowest abmtdance (26. 3.24%). The highest Simpson Dominance Index (0.26) 1vas recorded for B. dorsolls while other recorded slx fruit fly species were less dominant In the selected mango cultivation. Smdy tlndlngs will be Important for fruit cultivators to design and Implement fruit fly control measures.