Browsing by Author "Vinobaba, M."

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Assessment of Dengue Risk by means of Larval Indices and Insecticide Susceptibility in two Localities of Batticaloa District, Sri Lanka
(University of Kelaniya, 2012) Dharshini, S.; Vinobaba, M.
Dengue is the most important vector borne disease in Sri Lanka and globally due to its increasing incidence over the years. Climate changes coupled with rapid urban development result in increasing the breeding and survival of Aedes mosquitoes, the vector for dengue, hence the success of dengue virus transmission. This study aims to identify the relationship between Aedeslaval indices (House Index [HI], Container Index [CI] and Breteau Index [BI]) and dengue risk, and study the insecticide susceptibility to strengthen future mosquito control strategies in the Batticaloa district. The two locations selected for collection of Aedes larvae were Batticaloa and Oddamavadi, in Batticaloa District. Larval collections were made fortnightly using conventional ovitraps for nine months covering the dry and wet seasons. 15 Ovitraps were placed in randomly selected houses on each locality based on the data obtained from Anti Malaria Campaign where dengue cases were available. WHO kit with insecticide impregnated papers with the following concentration recommended by WHO were used for the susceptibility test (Malathion – 0.8%, DDT – 4% and Permathrin – 0.25%). This study demonstrates that all larval indices HI, CI and BI were higher than WHO standard. This indicated a high risk of DF/DHF transmission in both localities. Present investigations revealed that, Ae.aegypti and Ae.albopictus from all study sites were completely resistant to 4% DDT, moderate to high level resistance to 0.8% Malathion but were susceptible to 0.25% Permathrin. This study suggests that regular and continuous monitoring of resistance should be conducted in all dengueendemic sites, to confirm the continued efficacy of insecticides, and to help choose the most effective insecticides for dengue control.
Association of the ants and the cotton mealybug, Phenacoccus solenopsis (Tinsley) population and its influence on the spread of mealybugs in the home-gardens
(Department of Zoology and Environmental Management, University of Kelaniya, 2015) Prishanthini, M.; Vinobaba, M.; Gnaneswaran, R.
Distribution and Host Range of Paracoccus marginatus (Hemiptera: Pseudococcidae) in Batticaloa District, Sri Lanka
(University of Kelaniya, 2012) Prishanthini, M.; Vinobaba, M.
Papaya mealybug, Paracoccus marginatus Willams and Granara Willink, is a small invasive hemipteran that attacks several genera of host plants, including economically important tropical fruits and ornamentals. It is an alien invasive species and was reported for the first time in Sri Lanka in 2008. It was observed in the Eastern region of Sri Lanka during the middle of 2009 and a field survey was conducted from January 2010 to December 2011 to investigate the host range and distribution of the pest and the status of infestation caused by this pest. Twenty-five home gardens randomly selected from Kiran, Kaluthavalai, Vantharumoolai, Vaalaichenai and Batticaloa area of Batticaloa District were surveyed and mealybug samples, together with their host plants were collected. Papaya mealybug separated from host material was preserved in 70% ethanol permanently mounted on slides and identified using standard keys and illustrations. Host plants and distribution of papaya mealybug were determined through field observations and systematic sampling of infested plants in the sampling locations. The results show that papaya mealybug infested more than 12 host plant species. The predominant host in the study area was papaw and other favoured hosts were jak fruit, manioc, hibiscus, chrysanthemum, sunflower, marigold, gliciridia, ixora, mussenda, curry leaves and some other ornamental plants acting as alternative hosts. The infestation of papaya mealybug was found to be 52% on papaya plants. It was distributed uniformly in the study area and no significant differences were observed among different localities. A peak in population density was observed during February to April with the rise of temperature. However, the population density reduced during the rainy months from October to December as the insects were washed off with the rain waters. Association of papaya mealybug with cotton mealybug, Phenacoccus solenopsis, was also observed. More studies on population dynamics, natural enemies and host preferences are important to manage the problem of papaya mealybug in the region.
Food preferences of Solenopsis geminata workers in anthills located at the premises of Eastern University, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gunarathna, S. M. D. P.; Vinobaba, M.; Udayakantha, W. S
The tropical fire ant, Solenopsis geminata (Fabricius, 1804) causes ecological disruptions and economic damage in tropical regions of the world. Effective control strategies for tropical fire ants rely on understanding their ecology. The current investigation focused on recording the preferred food type among six food types, with an intention of developing an effective ant bait formulation, which is to be based on the preferred food types later. Three localities, each 100 m apart, were selected at the premises of the Eastern University of Sri Lanka, and two active S. geminata anthills were identified by recognizing worker ants at each site. A 1.1 g weight of selected food items, peanuts, crushed sugar, honey, soybean oil, corn grit, and corn flour, were placed 15 cm away from each anthill at approximately a 60º angle and protected from other animals. The number of ants attracted to each sample of food was counted from 8.00–10.00 a.m. and, remaining food was weighed and deducted from the original weight to determine the amount of the food consumed by the ants. This procedure was done over 12 consecutive sunny days with air temperatures ranging between 28 °C and 37 °C. ANOVA test followed by Tukey's HSD was applied to determine the significant differences between the mean weight of each food type consumed by the ants. Worker ants formed trails to gather soya bean oil and corn grit on all occasions, while only 50–65 of ants were observed around the other types of food. The results showed that S. geminata strongly preferred soya bean oil and corn grit over other commercially available food types (p = 0.01; Tukey's HSD), suggesting their potential use in effective bait formulations. Future research should explore the optimization of bait formulations incorporating soya bean oil and corn grit.
The role of Solenopsis geminata in affecting health and routine activities: A case study of undergraduate students at Eastern University, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Gunarathna, S. M. D. P.; Vinobaba, M.; Udayakantha, W. S.
The tropical fire ant, Solenopsis geminata, is an invasive species that damages agriculture, infrastructure, and human health globally. In Sri Lanka, research is limited. This study examines the impact of Solenopsis geminata on undergraduate students’ health, daily activities, and campus experience at Eastern University. A structured interview-type questionnaire survey, using both closed and open-ended questions, was conducted to investigate details about allergic responses caused by S. geminata stings and other related issues experienced by undergraduate students at the Eastern University of Sri Lanka from July to December 2023. The questionnaire consisted of 20 questions in three major sections, demographics, sting incidents, and other related information. A randomly selected general undergraduate sample of 120 students participated in the questionnaire survey and were shown live samples and photographs of S. geminata for identification. Seventy-eight (n = 78) students who identified the species continued with the survey. Their ages ranged from 21 to 30 years old, with a maleto-female ratio of 4:5. In the group surveyed, 100% reported experiencing S. geminata stings. The most frequent symptoms were a combination of redness, itching, and swelling (51.7%), or just redness and itching (24.1%). Additionally, 13.79% exhibited oozing, and 5.2% developed long-term scars. According to Turkey's HSD, there is no correlation between the number of bites received and gender (p = 0.46), but a significant correlation was found between the average reaction to bites and age (p = 0.005). The survey also revealed that 10.34% reported damage to stored staples, 10.34% to crops, 11.2% to selling items, 8.6% to physical equipment, and 4.3% to seeds. These descriptive statistics highlight the significant impact of S. geminata stings on students' health and daily life, the economic damage to their stored staples, crops, and equipment. Future recommendations include increasing education on the prevention, urging the usage of biopesticides and management of S. geminata stings among students and implementing effective control measures to reduce the population of these ants.