Field Evaluation of ovitraps with Piper nigrum to Assess its Larvicidal and Ovipositional Effects on Dengue Mosquito Vectors
Authors: de Las Llagas Lilian A. , Bertuso Arlene G. Bertuso , Mistica Myra S. , Samaniego Jocelyn B. 
Published: January 2025

The larvicidal potential and ovipositional effects of ovitraps consociated with an insect growth regulator, Pyriproxyfen (Sumilarv® 0.5 mg), and formulated larvicide Piper nigrum on dengue mosquito vectors were determined under field condition. The study was conducted in Barangay Batong Malake and Barangay San Antonio in Los Banos, Laguna from September 2010 to March 2011. 0vitraps were set up inside and outside fixed sample houses selected randomly from the 10% of the total number of houses located within 50-300 m radius of the dengue index case (i.e. house of a dengue patient) in each study site. Setting up of ovitraps was done in three phases, i.e., (1) pre-intervention and (2) post intervention, which refer to the periods when ovitraps were installed in each house for four weeks without any larvicide treatment and (3) intervention phase which refers to the period when larvicides [i.e. either 20% crude extract of Piper nigrum made into tablet or 0.5 g pyriproxyfen were placed inside the ovitrap. Ovitraps were inspected weekly for eggs or larvae of mosquitoes. Eggs on the paddle and larvae in the water from each ovitrap were collected and brought to the laboratory for counting and species identification. The ovitrap index (%01), adult productivity index (%API) and similar indices for those other key containers likely to have larvae were determined.

Results showed that both Aedes aegypti and Aedes albopictus were breeding in ovitraps, but the predominant species collected in both study sites was Aedes aegypti. The key containers capable of competing with the ovitraps for mosquito oviposition were drums, flower vases, used bottles, tin cans, refrigerator trays, trays under plate racks, flower pot trays, ornamental fountains, axiled plants, bamboo stumps and discarded materials, which were found either indoor or outdoor of the fixed sample house.

The study showed that the %OI of ovitraps prior to addition of Piper nigrum and Pyriproxyfen in both study sites were 44-49% and 44-50%, respectively. A slight reduction in %OI was observed in both study sites when the larvicides, Pyriproxyfen (ranges from 30 to 35%) and Piper (27-42%), were added in the ovitraps during the intervention period, indicating the larvicidal action of the treatments. However, there was no significant difference in the %OI in the larvicide-treated ovitraps in both study sites in the post intervention period. It has been observed also that there was a reduction in the percentage of key containers positive for larvae in houses when the ovitraps had larvicides. This suggests that the ovitraps with larvicides may be more attractive to mosquito and therefore may effectively compete with the key containers for oviposition. The larvicidal effects of the treatments on mosquitoes were most noticeable in the %API in both study sites. Both larvicides reduced or prevented the generation of adult mosquitoes as indicated by the reduction in %API. In general, no pupae were observed in ovitraps with Pyriproxyfen and Piper during the intervention period. Results demonstrated that formulated Piper is a very promising larvicide that can effectively reduce the generation of adult mosquitoes.