Larvicidal activity of Allium fistulosum (spring onion) leaf extract, Ocimum x citriodorum (lemon basil) leaf extract, and Cymbopogan citratus (lemongrass) leaf extract against Aedes aegypti: A comparative study

Proponents: Marjorie P. Oclarit
Jan Roliesa P. Llamos
Jakilyn R. Mulla

INTRODUCTION
Mosquitoes are known to be the deadliest animals all over the world. They carry diseases that cause sickness and deaths throughout the world that led to millions of death every year. They are one of the nuisance problems in residents, livestock, and even for the animals. Continuous spreading of mosquitoes can pose a great negative impact in the economy. For several years, the government has been fighting with the mosquitoes but there is yet no best potential larvicide that can stop the emerging mosquitoes.
According to the World Health Organization (WHO) report, dengue cases has increased 30 times greater for the past 30 years. Health Secretary Paulyn Ubial indicated that DOH has recorded 31.8 percent lower cases of dengue (2017) but even though it has reduced, still the risks should not be ignored. Highest dengue cases in the Philippines include Davao City, Mati City, Banganga and Governor Generoso for Davao Oriental, Panabo, Tagum, Island Garden City of Samal, New Corella, and Talaingod in Davao del Norte, Digos City for Davao del Sur, and for Compostela Province, the towns of Nabunturan, Pantukan, and Maragusan (SunStar PHILIPPINES, 2016).
Mosquito-borne diseases are referred to be “large and growing public health problem” by Emma Sarran Webster. There are lots of different kinds of commercial larvicide that are being produced nowadays, but still, mosquitoes keep on evolving and build up immunity from the produced larvicide. This made the larvae difficult to obliterate even with worst temperature and humidity conditions. So, the researchers conducted another study in finding an alternative and a more potential larvicide that pose less risks in the economy.
MATERIAL AND METHODS
Phase I – Plant Preparation for Extraction
Collection of Plants
The plants were collected at the Public Market in Poblacion, Nabunturan. The plants weighed more or less 5 kg each.
Extraction of Crude Extract from the Plant Samples
The plants undergone air dry process for 48 hours and were homogenized using a blender. Then the plants were soaked with ethanol for 48 hours with a ratio of 1:2 where 1 part plant and 2 parts ethanol. After 48 hours, it was filtered using a filter paper no. 1. Beakers were used for the collection of filtrate. Modified evaporation using oil bath technique was used for the modified rotary evaporation. The plant filtrate containing 400 mL was poured in the 500 mL distilling flask. It was then put in the water bathe, which contained cooking oil, and submerged the bottom of the distilling flask 1.5 inches while ensuring the oil to not overflow. Then, the hot plate was turned on to 300° C. After it, the condensed ethanol was collected in the beaker while the extract that remained at the bottom of the flask was also collected separately.
Phase II – Mosquito Larvae Experimentation
Culture of Mosquito Larvae
The larvae were cultured and was put in a bucket of water and checked frequently until it develop into 4th instar level. The larvae were identified in the Nabunturan Health Center.
Experimental Set-up
The concentrations of extracts are as follows: seventy-five percent (75%), and one-hundred percent (100%). The experiment consists of 2 treatments with 5 replicates each for the plant samples, positive control (Baygon), negative control (distilled water), and the Ethanol. The extracts were placed in the petri dishes with three larvae each. Time (minutes) when the larvae showed mortality results was recorded.

Disposal of Mosquito Larvae
After the experiment, the larvae were mixed in the water and was boiled for the disposal (Buckner, 1934). And was poured in an area with directed sunlight.

Phase III – Data Collection Analysis
Statistical Analysis
One-way Anova was used to determine the significant difference of the effectiveness of plant extracts of Allium fistulosum (spring onion), Ocimum x citriodorum (lemon basil), and Cymbopogan citratus (lemongrass) on mosquito larvae and was tested at 0.01 level of significance.