Capsules made of thyme oil and corn starch used to kill mosquito larvae
Aedes aegypti, the mosquito that transmits diseases such as dengue, zika, and yellow fever, is typically controlled utilizing insecticides that harm the environment. Now, however, scientists have created eco-friendly mozzie-killing microcapsules, made from cheap natural thyme oil and corn starch.
Developed by a team at Brazil's University of Campinas, the capsules' active ingredient is a biodegradable phenol known as thymol, which is found in the essential oil of the thyme plant. That thymol is encapsulated within a corn starch shell, which is also biodegradable.
When placed in small bodies of water where Aedes aegypti lay their eggs, the shells gradually disperse the thymol into the water. That chemical then proceeds to kill virtually all mosquito larvae present, but isn't released in quantities that are sufficient to harm humans.
In fact, only 20 percent of each capsule's thymol is dispersed upon initial contact with the water. This means that one application of the microcapsules could kill larvae through five raining/drying cycles, which alternately form and evaporate the puddles in which those larvae are typically found. And as an added bonus, the mosquitos shouldn't develop a resistance to the thymol.
"We succeeded in obtaining a particle that behaves exactly like eggs laid by A. aegypti," says principal investigator, Prof. Ana Silvia Prata. "While the environment is dry, it remains inert and keeps the active agent protected. As soon as it comes into contact with water, it begins to swell up and release the larvicide. After three days, when the eggs hatch and the larval stage begins, the particle starts to release lethal quantities of the active principle into the water."
It is hoped that once developed further, the microcapsules could be government-distributed to citizens who would then place them in potted plants, old tires, rubble and other places in which water accumulates. According to recent studies, small bodies of water in such locations account for approximately 50 percent of mosquito breeding grounds.
A paper on the research, which was funded by the São Paulo Research Foundation - FAPESP, was recently published in the journal Industrial Crops and Products.