A new study now suggests a method of improving the effectiveness of a cheaper, longer-lasting alternative – clove oil.

Thanks to a chemical compound within it known as eugenol, clove oil is already known for its ability to eradicate mosquito larvae when added to standing water. Not only is the oil safe for the environment, but the cloves from which it's made are inexpensive and readily available in regions where mosquito-transmitted diseases such as malaria, Zika and dengue fever are widespread.

Unfortunately, it's typically not as immediately effective as harsher synthetic insecticides. Those insecticides have problems of their own, however. Not only do they accumulate in soil, water and food – potentially causing health problems in both people and wildlife – but mosquitoes typically build up a resistance to them over time.

Because such is not the case with clove oil, scientists from India's Gauhati University set out to boost its larvae-killing capabilities. After experimenting with adding various synergist chemicals to clove-derived eugenol, it was found that a liquid organic compound by the name of piperonyl butoxide (PBO) had a particularly pronounced lethal effect on Aedes aegypti mosquito larvae.

"The use of synergists, either synthetic or natural, along with insecticides like eugenol helps to prevent resistance development," said Assoc. Prof. Bulbuli Khanikor. "In the present study, combining synergists like piperonyl butoxide with eugenol was found to enhance the effectiveness of eugenol significantly."

It should be noted that while PBO is considered to be only minimally toxic to humans, it is highly toxic to aquatic invertebrates and tadpoles – so its use should ideally be limited to the puddles where mosquitos frequently breed, as opposed to larger marshes or ponds.