Coffee Grounds for Mosquito Control

August 2, 2009

RECYCLE BIODEGRADABLE coffee grounds and simultaneously knockdown mosquitoes vectoring dengue, yellow fever, West Nile virus, malaria and other diseases. Hermione Bicudo at Universidade Estadual Paulista in Sao Paulo, Brazil, has been working towards that goal since the early 1980s. Mosquito control alternatives are needed, as mosquitoes are rapid, prolific breeders that rapidly develop resistance to pyrethroid, organophosphate and other types of insecticides.

Bicudo’s lab began studying caffeine effects on Drosophila fruit flies in the early 1980s. Drosophila fruit flies are a model insect widely used from the early twentieth century to unravel the mysteries of inheritance and genetics. Caffeine has been used relatively safely for centuries, and is found in medicines, cosmetics and food and beverages like coffee, tea, guarana and chocolate. Used coffee grounds are a ubiquitous waste product in modern caffeinated societies.

A resurgence of yellow fever mosquito, Aedes aegypti, in Brazil prompted Bicudo’s lab to test whether deleterious caffeine effects on Drosophila fruit flies (e.g. less frequent mating, less egg laying capacity, shorter life spans) might also slow mosquito population growth. Approximately four full soup spoons of used coffee grounds in a 250 mL glass of water killed 100% of aquatic mosquito larvae. This translated into fewer adult mosquitoes (the biting, blood-sucking stage) and less new mosquito egg laying (thus, lower mosquito populations over time). Used coffee grounds also have fertilizer value for plants, and can be dusted onto Bromeliads and other garden plants (possibly also puddles, ponds, tree holes, used tire breeding sites, etc.) where accumulated water forms potential mosquito breeding sites.

In contrast to other researchers, Bicuda’s lab found that caffeine solutions became more effective against mosquitoes with age. Day-old caffeine solutions took 20 days to kill 100% of mosquito larave; 25-day old caffeine solutions killed 100% of mosquito larvae in 1 day. Combined with elimination of mosquito breeding sites, used coffee grounds or caffeine solutions could prove very useful in IPM (integrated pest management) programs to slow pesticide resistance and reduce mosquito breeding.