To spray or not to spray? As Zika creeps northward, we’ve got a decision to make

| 27 Oct 2016 | 11:21

The most dangerous animals on earth

The ongoing outbreak of Zika virus disease in many parts of the world has reminded us forcefully of the risks posed by mosquitoes, which are by far the most dangerous animals in the world. Zika, malaria, dengue, west Nile, yellow fever, and other germs transmitted by mosquitoes globally kill almost 500,000 people each year and sicken many millions more, often with lifelong consequences.

Despite huge efforts to develop vaccines or medicines to combat these diseases, generally the only way to combat them effectively is to prevent mosquito bites. There are many ways to protect people from mosquito bites, and one important tool is aerial spray with pesticides like naled.

One rationale for area-wide use of pesticides that target adult mosquitoes (“adulticides”) is that other techniques simply don’t work well enough in many situations. Treated bed nets have dramatically reduced malaria, but Zika-carrying mosquitoes mostly fly and bite during the day. Screens and repellents are good ways to protect yourself and your family, but mosquitoes that target people will simply find those folks that aren’t protected — at worst diverting them to the poorest of us. Drainage and community hygiene are great if everybody does their part and keeps it up during the long mosquito season — sad experience has shown this to be impossible to maintain. Fish can’t reach the small and isolated larval habitats of Aedes mosquitoes, and birds and bats don’t eat enough mosquitoes to make a difference. Finally, chemical treatment of larval mosquitoes helps, but it is very hard to consistently find and treat all of the small habitats that support Aedes mosquitoes. If, despite our best efforts, there are infected adult mosquitoes flying around people, nothing effectively protects a community except adulticides.

Area-wide spraying does work. Wide experience over 50 years has shown that careful application of adulticides like naled in accord with the labels and in collaboration with the community can dramatically reduce the abundance of infected mosquitoes, and can reduce mosquito-borne disease without unreasonable risks.

Dr. Karl Malamud-Roam is public health pesticides program manager at Rutgers University.


Every third bite of food is there because of pollination by bees. Bees are in big trouble, and we still don’t know all the reasons colonies are experiencing mass die-offs.

Our growing concerns about the Zika, West Nile, and other mosquito-borne viruses have led to the institution of mosquito control programs across the U.S. One means of eliminating adult mosquitoes is aerial spraying with a pesticide called naled. Unfortunately, there’s been collateral damage to many beneficial insects.

A recent series of aerial sprayings in Dorchester County, South Carolina, killed millions of bees. Although short acting, naled is lethal to bees and the chemical is not meant to be used between sunrise and sunset, when bees are out foraging. The inappropriate timing of spraying has had the effect of “nuking” the colonies of many Dorchester County beekeepers. Dead worker bees were found in large clumps at hive entrances; one beekeeper lost 46 hives.

Although the county claims to have given advisories via email, beekeepers claim they didn’t receive the notice. One told CNN, “When they sprayed by trucks; they told me in advance, and we talked about it so I could protect my bees...But nobody called me about the aerial spraying.”

All this is happening at a time when another pesticide is devastating bee populations. Here’s one story:

In 2013, customers at an Oregon Target store arrived to see tens of thousands of dead and dying bumblebees in the parking lot. An investigation revealed that, the day before, a pest-control company had sprayed insecticide on surrounding trees due to an aphid infestation.

The pesticide was a neonicotinoid, or “neonic.” Developed by Bayer a decade ago, it differs from other pesticides in that it clears from the air a lot slower. Although Bayer is a German company, you can’t use neonics anywhere in the European Union. In the U.S., however, crops are sprayed with neonics, which are absorbed by the plant’s vascular system, making it poisonous to bugs.

When a neonic doesn’t kill a bee, it can damage its immune system and ability to navigate, leading to colony collapse disorder. A new study indicates that neonics harm drone bees’ sperm, causing a condition called “queen failure,” in which queen bees fail to have live offspring.

Eugene, Oregon has forbidden the use of this pesticide. We need others to follow their lead and the federal government to ban neonicotinoids and mandate wiser use of organophosphates like naled.

Given the stress that our bee population is already under, what will be the straw that broke the camel’s back?

Dr. Joe Alton is the author of The Survival Medicine Handbook and blogs at