Sugar Not So Sweet

The latest weapon for fighting pests is natural and safe to humans. And here's the sweetest part - it's sugar!

Well, it's not so sweet to some insects and mites. This isn't your grandmother's table sugar. While safe to humans, this sugar pesticide kills them quite effectively.

Scientists at the US Department of Agriculture added an extra chemical group to the sugar sucrose and applied it to plants as a diluted spray.

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"During application it coats the leaf's surface with a solution which can get in the trachea of insects and suffocate them, particularly small insects," Gary Puterka of the USDA's Agricultural Research Center. "The other mechanism is disruption of the insect's cuticle, causing rapid water loss."

The synthetic sugar kills from the inside out. Once it gets through small holes in an insect's hard, protective exoskeleton, the extra chemical group - called an ester - causes the insect to lose water, shrivel, and die of dehydration.

Safe to use, gross to eat

While its effectiveness as a pesticide is impressive, being safe for people is the sugar's real selling point. Our tough skin provides significant protection, and the dose needed to kill an insect is far too little to hurt a person.

The sugar solution washes off plants easily and is even used as a texturizing agent in some brownies. Note that it's used to enhance texture, not flavor.

"It's a bitter taste," Puterka said. "It's not sweet like sugar. Believe me."

It's also safe to the environment and doesn't leave behind nasty residues like some chemical pesticides.

"It's only active when it's wet," Puterka said. "It dries and kills quickly, then breaks down into smaller parts and becomes inactive."

Saving the honeybees

The main use for sugar pesticides right now is to kill the parasitic Varroa mites that are devastating the honey bee industry. By using a low dose, scientists can kill the mites but not the bees. But that's not all that protects the bees.

"The bees have a different cuticle than the mites," Puterka said. "Bees are also protected by the hairs that cover their body."

Sugar pesticides could soon find a home under your kitchen sink or in your closet as a killer of household pests like wasps and cockroaches. These applications are being looked at by the Environmental Protection Agency.

A report of Puterka's work was published in the June 2005 issue of Agricultural Research.