Making Insecticides Safer

Associate professor of chemistry Stephanie Sen’s research could lead to an environmentally safer method of controlling moths—pests that cause major agricultural damage and deforestation.

Words by Tony Marchetti ’96, MA ’02

Studies show that many broad-based, synthetic insecticides on the market have long-term, adverse effects on the environment and human health. The ideal synthetic agent is one that targets a specific type of insect while causing no harm to the other organisms that come in contact with it.

Stephanie Sen, associate professor of chemistry, is working toward such a solution for controlling moths—pests that cause major agricultural damage and deforestation. Yet with over 150,000 different species of this insect, it might seem an impossible task to develop an insecticide that kills only moths and has no cross-reactivity with other organisms.

Sen said the secret could lie in creating a synthetic molecule that controls a moth’s ability to produce Juvenile Hormone. This hormone, ubiquitous to all insects, controls a moth’s growth, development, and reproduction. But whereas the hormone is a single chemical in most insects, it is a family of five distinct chemicals in moths, Sen explained.

“When you look at those structures, you have a sort of ‘a-ha!’ moment and realize that moths” must be producing the hormone in a unique way, Sen said.

Her research has shown that moths use a series of proteins to produce Juvenile Hormone. Currently, she and her team of student researchers “are looking at the biochemical transformations that [occur], looking at very specific proteins that are involved in those transformations, and doing structural analyses to determine and map out exactly what the differences are between those proteins and homologous proteins that are present in other organisms,” Sen explained.

The goal is to design a molecule that “knocks out the ability of the insect to make those proteins,” Sen explained. “If we can do that, there will be a domino effect—the insect won’t make the hormone, because we’ve stopped the whole biochemical process…and [the moth] will die as a result.”

“It’s a medical-chemical solution to the problem” of pest control, Sen said.

Any synthetic agent that resulted from this research “would not be a fast-kill compared to…an insecticide that affected the moth’s neurotransmissions.” (Those fast-acting insecticides are the ones that are harmful because they affect all organisms’ neurotransmissions—including humans, Sen explained.) “But this would be a fast enough kill in the field that it could stop insects from damaging crops,” Sen said.

An insecticide using such a synthetic agent would be an ideal complement to an integrated pest management system, Sen continued. For example, farmers could use the targeted insecticide in conjunction with parasitic wasps—biological agents that are excellent at killing moths. “A multifaceted approach is always best” and reduces the chance of creating resistant insects in the process, Sen explained.

“This would be a synthetic agent,” Sen continued. “But the fact that we’re doing this with such a high level of precision, it’s a ‘green’ approach to solving the problem.”