Heptyl butyrate

Heptyl butyrate is a colorless liquid with a chamomile-like odor that is found abundantly in fresh apples and plums. In late summer, as these fruits begin to fall from trees, swarms of yellowjackets (Vespula spp.) can appear.

In the late 1960s, Entomologist Harry G. Davis, chemist Martin Beroza, and colleagues at the US Department of Agriculture were researching attractants for the little housefly (Fannia canicularis) when they discovered the effect of heptyl butyrate on yellowjackets. But the details of this attraction were not investigated until 2016, when Peter Landolt at the USDA (Wapato, WA) and Q.H. Zhang at Sterling International (Spokane, WA) studied various potential attractants and reported that heptyl butyrate was superior to other compounds for attracting Vespula and other wasp genera.

In 2009, a fact sheet issued by the US Environmental Protection Agency stated that heptyl butyrate is a safe, food-grade compound. Earlier that year, EPA had issued a pesticide registration for the compound to be used as an attractant in yellowjacket traps and other devices.

Heptyl butyrate also occurs in babaco (an Ecuadorean hybrid papaya-like fruit in the genus Vasconcellea). So if you like the smell of fresh fruit, you and yellowjackets are in good company.