Source: USDA ARS, 1/11/22
A team of Agricultural Research
Service (ARS) and university scientists has developed an electronic nose to
sniff out whitefly infestations of tomato plants.The "E-Nose" works by
detecting a specific cocktail of chemicals, called volatile organic compounds
(VOCs), that tomato plants release into the air when attacked by
whiteflies. In nature, these chemicals put other plants on high alert. Scientists
are hoping the E-nose will also warn growers so they can fine-tune their use of
whitefly-killing insecticides, biocontrol agents like parasitic wasps or other
measures. According
to Heping
Zhu, an agricultural engineer with the ARS Application
Technology Research Unit in Wooster, Ohio, who
co-developed the E-nose with collaborators at The Ohio State and University of
Tennessee-Knoxville, whiteflies are top insect pests of U.S. fresh-market
tomatoes, which were valued at $721 million in 2020. Left unchecked, adult whiteflies
and their immature nymphs probe the undersides of tomato plant leaves for sap,
causing them to turn yellow, curl or drop off. Whitefly feeding can also cause
uneven ripening of fruit and transmit viral diseases that weaken the plants
further. Whitefly monitoring typically involves checking for a threshold number of the pests per leaf on a sampling of plants or captured in sticky traps—both a time-consuming process. Towards that end, the researchers
designed a prototype E-nose device about the size of a shoebox that can operate
in the greenhouse. According to Zhu, the device mimics the mammalian sense of
smell and brain's ability to recognize certain odors. But instead of a nasal
passage, receptor cells and an olfactory bulb, the E-nose uses gas sensors,
data acquisition modules and other components. A key feature of the E-nose is a nerve-like circuitry board that helps convert VOC samples from the air into digital signals. These signals in turn are transmitted to the system's "brain," namely, a mathematical algorithm programmed to recognize specific types and concentrations—or "smell-fingerprints"—of VOCs that tomato plants give off when attacked. In greenhouse tests, the E-nose
displayed the VOC fingerprints of such plants as different lines with different
colors that rose sharply and steadily to the right of an LED screen. Moreover,
the system distinguished the smell-fingerprints of whitefly-infested tomato
plants from un-infested ones, as well as plants whose leaves were punctured
with pins for comparison. With additional testing and
development, the E-nose could give greenhouse growers another monitoring tool
to use in deciding where, when, and how best to tamp down whitefly infestations
before they reach economically damaging levels. Besides whiteflies, the E-nose
also successfully sniffed out tomato-infesting aphids and insect pests of other
greenhouse crops. "The future E-nose system
can be designed as a hand-held device for growers to take samples from
individual plants," Zhu said. "It can also be designed as a
computer-controlled cloud networking system which consists of multiple smart
sensors placed at different locations in the greenhouse, so the computer can
automatically collect samples and monitor infestations 24 hours a day." Details of the team's findings
were published in the October 2021 issue of Chemosensors and in the August 2019 issue
of Sensors. The Agricultural Research Service is the U.S. Department of
Agriculture's chief scientific in-house research agency. Daily, ARS focuses on
solutions to agricultural problems affecting America. Each dollar invested in
agricultural research results in $17 of economic impact. |