Harmonic Radar on Tiny Travelers Means Smarter Crop Protection

By: Todd Silver
Email: Todd.Silver@usda.gov

With their insatiable hunger for succulent fruits and vegetables, fruit flies from the Tephritidae family are the bane of farmers and consumers alike. But recent ARS findings suggest that wind could play a major factor in surveillance, containment, and eradication of this destructive pest. Advanced technology in tracking the effects of wind dispersal on tiny, winged creatures in the wild promises to refine fruit fly management strategies, identify outbreak sources, and help scientists anticipate their movement, feeding, and mating patterns.

Several fruit flies from the Tephritidae fruit fly family are invasive to the U.S. and combine to cause millions, and during some seasons billions, in crop losses to American farmers. Beyond direct damage and control costs, if these pests were to become established on the U.S. mainland, they would become major barriers to international trade and prevent U.S. farmers from exporting to many of our trading partners. 

Tephritid fruit fly with harmonic radar tag attached, marked with yellow fingernail polish.

The key to managing these pests is to understand their flying behaviors. Matthew Siderhurst recognized and addressed the complexity of tracing flies and deciphering wind-based patterns and now leads a team of scientists at the Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center in Hilo, HI, where their research will empower American farmers to protect their crops and reduce food waste. Groundbreaking research published in Environmental Entomology explains that harmonic radar tagging, initially developed for locating avalanche victims, can be used to study these fly pests. The method uses reflector tags that require no energy source of their own to bounce a signal back to a transceiver to map movement data.  

Though attaching harmonic radar tags to the fruit flies requires painstaking precision, the mechanism is relatively simplistic: a superelastic 4-centimeter wire is connected to a diode, or one-way current semi-conductor, with an ultraviolet-activated adhesive. Next, electrical connections between the wires and diode contacts are secured with conductive silver paint. Check out the radar tags in this video. 

Siderhurst said the study’s identification of outbreak patterns could predict environmental fluctuations influencing fruit fly behavior and enable farmers to adapt pest control methods. Contrary to historic consensus, this ARS-led research documented that fruit flies control their flight paths in response to wind cues as opposed to passive wind-driven movement. 

“Most of us have seen a housefly buzz around a room and that movement appears random, but when we look at fruit flies, we see they show a fairly high degree of directional persistence,” Siderhurst said. “That is, they move in much straighter lines than expected, and individual flies appear to hold to a general heading when moving between trees.” 

Tephritid fruit flies are about the size of a housefly and damage a wide variety of fruits and vegetables.

Further field testing with wild flies is warranted because the wind influenced the flies’ flight directionality, especially in movements between trees using lab-reared flies to avoid underestimating the flies’ natural movement abilities and overstate wind’s role in their flight. 

Siderhurst acknowledged that most of the research thus far has proven the technique’s effectiveness, but work remains to answer further biological questions with the new tool. Further research, he said, will ideally reveal how habitat, vegetation density, and factors such as age, diet, and time of day affect insect flight patterns, with consideration of environmental influences like wind and open landscapes. 

"Our approach is accessible and cost-effective,” Siderhurst said. “While you need good eyes and a steady hand, this technique is cost-effective and transceivers are available off the shelf, so there’s no need to build anything.” 

For more information, visit the Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center.

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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 U.S. agricultural research results in $20 of economic impact. USDA is an equal opportunity provider, employer, and lender.