NEXRAD Radar Can Track Insect Pest Migrations
A couple of weeks ago, the U.S. National Weather Service posted satellite photos of large clouds of monarch butterflies to their Facebook page.
Now scientists at the U.S. Department of Agriculture are also using radar, but this time they’re employing it to track the spread of bollworms (Helicoverpa zea), which cost cotton producers $200 million per year. In addition, these insects — which are also known as corn earworms and tomato fruitworms — cause considerable damage to corn and other crops.
Helicoverpa zea damage crops during the larval stage as caterpillars. Then as adult moths, they migrate at night, which makes them difficult to track.
Now USDA scientists have shown that signals routinely collected by the National Weather Service’s Doppler radar network could serve as an early-warning system to track them and other nighttime traveling pests.
Meteorologists John Westbrook and Ritchie Eyster focused on the capabilities of what is known as Next Generation Weather Radar, or NEXRAD. With more than 150 ground-based installations across the United States, NEXRAD monitors weather conditions by sweeping the atmosphere every 5 to 10 minutes and reading the energy reflected by rain, snow, and other precipitation. Algorithms normally remove energy reflected by flying insects, but scientists have used NEXRAD and other radar signals to track birds, bats, and insects.
Westbrook and Eyster obtained 15 days of NEXRAD data in Brownsville, Texas to see if they could use it to make aerial counts of corn earworm moths and determine their movement patterns during peak migration times from cornfields in the Lower Rio Grande Valley.
The researchers measured radar properties associated with aerial concentrations of moths at heights of up to 3,900 feet, using archived NEXRAD data collected in 1996. They then compared it with data from the same time period previously collected with a scanning “X-band” radar system. Unlike NEXRAD, which is constantly operating, the scanning X-band system is specifically designed to track insects, but must be set up and monitored each time it’s used. NEXRAD data is publicly available and can be used without any positioning or monitoring cost, so it would be less expensive.
The results showed that NEXRAD was not only capable of tracking insect migration patterns, but also was superior to the X-band system because it offered a larger detection range and could determine the direction and speed of the insects. The results of this work were published in the International Journal of Biometeorology.
More work is needed, but recent upgrades should make it easier to use NEXRAD radar to identify potential corn earworm infestations. Also, with refined algorithms, it should be able to track beet armyworms, grasshoppers, and other large-bodied insects.
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