Palo verde beetles are on the prowl for mates. What to know about the huge flying insects

Big black beetles with long antennae might be skittering around your yard or patio this time of year, but fear not: These are just the relatively harmless palo verde beetles, also known as palo verde root borers.

Active mainly at night, palo verde beetles lay their eggs near their namesake host trees, potentially damaging roots in the process. While palo verde beetles rarely enter homes, they may be attracted to light and occasionally find their way indoors.

Despite their intimidating appearance, palo verde beetles pose no threat to people or pets. So, if you spot one of these 3-inch giants, there's no need to panic. Here is everything you need to know about palo verde beetles in Arizona.

If you want to know more about the wide variety of insects, arachnids and reptiles in Arizona, we've got you covered: Here are guides to black widow spiders, pesky gnats, rattlesnakes and cicadas.

Why are they called palo verde beetles?

They are called palo verde beetles because they lay eggs underground around palo verde trees and their larvae feed on the tree roots.

Palo verde beetle size

Adult palo verde beetles are typically 3 to 4 inches long, though they can occasionally reach lengths of up to 5 inches.

“This is a very large beetle," said Richard Hofstetter, professor of forest entomology at Northern Arizona University. "One of the largest beetles in North America when it's an adult, and just for that reason people see it and are aware of it."

Where are palo verde beetles found?

Palo verde beetles are commonly found in regions with arid or semi-arid climates, including Arizona, California, Nevada, New Mexico, Texas and the Mexican states of Sonora and Baja California.

Palo verde beetles inhabit desert and scrubland habitats where palo verde trees and other woody shrubs are abundant. They may be found outside their native range if suitable host plants are present.

“They are native to the Southwestern U.S. and northern Mexico," Hofstetter said. "They basically live for almost three years in the ground, the larvae eating roots, and then they only come up for about a month when they’re an adult. When they're an adult, they're mostly just trying to lay eggs back into the ground.”

Do palo verde beetles fly?

Yes, palo verde beetles can fly. They take flight during the evening hours, especially during summer mating season, to search for mates and suitable locations to lay eggs, according to the Arizona-Sonora Desert Museum in Tucson.

What time of year do palo verde beetles come out?

Hofstetter says palo verde beetles typically emerge during the summer months, particularly after periods of rainfall. Peak activity is during the hottest, most humid parts of summer.

As nocturnal creatures, palo verde beetles are most active during the evening and nighttime hours, when they may be seen flying around and mating near palo verde trees and other host plants.

Is a palo verde beetle a cockroach?

No, a palo verde beetle is not a cockroach. Although palo verde beetles can be mistaken for cockroaches due to their large size and dark coloration, they are entirely different insects.

Is a palo verde beetle harmful?

Palo verde beetles are not considered harmful to humans or pets. Despite their large size and intimidating appearance, they are not aggressive and they do not bite or sting.

“People grab them and they aren’t very threatening and they won’t fight you. They are not going to be aggressive. They may make a little hissing type sound when you grab them and they just want you to let them go,” Hofstetter said.

Are palo verde beetles aggressive?

Palo verde beetles are not aggressive toward humans or animals. “Even if it lands on you, it's not going to bite you unless you, like, press it against your body and it's just going to try to get away,” Hofstetter said.

Are palo verde beetles harmful to trees?

Yes, palo verde beetles can be harmful to trees. Their larvae feed on the tree's root system, which can weaken or even kill the tree. Root damage also can make the tree more susceptible to stressors such as drought or disease.

“So what you end up seeing is they eat one of their roots and that will result in one of their branches dying, and sometimes you can get the death of a tree if it's weak or there's a lot of palo verde beetles eating the roots of that particular tree," Hofstetter said.

What keeps palo verde beetles away? How to get rid of palo verde beetles

According to the University of Arizona, “There are really no effective control measures for the palo verde beetles," but you can take steps to deter them:

• Remove food sources: Since adult palo verde beetles feed on nectar and pollen, reducing the availability of flowering plants can make the area less attractive to them.

• Reduce outdoor lighting: Palo verde beetles are attracted to light, so minimizing outdoor lighting, especially bright white or ultraviolet lights, can help reduce their attraction to specific areas.

• Block entry points: Ensure that doors, windows and other entry points are properly sealed to prevent palo verde beetles from getting indoors.

• Trim vegetation: Keep trees, shrubs and other vegetation well-trimmed and away from buildings to deter them from laying eggs near structures.

• Control moisture: Palo verde beetles are attracted to moisture, so repairing leaks and drainage issues can make your yard and house less hospitable.

• Add barriers: Physical barriers, such as fine mesh screens or plant covers, can prevent palo verde beetles from feeding or laying eggs on a plant.

• Use pesticides with care: Insecticides labeled for palo verde beetles may be applied to affected areas in severe infestations. These should be used judiciously and in conjunction with other preventive measures.

What if my dog ate a palo verde beetle?

Although palo verde beetles are not poisonous to dogs, monitor your pet closely for signs of illness or discomfort.

Ingesting any foreign object, especially an insect, could cause gastrointestinal upset or other health issues.

Although Hofstetter said palo verde beetles are not poisonous, it's possible they could eat something poisonous that might affect your pet.

Call your veterinarian if your dog exhibits vomiting, diarrhea, lethargy or difficulty breathing after eating a palo verde beetle.

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This article originally appeared on Arizona Republic: Palo verde beetle season 2024: Giant flying insects are coming soon