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Honeybees, beekeepers battle deadly parasite in Southwest Colorado

Parasitic mite can kill entire hives, bring economic damage
Honeybees face numerous environmental stressors, but a certain kind of mite poses one of their top, most-fatal threats. (Jerry McBride/Durango Herald)

One day in 2015, Nancy Logan, a hobbyist beekeeper in La Plata County, noticed a honeybee walking strangely. She looked closer and saw four tiny, red-brown insects on its back.

“I euthanized her, and three more mites jumped off her abdomen,” said Logan, now president of the 4 Corners Beekeepers Association. “That one bee had seven mites on her.”

She had found the Varroa destructor: an aptly named parasitic mite that can kill an entire hive and inflicts more economic damage than most honeybee diseases. The mites, first discovered in Indonesia in 1904, have spread to every continent except Australia. Beekeepers are trying everything, from thyme to selective breeding, to keep them at bay.

“A very experienced beekeeper told us in a seminar: Every one of you has Varroa mites in your colonies, and they will kill your colony within two to three years if you don’t control the population,” Logan said. “Now, people are saying they will kill your colony within one season.”

The United States honey industry was worth about $4.7 billion in 2017, according to the University of California Agricultural Issues Center. About 22,000 people relied on it for their jobs.

Honeybees are vital pollinators for three out of four crops across the globe. Their importance is celebrated by the United Nations through World Bee Day, May 20.

Angelina Jolie even hopped on board this year, posing for a photo covered in scores of the pollinating insects to raise awareness for a Women for Bees initiative, a program launched by the United Nations Educational, Scientific and Cultural Organization.

The U.S. had 2.98 million colonies as of April 2020, according to the Department of Agriculture. In Colorado, there were 38,000 hives in 2019, according to the Colorado Professional Beekeeping Association.

Lyle Johnston is president of the association and his family has been in beekeeping since 1908. He says they’re the oldest honey operation in Colorado.

The family runs 1,500 hives in the San Luis Valley and Salida. One hive can make 130 to 140 pounds of honey a year in perfect conditions.

The Johnstons have been fighting Varroa mites since 1987, when the pest arrived in the United States. The mites, parasites and vectors for viruses, were the No. 1 stressor for bees in 2019, according to a USDA report.

“It happens so quick. Within 90 days, a hive of bees can go from looking healthy down to death,” Johnston said.

Bees are vital pollinators for three out of four crops around the globe, according to the United Nations. (Jerry McBride/Durango Herald)
The parasite and the bee

When the Varroa mite – deaf and blind with a piercing, sucking mouth – infests a hive, its first step is to hide.

Then it feeds off bee babies and adults to survive.

“It causes a shorter life span, which means foragers die sooner. Nurse bees become foragers and can’t take care of the other bees,” said Eric Smith, president of the Colorado State Beekeepers Association, a hobbyist group. “The hive gets smaller.”

Honeybees are social insects that live together in well-organized family groups. Thousands of worker bees cooperate in nest building, food collection and brood rearing. Drones are part of the reproductive cycle, and queens can lay up to 1,500 eggs per day.

After the bee drops an egg and some food in a beeswax cell, a Varroa female sneaks in and hides under the larvae from the bees that tend to the brood. There, they feed on the food and the larvae for 10 days while reproducing, according to Varroa life-cycle research.

By the time the young bee hatches, it’s carrying multiple mites that can jump to other bees. The Varroa destructor uses the suckers on its feet to grip the bee’s body and its mouth to pierce the adult bee’s abdomen and feed on its fat bodies, tissue that stores nutrients and serves other uses, like immunity.

The whole process wounds the bees and can shorten their life cycle. Mites lead to crippled and crawling honeybees, impaired flight performance, larvae slumped in the bottom or side of the cell and a lower rate of return to the colony after foraging.

The mites spread numerous viruses to the bees. All of this ultimately causes a reduction in the honeybee population, replacement of queen bees and eventual colony breakdown and death.

“If you’re not controlling them, then the viruses are in the hive from the mites,” Johnston said. “The viruses are kind of the nail in the coffin. When you get to a certain level, there’s no going back.”

Defense tactics: Powdered sugar and science

When Logan saw the mite-covered bee in 2015, she quickly realized the colony had a high population of the parasite and started a thyme-based treatment, thymol wafers.

“You do the repeated treatments: Over that month, I think I had thousands of mites drop,” Logan said. “That hive was on the brink of dying. It came back.”

To manage the population, she tests the hives by using the powdered sugar roll technique: taking half a cup of bees, a couple of tablespoons of powdered sugar and shaking them in a mason jar.

The powdered sugar makes it difficult for the mites to hold onto the bees, and they fall through a screen on the jar. A population higher than nine mites means she has to treat, she said.

For his commercial operation, Johnston mixes essential oils, like lemongrass, with a Crisco grease ball and puts it on top of the hive. The fumes, he said, kill mites or at least control their population.

Volunteers and staff members with the 4 Corners Beekeepers Association prepare packages of bees in Durango on April 24. Members picked up 140, 3-pound packages of bees, each containing an average of 11,000 bees. (Jerry McBride/Durango Herald)

Johnston and Smith, like researchers around the world, have been experimenting with ways to speed up natural selection using bee species that have a slight resistance to Varroa destructor to help Western honeybees develop defenses against the mites.

Sometimes, beekeepers use formic acid, which occurs naturally in ants, or oxalic acid, an organic compound found in many plants.

They can also divide the colony early in the season, which gives the hive a brood break, a break in the bee reproductive cycle that interrupts the mite reproduction, Logan said.

Many hobbyists don’t want to treat for mites, Smith and Johnston said.

“They want to be ‘natural beekeepers,’ but their bees die. They end up getting them from California,” Smith said.

All three association presidents urged beekeepers to do something about the mites. There are plenty of management strategies and soft chemical or organic treatments, Logan said. She doesn’t recommend harsher chemicals.

“The main thing I stress, until we become resistant, you have to treat,” Johnston said. “You cannot do organic beekeeping or you’ll be picking up dead equipment.”


An earlier version of this story erred in saying mites were the No. 2 stressor for bees in 2019. They were the No. 1 stressor. The error was made in editing.

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