Sugar sours birds on eating valuable cherry crops

Eric Olson leans against several pallets of granulated sugar at his Naches, Washington, storage facility. Olson uses 45,000 pounds of sugar, mixed with water and sprayed on the cherries before harvest, to keep starlings and other area birds from eating his valuable crop. The sugar is purchased from Costco and delivered by tractor-trailer. (TJ Mullinax/Good Fruit Grower)

When Carlos Martinez del Rio first heard that orchardists spray sugar on their cherries to control birds, he thought it was a prank.

The University of Wyoming zoologist first posited way back in his 1995 doctoral dissertation that the inability of certain birds to digest sucrose may make sugar a viable pest control option. Few took him seriously, he recalled.

Today, however, sugar as bird control is one of the fruit industry’s worst kept secrets, especially in Washington. “I am so happy about this,” Martinez del Rio said when Good Fruit Grower told him about the practice. He plans to fly to Washington this year to take pictures of sugar applications.

Part home remedy, part amateur ornithology trick, growers in Washington have made a pretty widespread practice of spraying sugar water in their orchards as their fruit ripens to ward off birds such as starlings and robins.

“It’s phenomenal,” said Eric Olson, an orchardist in the Yakima, Washington, area.

We’re talking normal cane sugar, the kind you stir into your coffee. It works best on cherries but apple growers have had decent luck on their Honeycrisps, Fujis and Galas.

Some have used it for blueberries.

Of course, nothing totally prevents bird damage. Most growers stress the importance of a variety of controls, which include reflective tape, bird-scare cannons and other tactics.

Still, “Sugar has probably been our most effective tool,” said Denny Hayden, a Pasco, Washington, grower.

The inexpensive trick works because those types of birds, among cherry growers’ most loathed pests, can’t digest normal table sugar. It doesn’t kill the birds, just gives them a tummy ache and a little diarrhea. Growers have watched flocks of starlings — murmurations, actually — descend on their freshly sweetened crop, then quickly learn to leave the fruit alone.

So, growers buy lots of sugar from — where else? — Costco. Early on, they purchased it in 25-pound bags. But when the shelves began to run empty, the retailer arranged to deliver 50-pound packs by the pallet straight to farm shops. Most growers pay less than 50 cents a pound.

Some mix it with other chemicals, such as fungicides, cutting down costs even further.

“I’m shocked every year it keeps working,” said Marty Kers, an orchard consultant with D&M Chemical in Moxee, Washington.

Here’s why. Some bird families don’t secrete an enzyme that would allow them to digest disaccharide sugars. Sucrose is the most common disaccharide, widely available as table sugar. Starlings and robins, two of the most common fruit pests, are members of those families.

On the other hand, fructose, a form of simple sugar or monosaccharide, won’t work. Those birds can digest it, and the fruit they’re trying to eat in the first place contains fructose.

Mysterious origins

How that knowledge translated into what has become a standard technique is unclear. In Washington, most growers and crop consultants all seem to have heard it from someone else word of mouth.

“It doesn’t matter,” Kers said. “You can’t patent it.”

Kers first heard the idea from a grower a good 15 years ago and frankly called baloney. About eight years after that, another grower desperately begged him for advice, so they set up a small sugar trial on a 10-acre block of Lappins in Tieton, Washington. To their surprise, it worked. Kers now orders sugar bulk and delivers it to his growers along with the rest of their products.

At some point, Kers mentioned sugar bird control in passing to Alan Knight, an entomologist at the U.S. Department of Agriculture laboratory in Wapato, Washington. Knight had been using sugar to supplement his yeast during some spotted wing drosophila trials, but tested the bird control theory in an orchard and saw good results. He deflected credit though. “It wasn’t me,” he said. “I didn’t develop it.”

Knight then mentioned sugar to Cragg Gilbert, president of Gilbert Orchards in Yakima. Gilbert tried some on a 5-acre orchard near his house that faced a lot of starling pressure. “They were just taking half the crop,” he recalled.

Sure enough, the starlings started to avoid the block. Five days later, the birds would try again, and he had to reapply. Gilbert kept expanding the sugar applications to other blocks and now it’s his primary method of bird control.

The sugar seems to have few undesirable effects. It causes stickiness for the pickers, but he’s heard no complaints from warehouses. Many orchards hydrocool cherries before delivering to warehouses anyway.

He suggests growers give it time because the birds have to eat enough to get sick before they learn, something robins do more slowly than starlings. “They aren’t quite as smart a bird, I think, and they love cherries,” Gilbert said.

In Gilbert’s experience, the trick works better on cherries than apples, namely Honeycrisp. Starlings peck through the apple skin and eat the fruit from the inside. Gilbert doesn’t use sugar on wine grapes because they don’t get washed before processing and the extra sugar would affect fermentation.

As for Concords grapes, they don’t have a starling problem, said Mike Concienne of the National Grape Cooperative, which owns the Welch’s brand. Concords naturally produce methyl anthranilate, the active ingredient for many chemical bird repellents used on corn, rice and golf courses.

The practice is most popular in Washington. Researchers and growers reported little use in Michigan, New York, Oregon and California.
Science

The scientific paper trail on sugar as a bird repellent dates back to the 1990s.

Martinez del Rio, the Wyoming zoologist, pops up often in bibliographies. In his dissertation, co-authored with a researcher from the U.S. Department of Agriculture APHIS, he suggested that the monosaccharide indigestion of starlings and robins may warrant further studies of the potential for breeding fruit with higher sucrose concentrations. It never dawned on him to just spray sugar from a tank, he said.

Marvin Pritts, a Cornell University researcher who recommended using sugar applications for bird control in blueberries after his 1997 paper, had a similar reaction. “Fantastic that this is being used,” he said. “After all of these years, someone is finally picking up on it.”

Support wasn’t universal.

Washington State University horticulturist Leonard Askham wrote in a 1996 paper that sugar treatments made no difference in dissuading birds from eating fruit.

Askham, now a professor emeritus, is a principal in the Bird Shield Repellent Corp., a Pullman, Washington, company that makes a chemical repellent with methyl anthranilate as the active ingredient.

He has published research papers about the product on other crops, including corn and sunflowers. He declined to comment when reached by Good Fruit Grower, only to say the company is no longer doing business and is for sale.

Michigan State University researchers did a small pilot study in 2013 with blueberries but didn’t notice enough effects to pursue the topic further, said Catherine Lindell, an associate professor of integrative biology.

Growers hope a researcher holds the anecdotal evidence to scrutiny and develops some recommendations for concentration, rates and timing. Most growers mix the sucrose at rates anywhere from 8 pounds to 25 pounds per 100 gallons of water per acre. Olson figures that’s not nearly enough. He uses 400 pounds to 400 gallons for use on a single acre.

“You don’t have to save very many cherries for that to pay off,” he said. •

Simple solution, complex regulations

Spraying common table sugar on cherries and apples may be a simple way to prevent bird damage. Regulations on the practice are not so simple.

State and federal officials had varying and at times nebulous answers about whether growers can legally use sugar as a bird control.

“It’s not just an easy yes or no,” said Dale Mitchell, pesticide program manager for the Oregon Department of Agriculture.

U.S. Environmental Protection Agency regulations list sucrose sugar as one of several commonly consumed food products that are exempt from tolerance limits as long as they are used with good agricultural practices. However, the EPA often yields to state officials.

New York does not allow the practice because sugar is not labeled by the EPA. “The State Environmental Conservation Law does not have a pesticide registration exemption for the use of natural products unless the active ingredient is listed in the law as a minimum risk pesticide,” said Lori Sevino, a spokeswoman for the state’s Department of Environmental Conservation. “Sugar is not on that list; therefore, it cannot be used as an active ingredient under the ECL.”

Growers in New York aren’t sour about that though. Those who have tried it experienced mediocre results they attributed to their state’s humidity. Some also feared using sugar in an area with heavy early morning dew would make rot problems even worse.

Anything used to control pests is technically a pesticide, but regulators in Washington, Oregon and California are more concerned with distribution.

“A grower could use sugar water on their own crop and not violate state or federal laws since the grower is not ‘distributing’ an unregistered pesticide,” said Hector Castro, a spokesman for the Washington Department of Agriculture. The state does not endorse any pesticides, whether labeled or not. That includes sugar, he said. “But in most cases, its use would not be a violation of state or federal law.”

California had a similar response.

“We would regulate it only if somebody was doing premix sugar water,” said Craig Cassidy, a spokesman for the California Department of Pesticide Regulation.
Oregon and Michigan growers don’t typically use sugar as bird control, university researchers said.

– by Ross Courtney