Sweet solution stays on the shelf
Though effective against soft-bodied orchard pests, a sugar ester pesticide is not being commercialized for orchard use.
A pesticide made from sugar esters is being used by beekeepers to control the varroa mite, but is not yet being marketed for controlling orchard mites or other pests. The synthetic sugar ester, sucrose octanoate, was developed by U.S. Department of Agriculture researcher Dr. Gary Puterka, who also was one of the scientists who developed the kaolin particle film technology as a pest control. The particle film, sold by Engelhard Corporation, is widely used to control pests in pears.
Sugar esters are produced by reacting sugars with fatty acids. They’re used worldwide in bakery goods, drugs, and plastics for food packaging, for example.
Puterka began researching the insecticidal activity of synthetic sugar esters in the early 1990s, building on earlier research by ARS scientists who had discovered natural sugar esters that act as repellents to insects. They had found that the chemical produced by the leaf hairs of tobacco plants, which made insects twitch and die, were sugar esters and not nicotine as previously thought.
The esters kill insects or mites on contact by penetrating or breaking down the insect’s waxy cuticle. The pest then loses water, shrivels, and dies from dehydration.
Natural sugar esters proved to be too expensive to mass-produce as insecticides so ARS scientists in Georgia devised and patented synthetic versions, which were more suited to mass production but less potent than the natural versions.
In 1998, the Agricultural Research Service set up a Cooperative Research and Development Agreement with AVA Chemical Ventures, LLC, of Portsmouth, New Hampshire, to develop an effective synthetic sugar ester. Together, Puterka and AVA Chemicals patented sucrose octanoate and an environmentally sound process for manufacturing it.
Sucrose octanoate was registered four years ago by the U.S. Environmental Protection Agency for a wide variety of insects on agricultural crops including apples, grapes, and pears. It also is approved for use in organic production.
Puterka went on to develop another synthetic sugar ester, sorbitol octanoate, which was cheaper to produce than sucrose octanoate, and almost as effective. Sorbitol octanoate also has been registered by the EPA.
AVA Chemical is producing sucrose octanoate for control of the varroa mite, a parasite of the honeybee. It is being sold by Dadant and Sons, Inc., under the trade name Sucrocide. The product is sprayed onto bee frames, using a garden-type or backpack sprayer, and rapidly kills the mites without harming the bees.
Puterka believes a sugar ester product has great potential for controlling orchard pests, particularly mites, and would likely cost half as much as the miticides in current use, at about $30 per acre. As a miticide, it would be applied as a 0.8 to 1.0 percent solution (about half the rate of an insecticidal soap) from an airblast sprayer. It is extremely safe to workers and the environment, yet has quick knockdown of soft-bodied insects and mites. It has no residual effect. The product is inactive once it has dried and rapidly degrades into harmless sugar and fatty acids.
“I know it’s probably not as competitive with the residual materials, because growers like to have their sprays last longer,” Puterka said, “But I think in an IPM system developed with this material, it would work out fine. You just have to use a different approach.”
Puterka said the material is selective and is not harmful to bees or beneficial insects, such as lady beetles. Research in Florida citrus showed that key parasites and predators of aphids were unaffected by it. The selectivity has to do with the cuticular wax of a particular species of insect and the concentration of the sugar ester spray, he said. At a rate of 0.8 to 1.0 percent, it is selective towards mites.
The license to commercialize and market the sugar esters for use in fruit and vegetable production remains open.
Make an offer
Puterka said someone will need to make an offer to AVA Chemicals to market and distribute the product in order to get it into commercial use, but so far no one has been able to reach an agreement with AVA owner Tony Barrington to do that.
Barrington said he’s not been able to get anybody to take on the task of distributing the product as a foliar spray for agricultural use.
“It’s been looked at by a couple of companies, but they just didn’t take the bait,” he said.
One company was interested in it for organic production but found that the sugar ester outperformed their own popular pest control product, and he thinks the company didn’t want to cannibalize its own sales. He said a secrecy agreement prevented him from disclosing more details even though the company decided not to go ahead with the sugar ester.
Barrington said if the product were sold for orchard use, it would require a relatively large amount compared to the amount beekeepers use. He thinks most orchardists would balk at the cost of the amount of product it would take for a 1 percent solution applied at 200 gallons per acre.
He estimates it would cost $75 per acre for the sucrose product, or half that for the sorbitol material, although the cost would decline as the volume manufactured increased.
“Agriculture these days in this country is so cost conscious because of all the foreign competition, it’s very difficult to price it so you make money and give the grower a price he likes,” he said.
If he charged the same amount as he does for the bee product, it would cost $300 per acre, he said, whereas beekeepers consider it a bargain because it’s the least expensive treatment available for varroa mites.
Barrington said he’s been concentrating on niche markets where a little of the product goes a long way and it’s more economical. He’s planning to target orchid growers with a formulation that would come in a spray bottle.
Puterka’s research was supported by the Washington Tree Fruit Research Commission. Tom Auvil, research horticulturist, said the commission always hopes to see the commercialization of products that it has provided funding for, but it has encountered situations where companies have acquired research products that have just sat on the shelf because of competition.
“A lot of good ideas don’t go anywhere if you don’t have good partners,” Puterka said. “It gets frustrating. I wish it would have worked out better.”