[ANNUAL ANT CONTROL ISSUE] Cut the Honeydew, Derail the Ants

Experts long have thought that by getting rid of ant food sources near structures, they might reduce the likelihood of the pests finding their way indoors.

It’s a logical deduction, especially for Argentine and other ants that rely on honeydew, said Dr. Mike Rust of the University of California, Riverside. Honeydew is a sugary liquid produced by hemipteran insects — aphids, scale, mealybugs and whiteflies — that suck the sap of plants often used to landscape a structure’s perimeter.

Honeydew is a predictable, sustainable food source. It allows ant populations to build and the brood to be fed, said Syngenta Technical Manager Dr. Bob Cartwright.

By removing this preferred food, pest management professionals take away an important item the ants need.
And, according to a new study by Dr. Dan Suiter of the University of Georgia, Griffin, the ants will forage elsewhere.

In this study replication, Dr. Dan Suiter set up three pepper plants on each of several trays, then infested two plants on each tray with aphids.SUCCESS IN THE LAB.
In a controlled greenhouse environment, Suiter and horticulture colleagues set up an arena, or large 4-by-4-foot tray, containing three green pepper plants, chosen because they grow fast and are easily infested with aphids. A container of 2,000 to 3,000 Argentine ants was placed in the center of the tray. Wires were then wound from plant stems to the containers of ants, connecting the nests to the plants.

Suiter infested two of the plants with aphids. For the first nine days, the ants, which weren’t given any food, spent 80 percent of their time split evenly between the two aphid-infested plants collecting honeydew.

On the ninth day, Suiter injected 75 ml of thiamethoxam (Optigard Flex by Syngenta) by syringe into the soil of one of the aphid-laden plants. This water-soluble neonicotinoid is easily drawn up plants’ roots and dispersed throughout by the plants’ vascular system.

Over the next one to two days, the aphids sucked the sap of the treated plant and died, and the ants abandoned that plant in favor of the untreated one with aphids. “It was a very dramatic shift,” said Suiter, who noted the ants weren’t killed but “changed their foraging behavior.”

In 2009 and 2010, he conducted the experiment 20 times — four trials with five replicates each — and achieved consistent results.
Systemic pesticides have been used in agriculture for years to control hemipteran pests, but using them to change the behavior of a secondary, structural pest is a relatively new concept.

“I think we’ve proved it’s doable,” Suiter observed. “The question now is, how do you scale it up” to work effectively in the pest control industry.

He’ll begin a large-scale field trial using ornamental plants this spring and predicts this treatment will be effective against most ants that tend aphids, including rover and odorous house ants.

FIELD TACTICS.
But simply eliminating the ants’ food source won’t be enough to solve the ant problem, cautioned Corky Mizer, president of Corky’s Pest Control in San Marcos, Calif. Mizer has used food source elimination as part of a successful Argentine ant control program for 30 years.

If ants are coming into a house and you eliminate the hemipterans on nearby plants and expect the ants to go someplace else, “they won’t,” he explained.

Professionals first must probe out the existing colonies on the customer’s property, then eliminate the hemipterans, preferably before they hatch. Mizer sprays EPA-exempt botanical products on landscaping plants three times in early spring during regular six-week service visits to kill hemipteran eggs. This prevents scout ants from finding enough honeydew-makers to sustain a satellite colony, he said.

This tactic requires knowledge of regional plants vulnerable to hemipteran infestations, and the biology and behavior of sap-sucking insects.

It may be enough to see ants trailing into plant canopies over a number of days to assume the presence of honeydew makers, said Dr. Jules Silverman of North Carolina State University, Raleigh. But “just treating plants because you think they may be the source of the problem is probably excessive use of pesticide.”

And, it can be tricky. In 2009, Rust applied a product containing imidacloprid and beta-cyfluthrin as a soil drench and got “great control” in low-lying ornamentals. “We were able to reduce the hemipterans and get rid of the ants on those plants.” But taller Queen Palms and Jacaranda trees growing in the perimeter “presented a major challenge.” And some plants, like hibiscus, are highly sensitive to insecticide treatment.

Edible plants — fruits, vegetables and herbs — also require special attention. Systemic products have long residuals and should not be applied close to harvest.

Licensing is another issue. National Pest Management Government Affairs Director Gene Harrington advised PMPs to check with their state regulatory agencies to determine the scope of the 7a license before applying systemics. A turf and ornamental license may be needed, depending on the distance from the structure the product is being applied. Acquiring this license isn’t a major hurdle: Professionals only will need to pass another category exam, he explained.

STILL WORTH THE EFFORT.
Despite these challenges, experts said eliminating ants’ preferred food source will help control this elusive pest.

“It fits like a glove from an IPM perspective,” said Suiter. By treating select landscape plants, PMPs apply less material in a more focused way, compared to putting out gallons in perimeter treatment.

“With the right mix of chemicals, it is viable,” added Silverman. By interrupting ants’ access to their preferred food, the pests may find baits more palatable.

“It’s not a simple solution, especially when you’re dealing with a large area these ants could forage over,” but the current approach is “just a quick fix” and “often requires callbacks because you’re not considering what the ants are doing outside the home,” he said.

Incorporating a systemic insecticide into your protocol is “definitely” worth it, said industry expert Austin Frishman. It improves the effectiveness of perimeter control and is an easy shift for companies already doing lawn and ornamental work. Plus, eliminating hemipterans improves the health of customers’ landscaping plants: This is an opportunity for PMPs to grow their business, he added.
 

Research study photos courtesy of Dan Suiter. The author is a frequent contributor to PCT magazine. She can be reached at anagro@giemedia.com.

Eliminating Aphids the Natural Way
For more than 30 years, Corky’s Pest Control President Corky Mizer has made food source elimination a tenet of his successful Argentine ant control program.

The numbers speak for themselves: Re-treats account for less than one-half of one percent of his 40,000 customers.

In early spring, technicians spray EPA-exempt botanical products on landscaping plants to kill hemipteran eggs. They target only plants vulnerable to aphids, scale, mealybugs and whiteflies, and apply the botanicals three times during regular six-week service visits.

“The botanical treatments work wonderfully,” said Mizer, who’s been using these products for 15 years. “You don’t have to use any heavy-dose materials.” He said other options are horticultural oils and pyrethrum, but advised against using synthetic pyrethroids or systemic insecticides on fruit-bearing trees, which hemipterans love, because of the long residuals.

The goal is to eliminate the honeydew producers on the plants before scout ants can find them. After treatment, scouts may find a few hemipterans, but not enough to sustain a satellite colony.

But this approach isn’t a stand-alone solution, cautioned Mizer. Technicians also “have to probe out and control the ants currently on the property.” This requires an all-out “search and destroy operation.”

If existing colonies aren’t eliminated, the ants merely will travel farther for food and water, and eventually may find their way into the structure.

Clean-outs generally start in November for customers new to the program. “We work really hard all through the winter and all through the spring so that our customers don’t have any ants on their property” come summer. As a result, technicians have time to handle new trouble calls instead of doing re-treatments.

Technicians are trained on plants most vulnerable to hemipterans, conduct plant inventories and inspect for conducive conditions at every service visit. This control protocol takes “a little more time” but “the reality is it works very, very well.”

Corky’s Pest Control has 88 trucks covering San Diego, Riverside, San Bernardino and Los Angeles.
 

Aphids feeding on the sugars in a pepper plant leaf. Photo: Dan Suiter.Got Ants in Your Plants?
Argentine ants are tough nuts to crack. They’re clever, can travel 70 yards for food and water, nest in satellite colonies, and can explode in number due to multiple queens. When their shallow nests are flooded by rains or the temperature swings, they head indoors. At other times they come inside seeking water and even may build a temporary outpost to ferry water back to the main colony, said Corky Mizer, president of Corky’s Pest Control in San Marcos, Calif. Incredibly mobile, Argentine ants “don’t respect personal boundaries,” so the pests bothering your customer may be coming from a neighbor’s yard, said Dr. Jules Silverman of North Carolina State University, Raleigh. Step on a nest or apply pesticide and, if it doesn’t kill them, the ants will move their brood to return another time. That’s why pest management professionals are constantly doing re-treatments, Silverman explained.

But PMPs can gain an edge by exploiting the pests’ affinity for honeydew. This sugar-like liquid is produced by hemipteran insects — scale, aphids, mealy bugs and whiteflies — that suck the sap of plants often used in perimeter landscapes. Honeydew is almost pure sugar and is a very predictable food source, said Dr. Dan Suiter of the University of Georgia, Griffin. It’s what sustains the colony, added Syngenta Technical Manager Dr. Bob Cartwright. To ensure a good supply, some ants farm hemipterans, picking them up and moving them to other parts of the plant to get better honeydew production. They even can grab wasps that prey on these insects right out of the air, said Dr. Michael Rust of the University of California, Riverside. “They’re very protective.”

By eliminating honeydew, professionals take “that one piece of what the ant needs away,” Cartwright  said. A plant infested with honeydew producers is a conducive condition, he explained. It’s like having a leaky roof and termites: You can get rid of the termites, but unless you fix the roof the termites will come back.

“If you’re only spraying around that foundation, believe me, you’re not going to get rid of the ants,” said Mizer. They’ll find a tree limb, piece of string or walk across the bodies of nest mates that died in the perimeter to access the structure. A colony will send a thousand ants at your house, and will follow the trail of the one that comes back, he reminded.
 

Thiamethoxam is often applied as a soil drench, where it is drawn up by the plant’s roots. Photo: Syngenta.Thiamethoxam Labeled for Systemic Treatment
Thiamethoxam, the active ingredient in Optigard Flex, is labeled for systemic control of hemipteran insects.
The non-repellent insecticide can be applied to trees and shrubs to control the honeydew-producing insects ants rely on to furnish a primary food source. It also transfers effectively to knock down ant colonies.

Collier Pest Control owner Phil Hadley in Naples, Fla., used it in combination with a granular bait to gain control of recurring problems with white-footed and big-headed ants, which were nesting in inaccessible areas under decks and swimming pools.

“Right away we had success in knockdown and gained fast control of the nests, without actually treating the nests directly,” recalled Hadley. Callbacks were reduced significantly, he added.

When used as a systemic, thiamethoxam remains active in plants for two to six months, said Syngenta Technical Manager Dr. Bob Cartwright.  It also can be tank-mixed with other non-repellents and pyrethroids for added flexibility and time savings.

Although the product can be applied as a foliar spray, drenching the soil at the base of target plants is the preferred method of application. It’s more effective and results in less drift, said industry expert Dr. Austin Frishman.