[Stinging Insects] Mystery Nests

O ne of the pest management profession’s most interesting challenges is reconciling what the customer perceives and reporting back to them with the facts. We all know that when customers phone in problems with "bees," the insects in question could be bees, flower (syrphid) flies, yellowjackets or other wasps of a sort. Likewise, our customers get confused when it comes to distinguishing the actual nesting sites of various wasps and bees with sites that are conspicuous with the activity and abundance of these insects. The huge potential for confusion and misinformation serves to underscore the importance of scheduling on-site inspections before quoting any details of the service you intend to perform. Let’s look at some examples.

"NESTS" IN SHRUBS AND TREES. It is true that honey bee swarms will rest or build wax combs on the branches of trees and shrubs in addition to taking up residency in hollow trees. Also, it is true that paper wasps (Polistes and Mischosyttarus species) will construct their umbrella-shaped paper nests beneath leafy branches and fronds. And yes, baldfaced hornets and aerial-nesting yellowjackets (Dolichovespula species) build their large paper maché nests among the leafy branches of trees and shrubs. However, yellowjackets, paper wasps and even honey bees can be abundantly active among the leafy branches of certain shrubs and trees when no nest is present. Upon inspection, the pest management professional will notice that the wasps and bees are licking up honeydew from the foliage. The sugary liquid known as honeydew is excreted by homopterous insects like aphids, leafhoppers, treehoppers, mealy bugs and scale insects that infest the host plants in question.

Maples, willows, magnolias and arborvitae number among the plants that are notorious for fooling our customers into thinking that "a bee nest must be hidden in there somewhere." There are insecticides suited for treating the foliage of trees and shrubs; however, pest management professionals must be aware that: 1) the formulation must be compatible with the type of plant to be treated and recommended for the time of year that the treatment is to occur; 2) homopterous insects must be listed as target pests in the DIRECTIONS FOR USE section of the pesticide label; 3) harming honey bees may be a violation of the label and state laws; and, 4) in most states an ornamental applicator’s license is required in order to apply pesticides to trees and shrubs professionally and legally.

"NESTS" IN CHIMNEYS. Sometimes yellowjackets and honey bees will establish colonies in the space between the outer brick or sheathed casing of a chimney and the flue(s) contained therein. The insects may gain entry through missing mortar joints between courses of brick or between the tiles that form the flue. Similarly, paper wasps may attach their nests to the undersides of chimney cap rain hoods. Usually, some of the bees or wasps will find their way down the flue, past the damper door and into the fireplace. From there it is an easy flight out into the family room, towards sunlit windows, and in plain view of the homeowner.

On the other hand, bees and wasps do not have to be nesting in a chimney in order for these insects to emerge from the fireplace during certain times of the year. In states having temperate climates, autumn is a time when certain insects seek secluded refuges in which to overwinter. To a mated female yellowjacket or paper wasp, a chimney flue is an inviting refuge. Unfortunately, the other end of the flue is a confusing place to these insects because they encounter daylight and exceptional warmth via the damper door and fireplace below. Homeowners who experience the annoying autumn invasion of wasps via their fireplaces may phone in reports of "bees nesting in the chimney."

What is the remedy for this situation? It is not practical or safe to secure an insect screen over the chimney flue because that will impede the needed updraft for venting smoke and fumes. Residual insecticide applications to chimney caps and flues usually will not prevent wasps from entering either.

If the damper door cannot be made to secure tightly, one temporary measure for keeping wasps from entering the living spaces of a residence is to place a small, portable insect light trap in the fireplace and operate it for the period of time when these insects are seeking overwintering sites (i.e., September and October). This method works best if the fireplace opening is covered with dark plastic or cardboard temporarily to prevent competition from interior lighting.

"NESTS" IN EXTERIOR PLACES. Among the many concealed sites in which yellowjackets can nest, wall voids and boxed eaves (soffits) figure prominently. The high level of activity around nest entrances is similar to air traffic at a major airport. Also obvious are the nests of paper wasps and aerial-nesting yellowjackets in sheltered structural recesses, and if the nests are not apparent, the activity of the wasps coming and going certainly is. Deck hand railings, benches and understructures may harbor numerous concealed paper wasp nests.

Nevertheless, yellowjacket, hornet and paper wasp nests may be reported incorrectly to pest management professionals by homeowners who are disturbed by large numbers of these insects hovering around roofs, porches and decks or landing repetitively on wood surfaces, where they linger for a minute or two on each occasion. In the first instance, the hovering behavior of wasps near structural features usually is indicative of predators searching for prey and parasites searching for hosts. The wasps are content to sip simple carbohydrates in the form of honeydew and nectar but they must provide fresh protein to their larvae (brood). They must hunt daily for spiders, flies, the larvae of other insects, etc., to feed their young.

However, foundress wasps (queens) will search diligently for choice prospective nesting sites early in spring, giving homeowners the impression that nests already exist in those locations. In the second instance mentioned previously, a careful inspection of the wasp landing sites on exterior woodwork will reveal light-colored, shallow ruts chewed along the surface of the wood. Industrious female and worker wasps collect mouthfuls of the weathered surface wood, which they masticate into pulp with saliva to create the paper maché material used to enlarge their nests (see photo on page 76). This repetitive behavior may lead homeowners to believe that wasps are nesting near the wood-gathering sites.

Quite often, our new and existing customers demand an immediate end to the wasp activity on their homes, decks, outbuildings and fences. What is the best solution to this problem? Should the pest management professional spray copious volumes of residual liquid insecticide on every wood surface and into every structural recess that wasps find promising or useful as a resource? That could lead to health risks for residents, companion animals and beneficial, non-target organisms.

Undoubtedly, customer education and compromise should be part of the solution. However, PCOs may be able to apply insecticidal, repellent soap formulations to woodwork surfaces that wasps frequent, where product labels and state laws allow. Alternatively, some customers can be coached to apply an equivalent mixture of dishwashing liquid and water to the problematic sites to achieve the desired results.

OVERLOOKED NESTS. Sometimes the reverse of the previous scenarios occurs — when homeowners observe nest-related stinging insect activity somewhere on a structure; yet the attending pest management professionals cannot spot the nests or any entry points to nests. Such is the case with some populations of carpenter bees. Treatment of carpenter bee galleries usually is a routine process, when the 3/8-inch diameter entry holes are exposed on the underside or outside surface of infested woodwork.

However, seemingly more common are situations in which the entry holes are concealed and difficult to reach with residual insecticides. The only indication of the infestation site is the aggressive territorial behavior of resident male carpenter bees and characteristic splatters, comprised of bee excrement and rubbed-off pollen, that stain the surfaces directly below the entry holes (see photo on page 80). Pest management professionals should use the brownish-yellow stains as arrows to point the way upward to the hidden entry hole and treatment zone. An appropriately labeled residual microencapsulate or dust insecticide formulation can be injected into the gaps that the "clever" carpenter bees use to reach their entry holes. Alternatively, small holes can be drilled strategically into the fascia board or other infested timber to serve as injection ports for the insecticide to target the galleries within.

CONCLUSION. We are the ones who are trained and knowledgeable when it comes to wasps and bees. We need to get on-site and sort things out before we make decisions and promises to those who call upon us for help. Making snap decisions based upon information provided over the phone is risky business.

Customer care employees ought to be coached to field phone calls pertaining to "bees" and "nests" by suggesting a statement something like: "We will send over a technician to inspect your premises for stinging insect activity and possible nesting sites. The technician will take appropriate steps to resolve the problem, if the situation allows. If the technician is unable to resolve your particular problem, he or she will explain why and make helpful recommendations. The minimum charge for the service call is $____ (and, depending on the situation, may cost as much as $___.") Customers will appreciate your company’s honest approach to ambiguous pest situations.

The author is a board certified entomologist with Varment Guard Environmental Services Inc., Columbus, Ohio. He can be reached at gwegner@giemedia.com.