- Drywood Termite (Family Kalotermitidae)
- Incisitermies snyderi
- Cryptotermes brevis
- Incisitermes minor
Identification
It is important to know what termite you are dealing with because control measures can be significantly different in cost, application method and product selection. Drywood termites most commonly infest dry, sound (non-decayed) wood and are a problem more often associated with older structures. They can infest wood flooring, framing members, window sills, doors, fascia boards, and furniture. They are also known to infest attics where the external temperature of the wooden members can exceed 110°F.
General Information
Drywood termites are social insects that live in colonies in sound, dry wood. Each colony consists of offspring from an original mating pair (male and female). There are three growth stages – eggs, immatures and adults. Drywood termites are larger than subterranean species. In comparison to other termites, drywood colonies are rather small (a few thousand individuals), and the colony develops relatively slowly. They neither live in the ground nor maintain contact with the soil, and they do not build mud tubes.
Subterranean termites produce liquid feces, whereas drywood termites produce characteristic dry pellets. These six sided pellets are eliminated from the galleries through “kick-out holes”. Pellets tend to accumulate on surfaces located below the kick-out holes and are usually the first evidence of a drywood termite infestation.
Drywood termites tend to cut across wood grain destroying both the soft spring wood and the harder summer growth. Subterranean termites typically follow the grain of the wood, feeding primarily on the soft spring wood. The reproductives are winged or wingless males and females that produce offspring. The primary reproductives, also called swarmers or alates, vary in body color from dark brown to light yellowish tan. Their wings may be almost clear to smoke gray, and have few distinct veins in them. Swarmer drywood termites are about 7/16 inch (11mm) long, including the wings. If the primary reproductives die, they are replaced by immatures that can become capable of reproductive activity. They are known as replacement or secondary reproductives.
In most drywood species there is no true worker caste (subterranean termites do have a true worker cast); this function is taken over by immatures. These immatures are wingless, white to beige in color, 1/4 to 3/8 inch (6 -10mm) long and make up the largest number of individuals within a colony. They gather food, enlarge the nest and feed and care for the queen, younger immature forms and others in the colony. Soldiers resemble immatures in color and general appearance. However, they have large, brownish to yellowish-brown heads with enlarged, heavily sclerotized mandibles (jaws). Soldiers defend the colony against invaders, primarily ants. Soldiers are about 5/16 inch (8mm) long.
Suggested Thresholds
A dozen or more wings inside a building or one pile of pellets warrants further inspection in the vicinity where the wings or pellets were found.
Monitoring and Inspection
A telltale sign of drywood infestation is the accumulation of six-sided fecal pellets. Fecal pellets are also known as “frass.” Termites inside infested wood push frass out through pencil-tip sized “kick-out holes” (1-2 mm diameter) in infested material. Frass can resemble “sawdust” or “coffee grounds”, but are distinctly six-sided. The pellets have a gritty texture when rolled between your fingers and can be from light brown to almost black in color. The color is not related to the age or the color of the wood. Pellets usually collect into piles on the floor and other surfaces. A sign of advanced infestation is surface blistering or warping. Drywood termites sometimes tunnel just under the surface of the wood, giving it a blistered, uneven appearance. Infestations may be detected by tapping the wood every few inches with the handle of a screwdriver or by probing with a sharp tool. Damaged wood sounds hollow - a papery, rustling sound indicates tunnels just beneath the surface. Three of the most common drywood termites in the US include:
- The West Indian drywood termite soldier is easy to identify by its distinctive “phragmotic” head, which resembles a burnt match and is used to block the tunnels in the termite gallery system to protect the colony from intruders, especially ants. This termite typically infests picture frames, furniture, boxes, and structural woodwork. Interestingly, this species is never found in natural environments but only in wood in human-made structures. Depending on location, this termite usually swarms from April to early July and November to early December.
- Southeastern drywood termite colonies are generally larger than those of the West Indian drywood termite and occupy larger pieces of wood. These termites are found in both natural and human-made environments and are the most common drywood in Florida. Development of the colony is slow, but structural damage can be extensive if multiple colonies are present in the same structure. This termite usually swarms from May through November in most locations.
- The Western drywood termite (Incisitermes minor), is a non-native termite and is the number one drywood termite pest in the western US. Depending on location, it usually swarms from the end of August through November.
Nonchemical Control Measures
Used lumber, furniture and other wooden articles should be carefully inspected for termite infestations, including items before they are brought into a structure. Drywood termite reproductives may enter a building through the attic or foundation vents, under or directly through shingles or under eaves, or even open doors and windows. All vents, doors, and windows, especially those in the attic, should be screened with 20 mesh screen. A good coat of paint on exposed wood will provide some protection against termite entry. Before painting, all cracks and crevices should be filled with putty or plastic wood. Pressure treated wood is resistant to termite attack. Certain woods are also naturally resistant to termites; among these are heart wood of redwood, bald-cypress, mahogany, and Spanish cedar; however, these woods can be more expensive and will become susceptible after several years when subjected to aging and weathering.
Construction should be designed to eliminate moisture and water leaks. Remove and replace infested or damaged wood. Microwaves, electroguns and liquid nitrogen require thorough access to wood. Heat treatment can be used for whole structure or compartment treatments.
Carefully inspect wooden objects including furnishings and equipment before moving from one school building to another to avoid introducing drywood termites.
If damage is localized, a drywood termite colony may be controlled by removing and replacing the damaged wood. It is very important to carefully inspect all woodwork in the building for pellets and/or damaged wood, especially in attics, baseboards, windowsills, floor joists and furniture.
Chemical Control Measures
Most drywood termite infestations are not cause for panic and immediate treatment. The best course of action is to take some time to research the pest control companies in your area and find the best treatment option for your home or construction type. Soil treatments, either with liquid insecticides or termite baits, would be ineffective because drywood and dampwood termite colonies are inside the wood, not in the ground.
Localized treatments for drywood termites include directly treating the infested wood. Products registered for wood treatment are usually liquids. The product is applied by brushing or spraying it onto the wood surface. Wood can also be treated by injecting insecticide directly into a termite gallery through holes made with a drill or into the kick-out holes. Applications can also be made to cracks and crevices such as the spaces between wooden pieces or between different building materials, such as wood and concrete, if there is evidence of an infestation. Use a product labeled for indoor surface treatments if treating indoors, and outdoor treatment if treating termites found outdoors.
If the infestation is too extensive and advanced for local treatment, it may be necessary to tent and fumigate the entire building. Although this method can be very expensive and disruptive, it may be the only option that will kill all termites in the structure.
Sulfuryl fluoride gas is used to create a toxic atmosphere within a confined space; under a tarp, within a sealed structure or inside a fumigation vault. After fumigation, the structure is cleared of sulfuryl fluoride and thus termites are not prevented from re-entering the structure. Because sulfuryl fluoride is odorless and colorless, chloropicrin (“tear gas”) is used as a warning agent. Always read and follow the label. The label is the law. Pesticides must be used in accordance with federal, state and local regulations. Applicators must have proper credentialing to apply pesticides and should always wear personal protective equipment (PPE) as required by the pesticide label during applications. All labels and Material Safety Data Sheets (MSDS) for the pesticide products authorized for use in the IPM program should be maintained on file.
Evaluation Methods
Seal exit holes. After treatment, if exit holes are cleared, there is a high likelihood that the infestation is still active. If exit holes are not cleared, it is likely that the drywood termites have been controlled, at least in the area of the exit hole. If swarms inside the building were evidence of the infestation before treatment, the absence of swarms after treatment is also an indication of a successful treatment.
Authors: Compiled from publications by Faith Oi, Dennis Ring, PMSP
