Leaf-Footed Bug

Common Names: Leaf-footed bug, western conifer seed bug
Scientific Name: Leptoglossus occidentalis

Introduction. The common names reflect the fact that this species (1) has the tibia section of the hind legs flattened and leaf-like in appearance; and (2) is found on pine cones during late summer. The leaf-footed bug is commonly seen on and in buildings during late summer and autumn, particularly the sunlit sides of residences and buildings.

Recognition. Leaf-footed bug adults are about 2/3 to 3/4 inch long and elongate-oval in shape. They are symmetrically patterned with beige, medium brown and dark brown on the body and wings. The mouthparts are piercing-sucking and form a beak that is held beneath body when not in use. Nymphs are similar to adults but lack wings; although wing pads may be present.

Similar Insects. Squash bugs are similar in appearance but are more robust, darker (grayish-brown to black) and do not have the tibiae of the hind legs leaf-like.

Biology. Overwintering leaf-footed bug adults emerge from hibernation in late April and early May and fly to nearby host conifers. The females lay clusters of yellowish-orange eggs on or near the seed cones of pine, Douglas fir and incense cedar. These eggs hatch in about 2 weeks and the nymphs feed by sucking nutrients from the pine cones. During the summer, the nymphs pass through 5 instars (growth stages between molts). In Ohio there is 1 generation per year.

Habits. Leaf-footed bugs are good flyers. In warm weather, they are alert to approaching movement and will quickly take flight, making a buzzing noise as they fly to safety. Leaf-footed bugs have well-developed scent glands and, when handled, readily release a defensive secretion that smells like ripe pear or green apple essence.
In the autumn, leaf-footed bugs become gregarious and congregate by the dozens on the south side of trees and buildings having direct sun exposure. They readily enter buildings to hibernate for the winter. Indoors, these bugs are primarily a nuisance pest due to their periodic emergence in the living spaces of residences and workspaces of commercial buildings on warm or sunny days from late autumn through early spring.

Cultural Control & Preventative Measures. Control begins outside. Reducing the outside population can be achieved by calling upon an arborist or landscaping professional in the spring to spray all cone-bearing evergreen trees on the property with an appropriately labeled residual insecticide. However, if the host trees are on an adjacent property, a cooperative arrangement must be sought with that property owner.
The use of preventative physical barriers involves exclusion. Although total exclusion is probably not possible, all vents (roof, gable, soffit / eave) should be screened with at least 16-mesh screening. Weep holes should be stuffed with copper gauze or steel wool. Silicone sealer should be applied around cable and utility penetrations, windows, doors, and overhangs. These steps should be taken before late August.
Temporary but immediate indoor relief from leaf-footed bugs can achieved by removal with a vacuum cleaner fitted with a hose attachment. To prevent entry of more bugs, it is important to seal the possible routes of entry using silicone caulk and similar materials. Entry points include around window pulleys window frames, doorframes, and baseboards. For electrical outlets and switch boxes and heating duct and air return vents, it is recommended to remove the cover plates, seal, and replace. For light fixtures and ceiling fans, one should remove the fixture to its base plate, seal, and replace.
If leaf-footed bugs are in a false ceiling area, the population can be reduced by installing an insect light trap (ILT); if used, it is important to periodically empty the catch tray or replace the sticky panels. An alternative is to install a continuously burning 60-watt fluorescent bulb, which attracts flying and crawling insects and causes them to exhaust their food (fat), and die near the light. The dead insects ought to be removed with a vacuum cleaner. To speed the process, adhesive fly strips, glue boards, or other sticky traps can be suspended from the uppermost surface of the false ceiling void near the light. Sticky-capture devices should be replaced when filled or covered with insects. To reduce the number of leaf-footed bugs coming into a room from a false ceiling, all cracks through which light enters should be sealed using duct tape or caulk. In elevator shafts, a continuously burning 60-watt bulb can be installed just above the pit floor. Again dead insects should be removed periodically using a vacuum cleaner.

Professional Control. Rottler technicians prefer to apply treatments for leaf-footed bugs on strategic exterior surfaces of buildings in August and September. Preventative chemical barriers involve applying a long-lasting residual liquid insecticide (1) beneath the lowest course of siding at the foundation, (2) into structural junctures (e.g. molding, trim, seams and weep holes), and (3) on strategic, sun-lit vertical walls and the adjacent overhang. This application is made just before the late season search for overwintering sites begins. One application is required. If leaf-footed bugs have already begun to congregate and attempt entry into buildings, it may be too late for preventative action. Once buildings are entered, the best solution is physical removal with a good shop-type vacuum cleaner.
Rottler technicians prefer not to inject insecticides into the overwintering sites of leaf-footed bugs in buildings because the bodies of dead insects in wall voids attract dermestid beetles (e.g., larder beetles, carpet beetles and cabinet beetles). Dermestid larvae wander and will readily enter the living space, causing numerous complaints. However, temporary relief is possible by using a vacuum cleaner and sealing interior entrances.