Winter Tree Care: Identifying Common Tree Insects in Winter, Part 7
This is the seventh part of a series on winter tree insects. This article examines lace bugs and larder beetle.
Through the winter months, plants conserve their energy, often enduring inclement weather in anticipation of spring. Due to the frigid temperatures, many insects enter a state of dormancy, overwintering on or within their hosts. While some insects are visible during winter, others conceal themselves in bark crevices or beneath the soil surface. The following examines some of the most common insects to infest trees during winter, and how they may be observed.
Lace bugs are a group of insects that belong to the family Tingidae. There are approximately 140 species of lace bugs in North America. Most lace bugs target a specific host. Some of the most common lace bug species are Stephanitis pyrioides, which infests azaleas, Corythucha cydoniae, which is partial to hawthorns, Teleonemia scrupulosa, which feeds on lantana, and Corythuca celtidis, which attacks hackberry. Lace bugs are generally considered a minor nuisance. Dense populations are capable of causing mild to moderate defoliation of host plants.
Some of the most common lace bug hosts include alder, ash, avocado, azaleas, basswood, birch, buckeye, ceanothus, cherry, coyote brush, elm, fringetree, hackberry, hawthorn, lantana, London plane, photinia, poplar, rhododendrons, serviceberry, sycamore, toyon, walnut, and willow.
Symptoms of Infestation
The adults and nymphs can be observed feeding on the underside of leaves. Due to their small stature, a magnifying lens may be required to see them clearly. As the insects feed, they cause a stippling of the infested leaves. The stippling initially appears as a series of tiny, white spots on the leaf surface. The spots quickly coalesce, resulting in extensive leaf discoloration. By mid-summer, the leaves will have turned yellow. By the end of the growing season, they will become necrotic.
As they feed, the adults and nymphs expel specks of dark excrement, which infested leaves can become laden with. When abundant, the excrement may drip onto surfaces located beneath the host. Severely infested plants may prematurely shed their leaves. Prior to dropping, the leaves will often wilt and curl. Avocados that experience premature leaf drop may incur sunburn damage, resulting in a significant reduction in fruit yield. Broad-leaved evergreens that are exposed to full sun may expire if heavily infested.
- Begin inspecting vulnerable plants for lace bugs in late winter. Continue checking for lace bugs at least once a week throughout the growing season.
- Lace bugs do not often cause significant damage to their hosts. As such, most lace bug infestations can be tolerated, and offset by maintaining plants through sound cultural practices.
- Ensure that plants are sufficiently watered, especially during extended periods of drought.
- Apply a layer of organic mulch around vulnerable plants to improve the soil quality, moderate the soil temperature, and retain soil moisture.
- Stippled foliage should be promptly removed, and disposed of.
- When nymphs are abundant, they can be dislodged from plants with a strong stream of water. Direct the water at the underside of the leaves. Initiate this practice by late spring, and repeat it every 1 to 2 weeks to inhibit the growth of lace bug populations.
- Various insecticides may be employed to combat lace bug populations. Non-persistent, contact insecticides are recommended for use on lace bugs, as they are not as detrimental to beneficial insects. Begin applying insecticides by late spring. Continue to perform applications at three to four week intervals, until the growing season has ceased.
- When planting, select trees and shrubs that are suitable for the location. Plant susceptible trees and shrubs away from sidewalks and buildings. This will prevent the excrement produced by the lace bugs from accumulating on nearby surfaces. Replace or transplant trees or shrubs that are not thriving in a particular setting.
- Avoid exposing vulnerable plants to full sun, as it can render them more prone to infestation, and environmental injuries.
- Lace bug populations may be limited on various shrubs by removing mulch and leaf litter from beneath host plants during the winter months. Mulch can be replaced the following spring.
- In fall, rake and compost leaves that have been shed beneath plants infested by lace bugs.
- Lace bugs have a multitude of predators and parasites that help to suppress their populations. Some of the most effective include assassin bugs, lady beetles, lacewing larvae, jumping spiders, mites, and parasitic wasps.
- Horticultural oils can be sprayed on leaves to deter lace bug populations.
Larder Beetle (Demestes lardarius)
Larder beetle is a species of beetle in the family Dermestidae. It is is recognized as a commercial and household pest. For hundreds of years, larder beetle was notorious for infesting cured meats in Canada, Europe, and the United States. The advent of refrigeration, coupled with the purchase of meats in smaller quantities, significantly reduced the insect’s role as a commercial pest. The beetles are often found in locations containing accessible food sources. This can include households, market places, storage facilities, museums, mills, and other buildings. When larder beetles gather in abundance, they can cause significant damage to food and animal products.
Larder beetle larvae feast on cheese, dried meat, fish, pantry items, tobacco, insect carcasses, and animal by-products, such as furs, hides, horns, hair, and feathers. The insect is especially keen on grain, and pet food. The larvae will sometimes feed on bee and wasp nests.
Symptoms of Infestation
The larvae can bore into nearly any item or structure containing food products. They can penetrate dense materials, such as lead, tin, wood, cork, and plaster, and softer items, including books, magazines, and insulation. Any food items that the larvae attack may be rendered inedible. In museums and historical sites, the adults and larvae can destroy preserved animal specimens or documents. As they feed, the larvae expel fecal pellets, which can accumulate where food has been stored.
- Clean, inspect, and dispose of infested food sources.
- Infested materials can be sterilized with heat, or frozen.
- Place food items in jars, containers, or cans to discourage infestations.
- Examine areas where food is stored for the presence of the adults or larvae.
- Seal openings around buildings to deter the adults when they seek shelter.
- Residual pesticides can be applied to the exterior of buildings to combat the adults.
Photo courtesy of Ian Jacobs CC-by-2.0