Problem type: Insect

Name of problem: Lace Bugs

Plant name(s): Birch, elm, oak, hawthorn, cotoneaster, willow, maple, poplar

Symptoms / Characteristics:
The upper leaf surface may appear freckled or mottled, or in severe cases, leaves may be white and the foliage may have a leathery texture. Dark varnish-like faecal pellets are visible on the leaf undersides. Foliar damage is attributed to the piercing mouthparts of both adults and nymphs as they suck the sap from the leaf undersides. Lace bug damage often results in premature leaf drop if accompanied by dry conditions. Concern primarily surrounds unsightly appearance rather than reduced plant vigour. Prolonged infestations will render the plant vulnerable to secondary pests and may eventually contribute to plant death.

Most lace bugs overwinter in the adult stage under loose bark and under leaf debris. In early spring, masses of cylindrical eggs are laid on the leaf undersides and the nymphs emerge within a few weeks. The dark coloured, spine covered nymph eventually sheds its skin, which remains attached to infested leaves. The presence of this old skin confirms lace bug damage. The adult lace bug has a characteristic wing/thorax pattern that resembles lace netting and is laid flat over their body in a rectangular shape. Wing colours range from light amber to translucent.

Control / Preventions:
If populations are low, a high-pressure garden hose can be used to wash the lace bugs off the plant. Repeated insecticidal soap or horticultural oil applications are also effective. Heavy infestations may warrant the use of chemical sprays including Malathion and Sevin, depending on the plant being infested. Thoroughly cover the underside of the leaves as this is where most, if not all feeding takes place. Apply chemicals according to manufacturer directions, and ensure that the spray is safe to use on the host plant.

Photos:
adult_lace_bug
lace_bugs


Relevant web sites:
www.extension.umn.edu/projects/yardandgarden/ygbriefs/e452lacebug.html


Other references:
Johnson, W.T. and Lyon, H.H. 1988. Insects that Feed on Trees and Shrubs. Second Edition. Comstock Publishing Associates, Cornell University, Ithaca, NY. 556 pages.

Ives, W.G.H., and Wong, H.R. 1988. Tree and Shrub Insects of the Prairie Provinces. Information Report NOR-X-292, Northern Forestry Centre, Edmonton, AB. 327 pages.