Stephanitis pyrioides        Family: Tingidae

Common name: azalea lace bug
Host plant: azalea; rhododendron

Adult size: 2.5 mm (0.1 inch)

Type: Pest

Life cycle: Generations per year: two to four
                    Egg: 12 – 22 days
                    Nymph: 10 – 23 days through 5 instars
                    Adult: 1 – 4 months

Description & life cycle: Adult lace bugs are roughly 2.5 mm (0.1 in) long. Their cream-coloured body is slightly flat and elongated. The clear wings are laced throughout with tan-brown veins and they lay neatly folded and flat over the abdomen, extending just over the extremities. Given their colour and clear wings, these adult lace bugs can be rather difficult to spot with the naked eye on an infested shrub. Adult longevity is variable; one to four months within a temperature range of 20.5 °C (69 °F) and 32 °C (89.5 °F).

Each day, a female lace bug pierces the lower epidermis layer along the leaf midrib or margin in which to lay 5 – 7 eggs. She then covers them with a brown secretion which hardens to protect the eggs from damage and predators. Over their lifetime, females can lay about 300 eggs, or more.

The white eggs are tiny at a mere 0.36 – 0.43 mm (0.014 – 0.017 in) long and 0.16 – 0.23 mm (0.006 – 0.009 in) wide. They are oval-shaped with a slightly curled neck, resembling a tiny flask. The egg incubation period generally lasts for about 22 days when temperatures hover around 20.5 °C (69 °F); shorter at about 12 days when temperatures rise to around 32 °C (89 °F).

The young nymphs stay together and feed near the egg remnants for the first couple of instar stages before seeking out other feeding spots as they develop through the remaining three instars. They are very pale in their initial instar stages, gradually darkening to dark brown or black and forming spines around the lateral edge of their body. Nymphs are extremely minute at 0.1 mm (0.004 in) in their first instar to 1.8 mm (0.07 in) in their fifth instar. Nymph stage lasts for about 11 days at 32 °C (89 °F), up to 23 days at 20.5 °C (69 °F).

Special Notes: Native to Japan, the azalea lace bug has spread quite widely through the global movement of its very popular, and desirable, host plant. It was positively identified in New Jersey as early as 1915, and more recently in Washington State in 2008 and Oregon in 2009.

The young lace bugs develop on the underside of the leaves, inserting their stylet into the stomata and sucking the sap from the inner leaf tissue. As their population increases, the effects of this feeding results in a yellow mottled appearance on the upper side of the leaves.

Azalea lace bugs feed on both evergreen and deciduous azaleas and rhododendrons. Large populations of this pest can cause serious stress to the plant, even causing death.

Typically, lace bug populations are higher on plants situated in a sunny location versus a plant in a shadier area.

Remedial actions: Spray the upper- and undersides of the leaves with horticultural oil during the winter. This is to minimize killing any beneficial insects which may be nearby, feasting on the lace bugs. Beneficial insects include: ladybugs, lacewings, earwigs and spiders. Repeat to ensure all eggs have been coated with oil and thoroughly smothered.

Through the growing season, provide adequate water and fertilizer for the benefit of healthier plants which are better able to withstand pest damage. Placing mulch underneath the plant will help to keep the soil moist.

Posted on December 3, 2018