Common name: Pieris lace bug; Andromeda lace bug
Host plants: Pieris spp.; Rhododendron spp.
Life cycle: possibly as many as five generations per year, depending on region
Description & Life Cycle: Eggs…inserted into, or alongside, the mid-rib on the underside of the leaves and covered by a dark-coloured, varnish-like secretion…overwinter on pieris and rhododendron leaves. Hatching begins sometime in late April or early May, depending on temperature in your region. Egg hatching can extend over a period of roughly one month.
Emerging nymphs are relatively clear in colour…beginning to darken within a few days. Initially, the young nymphs will remain clustered together but start spreading out into new feeding territories after the second or third moult. They go through 5 instars, or growth stages…the whole growing and moulting process taking roughly about one month. By the time the nymphs reach the 4th instar, they have darkened to brown-black in colour and have grown spines on their bodies. At 5th instar, nymphs are half the size of an adult lace bug.
Adults are up to 0.2 of an inch (5.0 mm) long. Bodies are slightly flattened and black in colour. Clear wings, conspicuous because of the prominent black X- shaped marking, lay flat along the body. Females lay five to seven eggs per day…as many as 300 in their lifespan. There are multiple generations per year, depending on the temperatures and length of the growing season in your region. (Research conducted by the entomolgy department at Pennsylvania State University revealed two to three generations of Stephanitis takeyai occur in that state. The University of Connecticut claims four to five generations are produced every year in their state.)
Special Notes: Native to Japan, this pest was accidentally introduced into the United States around 1945…according to the University of Connecticut. And yet, reports from England claim the Pieris lace bug was not discovered in that country until 1998 when it was spotted in a garden near Windsor. But it is definitely on the move.
Both nymphs and adult lace bugs feed on the underside of Pieris spp. and Rhododendron spp. leaves…piercing the epidermis layer and sucking up the plant sap. Early clues this pest may be present are the yellowing and mottled appearance on the upper side of the leaves. This mottling and discolouration impacts on the photosynthesis process…reducing overall plant vigour and causing premature leaf drop.
Remedial Action: During winter months, check underside of pieris leaves for a line of varnish-like substance along the midrib. This could be hibernating eggs. Treat with horticultural oil at this stage. Keep an eye on shrubs in late April into May for any signs of hatching light-coloured nymphs. If spotted, and while they are still in a cluster, spray leaves with either horticultural oil or an insecticidal soap. Best results are treating the nymphs while their body is still soft. It will begin to harden by the third moult or so. Repeat spraying in ten to fourteen days to catch new hatching nymphs…and continue to monitor the shrub for any further pest activity.
For a photograph of the Pieris lace bug, visit the Royal Horticultural Society website at: https://www.rhs.org.uk/advice/profile?PID=663
Posted on January 31, 2015