Source: Bradley Higbee, Paramount Farming, Bugwood.org
During one part of its life it is a beneficial insect feeding on pests such as aphids, thrips, and pear psylla, but in the early season when fruits are forming it feeds on flowers and developing fruitlets potentially causing serious direct damage to the crop.
Description and life cycle
Mullein plant bug adults are gray-brown, elongate-oval, and 1/10 inch long. Nymphs are pale green, and when older, develop black spines on the legs. Nymphs may be confused with white apple leafhopper, but have a stouter-looking body and thicker, distinctly segmented antennae with a dark stripe near the base.
This plant bug overwinters as eggs in the woody tissues of several host plants, including apple and pear. Only a small part of the egg (1/28 inch long) is visible without slicing into the host tissue. In the spring, eggs hatch beginning about tight cluster and finishing about petal fall. There are two to four generations per year, with each lasting about 3 to 4 weeks.
Mullein plant bug stays primarily on woody host plants such as apple and pear in the spring, but later generations move to weedy hosts, most notably mullein, for most of the summer. In the fall they move back to woody hosts, mate, and lay eggs.
Around bloom and early fruit development mullein plant bug feeding on fruit produces a dark, raised, corky wart, often surrounded by a shallow depression. Multiple feeding punctures or "stings" on a fruit may cause the fruit to be misshapen. Stings are more notable on Golden Delicious than on red cultivars, and the scars may be light tan in color. Early blooming cultivars are more seriously affected. Many of the injured fruits will drop during June.
Monitoring and management
At this point, the mullein plant bug is an infrequent pest in Pennsylvania. If orchard records indicate feeding damage in past years, especially on yellow-skin varieties, then attention should be paid to this pest around the flowering period. If fruit damage was present but not heavy the previous year, then populations should be assessed just prior to and during bloom. A beating tray or close visual examination of flowering and fruiting structures may be used to determine the presence of small nymphs. If fruit damage was heavy in the previous year, an effective insecticide application is needed at the petal fall stage. Mullein plant bugs seen later in the season are not harmful to the crop. Specific chemical recommendations for home gardeners are in Fruit Production for the Home Gardener, and recommendations for commercial growers are in the Penn State Tree Fruit Production Guide.