Identification and Control Methods for the Rhododendron Lace Bug

Also known as the pear lace bug and pear flower lace bug, it belongs to the order Hemiptera, family Tingidae. It is distributed throughout the country. The nymphs and adults damage potted ornamental plants such as rhododendrons, Chinese roses, camellias, banana shrubs, jasmine, wintersweet and Chinese wisteria.

Damage symptoms: both adults and nymphs gather on the undersides of leaves to pierce and suck the sap, and the undersides of the damaged leaves show a black sticky substance that looks very much like splattered dirt. This feature makes it easy to distinguish from other sap-sucking pests. The entire underside of the damaged leaf turns rusty yellow, while the upper surface develops many pale spots; when the damage is severe, the spots merge into patches, so that the whole leaf loses its green color and looks pale from a distance, the leaves drop early, and no more flower buds form.

Morphological features: the adult body is about 3.5 mm long, flat in shape and dark brown. The antennae are filamentous and have 4 segments. The center of the pronotum is longitudinally raised and extends backward into a leaf-like projection, and both sides of the pronotum protrude outward into feather-like plates. The forewings are slightly rectangular. The forewings, both sides of the pronotum and the leaf-like projection on the back all bear very uniform reticulated patterns. At rest, the forewings fold over each other, and when the whole insect body is viewed from directly above, it looks like an "X" shape made up of multiple wings.

The egg is long oval, curved at one end, about 0.6 mm long, light green and semi-transparent when first laid, later turning light yellow.

The newly hatched nymph is milky white, later gradually turning dark brown, and is about 1.9 mm long. By the 3rd instar the wing pads are obvious and the appearance resembles the adult; on both sides of the pronotum, mesothorax and abdominal segments 3-8 there are obvious cone-shaped spines.

Life history and habits: the number of generations per year is 4-5 in the Yangtze River basin and 3-4 in North China, and in all areas the adults overwinter in dead branches, fallen leaves, weeds, bark crevices and gaps in soil and stones. In early to mid-April the overwintering adults begin to become active and gather on the undersides of leaves to feed and lay eggs. The eggs are laid inside the leaf tissue, with a yellow-brown gelatinous substance attached on top, and the egg stage lasts about half a month. Most newly hatched nymphs gather on both sides of the main vein to cause damage. The nymph molts 5 times and becomes an adult after about half a month. The first-generation adults appear in early June, and subsequent generations appear in early July, early August, and late August to early September respectively; because the adult stage is long and the egg-laying period is long, generations overlap and all stages are often present at the same time. Damage is most severe in July-August, the population density is highest in September, and from late October onward they gradually overwinter. Adults are active mostly at noon; the number of eggs laid by each female adult varies with the host, ranging from dozens to over a hundred, and the eggs are laid in batches, often several to dozens adjacent to one another, with a small black dot slightly sunken in the center on the outside of each egg-laying site.

Control methods: in winter, thoroughly clear away fallen leaves and weeds around potted flowers and bonsai gardens. Chemical control: for plants with thicker and rougher stems, brush on whitewash. The period from when the overwintering adults emerge and become active to when the first-generation nymphs begin to hatch is the most favorable time for chemical control. Spray 50% fenitrothion 1000x dilution, or 40% omethoate 1000-1500x dilution, or 10-20% pyrethroid insecticides 1000-2000x dilution, spraying once every 10-15 days for 2-3 consecutive applications.