Thorn treehopper

The thorn treehopper (Glossonotus crataegi) is a small insect belonging to the family Membracidae, order Hemiptera. Adult specimens typically measure between 7 and 9 mm in length.

The species is easily recognized by the prominent, thorn-like process on its pronotum, which gives it a distinct appearance resembling a hump. The body is usually brownish-grey, providing camouflage against the tree bark.

The body is covered with fine hairs, and the wings are held roof-like over the abdomen when at rest. Nymphs have a flattened shape and possess distinct, spine-like projections on their body segments.

This insect is closely associated with various woody plants, where it spends most of its life cycle. Adults and nymphs are active during the warm months, feeding on plant sap.

For accurate identification, experts often look for the characteristic oviposition sites, which appear as small incisions in the bark of young shoots.

The primary hosts for the thorn treehopper are members of the Rosaceae family. Most notable are hawthorn, apple, pear, plum, and apricot trees.

This pest mainly attacks young trees in nurseries and orchards, targeting one- or two-year-old shoots for feeding and egg-laying, which stresses the plants.

By feeding on phloem sap, the treehoppers disrupt the nutrient distribution within the plant. Additionally, the feeding sites provide entry points for fungal infections.

Significant damage occurs during egg-laying; the female creates deep cuts in the wood, causing deformation of shoots and premature wilting.

Heavy infestations can lead to stunted growth, premature leaf drop, and decreased cold hardiness of the damaged tree branches.

The thorn treehopper generally has a univoltine life cycle (one generation per year). They overwinter in the egg stage under the bark of young shoots.

Nymphs emerge in the spring, coinciding with bud burst and the onset of vigorous plant sap flow. They immediately begin feeding on the sap of young shoots.

The nymphal stage lasts throughout the spring and early summer, progressing through five instars. During this time, they remain relatively immobile and often live in colonies.

Transformation into adults occurs in mid-to-late summer. At this stage, they develop wings and become highly mobile within the tree canopy.

Mating occurs in late summer and autumn, after which females deposit their eggs, ensuring the survival of the next generation through the winter months.

A key indicator of infestation is the presence of longitudinal scars or cracks on the bark of young shoots, left behind by the female's ovipositor.

Upon close inspection of the branches, one can observe nymphs residing on the undersides of leaves or twigs, often secreting sticky honeydew.

The presence of honeydew attracts ants, which frequently guard the treehoppers from predators. Finding an ant trail on a young branch can be a sign of hidden colonies.

In severe cases, the tips of the infested shoots may curl or wither, which is clearly visible during a visual inspection of the orchard in mid-summer.

On sunny days, adults can be found resting on branches; their protective coloration makes them difficult to spot unless they are disturbed.

Control strategies involve a combination of cultural and chemical methods. It is crucial to prune and destroy infested shoots during the dormant season to eliminate overwintering eggs.

In the spring, when nymphs emerge, applying approved contact-stomach insecticides can effectively reduce the population before they mature.

Installing sticky bands on the tree trunks helps restrict ant activity, making it harder for ants to protect the treehoppers from natural predators.

Promoting biological control by creating habitats for natural enemies, such as egg parasitoids, is an effective long-term management strategy.

Providing proper irrigation and fertilization ensures that trees maintain a strong immune system, which helps them withstand and recover from mechanical injuries caused by the pests.