Pear psyllid

The pear psyllid (Cacopsylla liaoli) is a small sap-sucking insect belonging to the family Psyllidae. Adults typically measure about 2.5–3 mm in length.

Adults possess clear, roof-like wings and powerful hind legs adapted for jumping. Their coloration shifts between generations, ranging from yellow to dark brown.

Nymphs are flattened, wingless, and often encased in protective honeydew secretions, which make them difficult to detect without close inspection.

The insects are highly mobile and will quickly jump away when branches are shaken, which is a common diagnostic technique in orchards.

Overwintering adults find refuge under rough bark, in cracks, or within leaf litter at the base of the pear trees during colder months.

The pear tree is the primary host for this pest. Both adults and nymphs feed on the phloem sap of young leaves, shoots, and fruit buds.

Heavy infestations lead to leaf chlorosis, curling, and premature leaf drop, severely weakening the vigor of the pear tree.

Feeding on fruit stalks causes significant economic loss, often resulting in fruit drop, stunting, or poor development of the fruit set.

The honeydew produced by the nymphs coats the leaves and fruit, encouraging the growth of sooty mold, which reduces the marketability of the crop.

Besides direct damage, the pest acts as a vector for phytoplasmas, which are responsible for severe diseases like pear decline.

Activity begins in early spring as soon as temperatures rise above 5–8°C, often coinciding with the swelling of the pear buds.

Egg-laying occurs on twigs and leaves, and the life cycle includes several nymphal stages that overlap during the growing season.

There are typically three to five generations per year, depending on climatic conditions and temperature patterns in the orchard area.

Population density often peaks during hot and dry summer spells when the development of nymphs is at its fastest rate.

As the weather cools in autumn, the insects transition to their overwintering form to prepare for dormancy in protected areas.

The presence of honeydew on the upper surfaces of leaves is the most prominent indicator of an active psyllid infestation in the orchard.

A black, crusty sooty mold growth on the foliage and branches indicates that the pest population has been present for a significant duration.

Stunted growth of new shoots, leaf twisting, and yellowing are classic signs that the sap is being depleted by the feeding insects.

Affected trees often show signs of overall decline, with fruit that is small, deformed, and covered in sticky residue.

• Sticky honeydew secretions
• Black sooty mold accumulation
• Curled and discolored leaves
• Stunted terminal growth
• Visible jumping insects in the canopy

Dormant oil applications are essential in late winter to target overwintering adults before they start laying eggs on the trees.

In-season management requires monitoring with sticky traps to time insecticide applications accurately when nymphs are vulnerable.

Orchard sanitation, including pruning out water sprouts and removing leaf debris, significantly reduces the overwintering success of the psyllid.

Biological control through the preservation of natural predators like lacewings, lady beetles, and mirid bugs is highly effective in integrated programs.

If chemical control is necessary, rotating systemic and contact insecticides with different modes of action is vital to prevent resistance development.