The pear tree, valued in both home gardens and commercial orchards, offers sweet fruit but also presents a host for specific insect threats. Cultivating healthy, high-quality pears requires a proactive and well-timed management strategy. Successful pear growing depends on accurately identifying the species causing damage and implementing targeted control measures throughout the year. This guide provides practical information for identifying and treating the most common insect pests that challenge pear tree health and fruit quality.
Pests That Target Developing Fruit
The most significant threat to a pear harvest comes from insects whose larvae directly penetrate the fruit, rendering it unusable. The Codling Moth (Cydia pomonella) is the most damaging of these internal feeders, especially where multiple generations occur annually. The damage is caused by the pinkish-white larva, which bores into the fruit, often entering through the blossom end, and tunnels toward the core to feed on the seeds.
The pest’s presence is signaled by small entry holes on the fruit surface, frequently plugged with reddish-brown excrement known as frass. Monitoring uses pheromone traps to pinpoint the start of the moth’s flight period (biofix). This allows growers to use degree-day models to accurately predict when eggs will hatch, which is the most effective time to apply control measures.
Control sprays should be timed precisely for the larval hatch, about three weeks after the first generation’s peak egg-laying period. Physical exclusion offers a non-chemical alternative, involving bagging individual fruitlets approximately four to six weeks after petal fall. Removing loose bark from the trunk also helps, as mature larvae often seek these protected sites to spin cocoons before pupating.
Another pest that attacks developing fruit is the Plum Curculio (Conotrachelus nenuphar), a small, mottled grayish-brown snout beetle. This insect causes damage by feeding on young fruit and, more notably, by scarring the fruit during egg-laying. The female uses her snout to cut a characteristic crescent-shaped slit in the skin of the fruitlet, depositing an egg beneath the flap of skin.
This activity often causes the infested fruit to drop prematurely, or the resulting scar tissue remains and deforms the pear as it grows. The beetles overwinter in leaf litter and emerge in the spring, becoming active around the time of petal fall. Management focuses on controlling the adult beetle population as they migrate into the tree from overwintering sites.
Insecticide applications are most effective when timed for the period immediately following petal fall. A second application may be needed if cool, wet weather prolongs the beetle’s activity. Monitoring for fresh crescent-shaped scars on young fruitlets determines if a follow-up treatment is necessary. Applying insect-parasitic nematodes to the soil in the fall can also reduce the population by targeting larvae that drop to the ground to pupate.
Pests That Attack Leaves and Shoots
Insects that feed on foliage and new growth compromise the tree’s overall health and productivity. The Pear Psylla (Cacopsylla pyricola) is a sap-sucking insect that limits pear production. Adults are tiny, dark reddish-brown insects. The nymphs are the most destructive stage, feeding on the phloem sap of leaves and tender shoots.
As they feed, the nymphs excrete a sugary substance called honeydew. This sticky residue promotes the growth of black Sooty Mold fungus, which discolors the fruit and reduces its marketability. Heavy feeding can also cause “psylla shock,” leading to stunted growth, defoliation, and reduced fruit size. Control begins in the late dormant season, before the adults lay their eggs on the new buds and twigs.
The application of dormant oil in late winter or early spring is a primary control measure. The oil works by discouraging overwintering adults from laying eggs on the bark and buds, delaying the start of the infestation. Subsequent treatments often involve horticultural oils or insecticidal soaps, which are less harmful to beneficial insects. Because the pest rapidly develops resistance, rotating chemical classes is necessary if multiple sprays are required.
Another common foliage pest is the Pear Slug (Caliroa cerasi), which is the larva of a sawfly, not a true slug. These larvae are easily identified by their slimy, olive-green, tadpole-like bodies. They feed primarily on the upper surface of the leaves, chewing away the soft tissue between the veins.
This feeding results in characteristic leaf skeletonization, giving the foliage a brown, lacy, and scorched appearance. While the damage is mostly cosmetic on mature trees, heavy second-generation infestations can cause premature defoliation, reducing the tree’s vigor and subsequent year’s crop. For localized infestations, a forceful jet of water from a hose can dislodge the larvae.
The Pear Slug is highly susceptible to low-impact treatments such as insecticidal soaps or neem oil. Dusting the wet larvae with dry powders like wood ash or talcum powder can cause them to dry out and die. Other pests, such as Scale insects and Mites, are also managed by the thorough coverage provided by dormant oil sprays applied in the late winter.
Essential Year-Round Monitoring and Sanitation
Successful management of pear tree pests relies on consistent cultural practices and preventative care. Proper winter pruning increases air circulation and light penetration throughout the tree canopy. This practice helps foliage dry faster, reducing favorable conditions for diseases and making the environment less hospitable for some pests. Pruning also removes dead or damaged wood that could harbor overwintering pests like Codling Moth larvae or Scale insects.
Sanitation is a continuous process that reduces pest pressure for the following season. Prompt removal and destruction of fallen fruit are important, as these often contain developing larvae of pests like Codling Moth and Plum Curculio. Allowing infested fruit to remain on the ground permits larvae to complete development and overwinter. Fallen leaves and other debris should also be raked up and removed from the base of the tree, as they provide hiding places for overwintering stages.
Maintaining tree vigor through balanced fertilization and appropriate irrigation helps the tree resist damage from feeding pests. Stressed trees are more susceptible to severe infestations, especially from pests like Mites and Aphids. A healthy tree is better equipped to tolerate low-level pest populations without significant loss of yield or quality.
Regular visual inspection, often referred to as scouting, is the most important year-round activity. Growers should routinely examine leaves, shoots, and developing fruit for the first signs of damage, such as honeydew, frass, or crescent scars. Early detection allows for the application of targeted, localized treatments before a pest population builds to damaging levels. This awareness ensures that control measures are applied only when necessary, minimizing disruption to natural predators.