Pear trees are susceptible to several insect pests, making successful fruit production challenging. Effective management requires recognizing these invaders early, before their populations cause significant damage to the developing crop and overall tree health. Understanding the physical characteristics and life cycles of common pear pests is the first step in developing an effective strategy. Quick identification allows for targeted controls, minimizing the need for broad-spectrum treatments.
Identifying the Most Destructive Pests
Pear trees face threats from three primary pest types, categorized by their feeding methods: sucking, boring, and chewing. The Pear Psylla (Cacopsylla pyricola) is the most common sucking pest. Adults resemble miniature cicadas, measuring 0.08 to 0.1 inch long, with wings held in a roof-like position. The nymphs cause the most extensive damage, appearing as small, flat, yellowish-green insects that move slowly and are often partially encased in honeydew.
The Codling Moth (Cydia pomonella) is the primary boring pest, with the larval stage being the most destructive. The adult is a small, nondescript brownish-gray moth, approximately 10 millimeters long, active in the evening for egg-laying. Eggs hatch into small, cream-colored caterpillars that immediately bore into the developing fruit. They feed inside the fruit for several weeks before emerging to pupate.
The Pear Slug (Caliroa cerasi) is a type of sawfly larva that causes chewing damage to the foliage. These larvae are slug-like, dark green to orange, tadpole-shaped, and covered in a slimy, olive-green coating. They grow up to half an inch in length. The larvae feed on the upper surface of the leaves during two main generations, with the second generation in late summer often causing the most noticeable destruction.
Recognizing Damage and Symptoms
Visual evidence of pest activity often appears before the pest itself, aiding in proper diagnosis. The presence of honeydew—a sticky, sugary substance excreted by sucking insects—indicates a pear psylla infestation. Honeydew serves as a growth medium for sooty mold, a black fungus that coats leaves and fruit. This mold reduces the tree’s ability to photosynthesize and can cause the fruit surface to become russeted.
Codling moth damage is easily identified on the fruit, typically appearing as a small entry hole on the side or near the calyx (blossom end). The larva pushes out its waste, or frass, which appears as fine, reddish-brown sawdust near the entry point, confirming the internal borer’s presence. A “sting” is a shallow entry point where the larva died shortly after boring, leaving a small, dark blemish on the skin.
The pear slug leaves behind a characteristic pattern of damage known as skeletonization. The larvae feed only on the soft tissue of the upper leaf surface, leaving the veins and the lower epidermis intact. Heavily affected leaves take on a translucent, lacy, or scorched appearance, eventually browning and dropping prematurely. This premature leaf drop can stress the tree and impact fruit development.
Cultural and Biological Control Methods
Preventative and non-chemical strategies form the foundation of effective pear pest management. Pruning the pear tree properly is a cultural control that thins the canopy, increasing air circulation and sunlight penetration. This creates an environment less favorable to moisture-loving pests like pear psylla. Dormant oil applications, made before buds swell in late winter or early spring, smother overwintering pest eggs and adults, reducing the initial population of pear psylla and mites.
The use of beneficial insects provides a long-term biological solution by conserving natural predators and parasites. Tiny parasitic wasps, such as Trichogramma species, can be released to lay eggs inside codling moth eggs, preventing the larvae from hatching. Encouraging generalist predators like lacewings, ladybugs, and European earwigs helps control soft-bodied pests such as pear psylla nymphs.
Physical removal techniques offer immediate control without sprays. Kaolin clay (often sold as Surround) is an organic, white clay mixed with water and sprayed onto the tree. It forms a powdery barrier that repels and disorients pests like the codling moth and pear psylla. For soft-bodied pests like pear slug, a strong jet of water from a hose can physically dislodge them, or they can be hand-picked from the foliage.
Targeted Chemical Treatments
When cultural and biological methods are insufficient, low-impact chemical treatments can be applied with precision to minimize harm to beneficial insects. Insecticidal soaps and neem oil are low-impact options for managing soft-bodied pests such as pear psylla and young pear slug larvae. They work on contact and have little residual effect once dry. These materials must be applied to fully cover the pest, especially targeting the undersides of leaves where psylla nymphs congregate.
Effective treatment against the codling moth relies on proper timing, determined by monitoring the pest’s flight patterns. Pheromone traps use synthetic sex scents to attract and capture male moths, pinpointing the start of the reproductive cycle. Treatments, such as those containing the bacterial insecticide Spinosad, should be applied immediately following the first sustained catch of moths. This targets the brief window after the eggs hatch but before the larvae bore into the fruit.
Follow the product label instructions precisely, paying attention to pre-harvest intervals and ensuring the product is rated for use on pear trees. Avoiding broad-spectrum insecticides is important, as these chemicals eliminate beneficial insects and can lead to a pest resurgence due to the loss of natural control. Using the least toxic and most targeted product at the correct time maximizes effectiveness while preserving the orchard’s natural ecosystem.