Common Pests on Pear Trees and How to Control Them

Pear trees attract a small, predictable set of pests, and each one leaves damage distinctive enough to identify by sight. Matching the symptom to the pest matters more than reaching for an all-purpose spray. Some of the most useful pest control on a pear tree also comes from insects that eat the pests, and broad sprays kill them off.1California Agriculture. Effects of Predators on Control of Pear Psylla

How to Tell Which Pest Is Attacking Your Pear Tree

Inspect the tree in stages: fruit, the tops and undersides of leaves, and the bark each get their own look. A hand lens helps with mites and young psylla, which are easy to miss by eye. Cut a few suspect fruit open, because entry holes at the blossom end hide well.

A few mix-ups are common. Rough skin from mites can look like frost damage or ordinary weather russet, and more than one pest is often present at once. A chewed leaf is not always a slug’s work: pear slugs eat only the top surface and leave a lacy, brownish patch, while true holes through both sides point to a different caterpillar or beetle. Walk the tree weekly in spring and early summer and note the date you first see each symptom, so you know next year when to act.

Codling Moth and Plum Curculio Inside the Fruit

Codling moth caterpillars either die after boring a short way into the flesh, leaving a shallow “sting,” or tunnel to the core and feed on the seeds.8UC IPM. Common Pests on Pear Trees and How to Control Them The moths lay eggs mostly on the undersides of leaves near the fruit clusters.9Environmental Entomology. Codling Moth: 1 Egg and First Instar Mortality on Pear with Special Reference to Varietal Susceptibility 2 But on pears, 80 to 90% of caterpillars enter through the blossom end, opposite the stem.10Environmental Entomology. Codling Moth: 1 Egg and First Instar Mortality on Pear with Special Reference to Varietal Susceptibility 2 That means much of the damage can’t be seen without cutting the fruit open.11UC IPM. Common Pests on Pear Trees and How to Control Them

Pheromone dispensers flood the air with the female moth’s scent so males can’t find mates.12Journal of Economic Entomology. Suppression of the Codling Moth (Lepidoptera: Tortricidae) Population on Pears in Southern Oregon through Mating Disruption with Sex Pheromone In orchards that started with few moths, this gave about 90% control and kept males from finding traps for 16 weeks.13Journal of Economic Entomology. Suppression of the Codling Moth (Lepidoptera: Tortricidae) Population on Pears in Southern Oregon through Mating Disruption with Sex Pheromone It gave little or no control where moth numbers were already high.14Journal of Economic Entomology. Suppression of the Codling Moth (Lepidoptera: Tortricidae) Population on Pears in Southern Oregon through Mating Disruption with Sex Pheromone On a single backyard tree, though, disruption works poorly because the scent drifts away. It suits larger plantings or neighbors acting together.

On a home tree, sanitation does most of the work. Dropped fruit often holds a caterpillar about to leave and pupate, so pick it up every week and destroy it, sealed in a bag in the trash rather than left in a compost pile. Thin fruit so pears hang singly rather than touching, since moths and larvae favor the spot where two fruit meet, and thinning also lets you see each pear. On a small tree, slip a paper or fine mesh bag over each young fruitlet after thinning. It has to go on early, before eggs are laid. A pheromone trap catches male moths, and the date of the first catches tells you when egg laying is starting. On one tree it works as a timing tool for any spray, not as a control.

The female plum curculio cuts a crescent scar as she lays an egg in the young fruit.15New England Tree Fruit Management Guide. Plum curculio: New England Tree Fruit Management Guide The grub tunnels inside, and the fruitlet usually drops early.16New England Tree Fruit Management Guide. Plum curculio: New England Tree Fruit Management Guide Pears are among the fruits it attacks, alongside plums, peaches, cherries and apples.17Journal of Entomological Science. Host Utilization and Phenology of Injury by Plum Curculio (Coleoptera: Curculionidae) in West Virginia

The adult is a small, rough-looking beetle with a curved snout. It emerges in spring to feed and lay eggs on young fruit, so the weeks right after petal fall are when protection counts most. Fallen fruitlets with a crescent scar often hold a grub, so collect and destroy them promptly, before the larvae leave the fruit to pupate in the soil. On cool mornings the beetles are sluggish. Tap or beat the limbs over a light-colored sheet to drop them where you can see and destroy them, and repeat over several days during the egg-laying period.

Pear Psylla, the Sticky Leaf Pest

Pear psylla nymphs suck sap and excrete honeydew, a sticky sugary liquid. Black sooty mold then grows on the honeydew, and the share of blackened pears rises with the number of nymphs per leaf.18Environmental Entomology. Analysis of Pear Psylla (Homoptera: Psyllidae) Populations and Associated Damage in a Pennsylvania Pear Orchard As few as about 0.3 to 0.4 nymphs per leaf can start to scar or downgrade fruit.19Washington State University Extension. Common Pests on Pear Trees and How to Control Them Psylla also spread pear decline, a disease that weakens and can kill trees.20PubMed. Frequency and seasonal distribution of pear psylla infected with the pear decline phytoplasma in california pear orchards Overwintering adults carry and pass on the disease far more than summer ones, up to about 1 in 5 attempts in one species.21PubMed Central. Vector transmission and epidemiology of ‘Candidatus Phytoplasma pyri’ in Austria and identification of Cacopsylla pyrisuga as new pathogen vector

Kaolin clay, a fine white clay sprayed on as a film, keeps psylla off and kept numbers down all season.22International Journal of Pest Management. Impact of kaolin particle film, spirodiclofen acaricide, harpin protein, and an organic biostimulant on pear psylla Cacopsylla pyri (Hemiptera: Psyllidae) Season-long programs starting with clay or reflective mulch matched standard spray programs.23PubMed. Integrated Pest Management Programs for Pear Psylla, Cacopsylla pyricola (Förster) (Hemiptera: Psyllidae), Using Kaolin Clay and Reflective Plastic Mulch In an unsprayed orchard, predatory bugs and lacewings kept nymphs below one per leaf with no real damage.24California Agriculture. Effects of Predators on Control of Pear Psylla Psylla quickly build resistance to repeated pyrethroid sprays, up to 40-fold.25Pesticide Science. Resistance to insecticides in winter‐ and summer‐forms of pear psylla, <i>Psylla pyricola</i>

At home, the clay spray is mixed with water and leaves a white film that psylla find unattractive for feeding and egg laying, so it has to be on before they arrive. Start before buds open in early spring, when the overwintered adults return and begin laying eggs. Rain and new growth break up the film, so reapply after heavy rain and as fresh shoots expand, since new leaves have no coating. Cover the limbs, twig tips and both sides of the leaves, because any gap is a spot where psylla can settle. The film doesn’t harm the tree and washes or rubs off fruit at harvest.

Broad-spectrum insecticides kill lacewings, minute pirate bugs and other predators along with the psylla, and psylla rebound faster than the predators do. A few psylla on the tree are useful because they give predators something to eat, so a low, steady number of nymphs is a better sign than none. Lacewing larvae are small, spindle-shaped and alligator-like with curved jaws, and minute pirate bugs are tiny black-and-white adults. Learn to recognize them before spraying anything that would remove them.

Mites That Bronze Leaves and Roughen Fruit

Pear rust mites are too small to see without a lens. Their feeding bronzes leaves and causes russeting, rough brown skin that starts at the blossom end.26Pacific Northwest Pest Management Handbooks. Pear-Eriophyid mite Heavy feeding reduces leaf function and weakens the tree.27Koppert. Pear Rust Mite (Epitrimerus pyri) | Damage & Biological Control

Blister mites overwinter under bud scales and start feeding as buds open, once days average above about 10°C (50°F).28Quarantine and plant protection. Pearleaf Blister Mite (Eriophyes pyri Pgst.): Biological Features and Measures to Limit its Harmfulness in Pear Plantations of Ukraine Their blisters start light green, turn reddish-brown, then black. Heavy infestations stunt fruit and tree growth.29BİTKİ KORUMA BÜLTENİ. ARMUT YAPRAK UYUZU (ERİOPHYES PYRİ PGST.) ÜZERİNDE TETKİK VE GÖRÜŞLER

Timing decides whether control works. Once blister mites are inside the leaf blisters they are protected, so a summer spray aimed at the blisters arrives too late. The main tool is dormant oil applied in spring before the buds open, when the mites are exposed under the bud scales and haven’t begun to feed. Rough-skinned fruit is still safe to eat and often tastes fine; it mostly affects looks and, in bad cases, how well fruit stores or sells. Next spring, check the first leaves for blisters. If you see only a few, you can skip extra measures, since a few blisters do little harm to a mature tree.

Scale Insects and Pear Slugs

San Jose scale lives mostly on bark, especially on upper limbs, and sometimes on fruit, and less often on leaves.30The Canadian Entomologist. DISTRIBUTION AND DEVELOPMENT OF THE SAN JOSE SCALE (HOMOPTERA: DIASPIDIDAE) ON THE LEAVES, BARK, AND FRUIT OF SOME ORCHARD AND ORNAMENTAL TREES IN BRITISH COLUMBIA Red spots on fruit at harvest signal damaging numbers on the tree.31University of Kentucky College of Agriculture. San Jose Scale Bark under heavy scale turns scarlet instead of green.32University of Kentucky College of Agriculture. San Jose Scale Oystershell scale, a relative, attacks mainly wood.33Pacific Northwest Pest Management Handbooks. Pear-Scale

To check for scale, scrape a bit of bark on the upper limbs with a thumbnail or knife on a dry winter day. A juicy, yellowish layer beneath tiny gray crusts means living scale. Scale hides on high limbs that are hard to see from the ground, so use binoculars or a pole to check them. Heavily crusted twigs and small limbs can be pruned out and removed, which cuts the population directly. If you find live scale, note to apply dormant oil before buds open next season, when the tiny insects are most exposed.

Pear slugs are slimy sawfly larvae that eat upper leaf surfaces.34Hortsense. Pear: Pear slug (pear sawfly) Heavy feeding drops leaves and lowers vigor, yield and next year’s bloom, mostly on young trees.35Pacific Northwest Pest Management Handbooks. Pear-Pear sawfly (pear slug)

On a small tree, a strong spray of water from a hose knocks the larvae off, and they don’t climb back easily. You can also pick them off by hand with gloves. A mature tree can lose some leaf area to a few slugs with no harm, so leaving them alone is sensible when feeding is light. Look in summer, when the larvae are feeding, and give young trees closer attention because they have less leaf area to lose.

A Season-by-Season Control Calendar

Dormant oil smothers overwintering scale and mite eggs as they begin to breathe in spring.36Plant & Pest Advisory. Early Season Tree Fruit Pest Control for 2024 It can be applied safely up to the pink-bud stage, and it also suppresses early aphids.37Plant & Pest Advisory. Early Season Tree Fruit Pest Control for 2024

Late winter is the time to prune out crusted or crowded wood and then oil. Pruning first removes scale-covered twigs and lets the oil coat the remaining branches. The oil must be on before the buds reach the pink stage, so the window is set by what the buds look like, not by the date. Psylla and pear bloom are both arriving earlier in warming springs, by about two weeks for psylla.38Centaur. Pears, pests and natural enemies: modelling tri-trophic interactions in a changing climate

At bud break, apply clay to protect new growth, since the overwintered psylla adults are active then. After petal fall, begin curculio checks and watch young fruitlets for crescent scars. Through summer, pick up dropped fruit weekly, cut open a few fruit to check for codling moth entry, and look for pear slugs. Spray only when counts are high and predators scarce.39PubMed Central. Pear psylla and natural enemy thresholds for successful integrated pest management in pears In fall, clean up all fallen and leftover fruit and leaves, which removes places where pests spend the winter.

Choosing Pear Varieties That Resist Psylla

Of 285 pear types tested, about 94% were susceptible to psylla.40International Journal of Horticultural Science. Susceptibility of European pear genotypes in a gene bank to pear psylla damage and possible exploitation of resistant varieties in organic farming Kieffer was among the highly tolerant ones.41International Journal of Horticultural Science. Susceptibility of European pear genotypes in a gene bank to pear psylla damage and possible exploitation of resistant varieties in organic farming Crosses with Asian pear species showed some of the strongest resistance,42HortScience. Host Resistance to Pear Psylla of Breeding Program Selections and Cultivars and resistant breeding lines can be 5 to 10 times more resistant than standard varieties.43PubMed. Two pear accessions evaluated for susceptibility to pear psylla Cacopsylla bidens (Šulc) in Israel

When you shop, ask the nursery which varieties tolerate psylla and how they rate for fire blight, since a pear that dodges one problem may be prone to the other. Resistance lowers how many psylla settle and how much damage they do, but doesn’t remove them, so you still need to watch the tree and keep up basic care. Kieffer is widely sold and tolerant, though its fruit is generally considered coarse and better for cooking and canning than fresh eating.