Most fruit tree pest damage follows recognizable patterns, and learning to read those patterns is the fastest way to figure out what’s attacking your trees. Whether you’re finding tunnels inside your apples, sticky residue on leaves, or sawdust-like material oozing from bark, each sign points to a specific culprit. Here’s how to identify the most common fruit tree pests by the damage they leave behind.
Pests That Damage Fruit
Codling Moth
The codling moth is the classic “worm in the apple.” Adults are small gray or brown moths with square-tipped wings that fold roof-like over the body at rest. You’ll rarely spot the adults, though. What you will spot is the damage: a small entry hole on the fruit’s surface, often near the bottom (calyx end), surrounded by crumbly brown excrement called frass. Cut the fruit open and you’ll find a tunnel boring straight toward the core, where the larva feeds on seeds and surrounding flesh. The larvae themselves are pinkish-white caterpillars, only about 2 to 3 mm long when newly hatched but growing considerably before they exit.
Codling moth causes two types of injury. “Stings” are shallow entries where a larva burrowed in briefly then died or moved on, leaving a small brown blemish. Deep entries are the full tunnels to the core. Both ruin the fruit. Eggs are nearly transparent, flat, and oval, laid individually on leaves or fruit surfaces where they’re almost impossible to find with the naked eye.
Plum Curculio
This small snout-nosed beetle leaves one of the most distinctive calling cards in the orchard: crescent-shaped scars cut into the fruit surface. The female carves these crescent marks when depositing eggs just under the skin. On stone fruits like plums and cherries, larvae develop inside the fruit. On apples, the expanding hard flesh actually crushes developing larvae, but the feeding damage still causes fruit to drop prematurely. If you’re finding young apples on the ground with crescent-shaped scars, plum curculio is almost certainly responsible.
Apple Maggot
Apple maggot flies look like small houseflies with distinctive dark bands on their wings. Their damage differs noticeably from codling moth. Instead of a single tunnel to the core, apple maggot larvae create irregular brown trails that wind throughout the flesh in all directions. On soft-fleshed apple varieties, you’ll see small dark decayed spots on the skin where eggs were laid. On harder varieties, the egg-laying site appears as a dimple. As larvae grow, the tunnels widen and the fruit decays along the trails, turning the interior brown and mushy.
Borers That Attack Trunks and Branches
Borers are among the most destructive fruit tree pests because they attack the tree itself rather than just the fruit. The two most important species on stone fruits are the greater and lesser peach tree borers, and telling them apart comes down to where on the tree you find the damage.
The greater peach tree borer attacks the base of the trunk, typically 2 to 4 inches below the soil line. The giveaway is a raised mound of soil at the trunk base. Pull the soil away and you’ll find a mass of gummy sap mixed with sawdust-like frass, along with freshly chewed channels in the bark. You may even find the larvae themselves, which are white caterpillars with brown heads.
The lesser peach tree borer, by contrast, targets wounded tissue higher on the trunk and scaffold branches, typically 3 to 8 feet above ground. It establishes itself only in areas already damaged by pruning cuts, frost injury, or canker disease. The signs are similar (gumming mixed with wood shavings and frass) but concentrated around wounds rather than at the soil line. If you see oozing sap around an old pruning cut on a peach, cherry, or plum tree, investigate for lesser peach tree borer.
Sap Feeders on Leaves and Twigs
Aphids
Aphids are tiny, soft-bodied insects that cluster on new growth, shoot tips, and the undersides of leaves. They come in green, black, pink, or woolly white varieties depending on the species. The leaf symptoms are curling, puckering, and yellowing. Aphids also excrete a clear, sweet, sticky substance called honeydew, which coats leaves and anything beneath the tree. A black sooty mold often grows on this honeydew, giving affected leaves and branches a dirty, dark appearance. If your car or patio furniture beneath a fruit tree is covered in sticky residue, look up: aphids are likely the cause.
Scale Insects
Scale insects look like small bumps on bark, twigs, and sometimes leaves. They don’t move in their adult stage, which makes them easy to overlook. There are two broad types with different symptoms. Armored scales feed on plant cells and cause the tree to look water-stressed: leaves yellow and drop, twigs die back, and bark may crack and ooze gum. Soft scales produce large amounts of honeydew like aphids, leading to the same sticky coating and black sooty mold on leaves and fruit. If your tree looks drought-stressed despite adequate watering, check the bark closely for tiny raised bumps that can be scraped off with a fingernail.
Spider Mites
Spider mites are nearly invisible to the naked eye, but their damage is distinctive. The first sign is stippling: a fine peppering of tiny light dots across the leaf surface, as if someone poked the leaf with a pin hundreds of times. As feeding continues, leaves turn yellow or bronze and drop. Heavy infestations produce fine silken webbing that can enclose entire leaves and branch tips. Hold a suspect leaf over a white sheet of paper and tap it; the mites will fall off and appear as tiny moving specks.
Using Traps for Early Detection
Monitoring traps help you detect pest activity before damage becomes visible on fruit. Different pests require different trap styles, and placement matters as much as trap type.
For codling moth, use delta-style sticky traps baited with codling moth pheromone lures. Hang them in the upper third of the canopy using a pole, starting when flower buds are at the tight cluster stage. Check every couple of days early in the season. Once you catch at least one moth on two consecutive checks, you’ve established “biofix,” the reference point for timing any spray applications. After biofix, weekly checks are sufficient. A common action threshold is five moths caught in a pheromone trap in one week.
For apple maggot, red sticky ball traps mimic fruit and catch the flies as they land. Hang three traps along exterior rows of the orchard, especially near woods or abandoned orchards where flies breed. Place them at eye level in trees that have fruit, but remove any actual fruit within 18 inches of the trap so the trap stays attractive. An attached container of fruit essence acts as bait. If you catch five flies cumulatively over the season, it’s time to act.
Other moths like oriental fruit moth, leafrollers, and lesser appleworm are monitored with wing traps hung about 6 feet from the ground. Keep different trap types at least 20 feet apart so their pheromone plumes don’t overlap. Oriental fruit moth traps specifically should be placed at least 30 feet from any codling moth trap.
For San Jose scale, special sticky cards with pheromone lures go up around the pink bud stage, hung 5 to 6 feet high in trees where you suspect or have confirmed scale populations. Brown marmorated stink bug traps work best positioned between orchard edges and adjacent woods, clipped to stakes about 4 feet above the ground.
Timing Dormant Oil Sprays
One of the most effective preventive measures against overwintering aphid eggs, scale nymphs, and certain borer larvae is a dormant oil spray applied in late winter or early spring. The application window opens at bud swell and closes as leaves begin to emerge, but the exact cutoff differs by fruit type:
- Apple: half-inch green stage (ideally at green tip)
- Pear: green cluster
- Peach and nectarine: just before first bloom, when pink shows through the flower bud
- Cherry: white bud
- Apricot: just before first bloom
- Plum: green cluster
Apply oil on a clear, calm day when temperatures are between 50 and 70°F, and only if the temperature will stay above 40°F for the next 24 hours. Spraying too close to a freeze can damage buds, and wind reduces coverage.
Organic Controls for Active Infestations
Two organic products cover a wide range of fruit tree pests. Spinosad, derived from a naturally occurring soil bacterium, kills insect larvae when they ingest it. It’s effective against codling moth, leafrollers, and other caterpillar pests, and works best when applied shortly before or during egg hatch so larvae encounter it while feeding on treated surfaces.
Kaolin clay (sold as Surround) takes a completely different approach. It coats fruit and foliage with a white mineral film that irritates insects and drives them away. It doesn’t kill pests directly but creates a physical barrier that discourages egg-laying by codling moth, plum curculio, and apple maggot. Reapplication is necessary after rain washes the coating off.
Timing these products correctly matters more than which one you choose. Degree day models help predict exactly when pests become active. Codling moth egg hatch, for example, begins at roughly 250 degree days (base 50°F) after the first sustained moth catch in pheromone traps. Many state university extension services offer free online degree day calculators tied to local weather stations, letting you pinpoint the ideal spray window for your area rather than guessing by the calendar.