Crop hub · Garden · Home garden

Pear

Pears share most of their insects with apples, but one pest is theirs alone. Pear psylla breeds only on pear (WSU), and the honeydew from its nymphs russets the fruit and grows black sooty mould. Codling moth is the worm in the pear. It has two to three generations a year in California, and UC IPM warns that larvae entering at the calyx (flower) end are hard to spot without cutting the fruit. In the East, the University of Kentucky adds plum curculio, which it says can cause serious early-season damage to pears.

Some apple pests matter less here. The Pacific Northwest insect handbook calls pear only an incidental host of apple maggot, and Kentucky lists common pear among the plants that Japanese beetles seldom damage. What decides a pear crop is often restraint. UC IPM notes that broad-spectrum sprays for codling moth kill the natural enemies of pear psylla and set off outbreaks. Growing apples too? See the apple hub.

crop context · backyard pear tree, fruit set

What attacks a backyard pear tree

DELAYED DORMANT, THEN ALL SEASON

Pear psylla

Pears only. Nymph honeydew russets the fruit and grows sooty mould, and heavy feeding blackens parts of the leaves and can make them fall. A kaolin clay film before the overwintered adults lay is the key step.

ReleaseWild predators — earwigs, predatory bugs, a parasitic waspNothing to release — protect them by keeping broad-spectrum sprays off the tree (UC IPM)

DORMANT SEASON

San Jose scale

WSU calls it most destructive on apple and pear. A grey crust on the bark and red-ringed spots on the fruit; dormant oil is the control.

ReleaseTwicestabbed lady beetleNothing to release — conserve the native twicestabbed lady beetle

PETAL FALL TO EARLY SUMMER

Plum curculio

An eastern snout weevil that cuts crescent-shaped scars in fruitlets. Kentucky warns of serious early-season damage to pears. Pick up drops before the grubs leave them.

ReleaseEntomopathogenic nematode (supplement)Per package directions — the field trials checked give no home-orchard rate

FROM FIRST EGG HATCH

Codling moth

The larva tunnels to the core. Entries at the calyx end are hard to see without cutting the fruit. See codling moth on pears.

ReleaseCodling moth granulovirusLabel rate — Madex HP ½ tsp per 5 gal (its residential label names pear); Cyd-X 1 tsp per 5 gal

FROM SPRING · TWO GENERATIONS

Pearslug (pear sawfly)

Slimy, dark, slug-like larvae skeletonise the leaves down to the veins, and the second generation is usually more numerous than the first. UC IPM: wash them off with a hose, which spares their parasites and predators.

ReleaseWild parasites and predators, which UC IPM says often keep it in checkNothing to release

LATE SUMMER

Brown marmorated stink bug

NC State lists pears among its garden hosts, and WSU says pears appear to be at risk. Stink bug feeding on pears leaves dimples outside and white, pithy spots inside, mostly near the stem end (UC IPM).

ReleaseSamurai waspWild — conserve; not for release

Season calendar

US · QUALITATIVE READING · VARIES WITH BLOOM DATE

	J	F	M	A	M	J	J	A	S	O	N	D
Pear psylla	Jan: Quiet	Feb: Building	Mar: Building	Apr: Building	May: Building	Jun: Building	Jul: Building	Aug: Pest pressure high	Sep: Pest pressure high	Oct: Building	Nov: Quiet	Dec: Quiet
San Jose scale	Jan: Quiet	Feb: Quiet	Mar: Quiet	Apr: Building	May: Pest pressure high	Jun: Pest pressure high	Jul: Pest pressure high	Aug: Pest pressure high	Sep: Pest pressure high	Oct: Building	Nov: Quiet	Dec: Quiet
Plum curculio	Jan: Quiet	Feb: Quiet	Mar: Quiet	Apr: Quiet	May: Pest pressure high	Jun: Pest pressure high	Jul: Building	Aug: Quiet	Sep: Quiet	Oct: Quiet	Nov: Quiet	Dec: Quiet
Codling moth	Jan: Quiet	Feb: Quiet	Mar: Quiet	Apr: Quiet	May: Building	Jun: Pest pressure high	Jul: Pest pressure high	Aug: Pest pressure high	Sep: Building	Oct: Quiet	Nov: Quiet	Dec: Quiet
Stink bug	Jan: Quiet	Feb: Quiet	Mar: Quiet	Apr: Quiet	May: Quiet	Jun: Quiet	Jul: Building	Aug: Pest pressure high	Sep: Pest pressure high	Oct: Pest pressure high	Nov: Quiet	Dec: Quiet

Pest pressure high
Building
Release window
Quiet

Pear psylla · high pressure Aug–Sep
San Jose scale · high pressure May–Sep
Plum curculio · high pressure May–Jun
Codling moth · high pressure Jun–Aug
Stink bug · high pressure Aug–Oct

Starter program

A home plan for pears turns on two dates: the delayed-dormant kaolin spray for psylla, and first egg hatch for codling moth. The one biological product in it, a virus, is sprayed like any other product.

DORMANT SEASONHorticultural oilWet the bark of the trunk, limbs and twigs against overwintering San Jose scale, between 40 °F and 90 °F and never with or after sulfur. The label warns it is toxic to fish, so keep it out of water
DELAYED DORMANTKaolin clay (Surround WP)¼–½ lb per gallon in a hand sprayer (the label rate), three times 7–10 days apart from delayed dormant to green cluster bud, before the overwintered pear psylla lay. Renew the film when it stops leaving white on a dark cloth
AFTER BLOOMEase off the kaolinAt most two kaolin sprays after bloom; UC IPM and WSU warn that later use can set off mite outbreaks
FIRST EGG HATCHCodling moth granulovirusLabel rate, at least twice per larval generation and again after 6–8 sunny days (Madex HP). Check the fruit as well as the trap: UC IPM warns that pear fruit can be damaged even when traps catch no moths
MAY–JUNE ONPick up dropped fruitRemoves codling moth larvae before they crawl out (UC IPM), and plum curculio grubs, which in apples complete their development only in dropped fruit (Kentucky)
SUMMERPrune and hoseSummer-prune the vigorous leafy shoots to remove psylla nymphs and honeydew (WSU), and wash pearslug larvae off the leaves with a hose (UC IPM)

Setting up the garden

Most of what protects a pear tree is choosing it well and then leaving its predators alone.

Keep broad-spectrum sprays out of the tree

UC IPM notes that nonselective sprays for codling moth kill the natural enemies of pear psylla and set off outbreaks, and psylla readily becomes resistant to insecticides.

Leave the earwigs in the tree

WSU calls European earwigs an important predator in pear orchards; in one study, young earwigs ate as many as 1,000 pear psylla eggs a day. The parasitic wasp Trechnites insidiosus and predatory bugs do much of the rest.

Choose the rootstock and variety with care

Psylla spreads pear decline, and WSU rates trees on Asian-pear and Ussurian rootstocks the most susceptible. European pears suffer more from psylla than Asian ones (UC IPM), and early-maturing pears suffer less codling moth damage than late ones (UC IPM).

Tap the branches in winter

Hold a white tray under a branch and tap it three times to count the psylla adults waiting to lay. After bloom, UC IPM reads one to several nymphs per infested shoot as a sign predators are working; ten or more means they are not.

Go easy on nitrogen

Soft new growth favours psyllids (UC IPM), so don't push the tree with fertiliser.