helpfulbugs.com
Crop hub · Garden · Home garden

Apple

The University of Kentucky names five key apple pests: codling moth, plum curculio, oriental fruit moth, brown marmorated stink bug and San Jose scale. Codling moth is the worm in the apple, and UC IPM reports it infesting 20–90 % of the fruit on untreated trees, depending on variety and location. Plum curculio leaves crescent-shaped scars on young fruit.

Very little of this is fixed by buying insects. UC IPM says naturally occurring biological control of codling moth is not effective, and it calls bagging the fruit the only non-chemical method that works well enough. Where natural enemies do help, as with the lady beetles on San Jose scale and the predators of woolly aphid, the job is to stop killing them with broad-spectrum sprays. Kentucky's advice is to examine the trees weekly through spring and early summer, because not every orchard has every pest. Growing pears? Pear psylla and the pear timings are on the pear hub.

crop context · backyard apple tree, fruit set

What attacks a backyard apple tree

ABOUT A MONTH AFTER BLOOM

Codling moth

The larva bores to the core and leaves a hole plugged with brown frass. Bagging the fruit at ½–1 inch is the no-spray alternative.

ReleaseCodling moth granulovirusLabel rate — Cyd-X 1 tsp per 5 gal of water; Madex HP ½ tsp per 5 gal
PETAL FALL TO EARLY SUMMER

Plum curculio

A snout weevil that cuts crescent-shaped scars in fruitlets; infested fruit drops early. Pick up drops before the grubs leave them.

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

Apple maggot

The railroad worm: pinprick dimples outside, brown winding trails inside. Red sticky spheres time the action; bag, net or coat with kaolin.

ReleaseNo beneficial — bag, net or kaolin the fruitNothing to release
SPRING SHOOTS, THEN FRUIT

Oriental fruit moth

Mainly a peach pest, but it also attacks apple. Wild braconid wasps parasitise it most in late summer.

ReleaseBraconid waspsNothing to release — avoid broad-spectrum sprays
DORMANT SEASON

San Jose scale

A grey crust on the bark and red-ringed spots on the fruit. Kentucky warns it can kill limbs in a few years; dormant oil is the control.

ReleaseTwicestabbed lady beetleNothing to release — conserve the native twicestabbed lady beetle
LATE SPRING TO AUTUMN

Woolly apple aphid

White cottony tufts on bark and pruning cuts. The real damage is galls on the roots; the colonies above ground are mostly unsightly.

ReleaseHoverfliesWild — attract adults with open flowers
EARLY SPRING

Eastern tent caterpillar

Silk tents in the branch forks, with the leaves stripped around them. Treat while the caterpillars are small, as the tents first appear.

ReleaseBt (kurstaki)Label rate — Thuricide 2–4 tsp per gallon for tent caterpillar on apples

Season calendar

US · QUALITATIVE READING · VARIES WITH BLOOM DATE
JFMAMJJASOND
Codling mothJan: QuietFeb: QuietMar: QuietApr: QuietMay: BuildingJun: Pest pressure highJul: Pest pressure highAug: Pest pressure highSep: BuildingOct: QuietNov: QuietDec: Quiet
Oriental fruit mothJan: QuietFeb: QuietMar: QuietApr: BuildingMay: BuildingJun: Pest pressure highJul: Pest pressure highAug: Pest pressure highSep: Pest pressure highOct: QuietNov: QuietDec: Quiet
San Jose scaleJan: QuietFeb: QuietMar: QuietApr: BuildingMay: Pest pressure highJun: Pest pressure highJul: Pest pressure highAug: Pest pressure highSep: Pest pressure highOct: BuildingNov: QuietDec: Quiet
Woolly apple aphidJan: QuietFeb: QuietMar: QuietApr: QuietMay: BuildingJun: BuildingJul: Pest pressure highAug: Pest pressure highSep: Pest pressure highOct: BuildingNov: QuietDec: Quiet
Stink bugJan: QuietFeb: QuietMar: QuietApr: QuietMay: QuietJun: QuietJul: BuildingAug: Pest pressure highSep: Pest pressure highOct: Pest pressure highNov: QuietDec: Quiet
Tent caterpillarJan: QuietFeb: QuietMar: BuildingApr: Pest pressure highMay: BuildingJun: QuietJul: QuietAug: QuietSep: QuietOct: QuietNov: QuietDec: Quiet

Starter program

A home-orchard plan for apples is mostly about timing. The two biological products in it, a virus and Bt, are sprayed like any other product.

  1. 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
  2. EARLY SPRINGBt (kurstaki)On small tent caterpillars as the new tents appear, at the label rate
  3. 4–6 WEEKS AFTER BLOOMThin and bag the fruitThin to one fruit per cluster, then bag each fruit at ½–1 inch across (UC IPM)
  4. FIRST EGG HATCHCodling moth granulovirusLabel rate from first egg hatch. The labels say at least twice per generation and again after 6–8 sunny days; UC IPM advises weekly through egg hatch
  5. MAY–JUNE ONPick up dropped fruitRemoves codling moth larvae before they crawl out (UC IPM), and plum curculio, which only completes development in fallen fruit (Kentucky)

Setting up the garden

Most of what protects a home orchard is sanitation and restraint.

Keep broad-spectrum sprays out of the tree

The nonselective sprays used against codling moth kill the lady beetles and wasps that attack San Jose scale. On pears, UC IPM notes, they also set off pear psylla outbreaks (see the pear hub).

Scout weekly in spring and early summer

Kentucky recommends weekly examination of the trees through spring and early summer, because not every orchard has every pest every season.

Leave the earwigs in the tree

European earwigs chew soft fruit, but in apple trees they are valued predators of woolly apple aphid.

Clear the drops

Dropped fruit holds codling moth and plum curculio larvae. Pick it up promptly, especially in May and June (UC IPM, Kentucky).