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Garden cucumber

Cucumber pests come in two waves. The first is cucumber beetles on seedlings in late spring. On cucumber they do more than chew: the striped cucumber beetle spreads bacterial wilt, and cucumber and muskmelon are the cucurbits most susceptible to it. Row cover is the defence Minnesota, Wisconsin and Kentucky extension all recommend, and Minnesota and Wisconsin say to keep it on until the plants flower.

The second wave arrives in midsummer and later: spider mites in hot, dry weather, then melon aphids and, in the South, pickleworm. Not every cucumber plant problem is an insect. Yellow spotting on the leaves is often downy mildew or another disease, and yellow spots on cucumber leaves sorts the two apart.

crop context · trellised cucumbers, early summer

Common cucumber pests, in the order you meet them

SEEDLINGS · MAY–JUNE

Striped cucumber beetle

Eats seedlings, flowers and fruit, and spreads bacterial wilt. Act at half a beetle per seedling.

ReleaseGround beetlesNothing to release — ground beetles and wolf spiders reduce numbers (JIPM)
JULY IN THE NORTH

Spotted cucumber beetle

Migrates north each summer and feeds on every part above ground. Most abundant in the South.

ReleaseBraconid waspsWild — nothing to release (UF/IFAS lists braconids among its enemies)
JUNE–JULY

Squash bug

Prefers squash and pumpkin, but will feed on cucumber. Crush the bronze egg masses.

ReleaseTachinid fliesWild — keep nectar plants near the crop, no broad-spectrum sprays
LATE SUMMER

Melon aphid

Colonies under the leaves, and cucumber mosaic virus, which no natural enemy slows.

ReleaseHoverfliesWild — attract adults with open flowers
AUG–SEPT · SOUTH

Pickleworm

Bores into flowers and fruit. Cucumber is not a favoured host; summer squash is.

ReleaseGround beetlesNothing to release — no natural enemy reliably suppresses it (UF/IFAS)

Season calendar

TEMPERATE US · OUTDOOR CUCUMBERS · QUALITATIVE
JFMAMJJASOND
Striped cucumber beetleJan: QuietFeb: QuietMar: QuietApr: QuietMay: BuildingJun: Pest pressure highJul: BuildingAug: BuildingSep: QuietOct: QuietNov: QuietDec: Quiet
Spotted cucumber beetleJan: QuietFeb: QuietMar: QuietApr: QuietMay: QuietJun: BuildingJul: Pest pressure highAug: Pest pressure highSep: BuildingOct: QuietNov: QuietDec: Quiet
Squash bugJan: QuietFeb: QuietMar: QuietApr: QuietMay: BuildingJun: Pest pressure highJul: Pest pressure highAug: BuildingSep: BuildingOct: QuietNov: QuietDec: Quiet
Spider miteJan: QuietFeb: QuietMar: QuietApr: QuietMay: QuietJun: BuildingJul: Pest pressure highAug: Pest pressure highSep: BuildingOct: QuietNov: QuietDec: Quiet
Melon aphidJan: QuietFeb: QuietMar: QuietApr: QuietMay: QuietJun: BuildingJul: BuildingAug: BuildingSep: Pest pressure highOct: Pest pressure highNov: QuietDec: Quiet
Pickleworm (South)Jan: QuietFeb: QuietMar: QuietApr: QuietMay: QuietJun: BuildingJul: BuildingAug: Pest pressure highSep: Pest pressure highOct: BuildingNov: QuietDec: Quiet

Starter program

There is no release that protects cucumber seedlings from beetles. Row cover does that job. The one purchase that can pay is predatory mites, and only once spider mites are confirmed.

  1. AT SOWINGGround beetlesNothing to release. A thick straw mulch shelters them and also slows cucumber beetles. Keep the crop under row cover until it flowers.
  2. SUMMERTachinid fliesNothing to release. Keep nectar plants near the vines and avoid broad-spectrum sprays; Trichopoda parasitises adult squash bugs.
  3. ON FINDING MITESPhytoseiulus persimilis2–50 /m² per release, repeated once or twice at weekly intervals, concentrated on hot spots. It loses ground above about 86 °F (30 °C) in dry air, so mist the leaf undersides in dry spells.
  4. LATE SUMMERHoverfliesNothing to release. Keep open flowers near the bed and leave aphid colonies that already have larvae in them.

Setting up the garden

Most cucumber pest control is done at sowing, before a beetle has landed.

Cover until the first flowers

Row cover or fine mesh keeps cucumber beetles off the seedlings. Take it off when flowering starts so bees can pollinate.

Grow non-bitter varieties

Bitter varieties are more attractive to cucumber beetles, so non-bitter ones carry fewer.

Water the soil, not the leaves

A drip or soaker hose keeps the foliage dry, which slows the leaf diseases that are so often mistaken for insect damage.

Spare the predators

Broad-spectrum insecticides kill the predators that hold spider mites down, and carbaryl and some pyrethroids can even favour the mites. In hot weather, mites can flare within a few days of a spray.