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Ministry of Agriculture, Food and Rural Affairs

White Marked Tussock Moth

Tussock moth larva Tussock moth larva Tussock moth damage Tussock moth larvae
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Beginner

Scientific Name
Orygia leucostigma

Identification
Eggs:

  • Laid in a foamy white egg mass.

Larvae:

  • 35 mm in length,
  • Reddish-orange head,
  • Hairy body,
  • Two light yellow lines running along its length,
  • Has four brush-like tufts or bunches of light tan hairs on the back (top of the first four abdominal segments) and red dots (abdominal segments six and seven),
  • A pair of longer tufts of black hairs rises from the prothorax (these hairs can irritate the skin),

Pupae:

  • Dark grey cocoons spun of silk and body hairs
  • Found on twigs, branches and crevices in bark.

Adults:

  • Male moth is ash gray with a wingspan of 26-30 mm, forewings are marked with darker wavy bands,
  • Females are creamy white to gray, hairy and flightless.

Damage:

  • Leaves become skeletonized,
  • As larvae mature they consume the entire leaf except for the main veins and petiole,
  • They tend to feed on the upper third of the tree first,
  • If uncontrolled, they can cause severe defoliation.

Often Confused With

  • Gypsy moth feeding- Both gypsy moth and tussock moth feed heavily on leaves, and can defoliate trees.  Gypsy moth caterpillars are black with a yellow head, while tussock moth larvae are light in colour with distinct tuft like hairs on their back.

Period of Activity
This is a rare pest of apples, but may be present in orchards near adjacent woodlots. Eggs hatch in late June and early July, and larvae may be present from June through August. 

Scouting Notes
Larvae are found in trees in July and August when they are large and close to maturity. Through the winter, egg masses are found on trunks and branches of trees.

The hairs on the tussock moth are hollow and contain a toxin that penetrates skin. People handling these insects often exhibit allergic reactions such as painful rashes or respiratory problems.

Thresholds
This is a rare pest of apples and there are no thresholds for this pest, but management is necessary if defoliation occurs.

Advanced

Scientific Name
Orygia leucostigma

Identification
Eggs: Eggs are laid in a foamy white egg mass.

Larvae: A mature larva is 35 mm in length with a reddish-orange head and hairy body that has two light yellow lines running along its length. It has four brush-like tufts or bunches of light tan hairs on the back (top of the first four abdominal segments) and red dots (abdominal segments six and seven). A pair of longer tufts of black hairs rises from the prothorax. These hairs can irritate the skin.

Pupae: Pupation occurs within dark grey cocoons spun of silk and body hairs. These pupae are found on twigs, branches and crevices in bark.

Adult: The male moth is ash gray with a wingspan of 26-30 mm. Forewings are marked with darker wavy bands. Females are creamy white to gray, hairy and flightless.

Damage: Young larvae skeletonize the leaves of deciduous trees. As they mature, larvae consume the entire leaf except for the main veins and petiole. Damage occurs on the upper third of the tree first. If uncontrolled, severe defoliation can occur. Repeated years of defoliation cause tree mortality and wood loss.

Often Confused With

  • Gypsy moth feeding- Both gypsy moth and tussock moth feed heavily on leaves, and can defoliate trees.  Gypsy moth caterpillars are black with a yellow head, while tussock moth larvae are light in colour with distinct tuft like hairs on their back.

Biology
Tussock moths overwinter as eggs within an egg mass. Eggs hatch from late June to early July, and emerging larvae migrate to leaves or needles where they consume everything except the main veins. Male larvae have five larval instars, and females have six. Feeding and development continue over a five-week period prior to pupation in mid August. Dark grey cocoons are found on twigs, branches or bark. Adults emerge from late August to early September. Females are flightless and mate immediately after emergence, laying their eggs on or near their cocoons. This pest is primarily a problem in woodlots, and they also move into apple orchards from adjacent woodlots.

Period of Activity
This is a rare pest of apples, but may be present in orchards near adjacent woodlots. Eggs hatch in late June and early July, and larvae may be present from June through August. 

Scouting Notes
Larvae are found in trees in July and August when they are large and close to maturity. Through the winter, egg masses are found on trunks and branches of trees.

The hairs on the tussock moth are hollow and contain a toxin that penetrates skin. People handling these insects often exhibit allergic reactions such as painful rashes or respiratory problems. 

Thresholds
There is no threshold for white marked tussock moth, but controls are necessary if defoliation begins.

Management Notes

  • Outbreaks of tussock moth can last two to four years.
  • Their populations are suppressed by viruses, parasitoids, natural predators and diseases.
  • They are a rare pest in apple orchards, but when present in high numbers cause considerable damage.
  • Where controls are necessary, early application of a biological control agent such as Bacillus thuringiensis to control other pests provides secondary control of tussock moth.