Skip to content.
Français

Some features of this website require Javascript to be enabled for best usibility. Please enable Javascript to run.

Ministry of Agriculture, Food and Rural Affairs

Pear (leaf) Blister mite

Blister mite damage Characteristic blister Blister mite damage to pear shoot Blister mite damage to pear shoot Click to enlarge.

Beginner

This pest affects:

Pear;

Scientific name
Eriophyes pyri

Identification
Eggs

  • Dull white
  • Oval, 0.05mm in length

Nymph

  • Resembles the adult, 0.07mm long – not visible with a hand lens

Adults

  • White or light red colour, 0.16-0.25mm long – not visible with a hand lens
  • Body is long, striated and tapered at posterior end
  • Two pairs of legs attached just behind the head
  • Long hairs on the legs and five pairs on the sides of the body
  • Abdomen is annulated, or striated, giving the appearance of narrow rings

Damage
Buds

  • dry up and fail to develop

Leaves

  • Blisters, 3 mm in diameter, on the underside of leaves
  • Blisters first appear as small green pimples. These soon take on a reddish appearance, eventually turning brown
  • Blisters may be massed together, covering the underside of the leaf. This blistering can seriously impair photosynthesis
  • All leaf tissue is at risk for feeding damage (blisters), even new leaves which have not yet unfolded
Fruit Spots
  • Early feedings can cause depressed russet spots. The fruit normally becomes deformed or misshapen. These oval russet spots, usually depressed with a halo of clear tissue are a tell tale symptom of blister mite. Bartlett pear is the most susceptible to blister mite

Often confused with
Pear Rust Mite – smooth, light russeting of the fruit; no galls formed on leaves

Winter Bud Damage –Bud injury can lead to dehydration, oxidation and development failure in spring

Period of activity
Feed from green tip to mid-summer.

There are 2-3 generations per year.

Scouting Notes

  • A microscope is required to examine this pest.
  • In the spring, inspect the undersides of the leaves for early blisters. These early blisters will appear as small, green pimples, eventually turning red, then brown and necrotic.
  • Examine terminal and fruit buds for mites during dormancy and again just before bloom. During the summer, examine shoot foliage and the calyx end of developing fruit.
  • Check before bloom in the younger leaves which will have noticeable blistered areas where mites have been feeding. These are often visible before the leaves even unfold.

Thresholds
There are currently no thresholds. Unless leaves are heavily infested early in the season, pear blister mite is not usually of economic concern on mature trees. However, early season infestation on young trees should be dealt with promptly. As the season progresses, control becomes more difficult.

Advanced

This pest affects:

Pear;

Scientific name
Eriophyes pyri

Identification
Eggs 

  • Dull white
  • Oval, 0.05mm in length

Nymph

  • Resembles the adult, 0.07mm long – not visible with a hand lens

Adults: 

  • White or light red colour, 0.16-0.25mm long – not visible with a hand lens
  • Body is long, striated and tapered at posterior end
  • Two pairs of legs attached just behind the head
  • Long hairs on the legs and five pairs on the sides of the body
  • Abdomen is annulated, or striated, giving the appearance of narrow rings

Damage
Buds

  • dry up and fail to develop

Leaves

  • Blisters, 3 mm in diameter, on the underside of leaves
  • Blisters first appear as small green pimples. These soon take on a reddish appearance, eventually turning brown
  • Blisters may be massed together, covering the underside of the leaf. This blistering can seriously impair photosynthesis
  • All leaf tissue is at risk for feeding damage (blisters), even new leaves which have not yet unfolded
Fruit Spots
  • Early feedings can cause depressed russet spots. The fruit normally becomes deformed or misshapen. These oval russet spots, usually depressed with a halo of clear tissue are a tell tale symptom of blister mite. Bartlett pear is the most susceptible to blister mite

Often confused with
Pear Rust Mite – smooth, light russeting of the fruit; no galls formed on leaves

Winter Bud Damage –Bud injury can lead to dehydration, oxidation and development failure in spring

Biology
Adult mites overwinter in the second or third bud scale starting in August or September. In the spring, when the foliage comes out, the overwintering mites migrate to the tender leaves and burrow beneath the epidermis of the under surface to feed. This irritation produces a thickening of the leaf tissue (a gall). The eggs of the blister mite are laid in this gall and the young will remain there until they are mature.

Adults leave the gall through a minute opening in the underside. They move to new leaves and start new blisters. Reproduction is continuous and new galls are formed throughout the entire growing season.

It takes between 20 to 30 days to develop from egg to adult during the spring. It is the feeding of the females and the offspring that cause the blister. When the blisters begin to appear, the leaf cells near the middle of the blister die and pull apart. The surrounding cells enlarge to compensate, creating a hole in the leaf. These holes are used as an entrance for the spring generation, who then feed on the soft inner tissue.

Throughout the summer, many generations develop within the blisters. The summer generations require only 10-12 days to develop. Once the leaf becomes crowded, mites travel to the growing terminals and begin to feed there. The fruit damage is caused in the buds before blossom. It is not known how blister mite infestations spread throughout an orchard, but it is suggested they can be carried by wind, birds or insects.  During the winter, the mite can continue to feed on the bud scale and it is believed that this can cause the bud to dry and fail to develop.

Period of activity
Feed from green tip to mid-summer.

There are 2-3 generations per year.

Scouting Notes

  • A microscope is required to examine this pest.
  • In the spring, inspect the undersides of the leaves for early blisters. These early blisters will appear as small, green pimples, eventually turning red, then brown and necrotic.
  • Examine terminal and fruit buds for mites during dormancy and again just before bloom. During the summer, examine shoot foliage and the calyx end of developing fruit.
  • Check before bloom in the younger leaves which will have noticeable blistered areas where mites have been feeding. These are often visible before the leaves even unfold.

Thresholds
There are currently no thresholds. Unless leaves are heavily infested early in the season, pear blister mite is not usually of economic concern on mature trees. However, early season infestation on young trees should be dealt with promptly. As the season progresses, control becomes more difficult.

Management Notes
When monitoring indicates a need, special summer sprays can be made. For more information on managing blister mite, see OMAFRA Publication 360, Fruit Crop Protection Guide.

Chapter 5 - Pear Calendar: Special Sprays (when monitoring indicates need at First Cover).

Some information included above excerpted from;