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Ministry of Agriculture, Food and Rural Affairs

Leafcurling midge

Leafcurling midge damage Leafcurling midge damage Leafcurling midge
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Beginner

Scientific Name
Dasineura mali

Identification
Eggs:

  • Laid individually in the leaf folds or along the margins of developing leaves.
  • Transparent pink to pale red in colour.
  • Elliptical in shape.

Larvae:

  • Red coloured initially, becoming clear white until the final instar when they acquire a bright orange red colour.
  • 2-3 mm in length

Pupae:

  • Light orange capsules in a white silken cocoon.
  • Generally spun just beneath the surface of the ground.

Adults:

  • Small fly approximately 1.5-2.5 mm in length. 

Damage:

  • Leaves become thick and curl inward tightly towards the midvein.
  • Leaves become discoloured (red or purple), brown and brittle, and eventually fall from the tree.
  • Terminal shoots may be stunted.

Often Confused With

  • Leafroller damage– Leaves are curled and folded similar to leaf roller damage.  However, leaf curling midge causes leaves to become discoloured (red or purple) brown and brittle, and there is no webbing associated with the damage.

Period of Activity
Adults (first generation) emerge in May, mate and females begin to lay eggs on developing leaves. Eggs can take 2-10 days to hatch, depending on temperature. Eggs hatch and larvae begin to feed on leaves. There are two or three generations produced each season. Leaf curling from larvae can be seen in orchards from petal fall through harvest.

Scouting Notes
Leaf curling and discolouration can be observed during regular orchard monitoring. The presence of this insect is confirmed by yellow or orange larvae inside the curled leaves.

Thresholds
There are no thresholds for leafcurling midge. Management of this insect is generally unnecessary, particularly on mature trees with many leaves which can withstand higher pest pressure. High insect populations in nurseries or in young trees may result in reduced photosynthesis, and stunt the growth of terminal shoots, and control may be needed. For products available to manage this pest refer to OMAFRA Publication 360, Guide to Fruit Production.

Advanced

Scientific Name
Dasineura mali

Identification
Eggs are laid individually in the leaf folds or along the margins of developing leaves. Eggs are transparent pink to pale red in colour and elliptical in shape. The larvae are red coloured initially, becoming clear white until the final instar when they acquire a bright orange red colour. It takes approximately 20 days for larvae to reach maturity. Pupae are light orange capsules in a white silken cocoon, generally spun just beneath the surface of the ground. The adult is a small fly approximately 1.5-2.5 mm in length. Adults are rarely seen in orchards.

Larval feeding on the margins of developing leaves causes leaves to become thick and curl inward tightly towards the midvein. These infested curled leaves often become discoloured (red or purple), brown and brittle, and eventually fall from the tree. Terminal shoots may be stunted.

Often Confused With

  • Leafroller damage– Leaves are curled and folded similar to leaf roller damage.  However, leaf curling midge causes leaves to become discoloured (red or purple) brown and brittle, and there is no webbing associated with the damage.

Biology
The biology of this pest is not well understood, however the apple leafcurling midge overwinters as pupae in soil under infested trees. Adults (first generation) emerge in May, mate and females begin to lay eggs on developing leaves. Leaves are the preferred site for egg laying, but oviposition also occurs on buds and developing flowers. Several midges may oviposit on the same leaf, or a single female may oviposit on several leaves.

Females generally lay 30-40 eggs per leaf and eggs can take 2-10 days to hatch, depending on temperature. Eggs hatch and larvae begin to feed on leaves. Margins of leaves infested with leafcurling midges are rolled in towards the midvein of the leaf. Larval feeding prevents the infested leaf from unfolding, and the leaf continues to become more tightly rolled as the leaf continues to grow. Mature larvae can pupate in the rolled leaves, but most drop to the ground and pupate in leaf litter on the ground. There are two or three generations produced each season.

Period of Activity
Adults (first generation) emerge in May, mate and females begin to lay eggs on developing leaves. Eggs can take 2-10 days to hatch, depending on temperature. Eggs hatch and larvae begin to feed on leaves. There are two or three generations produced each season.  Leaf curling from larvae can be seen in orchards from petal fall through harvest.

Scouting Notes
Leaf curling and discolouration can be observed during regular orchard monitoring. The presence of this insect is confirmed by yellow or orange larvae inside the curled leaves.

Thresholds
There are no thresholds for leafcurling midge. Management of this insect is generally unnecessary, particularly on mature trees with many leaves which can withstand higher pest pressure. High insect populations in nurseries or in young trees may result in reduced photosynthesis, and stunt the growth of terminal shoots, and control may be needed.

Management Notes

  • Hot dry summers affect the abundance and phenology of apple leafcurling midge. Rainfall softens rolled leaves making it easier for larvae to escape, and reduced rainfall delays development by up to 10 days. 
  • Several beneficial insects (minute pirate bugs Orius spp.) and parasitoids feed leafcurling midge larvae. In Nova Scotia the introduced European parasitoid Platygaster demades (Walker) has been shown to effectively reduce (40% to 90%) the first generation leafcurling midges. It is not known if this parasitoid is present in Ontario.
  • It is very difficult to manage this pest using insecticides since midges are well protected inside curled-up leaves.
  • For a list of products to control this pest refer to OMAFRA Publication 360, Guide to Fruit Production - Chapter 3 Apples (PDF) or Apple Calendar only (PDF) :
  • Broad-spectrum products applied to control other pests in the orchard may be efficacious against apple leafcurling midge.