Insect Pests of Saskatoons

 
 
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  Apple curculio | Saskatoon sawfly | Wooly elm aphid | Prairie tent caterpillar | Leaf rollers |Saskatoon bud moth | Plant bugs | Cherry shoot borer | Hawthorn lace bug | Cecidomyiid midges | Pear slug

An important part in the production of any fruit crop is to know what type of insects could cause production losses. A crop is at risk throughout the fruiting cycle. Insects can attack plants during flowering, fruit formation or just before harvest of the plump, juicy berries. A successful pest management program includes: insect identification; pest number and damage monitoring; what population numbers warrant control and knowing when the pest can be effectively controlled.

Apple Curculio
(Tachypterellus quadrigibbus)

Identification

  • 5 mm long, reddish brown weevil with a long curved snout
Life cycle
  • adults appear 5-10 days after petal fall
  • adults lay eggs, one per fruit, about 28-33 days after the peak flowering period
  • egg laying punctures on the young fruit are at the base close to the stem
  • the puncture is sealed with excrement
  • larval development takes less than 31 days, pupation less than 7 days
  • larva feed on the developing seed in the fruit
  • adults emerge from fruit mid July
  • adults drop to ground and overwinter in leaf litter
  • there appears to be no feeding after emergence
Damage
  • misshapen, hard fruit

Apple Curculio on a Saskatoon


Apple Curculio egg in a
Saskatoon berry

Saskatoon Sawfly
(Hoplocampa montanicola)

Identification
  • adults are a 6 mm long sawfly with yellow with brown markings
  • mature larvae are 6 mm long with yellow-brown head
Life cycle
  • appears in May, just prior to maximum flowering (25% bloom)
  • lay eggs in the nectaries of flower blossoms, the position is marked externally by a dark scar along the calyx of the flower
  • one egg is laid in each flower
  • eggs hatch after petal drop
  • the larvae feed on the top of developing fruit
  • on average, one larva will ruin 2 fruit per cluster
  • the last fruit attacked is completely hollow
  • mature larva drop out of the fruit at the end of June
  • overwinters in the soil
  • pupates in the spring

Immature sawfly larva

Damage
  • can cause large numbers of fruit to drop
  • more than 90% of the potential fruit crop can be lost
  • causes fruit to be hollow and mummified

Wooly Elm Aphid
(Eriosoma americanum)

Identification
  • blue-black in color with white woolly masses on posterior end
Life cycle
  • overwinters on an elm tree as an egg
  • the egg hatches into a "stem" mother; which moves to the leaves, where she starts feeding
  • without mating, the stem mother gives birth to live young
  • while feeding, the aphid injects fluid into the elm leaves, causing the leaves to curl and galls to form
  • approximately the time the wild roses and lilacs bloom, aphids move from the elm tree to the roots of the saskatoon and establish colonies there
  • in the fall, the aphids return to the elm tree to lay eggs for overwintering
Damage
  • heavily infested saskatoons may fail to leaf out in spring
  • moderately infested saskatoons may leaf out in spring, but will not grow vigorously
  • may have small chlorotic leaves
  • once exposed to hot weather, the plants die
  • seedlings and plants less than 5 years old seem to be most affected


Winged Wooly Elm Aphid


Wooly Elm Aphid in roots of Saskatoon

Prairie Tent Caterpillar
(Malacosoma c. lutescens)

Identification
  • adults are stout bodied moths, chocolate brown to dark buff in color with two whitish bands across the front wings
  • wingspan of 30-40 mm
  • the caterpillar has a black back with a whitish middorsal stripe
  • the sides of the caterpillar body are light blue with sparse hairs
  • the cocoon is multi-layered and yellowish white
Life cycle
  • the eggs are laid at the base of host plant, within 30 cm of ground
  • they are covered with a frothy substance
  • they hatch in the spring with a flushing of host foliage
  • the caterpillar construct silken nest near fork in stem
  • when feeding, the caterpillar move out from nests leaving a trail of silk behind
  • they return to the nests at night or during bad weather
  • they feed for 6-8 weeks, depending on the weather
  • then spin a cocoon and emerge in about 3 weeks
  • one generation per year
Damage
  • the caterpillars spin webbed tents around leaves and branches of host plant
  • they feed inside the tent
  • repeated defoliation results in a setback of fruit production

Leaf Rollers
(Archips argyrospilus/Choriostoneura rosaceana)

Identification
  • a diverse group of moths
  • the caterpillar is slender, green to brown, 12 mm in length with a dark-brown or black head
  • usually very active and moves backwards when disturbed
Life cycle
  • the eggs are laid on leaves
  • the larvae change from pale green to greyish brown as they mature
  • the larvae roll a leaf around their body to pupate
  • could be 2 generations per year
Damage
  • holes are eaten in leaves, later the leaves are folded in half and webbed together, which causes the leaves to turn brown and die
  • leaf rolling includes the fruit, resulting in lower yields


Fruit-tree Leafroller


Fruit-tree Leafroller in pupate

Saskatoon Bud Moth
(Epinotia bicordana)

Identification
  • the adult is a small greyish-black moth with tinges of brown
  • the larva is a light green to whitish worm, with dark head
Life cycle
  • adult emerges in April, lays eggs at bud base and in crevices of bark
  • larvae hatch in late April to early May
  • larvae burrow into the buds around the time of flower bud break (green tip) to tight bud cluster
  • they feed on the interior of flower buds
  • as the insect matures, they web individual flowers in the flower cluster together and continue feeding
  • larva numbers of 1 or more per bud cluster are common
  • larva development is complete shortly after the flower petals fall

Bud Moth


Bud Moth Larva


Plant Bugs
(including the tarnished plant bug Lygus lineolaris)

Identification
  • adults are 5-6 mm long, 2.5 mm wide and flattened
  • they are pale green to reddish-brown in colour with a distinct triangle or "V" mark 1/3 way down back
  • they are difficult to see because they fly or move rapidly
  • young nymphs are dull blue-green
  • they look similar to aphids, but lack cornicles and move much faster
Life cycle
  • adult overwinters under debris or plant cover along fence lines
  • in the spring, they feed on early growing plants
  • they mate, then migrate to crops suitable for feeding
  • egg laying begins as early as mid May (in south) to mid June (in Peace country)
  • nymphs develop into adults in 12-34 days, depending on the temperatures -- the hotter the weather, the faster they develop
  • they are strong flyers
Damage
  • when feeding, the Tarnished Plant Bug punctures the plant tissue and sucks the sap

Cherry Shoot Borer
(Argyresthia oreasella)

Identification
  • small, silver white moth with dark gold markings
  • present in June and again in late July to mid Aug
  • the light green caterpillar is 7 mm when full grown
Life cycle
  • overwinters as an egg on leaf buds
  • the larva tunnel into young shoots in May
  • the larva exits the stem, then pupates
Damage
  • late May or early June--new green shoots wither and die
  • look for a small hole at the base of the stem and cut open, then look for light a green caterpillar

Hawthorn Lace Bug
(Corythucha cydoniae)

Identification
  • the adult is oval or rectangle in shape
  • it has a lace-like appearance and the head is covered with a hood
  • the larvae are identical to the adults, just smaller


Hawthorn Lace Bug eggs on Saskatoon leaf

Life cycle
  • the eggs are laid in early spring on leaf underside
  • the eggs hatch in 3 weeks, then the larvae feed on the leaves
  • the adults emerge in mid summer
  • the second generation completes its development by early fall
  • overwinters as adult in leaf litter
Damage
  • mottling of foliage
  • leaves become leathery and tend to drop prematurely
  • will also leave dark, tarry excrement drops on the leaf underside

Cecidomyiid midges
(Cecidomyia sp.)

Identification
  • the adult is a slender fly
  • the larvae are small, legless maggots
Life cycle
  • little is known of the life cycle
Damage
  • finger-like galls on the leaves
  • they do not cause serious damage to the host plant

Pear Slug
(Caliroa cerasi)

Identification
  • green-black, slug-like larva
  • adults are a shiny black sawfly and house fly size


Pear Slug damage to Saskatoon

Life cycle
  • two generations per year
  • adults lay eggs in slits in leaves
Damage
  • larvae rasp away the leaf surface
  • skeletonized leaf turns brown and dries up
  • feeding damage occurs in June and again in late August
 
 
 
 
For more information about the content of this document, contact Shelley Barkley.
This information published to the web on November 27, 2001.
Last Reviewed/Revised on November 24, 2008.