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Beginner

Scientific Name
Choristoneura roseceana

Identification
Eggs:

• Laid on the upper surface of the leaves in patches (7-14 mm) that contain several hundred eggs and resemble small overlapping scales.
• Masses are light green to yellowish green in colour.
• Prior to hatching, contents of individual eggs turn black and the dark head of larva is seen.
• After hatching, empty egg masses often remain on leaves and appear white against the dark green leaf.

Larvae:

• Six instars.
• 20-30 mm long at maturity.
• Body is light green to yellowish green to dark green.
• Head capsule is usually dark brown or black with a similar coloured segment just behind the head (prothoracic shield).
• The edge between the head capsule and prothoracic shield is often white or cream.

Pupae:

• Dark reddish brown.
• Develop in protected places, often found inside leaves rolled by the larvae.
• Length varies from 11-14 mm.

Adults:

• A moth that is variably coloured, light tan to dark brown with darker bands on the forewings.
• Females are larger and generally darker than the males.
• The wingspan of the males ranges from 16-22 mm, and the female from 24-30 mm.
• Females are poor flyers, and both sexes are most active at dusk (crepuscular).

Damage:

• Overwintering larvae feed on developing fruitlets resulting in deep gouges in small apples; these fruit often abort, if not they have large russetted indentations and corky scars.
• Summer generation larvae feed on the surface of fruit and can cause extensive damage that scabs over and is often surrounded by light coloured areas where leaves are attached.
• Late season damage is characterized by several tiny, or a singular circular excavation on the fruit surface.

Often Confused With

• Red banded leaf roller and green fruit worm larvae- to distinguish the obliquebanded leafroller from other leafrollers look for dark brown or black head capsules and green bodies.
• Damage by other spring-feeding caterpillars- Damage to fruit by the obliquebanded leafroller resulting in large russetted indentations and corky scars is indistinguishable from feeding damage by other spring-feeding caterpillars.
• Bird pecks or codling moth stings- Late season pin point damage by obliquebanded leafroller can be mistaken for bird pecks, or for codling moth stings.  However codling moth stings have frass, and the hole extends deeper into the fruit, while obliquebanded leafroller are surface chewing that often have white webbing around the hole.

Period of Activity
The first generation of leaf rollers is a problem from the end of tight cluster until the beginning of petal fall. The second generation is active from the end of petal fall until harvest.

Scouting Notes
Monitoring techniques for obliquebanded leafroller vary depending on the generation targeted. For overwintering larvae present during the period between tight cluster and petal fall, check 5 terminal shoots and 5 fruit buds in each of 10 trees (50 terminals and 50 fruit buds in total) for signs of caterpillar feeding activity. After petal fall inspect 10 terminals from 10 trees for damage/larvae.

Thresholds
Apply an insecticide in orchards if 1% to 2% of terminals or buds have larvae or damage, or if orchards have a history of damage. Apply insecticides for overwintering larvae at petal fall.

Predict the timing and application of products to manage the summer generation with pheromone traps and a degree day model, then follow up with field monitoring for larvae and fruit damage.

Advanced

Scientific Name
Choristoneura roseceana

Identification
Eggs are laid on the upper surface of the leaves in patches (7-14 mm) that contain several hundred eggs and resemble small overlapping scales. Egg masses are light green to yellowish green in colour. Prior to hatching, contents of individual eggs turn black and the dark head of larva is seen. After hatching, empty egg masses often remain on leaves and appear white against the dark green leaf.

Larvae progress through six instars, growing to a final length of 20-30 mm. The body is coloured light green to yellowish green to dark green. The head capsule is usually dark brown or black with a similar coloured segment just behind the head (prothoracic shield). The edge between the head capsule and prothoracic shield is often white or cream.

Pupae are a dark reddish brown, and develop in protected places, often found inside leaves rolled by the larvae. Length varies from 11-14 mm.

The adult moth is variably coloured, light tan to dark brown with darker bands on the forewings. Females are larger and generally darker than the males. The wingspan of the males ranges from 16-22 mm, and the female from 24-30 mm. Females are poor flyers, and both sexes are most active at dusk (crepuscular).

Overwintering larvae feed on developing fruitlets, resulting in deep gouges in small apples. These fruit often abort around June drop. Fruit that remains until harvest has large russetted indentations and corky scars.

Larvae also feed on terminal shoots in spring or summer. The summer generation larvae feed on the surface of fruit often under a leaf or where two apples contact. Damage can be extensive and appear as corky russetting at harvest, and is often surrounded light coloured areas where leaves were attached.

Late season damage to fruit is characterized by several tiny, or a single circular excavation on the fruit surface where young overwintering larvae chew small holes in the skin of the apple. Late season damage, or pinpoint damage, is often not noticeable at harvest but becomes apparent as flesh around the hole decays or dries out in storage. Fruit injury in all cases is most common where two or more fruit are clustered or where a leaf is in contact with a fruit. These areas offer a great degree of shelter to the larvae.

Often Confused With

• Red banded leaf roller and green fruit worm larvae- to distinguish the obliquebanded leafroller from other leafrollers look for dark brown or black head capsules and green bodies.
• Damage by other spring-feeding caterpillars- Damage to fruit by the obliquebanded leafroller resulting in large russetted indentations and corky scars is indistinguishable from feeding damage by other spring-feeding caterpillars.
• Bird pecks or codling moth stings- Late season pin point damage by obliquebanded leafroller can be mistaken for bird pecks, or for codling moth stings.  However codling moth stings have frass, and the hole extends deeper into the fruit, while obliquebanded leafroller are surface chewing that often have white webbing around the hole.

Biology
The overwintering generation exists as second or third instar larvae in hibernacula (temporary cocoons) under the bark or in the limb crotches. Larvae become active in early spring (tight cluster to bloom), once temperatures rise above 10ºC, and move to developing fruit spurs and flower buds. As leaves expand, larvae move to new terminal growth where they web and roll up the terminal leaves, hence the name leafroller. This strategy evolved as a defense from predators such as birds, and also serves to protect larvae from insecticide treatments. Pupation usually takes place in early June inside rolled leaves. Moths emerge over a four to five week period from late June through July. Much of the mating and egg laying occurs in the upper portions of the trees, and egg masses are also found in the lower canopy. Newly emerged larvae (or summer generation larvae) disperse from egg masses by crawling to other leaves or dangling from silken threads. Wind currents disperse these ballooning larvae to surrounding trees. These larvae initially feed on leaves in and around terminal growth. By early July, when terminal growth begins to harden off, larvae move to fruit clusters and feed on fruit and adjacent leaves. Larvae then pupate and adults emerge from early August through early September. Adults mate and lay eggs and larvae from this generation are active well into September when enter overwintering hibernacula. The obliquebanded leafroller has two generations a year. 

Period of Activity
The first generation of leaf rollers is a problem from the end of tight cluster until the beginning of petal fall. The second generation is active from the end of petal fall until harvest.

Scouting Notes
Monitoring techniques for obliquebanded leafroller vary depending on the generation targeted. For overwintering larvae present during the period between tight cluster and petal fall, check 5 terminal shoots and 5 fruit buds in each of 10 trees (50 terminals and 50 fruit buds in total) for signs of caterpillar feeding activity. After petal fall inspect 10 terminals from 10 trees for damage/larvae.

Predict the timing and application of products to manage the summer generation with pheromone traps and a degree-day model, and then follow up with field monitoring for larvae and fruit damage.

After petal fall, four pheromone traps are hung in each 10 ha block at a distance of 30 m between traps along an orchard row. Place in easily accessible areas in block ideally with historically high injury problems. Fasten traps to limbs at eye level where airflow is good. Check traps twice a week and record all moth catches.

The degree day accumulations for the obliquebanded leafroller degree model starts when first sustained moth catch occurs. Using recorded daily maximum and minimum temperatures, daily degree days Celsius (DDC) are calculated using the following equation:

DDC = maximum ºC + minimum ºC    - 6.1ºC
                                             2

DDCs are summed each day. At 244 DDC, egg hatch of the summer generation begins and at 433 DDC, 95% egg hatch has occurred. Immature larvae are very small and difficult to see. Larvae initially feed on tender growing terminals, water sprouts and developing fruit. After they reach the third instar, larvae cause more damage to fruit. Monitor for emerging larvae by examining 10 shoots and 10 fruit on 10 trees in a 4 ha block for the presence of larvae or feeding damage. Often damage is more apparent in orchards than are larvae.

Thresholds
Management for the summer generation is recommended if 1% to 2% of terminals or fruit/blossoms are infested. Resample the orchard in three to five days to ensure the population was not underestimated. Once 240-280 DDC is reached and 1% to 2% of terminals or fruit are infested, an insecticide is recommended. Follow up sprays may be required because of the extended larval emergence of the summer generation (four to five weeks).

Management Notes

• Although obliquebanded leafroller attack all apple cultivars, some such as Gingergold, Paulared, Jerseymac and other early varieties, sustain greater amounts of damage – perhaps since these varieties are more difficult to thin and have larger leaves. Injury levels of up to 50% are observed on Red Delicious, McIntosh, Ida Red, Golden Delicious, Mutsu, Spartan and Cortland.
• A number of parasitic wasps (Ichneumonidae, Braconidae, Trichogrammidae) and flies (Tachinidae) will attack obliquebanded leafroller larvae. These parasitoids can suppress population numbers, but cannot provide complete biological control.
• Several cultural practices reduce the severity of injury from obliquebanded leafroller. Diligent chemical and hand thinning of fruitlets to singles make less favourable feeding sites.
• Annual pruning to maintain an open canopy improves spray coverage.
• Avoid excess nitrogen to prevent excessively lush and prolonged vegetative growth that is attractive to obliquebanded leafroller.
• Implement resistance management programs to ensure long-term effectiveness of available insecticides, see OMAFRA Publication 360, Fruit Crop Protection Guide, for more information.
• When using chemical control, always use the same insecticide within a generation.
• When applying an insecticide for both generations, be sure to use a product from a different chemical family for each generation.
•  For more information on the products available to manage obliquebanded leafroller and resistance strategies, see OMAFRA Publication 360, Fruit Crop Protection Guide - Chapter 2 Apples or Apple Calendar only :
  • Recommendations for oblique-banded leafroller at Petal Fall/Calyx, Special sprays as well as in Non-bearing orchards