Fruit IPM Fact Sheet Fruit IPM Fact Sheet
Obliquebanded Leafroller
Choristoneura rosaceana (Harris)
Family - Tortricidae
Adapted from: Common Tree Fruit Pests NCR 63. by: Angus Howitt, 1993.
Michigan State University
The Obliquebanded Leafroller Choristoneura rosaceana (Harris) occurs throughout the apple-growing areas of the Northeast and Midwest. Until the 1970s, it was considered a minor problem, but since that time, it has become a major pest that has demonstrated a considerable propensity for developing resistance to pesticides.
Host Range
This is a native species that occurs throughout southern Canada and the United States. It infests apple, pear, cherry, plum, peach, rose, raspberry, gooseberry, currant, strawberry and many weeds and it is a major pest of blueberries.
Life Stages
Egg: The eggs are laid in patches that measure about 7 by 14 mm and contain up to 200 eggs. The mass is covered with a cement that, when dry, gives the mass a dull greenish yellow color. Just before hatching, the black head capsule can be seen.
Larva: The head capsule is 1.7 to 1.9 mm wide and light to dark brown or black, though color can vary considerably. All instars have dark brown or black heads, thoracic shields and legs and yellowish green bodies. The coloration of the prothoracic shield varies considerably. Summer generation larvae have little brown pigmentation; spring larvae and overwintering larvae have more extensive and darker coloration. With bodies that range from 20 to 30 mm long, the obliquebanded leafroller larvae are the largest leafroller larvae found in commercial orchards.
Pupa: The pupae at
first are light greenish brown, but they change to a deep reddish brown later. Pupae are
about 11.4 to 13.5 mm long.
Adult: The adults are banded with various shades of tan to chocolate-brown scales. The female is much larger and usually more strongly colored in the forewings; in the hindwings, the distal half is yellowish. Wing span is 24 to 30 mm for females and 17 to 23 mm for males.
Life History
This insect overwinters as a second-or-third-instar larva within a hibernaculum. The hibernacula are found under old bud scales or fragments of the bark, within cracks or roughened areas, and in twig crotches. The hibernacula exteriors are covered with fecal pellets that weather to a dirty gray similar to the color of surrounding plant surfaces. Activity resumes in the spring when the larvae leave the hibernacula and bore into the opening buds. Later, when the leaves become larger, they fold leaves into tubular chambers, where they remain concealed except when feeding. When disturbed, they will desert this shelter, spinning down on a strand of silk.
Pupation occurs within the feeding site and lasts 10 to 12 days. Moths emerge from mid-June to mid-July. Peak activity occurs during the latter part of June. The eggs are laid on leaves shortly after mating. The incubation period of the eggs is 10 to 12 days. A female is capable of laying up to 900 eggs in her seven-to-eight-day oviposition period.
Newly hatched larvae quickly desert the leaves on which they hatched and crawl to leaves nearby or lower themselves by silk strands to other leaves. Winds can transport larvae on these threads for some distance. The larvae select an initial site for feeding on the undersurface of a leaf along the midrib or other large vein. First-generation larvae complete their development sometime between late July and late August. They feed on water sprouts and fruit. A shortage of water sprouts may limit their numbers because first-instar larvae need actively growing leaves or fruit tissue. Pupation takes place in their final feeding sites.
Adults are on the wing from mid-August to late September. The incubation period and the activity of the second-generation larvae are the same as those of the first generation. Most of the larvae overwinter on the host plant. Some first-instar larvae will be carried on their silken threads to other hosts. Second-generation larvae feed until they reach the third instar. At this time, they seek out suitable winter quarters on the tree and spin a hibernaculum. This usually occurs between late August and late September.
Injury or Damage
During the prebloom period, overwintering larvae feed inside bud clusters and on various floral parts. Larvae continue to feed on the flowers during bloom and on developing fruit after petal fall. When apple fruits are attacked, the more heavily damaged ones fail to survive. Surviving apples bear corked-over-scars at harvest. This injury cannot be distinguished from damage by fruit tree leafroller and green fruitworm but is generally deeper and wider than that of the redbanded leafroller. They gouge deeply into young fruit. Numbers of overwintering larvae decrease after petal fall, but fruit damage increases as the remaining large larvae feed more on fruit as the season progresses.
Though most damaged fruits drop before harvest, some remain on the tree. Most of the severe damage to fruit caused by overwintering larvae occurs after petal fall. The larger the fruit becomes before it is damaged, the more likely it is to develop and remain on the tree until harvest. In late July, larvae of the summer generation can be found on actively growing terminals inside the canopy and on terminals and older leaves near fruit clusters.
Monitoring
Using a base of 43 degrees F, degree-days (DD) 43 for obliquebanded leafroller activity are:
| 600 DD | first adult emergence |
| 800 DD | first eggs laid. |
| 1,150 DD | peak adult emergence |
| 1,250 DD | peak egg laying |
| 2,050 DD | first emergence of second-generation adults |
| 2,300 DD | first eggs laid by second-generation adults |
Because of a wide host range, pheromone traps are unreliable for indicating whether sprays are needed. At tight cluster examine 10 clusters per tree on 10 trees, the treatment threshold is 5 damaged clusters. At the early petal fall stage, examine 20 clusters per tree in five trees for each orchard. On each tree, look for larvae or larval feeding on six clusters on the outside of the tree , 6 clusters in the center and eight clusters near the treetop. Treatment is recommended if you find an average of two or more larvae or fresh feeding sites per tree. Use pheromones to determine when emergence of summer brood starts; then each week, examine 10 fruit clusters and 10 terminals in the outside, center and top of five trees per orchard. Treatment is recommended if there is an average of three or more larvae per tree. Pheromones can also be used to time a pesticide application to 10% egg hatch. Controls are applied 330 DD 42 after biofix (capture of 1st adult in trap).
Control
Broad spectrum insecticides will usually control this pest in larval and adult stages. Sprays applied at pink stage or petal fall will prevent damage from the overwintering larvae. Timing of summer sprays should be based on pheromone trap catches. In some areas, this pest has become resistant to some pesticides, including organophosphates, so chemicals with a different mode of action may be required to control it.
