Mid-November may feel like an odd time to be talking about caterpillars, but the delayed dormant period is a good time to start managing obliquebanded leafrollers before they have a chance to damage your fruit trees and it's good to be prepared.
Damage caused by obliquebanded leafrollers
Obliquebanded leafrollers (Choristoneura rosaceana) cause different types of damage: their leafrolling behavior reduces photosynthesis; fruit feeding sets the stage for brown rot and deformed fruit, and early stem-feeding can significantly reduce crop size. These pests are primarily attracted to members of the rose family, specifically cherry, pistachio, and plum trees. They have also feed on apple, chestnut, hazelnut, pear, and stone pine trees, as well as blueberries, cane fruits, strawberry plants, and sunflowers. Several popular ornamentals also host these pests.
Obliquebanded leafroller description
Obliquebanded leafroller adults are light- to reddish-brown moths with a unique squarish back end and something of a ridge just behind the head (thorax). They are a mottled tan to brown with wide, offset (oblique) bands of alternating color. The wingspan ranges from 3.0 to 5.5 inches across, with the females being significantly bigger than the males. If you were to get your hands on one of these moths, you would be able to see that the forewings tend to be much darker than the underwings. Obliquebanded leafroller moths look like fruittree leafrollers (Archips argyrospila) and three-lined leafrollers (Pandemis limitata).
Caterpillars are green to yellowish-green with dark heads. [Sorry, I couldn’t find a photo I could use.] They average one inch in length. These garden pests have the unique behavior of crawling backward when disturbed and dropping to the ground with the aid of a silk thread. Left to their own devices, obliquebanded leafrollers, being true to their name, will fold or roll leaves together to create a protective tent while they feed.
Obliquebanded leafroller lifecycle
Masses of 200-900 eggs are laid on the tops of leaves and then covered with a protective wax. They hatch in a week or so. The first instar larvae crawl to safer places, such as the underside of leaves, in buds, or under the calyx of fruit. [The calyx is the protective growth that encases flower buds.] They may also balloon themselves to nearby plants using a silk thread. As these caterpillars go through six instars, they roll leaves around themselves for protection as they feed. Obliquebanded leafrollers overwinter as second-instar caterpillars in crevices of trees, under flower bud scales, and bark. Eventually, they drop to the ground, where they pupate in the soil.
Obliquebanded leafroller management
Most management practices take place in spring and summer. As young caterpillars begin to emerge in spring, you can spray Bacillus thuringiensis on them, followed by spinosad sprays in summer. You can also use pheromone traps to monitor for adult moths.
Assassin bugs, Exochus ichneumon wasps, lacewings, minute pirate bugs, and parasitic Goniozus wasps will attack obliquebanded leafrollers. You can attract these garden helpers by adding insectary plants to your landscape and avoiding the use of broad-spectrum pesticides.
During the delayed dormant period, be sure to spray your trees with the appropriate dormant oil to help control these and other pests. The delayed dormant period is after full dormancy but before the green bud stage. You can also reduce the problems associated with obliquebanded leafrollers by removing water sprouts and thinning fruit properly.
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