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How to Manage PestsUC Pest Management Guidelines
DESCRIPTION OF THE PESTSFruittree leafrollers overwinter in the egg stage on limbs. Eggs hatch in early spring. Larvae are dark green with black heads and are about 1 inch long when fully grown; they are difficult to distinguish from obliquebanded leafroller. Adult moths emerge in June or July and deposit overwintering eggs. Adults appear bell shaped when at rest and have dark brown bands running at oblique angles across their wings. The wings are mottled with gold and white flecks. There is one generation a year. Obliquebanded leafrollers occur on a wide range of plants. These leafrollers overwinter as either a second- or third-stage larva within a silken case or hibernaculum. These hibernacula can be found in protected areas of the scaffold limbs, such as pruning scars. The overwintered larvae become active as the buds begin to open. They begin to feed by tying together a number of leaves with silk. They first feed on watersprouts and then move throughout the tree. Those feeding on developing flower buds do so before bloom and continue to consume floral parts throughout the blossom period. This is when they cause the most damage to the almond crop. After petal fall, these larvae continue to feed on developing fruit. Pupation occurs within these sheltered areas and the adult moths generally appear during late May and early June. Eggs are laid in flattened, overlapping masses of up to 300 on the upper surface of leaves. Emerging larvae are greenish yellow caterpillars, usually with black heads but sometimes with lighter-colored heads. Adults are reddish brown moths with alternating light and dark brown bands on the wings; the bands are oblique or chevron shaped. There are two or three generations a year in the Central Valley. DAMAGELeafrollers are occasional pests of almonds. The primary damage occurs early in the season when larvae of the overwintered generation feed on developing nuts and hollow them out. Many of the damaged nuts are lost in the June drop, presumably reducing yield. The summer generation of the obliquebanded leafroller ties leaves and nuts together and feed on the hulls. Leafroller feeding on the hulls increases later nut infestation by navel orangeworm. MANAGEMENTTreatment is not normally needed for leafrollers unless populations are high. If treatment is required, Bacillus thuringiensis and spinosad (Entrust, Success) are environmentally sound insecticides that control leafrollers with less negative impact on natural enemies.
Biological Control
Organically
Acceptable Methods
Monitoring and
Treatment Decisions Degree-day
calculator Degree-day
table In orchards with a history of obliquebanded leafroller problems, monitor after bloom by putting out pheromone traps and sampling developing fruit. Put out pheromone traps by mid-April. (The lower load rate pheromone lures are the best indicators of population levels.) Begin accumulating degree-days once moths have been caught in pheromone traps on two or more consecutive observation dates (the biofix). Use a lower threshold of 43°F and an upper threshold of 85°F (vertical cutoff). (For assistance in calculating degree-days, see "Degree-days".) Begin sampling for larval feeding or for leaves that are tied together at 930 degree-days from the biofix. Apply a treatment when larval activity is first detected; larvae are difficult to control once they are sheltered in leaves that are webbed together.
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UC IPM Pest Management Guidelines: Almond |
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