How to Manage Pests
UC Pest Management Guidelines
Scientific name: Choristoneura rosaceana
(Reviewed 10/14, updated 10/14, corrected 10/16)
In this Guideline:
DESCRIPTION OF THE PEST
Obliquebanded leafroller overwinter as third-instar larvae under loose scales or pieces of bark. The overwintered larvae pupate in spring and the first generation of adults emerges in late March or April. Larvae are yellowish green with brown to black heads. As they mature, larvae construct tubular shelters from a single leaf. Adults are reddish brown moths with dark brown bands on the wings. There are two or three generations a year in the Central Valley; it is rarely found in Central Coast orchards.
Infestations of obliquebanded leafroller can occasionally reach damaging levels in apricots. Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest.
Delayed dormant treatments and bloom applications for other pests help keep leafroller numbers under control. However, regular monitoring each season is important so that prompt action can be taken if damaging numbers develop.
A number of parasites, including species of Macrocentrus, Cotesia (=Apanteles), and Exochus, attack leafroller larvae. General predators such as lacewings, assassin bugs, and minute pirate bugs may feed on eggs and larvae. Preservation of natural enemy populations is an important part of keeping leafroller numbers low. Use selective materials that are least disruptive of biological control when treating other pests.
Organically Acceptable Methods
Use biological controls, delayed-dormant oil sprays combined with the Entrust formulation of spinosad, bloom sprays of Bacillus thuringiensis, and springtime sprays of Entrust on organically grown apricots.
Calculate degree-days for obliquebanded leafroller in your location.
Learn to use degree-days to time insecticide applications.
Check the orchard in early spring for the presence of larvae and rolled leaves. The best timing for control of overwintering larvae is at full bloom or early petal fall. Fruit harvested before June 15 will not need additional treatments. Fruit harvested after June 15 will need to be monitored for the summer generation.
Place pheromone traps in the orchard of late-maturing varieties in mid- to late April to determine when to make a summer treatment. Using a lower threshold of 43°F and an upper of 85°F, begin accumulating degree-days when the first moths are trapped (generally late April in the southern San Joaquin Valley to May in the central San Joaquin Valley).
Monitor fruit and leaves for caterpillars when about 500 degree-days have accumulated. Currently there are no treatment thresholds. If a decision is made to apply pesticide, make an application at 600 to 700 degree-days from the biofix (i.e., when the first moths were trapped).
Treatments using degree-day timing benefit management of obliquebanded leafroller on late harvested (June through July) varieties or pest abundance the following year. For fruit harvested in May and June, larval treatment is necessary.
Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (example form— ).
UC IPM Pest Management Guidelines:
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
Acknowledgment for contributions to Insects and Mites:L. C. Hendricks, UC Cooperative Extension, Merced County
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