How to Manage Pests

UC Pest Management Guidelines

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.

DAMAGE

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.

MANAGEMENT

Delayed dormant treatments and bloom time applications for other pests help keep leafroller populations under control. However, regular monitoring each season is important so that prompt action can be taken if damaging populations develop.

Biological Control
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
Biological control is acceptable for use on organically grown apricots as are delayed-dormant oil sprays combined with the Entrust formulation of spinosad, bloom sprays of Bacillus thuringiensis, and springtime sprays of Entrust.

Monitoring and Treatment Decisions
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). For assistance in calculating degree-days, see "Degree-days".

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 treat, make an application at 600-700 degree-days from the biofix (i.e., when the first moths were trapped).

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 (sample form—115 KB, PDF).

• Summary of Important Links

IMPORTANT LINKS

• Degree-day calculator
• Degree-day table
• Harvest fruit damage evaluation form (115 KB, PDF)

Back to management

PUBLICATION

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito Co.
R. A. Van Steenwyk, Insect Biology, UC Berkeley
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare Co.
K. A. Kelley, UC Cooperative Extension, Stanislaus Co.
J. L. Caprile, UC Cooperative Extension, Contra Costa Co.
Acknowledgment for contributions to the insects and mites section:
L. C. Hendricks, UC Cooperative Extension, Merced Co.

Top of page

PDF: You need a PDF reader, such as Acrobat Reader version 8 or later, to view or print this PDF. If no reader is installed on your computer, you can download a free copy of Adobe Acrobat Reader.