How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

Obliquebanded leafroller overwinter as third-instar larvae under bud scales. The overwintered larvae pupate in spring, and the first generation of adults emerges in late April or May. 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 usually two generations a year in the Sacramento Valley and up to three in the San Joaquin Valley.

DAMAGE

Infestations of obliquebanded leafroller can occasionally reach damaging levels in nectarines. Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest. Because of the high cyanide content of nectarine leaves, larvae generally concentrate their feeding on fruit; consequently, lower numbers of larvae may cause more damage in nectarines than in other crops. This leafroller is more damaging than fruittree leafrollers because it has one to two summer generations.

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. Throughout the season, watch for the presence of leafrollers while monitoring for other pests. This is especially important in orchards where bloom time sprays and pheromone confusion are used to control peach twig borer and oriental fruit moth.

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
Organically acceptable management tools include biological control and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad.

Monitoring and Treatment Decisions    Degree-day calculator    Degree-day table
Check the orchard in early spring (March–April) for the presence of larvae and feeding damage on flowers (see EARLY SEASON MONITORING). If damaging populations are observed, a number of environmentally friendly insecticides are effective in controlling this pest, including Bacillus thuringiensis, spinosad (Entrust, Success), and methoxyfenozide (Intrepid). The best timing for control of overwintering larvae is at full bloom or early petal fall.

Pheromone traps placed in the orchard in mid-April (see PHEROMONE TRAPS) will help to monitor the population levels of this insect and provide information for management of the summer generations. Based on research done in California pistachio orchards, begin accumulating degree-days as soon as traps begin to catch moths using a lower threshold of 43°F and an upper threshold of 94°F. (For assistance in calculating degree-days, see "Degree-days ".). Make treatments between 600 and 1000 DD.

Also, fruit samples taken every other week after color break (see PREHARVEST FRUIT SAMPLES) will help detect damage from this pest, and a fruit damage sample at harvest will help to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT EVALUATION AT HARVEST). Record results on monitoring forms for preharvest (100KB, PDF) and harvest (100KB, PDF) samples.

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PUBLICATION

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to the insects and mites section:
R. E. Rice, Kearney Agricultural Center, Parlier

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