Description of the Pest
Larvae of the obliquebanded leafroller are yellowish green caterpillars with a dark head capsule. When disturbed, they wiggle backwards and drop to lower leaves or to the ground on a silken thread. Larvae fold or roll leaves together to form protective shelters in which they feed. Adult moths have dark brown bands running at oblique angles across their wings. Obliquebanded leafroller overwinters as second-instar larvae under bark and in crevices of trees. There are three generations each year in the pistachio-growing areas of the state.
Obliquebanded leafroller larvae cause two types of damage to pistachios. When populations are high, leaves are tied together, which kills portions of leaves and reduces the overall photosynthetic capacity of the trees. The most important damage to the crop, however, is when larvae invade the clusters from June to August and feed on the peduncles (stems). This causes the peduncles to dry and shrivel, thus reducing crop yield.
Spring treatments of young caterpillars with Bacillus thuringiensis or spinosad and monitoring with pheromone traps to time summer applications are the key approaches to monitoring this pest in pistachio.
There are several parasite species (Macrocentrus iridescens, Habrobracon gelechiae Bracon sp. and Goniozus sp.) that attack obliquebanded leafroller and can significantly reduce its populations in the second and third generations. None of these parasitoids are commercially available (the Goniozus species that attacks obliquebanded leafroller is not the same species (G. legneri) that attacks navel orangeworm.
Organically Acceptable Methods
Springtime sprays of Bacillus thuringiensis and summer spray of the Entrust formulation of spinosad are acceptable for use in an organically managed orchard.
Monitoring and Treatment Decisions
Calculate degree-days for obliquebanded leafroller in your location.
Learn how to use degree-days to time insecticide applications.
Right after budbreak, start looking for obliquebanded leafroller strikes and leaf ties. Record observations for future pheromone trapping and management decisions.
To time summer treatments,
- Put out pheromone traps by late-April.
- Check traps twice per week to identify the biofix date.
- Continue to examine trees for leaf rolls, leaves tied together, and live larvae when traps indicate adults have emerged.
- When male moths are first found in traps (biofix), begin degree-day calculations (upper threshold 94°F, lower threshold 43°F).
- Treat when 800 degree-days have accumulated.
|Common name||Amount per acre**||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|A.||BACILLUS THURINGIENSIS ssp. KURSTAKI#|
|(various products)||Label rates||4||0|
|MODE-OF-ACTION GROUP NUMBER1: 11.B1|
|COMMENTS: Apply when trees are beginning to leaf out and small larvae first emerge from bark scales. Bacillus thuringiensis is a stomach poison and must be consumed by the caterpillar; therefore, it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective when larvae are young. May require more than 1 treatment; apply second application 7 to 10 days after the first. Can be used during bloom.|
|MODE-OF-ACTION GROUP NUMBER1: 5|
|(Intrepid 2F)||8–16 fl oz||4||14|
|MODE-OF-ACTION GROUP NUMBER1: 18A|
|MODE-OF-ACTION GROUP NUMBER1: 28|
|MODE-OF-ACTION GROUP NUMBER1: 6|
|COMMENTS: Do not apply near aquatic areas. Proclaim is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.|
|(Brigade WSB*)||8–32 oz||12||7|
|MODE-OF-ACTION GROUP NUMBER1: 3|
|COMMENTS: Do not apply near aquatic areas. Brigade WSB is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.|
|(Warrior II with Zeon*, etc.)||1.28–2.56 oz||24||14|
|MODE-OF-ACTION GROUP NUMBER1: 3|
|COMMENTS: Do not apply near aquatic areas. Warrior II is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.|
|(Danitol 2.4EC*)||10.66–21.33 fl oz||24||3|
|MODE-OF-ACTION GROUP NUMBER1: 3A|
|COMMENTS: Do not apply near aquatic areas. Danitol 2.4EC is a restricted-use pesticide because it is highly toxic to fish and aquatic organisms.|
|(Imidan 70W)||4–4.33 lb||72||14|
|MODE-OF-ACTION GROUP NUMBER1: 1B|
|COMMENTS: Do not apply after hull split reaches 10%. Buffer water to pH 5 prior to mixing insecticide.|
|**||Unless otherwise noted, apply with enough water to ensure adequate coverage.|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.|
|#||Acceptable for organically grown produce.|
|1||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.|