June 10, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, June 10th, 2014, 8:00 – 9:00 a.m.
Presenter: John Aue, Threshold IPM.
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 10th call download: Click Here

Disease update
Black and white rot
Black and white rot are fungal diseases produced by fungi ubiquitous in forests, orchards and woodlots.  The genus of fungi responsible for these disease are decomposers and are not highly contagious.  Spores remain static with the onset, and spread, of disease resulting from environmental stressors, i.e., cold temperatures, drought and fruit load.  Symptoms can include: delayed development, i.e., small leaves and late bloom, loss of scaffold limbs and tree death.  Options to prevent further infections are removing sources of inoculum, i.e., dead trees, infected limbs and pruning debris, irrigating to reduce drought stress, applying foliar fertilizer for immediate remediation of stress (more effective than ground application for quickly correcting nutrient deficiencies) and defruiting.  Chemical controls are limited to protectant fungicide, i.e., Captan (captan).  Single-site fungicide (apple scab resistance concerns) and sulfur are not recommended.

Fire blight
New trees, in bloom, are highly susceptible to fire blight.  More bacteria are present now then during bloom.  Older flowers, in petal fall, are not vulnerable.  Options for control in this situation are removing blossoms or applying streptomycin within 24 hours of rain event.

Fruit load and thinning report
Crop overall seems light to moderate in most orchard.  Orchards that applied thinners over the week of June 2nd experienced heavy thinning.  Regional fruit set, on average, is one to two fruitlets per cluster.  As a result, many growers are choosing not to thin this season.

Insect update
Plum curculio management
Scouting is suggesting a resurgence in plum curculio populations this season. Orchards with wild hosts are experiencing above average damage.  Damage is continuing for some orchards that have applied perimeter sprays, which may suggest continued weevil immigration into the orchard.  While scouting it is important to continue monitoring perimeter and interior rows to determined appropriate method, i.e., perimeter, alternate-row middle or full cover, of pesticide application. Research suggest that plum curculio immigration ceases at 308 DD, base 50°F, after McIntosh petal fall. Note: materials applied more than a week ago may not be effective.  Most materials used for codling moth control are not effective on plum curculio.  If continued immigration is suspected, a perimeter application is still acceptable. Organic options include maintaining a protective coating of Surround WP (kaolin) on exposed blocks.

Codling moth
Managing resistance
Codling moth has two generations per year and enhance the likelihood of developing resistance to insecticides over time when the same insecticide mode-of-action is targeted to multiple generations during one season.  To prevent resistance it is important to accurately time applications with appropriate materials and to monitor weather conditions between applications.  Monitoring pheromone traps and establishing biofix is critical for effective control.  Traditionally, 250 DD, base 50°F, from biofix is the earliest a larvicide is applied; when population is at three percent hatch.  If high trap counts (10-15 moths in first week) are experience at biofix, it is suggested to apply a material at this time.  If captures are low and higher numbers are experienced later in the flight waiting to apply a material later may be wise. Applying a larvicide at 350 DD allows a greater number of larvae to come in contact with the product.

Resistance results from failing to rotate products between generations and exposing larvae to sublethal material, resulting from incorrect rates and excessive weathering between applications. Resistance can begin to be shown as later flights of codling moth. Note: It is better to miss early in the hatch, when larvae are not exposed, than later in the hatch when, material is present, and larvae are exposed to a sublethal dose.

Mating disruption
If codling moth mating disruption is used, it is important to also monitor lesser apple worm (LAW) and Oriental fruit moth (OFM).  These secondary pests are not affected by mating disruption, yet damage is easily mistaken for codling moth damage and can quickly become severe.  There is not an established threshold for LAW and OFM, rather if high numbers (greater than 30/week) are captured an insecticide application is justified.  Materials registered for codling moth control are also effective for LAW and OFM management.  Note: Orchards without mating disruption should also monitor these species to determine population trends.

Pesticides and acidity
Remember to check pesticide labels for pH requirements.  Do not tank mix products with differing pH requirements. Compatibility should not be a concern for products applied at different times, since pH is only required when the product is in the liquid state.  Most spray particles are dry within minutes of application.