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Pear Psylla Phenology Update

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Written by Louis Nottingham, August 9, 2021

Pear Psylla’s Current Status:

The 2nd generation of summerform adults are at or past peak in most regions. Young nymphs of the 3rd generation are nearing peak and increasing. Hardshells of the 3rd generation are within the first 25% and rising. If biocontrol is present in orchards (IPM and organic orchards) the nymphs of the 3rd generation will likely remain below injury level without need for further management.

graphs showing the current pear phenology (adult and egg, blue; early nymph yellow; old nymph orange) for three sites: cashmere, Hood River and Wapato, and Medford

Graphs: Pear psylla life stages (curves) by degree days (x-axis) for three pear growing regions. Each life-stage curve shows relative abundance of the total predicted population. Adults and eggs are combined because the summer generations occur almost simultaneously. The vertical line represents Aug 8, 2021.

Pear Psylla IPM Recommendations (by Category):

  • Particle Films: Due to the proximity to harvest, it is not recommended to spray particle films. Additionally, particle films can increase pressure from spider mites and rust mites.
  • Honeydew Washing: Nymph numbers are increasing; honeydew washing may be necessary in the next 1-2 weeks, targeting 3700DD (between early nymph and hardshell peak). Scout weekly looking for dripping leaves and wash as necessary to remove honeydew.
  • Summer Pruning (“suckering”): Manually removing vegetative shoots is an effective way to remove psylla nymphs and improve spray coverage. However, this tactic can be risky at this point in the season due to the potential for sunburn. If you choose to summer prune, consider lighter pruning (20-50% shoot removal). Have pruners select shoots with the most honeydew to remove as much psylla and potential injury as possible.
  • Psylla Insecticides:
    • Conventional: The optimal time to spray (if necessary) is at 3500DD when young nymph are at peak, which will occur within the next 1-2 weeks, depending on your region. Choose a material that has low potential to disrupt natural enemies and offers some systemic action such as Admire Pro (imidacloprid) or Actara (thiamethoxam). Be mindful of your harvest time and the PHIs of each material.
    • Organic: Most organic orchards should have adequate biological control to make spraying for psylla unnecessary at this point. If this is not the case, the two most effective materials for psylla are neem products (Aza-Direct, Neemix, Rango) and Cinnamon oil (Cinnerate). These products can be safely mixed to increase efficacy and they are still unlikely to harm natural enemies. Be aware that either of these products can pool at the calyx end of fruit causing a ring. This seems to be related to spray volumes around 200 gpa, so it is important to calibrate sprayers to avoid this marking. Do not use neem product on Comice due to phytotoxicity.
  • Spider Mites:
    • Conventional: Many people have been battling mites all year. It is important to remember that mites are induced by over-spraying broad spectrum insecticides and miticides or particle films. In the future, follow soft or organic spray programs to avoid this issue. Soft materials that are still (relatively) effective against spider mites include Nealta, Onager, Apollo, and Acramite; Vendex. Envidor, Agri-mek, and Zeal are moderately soft. Other products that may still be effective but are less selective are FujiMite and Nexter. Be sure to check PHIs of any material selected.
    • Organic: Organic options for mite control are limited, but mites are often less of a problem in organic orchards due to biocontrol. Mites can be flared by some organic materials such as particle films or spinosad products like Entrust. Cinnerate and Rosemary oils (TetraCurb, Ecotec and others) help suppress spider mites with minimal non-target effects.

Codling Moth:

Codling moth is more of a challenge in further south regions and when more apples are present. If you are in a region that primarily grows pears and is cooler, codling moth is probably easily controlled with mating disruption, oil and 1 or 2 Altacor applications. If your pressure is high, you may need to include additional sprays, but they can still be soft. Consider using virus (Cyd-x HP) for mid to late summer sprays. Soft codling moth programs are much more effective when coupled with mating disruption, so if you are not currently using it, consider doing so next year.

collage of four photos showing closeups of "derry" psylla predator, ladybugs, lacewing eggs and trechnitesNatural Enemies:

Keep an eye out for natural enemies in your orchards (check out this beat tray sampling tutorial: https://www.youtube.com/watch?v=y-kXrHh0MP0). If you can find at least 1 natural enemy in 10-15 taps, you likely have better biological control than you realize. These predators and parasitoids will control your psylla and mites for free, so try to conserve them by using soft spray materials and avoiding unnecessary sprays.

Funding and Acknowledgements: This project is funded by the Fresh and Processed Pear Committees of Washington and Oregon and a WSDA Specialty Crop Block Grant. The psylla model was developed by Dr. Vince Jones. Model visualization graphics are being performed by Dr. Robert Orpet. Thanks to Dr. Rebecca Schmidt-Jeffris and Tianna Dupont for data and help with recommendations.

Funding and Acknowledgements: This project is funded by the Fresh and Processed Pear Committees of Washington and Oregon and a WSDA Specialty Crop Block Grant. The psylla model was developed by Dr. Vince Jones. Model visualization graphics are being performed by Dr. Robert Orpet. Thanks to Dr. Rebecca Schmidt-Jeffris and Tianna Dupont for data and help with recommendations.

Use pesticides with care. Apply them only to plants, animals, or sites listed on the labels. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions. If pesticides are spilled on skin or clothing, remove clothing and wash skin thoroughly. Store pesticides in their original containers and keep them out of the reach of children, pets, and livestock.

YOU ARE REQUIRED BY LAW TO FOLLOW THE LABEL. It is a legal document. Always read the label before using any pesticide. You, the grower, are responsible for safe pesticide use. Trade (brand) names are provided for your reference only. No discrimination is intended, and other pesticides with the same active ingredient may be suitable. No endorsement is implied.

Written by:
Louis Nottingham, Ph.D.
Research Assistant Professor
Dept. of Entomology, WSU TFREC, Wenatchee WA
louis.nottingham@wsu.edu

Washington State University