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New Phenology Based Psylla Management

March 1, 2022

Pear Psylla Phenology IPM Guide will help manage pear psylla using the new degree day model!

As temperatures warm and the snow melts, it is time to think about pear psylla management. In warmer areas like Oregon and southern Washington, psylla are already back in the orchards and laying eggs. In central and northern WA, psylla will move into orchards once the snow melts.

IPM strategies for pear psylla provide optimal season-long control by utilizing selective sprays and cultural strategies to suppress psylla while conserving natural enemies. If you have ever wondered why psylla control falls off toward the end of the season, it is likely due to a lack of natural enemies from too many broad-spectrum sprays. This is why we encourage the use of selective management approaches, such as kaolin clay, insect growth regulators (IGRs), organic insecticides, and cultural techniques like tree washing and summer pruning.

In order to help you choose the right approach for your orchard and better understand the development of pear psylla in your region, WSU has created a pear psylla degree day model and associated management strategies. Visit the new page Phenology Based Pear Psylla Integrated Pest Management for the model and strategies. The website is a work in progress and subject to change as we continue to perform experiments and refine the conventional and organic management strategies.

2021-2022 Pear IPM Study Circles

green anjou pear with droplets of water on the side

Join us for pear study circles this winter – they’re free!  It’s a great learning opportunity for growers, consultants, researchers, and industry professionals.  Our goal is to improve pear profitability and sustainability. Each study circle will include a 30 minute presentation and 2 hours of facilitated discussion.

Topics include:

  • Oct 19, 2021 – Choosing products that work: A discussion of pesticide efficacy
    2019-2021 research results from Louis Nottingham, WSU Entomology. Grower experience from the field.
  • Nov 23, 2021 – Honeydew Washing Systems – Adding a Cultural Control to your Toolbox
    2020 research results from Tianna DuPont, WSU Extension. Grower presented case studies.
  • Dec 14, 2021 – Using pear psylla phenology to better time applications
    Outline of the new psylla phenology model from Louis Nottingham, WSU Entomology. Examples of scouting information showing when the model has worked and when it has not. Brief intro to potential scouting app. Discussion of getting weather stations to improve accuracy. Discussion of how growers/consultants want to best access data.
  • Jan 11, 2022 – Assembling IPM programs that work
    Discussion of IPM and bio-based IPM programs step by step through the season and new research on natural enemy impacts of current products, Louis Nottingham, WSU Entomology.
  • Feb 8, 2022 – How can we integrate thresholds and scouting?
    Current research on thresholds for psylla and natural enemies. Input on phone application/website for data access.

Download a flyer here, or visit the WSU Tree Fruit web site events page for more information.  Hope to see you there!

Pre-Harvest Pear Phenology Update

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

Pear Phenology Update, 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: 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.

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.


head shot of a smiling man with dark hair wearing a dark suit with a white shirt and striped tieWritten by:
Louis Nottingham, Ph.D.
Research Assistant Professor
Dept. of Entomology, WSU TFREC, Wenatchee WA

Psylla Phenology and Recommendations

June 1, 2021

Pear Psylla’s Current Status:
Some old nymphs from the first generation are still present but declining. Summerform adults and eggs are building in orchards (about 25-30% of the peak population are now present). Adults and eggs will increase until the peak at 1500 DD. Early instar nymphs of the second generation are beginning (10-15% of total population are present). No late nymphs of the second generation should be present.

Pear psylla life stages (curves) by degree days (x-axis) for three 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 shows where we are as of May 26 2021. (Model created by Dr. Vince Jones. Graphic visualization by Dr. Robert Orpet)

Pear psylla IPM Recommendations (by Category):

Particle Films: If you have not applied a postbloom particle film yet, you can still do so to help deter egg-lay, but it should be done immediately because egg-lay is getting closer to peak. Our experiments have shown that spraying particle films after egg-lay provide some control of nymphs, however, it is less effective than spraying before egg-lay. It is still early enough that particle films will not leave lasting residues on the fruit.

Conventional IPM Insecticides: The first Ultor (spirotetramat) application may have already occurred, but it can still be made at this point if not. Perform the first spray now if you have moderate pressure (around 1 adult per tray on average). If you have consistently more than 1 adult per tray, you can apply Ultor + Esteem (pyriproxyfen, which is also a soft and effective codling moth material). Apply a second Ultor spray 14 days after the first if pressure remains high or increases. Neither Ultor nor Esteem will reduce adult numbers, so this should not be expected. Instead, they will prevent nymph development. While it may not be immediately gratifying, this slow kill has the benefit of providing food to grow predators while suppressing the psylla population.
*Both Ultor and Esteem can only be used twice per season, and consecutive sprays cannot be applied less than 14 days apart.

Organic Management: Now is an excellent time to use Cinnerate and/or neem products (but no neem on Comice) at high label rates. These products should be applied at least twice, if not 3 to 4 times during this generation; ideally, at least one spray would have already been applied. If adult pressure is moderate (around 1 adult per tray on average), either product alone may be effective, especially if a particle film was already used. If pressure is high (greater than 1 adult per tray), these products can be tank mixed to improve efficacy.

Cultural Strategies: Two main cultural strategies can be used for pear psylla: 1. Summer pruning and 2. Honeydew washing. Summer Pruning: The removal of vegetative shoots (water sprouts) from trees. This not only improves spray penetration, it can reduce the psylla population and amount of honeydew in trees, if timed correctly. Aim for 2000-2200DD, before the 3rd generation of adults have begun emerging and all psylla will be in nymph stage and on the shoots. Summer pruning can occur later in the season at 3100DD as well, however, there is a greater a risk of sunburned fruit. Honeydew Washing: The process of washing honeydew from trees by overhead sprinklers or airblast sprayer. This method is different from overhead irrigation because it is only used to remove honeydew (we highly recommend performing general irrigating with under tree sprinklers to reduce the risk of diseases). Because washing too often and for too long can cause disease issues, it is important to only wash when it is necessary. We recommend targeting old nymphs of the second and third generations, so 1600 and 3000 DD. But remember, there is no need to wash if you do not have a fair amount of visible honeydew. If using overheads, we recommend about 6 hours of runtime for a system delivering ~70 gallons of water per acre per minute. A nonionic surfactant like Regulaid can be mixed in halfway through the cycle to improve honeydew removal. For airblast sprayer washes, use at least 800 GPA for smaller trees, and increase gallonage with tree size; the goal is to make water run off all leaves.

Pear Psylla Phenology Update

May 18, 2021

A phenology model for pear psylla was recently developed by Dr. Vince Jones. This model predicts the relative number of pear psylla from each life stage occurring as degree days are accumulated. Below is a graph showing the psylla degree day model and the status of psylla development on May 6th 2021. Degree days were averaged among weather stations in Medford, OR, Hood River, OR, Wapato, WA and Cashmere, WA; the difference from the coolest to hottest location was approximately 110 DD.

Click the graph for the full article.


Codling Moth Task Force

close up of a red apple with multiple black ringed holes indicative of codling moth damage

Mach 9, 2021

Codling Moth Task Force

Codling moth has been the key pest of pome fruits across the growing regions of Washington and Oregon for over 100 years. During that time, pest management programs regularly evolved as key pesticides were phased out and new technology was incorporated. As we continue to adapt new tools and tactics, there is a need to synthesize and evaluate past and current codling moth research and management recommendations, and to communicate that information to stakeholders. The Codling Moth Task Force was created to take the lead in this issue.

Nottingham, L,, C. Adams, E. Beers, M. Doerr, and D. Epstein. 2021. New task force tackles codling moth.  Good Fruit Grower Magazine, March 1, 2021.

Evaluation of IPM for central WA pear orchards

article title and abstract in the journal biological control

February 9, 2021

IPM for Central WA Pear Orchards

Pear psylla and honeydew marking to fruit cause significant economic damage to pears in Washington, a key pear growing region of the United States. The goal of this project is to compare an integrated pest management (IPM) program using materials which selectively target pests and relies on large natural enemy populations to grower standard conventional and organic pear pest management.

Dupont, T., C. Strohm, L. B. Nottingham and D. Rendon. 2021. Evaluation of an integrated pest management program for central Washington pear orchards. Biol. Control. 152: 104390.