Skip to main content Skip to navigation

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

Pear Psylla Phenology Update

June 7, 2021

Pear Psylla’s Current Status: Old nymphs (hardshells) from the first generation are still present but declining. Summerform adults and eggs are rapidly building in cooler locations (Cashmere) and nearing peak at 1500DD in warmer ones (Medford). Early instar nymphs of the second generation are building in all locations, and will peak at 1750DD. Hardshells of the second generation are just starting in all locations.

Fig 1. 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 shows where we are as of June 2, 2021. (Model created by Dr. Vince Jones. Graphic visualization by Dr. Robert Orpet)

Pear psylla IPM Recommendations (by Category):


Particle Films

A particle film should have been applied at 800DD, but if not, do so ASAP to help deter further egg-lay. Our experiments have shown that spraying particle films after egg-lay provides 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 problematic lasting residues on fruit; however, past the first week in June there could be issues, especially for early harvested red pear varieties.

Conventional IPM Insecticides

Two Ultor sprays should occur after petal fall, one at 1000DD and a second 14 days later. If your populations are consistently above 1 psylla adult per tray, you can apply Ultor + Esteem together. Neither Ultor or Esteem will reduce adult numbers but will prevent nymph development. While it may not be immediately gratifying, this slow kill is much better for promoting natural enemies.

*Both Ultor and Esteem can only be used twice per season, and consecutive sprays cannot be applied less than 14 days apart.

Organic Management

Cinnerate and/or neem products (but no neem on Comice) are effective on psylla, but may need to be sprayed as tank mixes and repeatedly from 1000 to 2200DD (around July 1) to keep populations suppressed. Monitor populations to determine spray frequency and tank mixing needs. The goal is to keep your population at or below one psylla per tray. Stop spraying after 2220DD, because these products will not control hardshell nymphs.

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 20002200DD to maximize psylla removal. 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 there is enough honeydew to cause injury. Wash near the end of the hardshell stage for each generation, around 1400, 3000, and pre harvest if honeydew is high. These timings are not exact, but research to determine thresholds and timings for washing is currently underway. If using overheads to wash, 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.

Codling Moth

Remember, a soft codling moth program is critical to conserve natural enemies that control pear psylla. Mating disruption and first sprays should have already occurred by this point. Soft codling moth spray materials include: oil, granulosis virus, Intrepid (methoxyfenozide), Esteem (pyriproxyfen) and Altacor (chlorantraniliprole).

Natural Enemies

All the methods suggested above will have low impacts on natural enemies. Natural enemies like lady beetles (Fig. 2A), predatory bugs (Fig. 2B), and parasitoid wasps (Fig. 2C) are critical to prevent psylla and mite population explosions closer to harvest, and they do it for free! So avoid broad spectrum materials, especially multiple products at a time.

Fig 2. Natural enemies of pear psylla; i.e., your friends! A) Lady beetle feeding on psylla nymphs (L. Nottingham). B) Deraeocoris brevis feeding on psylla nymph (B. Higbee). C) Trechnites insidiosus parasitizing psylla nymph (R. Schmidt-Jeffris).

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.


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.