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.
Pear psylla phenology, pre‐bloom kaolin, and insect growth regulators, summer pruning, timing honeydew washes, summer covers, fall kaolin. A presentation by Louis Nottingham, WSU Entomology at North Central Washington Tree Fruit Days, January 20, 2022.
On Thursday, February 18, 2021 as part of an OSU/WSU webinar, Stijn van Laer gave a talk on pear psylla management in northern European pear orchards. Stijn is a crop consultant that works for company called FruitConsult based in Belgium. They are a private consulting firm that does not sell products (i.e., chemicals), just management recommendations. Stijn discussed management of pear psylla in European orchards with conservation biological control (i.e., only using soft insecticides and at economic thresholds) and by augmentation of earwigs. He also discussed the importance of proper sprayer calibration and how this can make or break effective management.
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.
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.
Test of plant defense elicitors for arthropod pest suppression and PR-1 gene induction in pear orchards
Plant defense elicitors (PDEs) are chemicals that stimulate plant defenses against pathogens and herbivores. Previous work shows that PDEs acibenzolar-S-methyl (ASM) and harpinab protein (harpin) can induce the pathogenesis-related gene PR-1 in plants and suppress herbivorous arthropods. In this study, we tested the potential for these PDEs to induce PR-1 in pear, Pyrus communis L. (Rosaceae) orchards and suppress pear psylla, Cacopsylla pyricola (F€orster) (Hemiptera: Psyllidae), and spider mites, Tetranychus spp. (Acari: Tetranychidae). In 2017, we compared densities of each pest on mature pear trees following a single application of either an ASM product (Actigard; Syngenta), a harpin product (Employ; Plant Health Care), or no PDE treatment in four commercial and two research center orchards. In 2018, we sampled pear psylla and used qPCR to assess PR-1 induction in pear leaf samples before and after PDE treatments at one commercial orchard. Neither PDE treatment showed evidence of pest suppression in either year, and no differences in PR-1 expression were detected. Potted greenhouse trees treated with ASM in 2019 showed higher PR-1 expression relative to untreated trees, verifying that our procedures can detect induction and suggesting that a single PDE application was sufficient to induce PR-1 in potted but not mature pear trees. We conclude that plant defense elicitors may contribute to pear pest suppression in some contexts, but effects are unlikely to be strong or consistent. Our results highlight the need for field experiments to advance plant defense elicitor knowledge towards effective field applications.
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: 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.
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.
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 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.
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.
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 firstname.lastname@example.org
Louie Nottingham demonstrates how to sample for pear psylla using the tray tap method, also known as the beat tray method. You will need an 18″ x 18″ beat tray (DYI or available for purchase at some ag chemical companies), a tapping stick and a sampling plan for your orchard.
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.
Pear psylla IPM Recommendations (by Category):
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.
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.
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 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.
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).
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.
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.