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Pear Psylla Phenology Model

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Authors: Louis Nottingham, Robert Orpet, WSU Entomology. March 1, 2022

How to use this Webpage

  1. Consult the degree-day table to determine the current cumulative pear psylla degree-days from your closest weather station
  2. Visualize current and projected pear psylla phenology on the management timings figure
  3. Consult the table of conventional and organic management for guidelines on current and future management

More Info

  • Subscribe to DAS for the full version updated daily for all weather locations across Washington, and also get access to other useful models like codling moth, fire blight, natural enemies and pear bloom (new!).
  • You can learn more about this webpage including the development of the management guidelines, the phenology model, and biocontrol and natural enemies at the bottom of this page.
  • Download a two-page summary handout.

Pear Psylla Degree Days and Management Timings

graph showing the different lifestages of pear psylla against degree days

 

2022 Pear Psylla Degree Days (PDD), Updated Weekly

Rotate your mobile device to see the full table width

2022 Cashmere Omak Peshastin Wapato Wenatchee Hood River Medford
28-Feb 57 6 48 92 55 113 313
7-Mar 99 27 78 146 95 161 354
14-Mar 125 48 95 183 123 196 408
20-Mar 160 80 120 220 159 228 447
27-Mar 240 143 188 298 242 308 542
3-Apr 310 208 246 372 321 372 615
10-Apr 353 253 273 419 368 409 681
17-Apr 365 274 281 427 382 424 704
24-Apr 419 324 322 483 442 474 762
1-May 491 391 377 555 523 532 832
8-May 575 483 442 639 620 606 907
15-May 646 552 497 721 705 680 983

 


 

Dormant, 75 – 100 PDD

Conditions:

  • Pear psylla: winterform adults are colonizing orchards. Egg lay is starting on woody areas around buds.
  • Natural enemies: Trechnites wasps are overwintering in parasitized pear psylla nymphs, Campylomma are overwintering as eggs under bark scales, and Deraeocoris adults are present.

75-100 PDD Conventional Management:

  • Pear psylla: spray a particle film as soon as you can after 75 PDD or March 1 (whichever is earlier) to deter pear psylla adult colonization and eventual egg laying. Particle films (Surround CF or Celite 610 at 50 lb/acre) reduce pear psylla adult colonization and egg lay by 80–99%. This reduces pear psylla pressure substantially for the entire first generation. Adding a spreader sticker increases the residual effectiveness of particle films. Mix particle films carefully and clean filters frequently to avoid clogged filters and nozzles.
  • Pear psylla/mites: lime sulfur can suppress pear rust mites, spider mites, and pear psylla adults. Wettable sulfur is effective against mites but is less effective against pear psylla than lime sulfur. Surround CF is not labeled to mix with sulfur products (but Surround WP is), so these sprays must occur separately.

75-100 PDD ORGANIC Management:

  • Pear psylla: spray a particle film as soon as you can after 75 PDD or March 1 (whichever is earlier) to deter pear psylla adult colonization and eventual egg laying. Particle films (Surround CF or Celite 610 at 50 lb/acre) reduce pear psylla adult colonization and egg lay by 80–99%. This reduces pear psylla pressure substantially for the entire first generation. Adding a spreader sticker increases the residual effectiveness of particle films. Mix particle films carefully and clean filters frequently to avoid clogged filters and nozzles.
  • Pear psylla/mites: lime sulfur can suppress pear rust mites, spider mites, and pear psylla adults. Wettable sulfur is effective against mites but is less effective against pear psylla than lime sulfur. Surround CF is not labeled to mix with sulfur products (but Surround WP is), so these sprays must occur separately.

75-100 PDD Not recommended (Conventional and ORGANIC):

  • Malathion (Malathion 5EC) is highly toxic to pear psylla, but it has a short residual and pear psylla adults will continue spring migration into orchards after the spray. Malathion is highly toxic to natural enemies overwintering in orchards such as Campylomma, Trechnites, Deraeocoris, and lady beetles.
  • Lambda-cyhalothrin (Warrior II) and other pyrethroids are not effective against pear psylla and are highly toxic to all natural enemies.
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.

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1-10% Budburst, 200 PDD (see photo)

Conditions:

  • Pear psylla: adults are near their peak and are laying eggs around the woody parts of buds. Pear psylla adults will lay eggs on soft green bud tissue emerge once they emerge from the bud tip (“budburst”).
  • Natural enemies: Trechnites wasps are overwintering in parasitized pear psylla nymphs, Campylomma are overwintering as eggs under bark scales, and Deraeocoris adults are present.

200 PDD Conventional Management:

  • Pear psylla:
    • closeup of a twig with a green bud starting to show at the end. a small black, winged insect is on the green bud.A second particle film (Surround CF or Celite 610 at 50 lb/acre) spray at budburst will renew residues and repel pear psylla adults from trees, preventing egg lay on developing buds. If your orchard is difficult to access in spring, this timing may be your first particle film spray. Adding a spreader sticker increases the residual of effectiveness of particle films. There is no evidence that particle films inhibit action of pesticides when mixed.
    • The insect growth regulator pyriproxyfen (Esteem 35WP) will sterilize pear psylla adults and have little effect on natural enemies.
    • If greater suppression is needed, mix pyriproxyfen with other non-disruptive materials such as diflubenzuron (Dimilin 2L), buprofezin (Centaur WDG), Cinnerate, or azadirachtin (Aza-Direct or Neemix 4.5).
    • Avoid broad-spectrum materials, but using just one across the season can be compatible with biological control. If pear psylla adult pressure is high (above 4 adults per tray on average), then tolfenpyrad (Bexar), acetamiprid (Assail 70 WP), or abamectin (AgriMek SC) can knock down pear psylla before they lay eggs on buds.
  • Pear psylla/scale: pyriproxyfen will suppress both pear psylla and scale insects.

200 PDD ORGANIC Management Details:

  • Pear psylla: A second particle film (Surround CF or Celite 610 at 50 lb/acre) spray at budburst will renew residues and repel pear psylla adults from trees, preventing egg lay on developing buds. If your orchard is difficult to access in spring, this timing may be your first particle film spray. Adding a spreader sticker increases the residual of effectiveness of particle films. There is no evidence that particle films inhibit action of pesticides when mixed.
  • Pear psylla/mealybug/scale: Use Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) to increase pear psylla adult suppression if needed and suppress mealybug and scale.

200 PDD Not Recommended (Conventional and ORGANIC):

  • Malathion (Malathion 5EC) is highly toxic to pear psylla, but has a short residual and pear psylla adults will continue their spring migration into orchards after the spray. Malathion is highly toxic to natural enemies overwintering in orchards such as Campylomma, Trechnites, Deraeocoris, and lady beetles.
  • Lambda-cyhalothrin (Warrior II) and other pyrethroids are not effective against pear psylla and are highly toxic to all natural enemies.
  • Novaluron (Rimon 0.83EC) is not highly effective against pear psylla and is harmful to natural enemies.

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Popcorn, 350 PDD (see photo)

Conditions:

  • Pear psylla: Pear psylla adults are laying eggs on separated flower pedicels and leaves. Flower buds have closed white petals.
  • Natural enemies: Trechnites wasps are overwintering in parasitized pear psylla nymphs, Campylomma are overwintering as eggs under bark scales, and Deraeocoris adults are present.

350 PDD Conventional Management:

  • Pear psylla:
    • a cluster of buds on a pear tree twig starting to open. some of the buds are round white balls that look like popcornThe insect growth regulator pyriproxyfen (Esteem 35WP) will sterilize pear psylla adults and have little effect on natural enemies. Only two sprays of pyriproxyfen are allowed per year and must be spaced at least 14 days apart.
    • Other selective materials such as Cinnerate, azadirachtin (Aza-Direct or Neemix 4.5), diflubenzuron (Dimilin 2L), or buprofezin (Centaur WDG) can be used instead of pyriproxyfen if the 14-day window is not met or you wish to save pyriproxyfen for later.
    • If pressure remains high (2 or more adults per tray), a particle film (Surround CF or Celite 610) spray just before bloom renews the particle film residues to repel pear psylla adults from trees. If two particle film sprays have already occurred, lower rates can be used. There is no evidence that particle films sprayed before bloom will affect honey bee pollination in pears. There is also no evidence that particle films inhibit the action of pesticides.
  • Pear psylla/mealybug: buprofezin (Centaur WDG), aids in both pear psylla and mealybug suppression at popcorn.

350 PDD ORGANIC Management:

  • Pear psylla: If pressure remains high (2 or more adults per tray), a particle film (Surround CF or Celite 610) spray just before bloom renews the particle film residues to repel pear psylla adults from trees. If two particle film sprays have already occurred, lower rates can be used. There is no evidence that particle films sprayed before bloom will affect honey bee pollination in pears. There is also no evidence that particle films inhibit the action of pesticides.
  • Pear psylla/mealybug/scale: Use Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) to increase pear psylla adult suppression if needed and suppress mealybug and scale.

350 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum insecticides like acetamiprid (Assail 70WP), tolfenpyrad (Bexar), malathion (Malathion 5EC), novaluron (Rimon 0.83EC), or lambda-cyhalothrin (Warrior II) because they will harm natural enemies and pollinators, which are abundant as flower petals open.
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.

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Bloom, 400–700 PDD

Conditions:

  • Pear psylla: Pear flowers are blooming, and most orchards have honeybees. Pear psylla eggs that escaped sprays are beginning to hatch.
  • Natural enemies: Deraeocoris brevis adults, Campylomma nymphs, and Trechnites wasps are present. If broad-spectrum sprays were avoided, natural enemy populations will grow and feed on nectar, pollen, and the pear psylla that survived previous sprays.

400-700 PDD Conventional Management:

  • Pear psylla:
    • No pear psylla management is necessary if suppression has been good. If you choose to spray at this time, it would be to target young pear psylla nymphs that escaped previous management.
    • Some organic sprays, such as azadirachtin (Aza-Direct or Neemix 4.5) or Cinnerate, are safe to use if pear psylla populations are higher than desired. If these sprays are made, applications should occur in the morning to allow for drying time and to avoid pollinators and natural enemies.
  • Codling moth: Mating disruption is essential. To effectively suppress pear psylla, all pests must be managed in a selective manner. Mating disruption allows you to spray less frequently and with more selective materials.

 400-700 PDD ORGANIC Management:

  • Pear psylla:
    • No pear psylla management is necessary if suppression has been good. If you choose to spray at this time, it would be to target young pear psylla nymphs that escaped previous management.
    • Some organic sprays, such as azadirachtin (Aza-Direct or Neemix 4.5) or Cinnerate, are safe to use if pear psylla populations are higher than desired. If these sprays are made, applications should occur in the morning to allow for drying time and to avoid pollinators and natural enemies.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingCodling moth: Mating disruption is essential. To effectively suppress pear psylla, all pests must be managed in a selective manner. Mating disruption allows you to spray less frequently and with more selective materials.

400-700 PDD Not Recommended (Conventional and ORGANIC):

  • Do not spray insecticides other than bee-safe organic products during bloom. If possible, avoid insecticides all together.
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.

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900 PDD

Conditions:

  • Pear psylla: First generation hardshells are the dominant life stage, but summerform adults and eggs will increase over the following weeks. Young nymphs will start to increase but may not be detectable for two or more weeks depending on weather and suppression of the previous generation.
  • Natural enemies: Campylomma nymphs, Deraeocoris adults, green lacewing Chrysoperla carnea may be present if broad-spectrum sprays are avoided.

 900 PDD Conventional Management:

  • Pear psylla:
    • Applying a particle film (Surround WP or Celite 610 at 50 lb/acre) repels emerging summerform pear psylla adults from trees, preventing egg lay. Adding a spreader sticker increases the effectiveness and longevity of particle films. Mix carefully and clean filters and nozzles frequently. Be prepared to apply another particle film at 1200 PDD.
    • Spirotetramat (Ultor or Movento) is a systemic insecticide that will reduce survival of upcoming generation of nymphs. This material works best when two applications are made, so a second application can be made 14 days later, at around 1200 PDD. Spirotetramat can only be applied twice per season, and applications must be at least 14 days apart.
  • Codling moth/pear psylla/mites: use 1% oil, methoxyfenozide (Intrepid 2F), or chlorantraniliprole (Altacor) to kill codling moth eggs. Oil also increases suppression of psylla and mites.
  • Mites: If spider mites are found in low numbers, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

 900 PDD ORGANIC Management:

  • Pear psylla: Applying a particle film (Surround WP or Celite 610 at 50 lb/acre) repels emerging summerform pear psylla adults from trees, preventing egg lay. Adding a spreader sticker increases the effectiveness and longevity of particle films. Mix carefully and clean filters and nozzles frequently. Be prepared to apply another particle film at 1200 PDD.
  • Codling moth/pear psylla/mites: use 1% oil to kill codling moth eggs. Oil also increases suppression of psylla and mites.

 900 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials, even if they will kill multiple types of pests. It is critical to use only selective materials to avoid pear psylla and spider mite outbreaks. Avoid acetamiprid (Assail 70WP), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage, but easy to harm natural enemy populations.
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.

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1200 PDD or 14 days after 900 PDD

Conditions:

  • Pear psylla: Summerform pear psylla adult and egg abundance will increase for the next couple weeks. Young nymphs will also hatch and increase.
  • Natural enemies: Multiple species may be present, including Deraeocoris nymphs and adults, Campylomma adults and some nymphs, and lacewing Chrysoperla carnea Young earwig nymphs are active on the orchard floor and will begin moving into trees. Second generation Trechnites adults are emerging from parasitized psylla.

1200 PDD Conventional Management:

  • Pear psylla:
    • A second post-bloom particle film (Surround WP or Celite 610 at 50 lb/acre) repels summerform pear psylla adults from trees, preventing egg lay. Adding a spreader sticker increases effectiveness and longevity of particle films, but it is essential to mix carefully and clean filters and nozzles frequently. No more than two particle film applications should be made after bloom, as this can increase the risk of mite outbreaks.
    • Spirotetramat (Ultor or Movento) is a systemic insecticide that will reduce survival of the upcoming generation of nymphs. This material works best when two applications are made and can only be applied twice per season, at least 14 days apart. If this is the first spirotetramat application, a second can be made in 14 days, at approximately 1500 PDD.
  • Mites: If spider mites are found in low numbers, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

 1200 PDD ORGANIC Management:

  • Pear psylla:
    • A second post-bloom particle film (Surround WP or Celite 610 at 50 lb/acre) repels summerform pear psylla adults from trees, preventing egg lay. Adding a spreader sticker increases effectiveness and longevity of particle films, but it is essential to mix carefully and clean filters and nozzles frequently. No more than two particle film applications should be made after bloom, as this can increase the risk of mite outbreaks.
  • Codling moth/pear psylla/mites: use 1% oil to kill codling moth eggs. Oil also increases suppression of psylla and mites.

 1200 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid broad spectrum materials. Most are not effective now because it is difficult to achieve adequate spray coverage, but easy to harm natural enemy populations and induce pest outbreaks. Avoid acetamiprid (Assail 70 WP), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO[Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.

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1500 PDD or 14 days after 1200 PDD

Conditions:

  • Pear psylla: Summerform pear psylla adults and eggs are at their peak and will begin to decrease. Young nymphs are nearing peak and are starting to molt into hardshells.
  • Natural enemies: Multiple species may be present, including Deraeocoris nymphs and adults, Campylomma adults and some nymphs, and lacewing Chrysoperla carnea Young earwig nymphs are active on the orchard floor and will begin moving into trees. Second generation Trechnites adults are emerging from parasitized psylla.

1500 PDD Conventional Management:

  • Pear psylla:
    • If only one particle film (Surround WP or Celite 610 at 50 lb/acre) was applied after bloom so far, a second (final) application now will repel the remaining summerform adults and prevent further egg lay. Adding a spreader sticker increases the effectiveness and longevity of particle films, but it is essential to mix carefully and clean filters and nozzles frequently. No more than two particle film applications should be made after bloom, as this can increase the risk of mite outbreaks.
    • Spirotetramat (Ultor or Movento), is a systemic insecticide that kills young nymphs after they hatch. If only one application has been made and it has been 14 or more days, a second can be applied now to suppress the ongoing generation of nymphs.
    • If pear psylla pressure is still high, adding selective insecticides such as diflubenzuron (Dimilin 2L), Cinnerate, or azadirachtin (Aza-Direct or Neemix 4.5) can increase suppression. Do not use azadirachtin products on Comice pears.
  • Codling moth: If in a high-pressure area for codling moth, selective insecticides such as granulovirus (Cyd-X HP) or diflubenzuron (Dimilin 2L) will help.
  • Mites: If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

1500 PDD ORGANIC Management:

  • Pear psylla:
    • If only one particle film (Surround WP or Celite 610 at 50 lb/acre) was applied after bloom so far, a second (final) application now will repel the remaining summerform adults and prevent further egg lay. Adding a spreader sticker increases the effectiveness and longevity of particle films, but it is essential to mix carefully and clean filters and nozzles frequently. No more than two particle film applications should be made after bloom, as this can increase the risk of mite outbreaks.
    • If pear psylla pressure is still high, adding selective insecticides such as diflubenzuron (Dimilin 2L), Cinnerate, or azadirachtin (Aza-Direct or Neemix 4.5) can increase suppression. Do not use azadirachtin products on Comice pears.
  • Codling moth: If in a high-pressure area for codling moth, selective materials such as codling moth granulovirus (Cyd-X HP) will help control codling moth.
  • Codling moth/pear psylla/mites: use 1% oil to kill codling moth eggs. Oil also increases suppression of psylla and mites.

1500 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials, even if they will kill multiple types of pests. It is critical to use only selective materials to avoid pear psylla and spider mite outbreaks. Avoid acetamiprid (Assail 70WP), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage, but easy to harm natural enemy populations.
  • Particle Films to Avoid: Cocoon (kaolin) and Microna (calcium carbonate) are not labeled for use as pesticides, and therefore cannot be used in place of Surround CF/WP or Celite 610 for control of pear psylla. Cocoon and Microna can be used for non-insecticidal purposes in orchards, but be advised, despite their similar appearance to Surround and Celite, they do not provide control of pear psylla.
  • Do not use particle films past 1500 PDD as they can leave residues on the fruit, and spray coverage is too poor for them to be effective. In addition, no more than two particle films should be used after bloom, as this will increase the risk of mite outbreaks.

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1700 – 2100 PDD

Conditions:

  • Pear psylla: second generation nymphs are at their peak and hardshells are increasing.
  • Natural enemies: a mix of species and life stages are present in orchards with selective spray programs.

1700-2100 PDD Conventional Management:

  • Pear psylla: You are unlikely to meaningfully suppress pear psylla or mites by using pesticides because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a summer explosion of pear psylla in their next generation. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Mites: If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

1700-2100 PDD ORGANIC Management:

  • Pear psylla: You are unlikely to meaningfully suppress pear psylla or mites by using pesticides because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a summer explosion of pear psylla in their next generation. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Mites: If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

1700-2100 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials, even if they will kill multiple types of pests. It is critical to use only selective materials to avoid pear psylla and spider mite outbreaks. Avoid acetamiprid (Assail 70 WP), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WP), spinosad (Entrust SC ), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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2100 – 2400 PDD

Conditions:

  • Pear psylla: Pear psylla second generation young nymphs are decreasing and hardshells are at their peak. Very few adults are present.
  • Natural enemies: a mix of species and life stages are present in orchards with selective spray programs.

2100-2400 PDD Conventional Management:

  • Pear psylla: You are unlikely to meaningfully suppress pear psylla or mites by using pesticides because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a summer explosion of pear psylla in their next generation. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Summer pruning can reduce the pear psylla population. Between 2100 and 2400 PDD is a good time for this because you will be removing infested shoots before hardshells produce much honeydew. If only partial pruning is performed, target shoots with the most honeydew. Summer pruning will also improve spray coverage and light penetration into the canopy.
  • Mites: If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

2100-2400 PDD ORGANIC Management:

  • Pear psylla: You are unlikely to meaningfully suppress pear psylla or mites by using pesticides because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a summer explosion of pear psylla in their next generation. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Summer pruning can reduce the pear psylla population. Between 2100 and 2400 PDD is a good time for this because you will be removing infested shoots before hardshells produce much honeydew. If only partial pruning is performed, target shoots with the most honeydew. Summer pruning will also improve spray coverage and light penetration into the canopy.

2100-2400 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials, even if they will kill multiple types of pests. It is critical to use only selective materials to avoid pear psylla and spider mite outbreaks. Avoid acetamiprid (Assail 70 WP), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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2600 PDD

Conditions:

  • Pear psylla: we are at the start of the third generation of pear psylla. Adults, eggs and young nymphs are increasing but should remain very low in selective programs following these guidelines. Orchards that used multiple broad-spectrum insecticides earlier in the season are at risk of high pear psylla abundance and population growth.
  • Natural enemies: a mix of natural enemy species and life stages are present in orchards with selective spray programs.

2600 PDD Conventional Management:

  • Pear psylla:
    • Only consider spraying if there are considerable adults present. Less two adults per tray or one young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, use an insect growth regulator, such as pyriproxyfen (Esteem 35WP) or diflubenzuron (Dimilin 2L). Alternatively, the organic insecticides Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: Insect growth regulators such as pyriproxyfen (Esteem 35WP) and diflubenzuron (Dimilin 2L), granulovirus (Cyd-X HP), or 1% oil can also help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites. If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

2600 PDD ORGANIC Management:

  • Pear psylla:
    • Only consider spraying if there are considerable adults present. Less two adults per tray or one young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: granulovirus (Cyd-X HP), or 1% oil can help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites.

2600 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials even if they will kill multiple types of pests; doing so will eliminate your natural enemies and cause outbreaks of pear psylla and spider mites. Broad spectrum materials to avoid include (but are not limited to) acetamiprid (Assail 70 WG), thiamethoxam (Actara), imidacloprid (Admire Pro, Macho, others), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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2900 PDD

Conditions:

  • Pear psylla: Third generation adults, eggs, and young nymphs are increasing, but the increase is usually low or undetectable if a selective pesticide program was used. Programs that used multiple broad-spectrum insecticides earlier in the season are at risk of high pear psylla abundance and population growth.
  • Natural enemies: A mix of natural enemy species and life stages are present in orchards with selective spray programs.

2900 PDD Conventional Management:

  • Pear psylla:
    • Only consider spraying if there are considerable adults present. Less two adults per tray or 1 young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, use an insect growth regulator, such as pyriproxyfen (Esteem 35WP) or diflubenzuron (Dimilin 2L). Alternatively, the organic insecticides Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: Insect growth regulators such as pyriproxyfen (Esteem 35WP) and diflubenzuron (Dimilin 2L), granulovirus (Cyd-X HP), or 1% oil can also help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites. If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

2900 PDD ORGANIC Management:

  • Pear psylla:
    • Only consider spraying if there are considerable adults present. Less two adults per tray or 1 young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: granulovirus (Cyd-X HP), or 1% oil can help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites.

2900 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials even if they will kill multiple types of pests; doing so will eliminate your natural enemies and cause outbreaks of pear psylla and spider mites. Broad spectrum materials to avoid include (but are not limited to) acetamiprid (Assail 70 WP), thiamethoxam (Actara), imidacloprid (Admire Pro, Macho, others), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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3200 PDD

Conditions:

  • Pear psylla: adults and eggs are at their third-generation peak. Young nymphs are near peak and molting to the hardshell stage. However, the increase is usually low or undetectable if a selective pesticide program was used. Programs that used multiple broad-spectrum insecticides earlier in the season are at risk of high pear psylla abundance.
  • Natural enemies: All natural enemies and life stages are occurring in selectively sprayed orchards.

3200 PDD Conventional Management:

  • Pear psylla:
    • Only consider spraying if there are considerable pear psylla adults present. Less two adults per tray or 1 young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, use an insect growth regulator, such as pyriproxyfen (Esteem 35WP) or diflubenzuron (Dimilin 2L). Alternatively, the organic insecticides Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: Insect growth regulators such as pyriproxyfen (Esteem 35WP) and diflubenzuron (Dimilin 2L), granulovirus (Cyd-X HP), or 1% oil can also help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites. If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

3200 PDD ORGANIC Management:

  • Pear psylla:
    • Only consider spraying if there are considerable pear psylla adults present. Less two adults per tray or 1 young nymph per leaf generally results in less than 5% fruit damage. If you have followed a selective spray program, you likely have natural enemies present in your orchard, so it is not necessary to perform preventative sprays.
    • If pear psylla are projected to surpass damage thresholds, Cinnerate or azadirachtin (Aza-Direct or Neemix 4.5) can also suppress pear psylla. Do not use azadirachtin products on Comice pears.
  • Pear psylla/codling moth: granulovirus (Cyd-X HP), or 1% oil can help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites.

3200 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials even if they will kill multiple types of pests; doing so will eliminate your natural enemies and cause outbreaks of pear psylla and spider mites. Broad spectrum materials to avoid include (but are not limited to) acetamiprid (Assail 70 WP), thiamethoxam (Actara), imidacloprid (Admire Pro, Macho, others), tolfenpyrad (Bexar), novaluron (Rimon 0.8.3 EC), lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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3500 PDD

Conditions:

  • Pear psylla: Third generation young nymphs at peak and hardshells are increasing. However, the increase is usually low or undetectable if a selective pesticide program was used. Programs that used multiple broad-spectrum insecticides earlier in the season are at risk of high pear psylla abundance.
  • Natural enemies: All natural enemies and life stages are occurring in selectively sprayed orchards.

3500 PDD Conventional Management:

  • Pear psylla: you are unlikely to meaningfully suppress pear psylla or mites by using sprays because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a late-season explosion of pear psylla. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Pear psylla/codling moth: Insect growth regulators such as pyriproxyfen (Esteem 35WP) and diflubenzuron (Dimilin 2L), granulovirus (Cyd-X HP), or 1% oil can also help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites. If spider mites are found, give predators time to suppress them. In areas where mites are becoming a problem (pear rust mite or spider mites) selective miticides such as fenbutatin (Vendex 50WP), spirodiclofen (Envidor 2SC), or cyflumetofen (Nealta) are effective and are relatively safe for natural enemies.

3500 PDD ORGANIC Management:

  • Pear psylla: you are unlikely to meaningfully suppress pear psylla or mites by using sprays because pear psylla hardshells are hard to kill, and spray coverage is poor. Sprays now will only give you a natural enemy deficit, setting you up for a late-season explosion of pear psylla. Instead of spraying, consider honeydew washing.
  • graph showing the different lifestages of pear psylla against degree days with colored boxes for cultural control timingHoneydew washing: remove pear psylla honeydew and prevent injury via overhead sprinklers or airblast sprayers with high water volumes (at least 800 gpa). Do not wash more than necessary, as it can increase disease risk. If at least 30% (15 of 50 leaves) have visible honeydew, you should wash. Wash for 12 hours and let dry before scouting again. Continue this process until 2400 PDD.
  • Pear psylla/codling moth: granulovirus (Cyd-X HP), or 1% oil can help suppress codling moth but may not be necessary if pressure is low and mating disruption is in place. Spray based on the codling moth model and trap capture.
  • Pear psylla/mites: 1% oil will help to suppress pear psylla and mites.

3500 PDD Not Recommended (Conventional and ORGANIC):

  • Avoid using broad spectrum materials even if they will kill multiple types of pests; doing so will eliminate your natural enemies and cause outbreaks of pear psylla and spider mites. Broad spectrum materials to avoid include (but are not limited to) acetamiprid (Assail 70 WP), thiamethoxam (Actara), imidacloprid (Admire Pro, Macho, others), tolfenpyrad (Bexar), novaluron (Rimon 0.83 EC) lambda-cyhalothrin (Warrior II), spinetoram (Delegate WG), spinosad (Entrust SC), pyridaben (Nexter SC), and fenpyroximate (FujiMite XLO [Note: FuijiMite XLO is only allowed once per season]).
  • For organic, avoid broad spectrum insecticides like spinosad (Entrust SC).
  • Most of these materials are not effective against pear psylla now because it is difficult to achieve adequate spray coverage but easy to harm natural enemy populations.
  • Particle films should no longer be used as they can increase the risk of mites and leave residues on picked fruit.

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About this Webpage

Management Guidelines

This webpage outlines season-long integrated pest management (IPM) program guidelines for pear. The guidelines a built around a degree day model that predicts the development of pear psylla life stages and generations. The guidelines in this page (above) place specific strategies at timings where they can affect vulnerable life stages while minimizing harm to natural enemies. Most sprays target adults and eggs. Sprays are less effective on pear psylla nymphs, which are better suppressed by natural enemies (for example, the parasitoid of pear psylla, Trechnites insidiosis, only attacks nymphs, not eggs or adults). Further, thresholds help to avoid unnecessary sprays when pest populations are too low for concern. Timings for non-chemical tactics, such as tree washing and pruning for pear psylla and mating disruption for codling moth, further support this goal. Altogether, this program supports effective pest management while reducing input costs and enabling biocontrol.

Phenology Model

graph showing the phenology curves of pear psylla life stages from 0 to 4000 degree daysInsect development rates depend on temperature. After making observations and using them to build mathematical models, we can predict the relative abundance of a pest’s life stages across its generations within a season based on accumulated temperature units called degree-days. This degree-day phenology model for pear psylla was developed by Vince Jones of WSU in 2019. Learn more about degree-day models and how they are made on the Degree Day page.

Biocontrol and Natural Enemies

The term “biocontrol” means suppression of pest organisms by other living organisms. We also use the term “natural enemies”, referring to the naturally occurring predators or parasitoids that kill pear psylla or mites (therefore, providing biocontrol). More information on natural enemies in pear orchards can be found Pear IPM Natural Enemies page.

How These Guidelines Work Alongside Biological Control

a large brown and cream colored insect is on a green leaf feeding on a much smaller light colored psylla nymph.The management guidelines on this page work by conserving natural enemies while suppressing pear psylla. This approach results in less pear psylla pressure later in the season (both before and after harvest) because of the natural enemy populations you will cultivate. Programs that use multiple broad-spectrum insecticides, on the other hand, may appear to control pests early in the season, then lead to pest outbreaks in mid-summer. When using the phenology-based guidelines on this page, you may find pear psylla adults, eggs, or nymphs at higher levels than were common in the broad-spectrum insecticide programs. However, the chance for injury will be much lower because predators and parasitoids are present. So, try not to abandon the program if you see some psylla – remember, psylla are predator food! Allowing natural enemies to build through the season will control psylla populations in the fall, resulting in fewer psylla the following year. Natural enemies cannot perform this service if multiple broad-spectrum insecticides are used. Try to limit yourself to no more than one broad-spectrum spray per season, preferably prebloom at 200 PDD, and only if pear psylla pressure is high. If you do make one broad spectrum spray, natural enemies can recover, so do not abandon the overall selective approach.

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Contact:

Dr. Louis Nottingham
Assistant Professor
WSU Tree Fruit Research & Extension Center
1100 N Western Ave., Wenatchee, WA 98801
louis.nottingham@wsu.edu
540-798-2044 (cell)

Dr. Robert Orpet
Postdoctoral Research Associate
WSU Tree Fruit Research & Extension Center
1100 N Western Ave., Wenatchee, WA 98801
robert.orpet@wsu.edu

This Project was Funded by:

 

 

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Disclaimer: 

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.

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