Pear Programs


Major Diseases

Botrytis-Grey Mold
Botrytis is the second most important apple fruit disease and can be the most important disease affecting pear as shown in recent statewide and regional surveys in the Pacific Northwest. Flowers of both crops are susceptible to Botrytis infections which persist throughout the growing season until harvest. Botrytis infections remain dormant until storage where the fungus causes Gray Mold with symptoms becoming visible after a few months in storage. Afterward, the fungus can spread to healthy fruit. Temperatures between 64F and 78F are optimal for infections. Because infections occur EXCLUSIVELY in the orchard, it is important to start management as early as possible. Delayed management will fail to control infections that started weeks or months before harvest. The fungus is ubiquitous and overwinters on mummified fruit left on trees and fallen leaves. Good sanitation practices will reduce inoculum loads but because of the explosive nature of this disease, fungicide applications are necessary to achieve good control. At bloom time and during spring, fungicides from FRAC groups 7, 9 and 11, used to control apple powdery mildew or scab, will be effective against Botrytis if resistance is absent. Fungicides from FRAC 3 have a limited efficacy against Botrytis infections. As fruit mature, they become more susceptible to Botrytis. Late season management is especially important for cultivars picked after mid-September in WA when wet, disease conducive weather is more likely. Preharvest applications and ROTATIONS of fungicides from the FRAC groups 1, 7, 11 and 19 control Botrytis. Tank-mixture of single-site fungicide with Ziram or captan will increase efficacy and delay the selection for resistant populations. IMPORTANT: Botrytis cinerea is the MOST RISKY fungus when it comes to fungicide resistance as the fungus can develop resistance to multiple fungicides simultaneously. Remember this aspect when spraying for other diseases such as powdery mildew, as the same fungicides sprayed early in the season can select for resistant Botrytis populations which will persist throughout the season and to the storage rooms resulting in limited efficacy of eventual postharvest treatment.

Bull's eye rot
Bull's eye rot is a major disease of apple and pear. The disease can be caused by four different fungal species from the genus Neofabraea. The main species causing Bull's eye rot of apple in eastern Washington is N. perennans, whereas N. malicorticis was reported to be predominant in western Washington. It infects fruit and causes cankers on trees where it overwinters until conditions become favorable in the following spring to start new infections. Fruit are infected exclusively in orchards but bull's eye rot symptoms are only seen after several months in cold storage. Therefore, preharvest management is key to reducing decay rates in the packinghouse. Prune cankered branches to reduce the inoculum load and use fungicide applications prior to harvest to control. Ziram applied within two weeks before harvest is recommended for control of Bull’s eye rot in the Pacific Northwest. Topsin-M is ONLY recommended under wet conditions and for cultivars, such as Golden Delicious, Pinata, Fuji and Granny Smith, more susceptible to bull's eye rot. Frequent sprays may increase risks of resistance development to Mertect, a fungicide from the same group as Topsin-M (1) used after harvest. Tank-mixtures of Ziram with other single-site fungicides are recommended to increase efficacy and reduced risks of fungicide resistance development.

Fire blight
There is a risk of fire blight infection any time there are flowers on the tree, the weather is warm, and wetting occurs. Early bloom. Apply biologicals (Blossom Protect) during early bloom. If fire blight was in the orchard last year apply two applications of the biological. Reapply biological a second time if lime sulfur was applied (Lime sulfur is antimicrobial and kills biological). Full bloom to petal fall. Watch the model. If an infection event occurs, apply an antibiotic as soon as possible, but within 24 hours of infection (usually wetting of flowers). Repeated antibiotic sprays may be necessary during extended high or extreme risk periods. Best results are obtained when applied within 24-hour window before flower wetting during a high infection risk period. Beneficial only for flower infection prevention. Product used must contact the interior of the flowers in sufficient water and approved wetting agent to completely wet the interior. One pound of any 17% oxytetracycline product per 100 gallons gives a 200 ppm solution. Kasugamycin is another effective antibiotic. Applications of less than 100 gal/A can be effective on small trees if flower interiors are well covered, but do not drop the ppm below 200 (oxytetracycline). Application by ground equipment on each row is highly recommended. Application of antibiotics by aircraft is not recommended. Many fire blight bacteria in the Pacific Northwest are resistant to streptomycin, another registered antibiotic. Organic. Prebloom. Fixed copper sanitation if fire blight was in the orchard last year. Early bloom. Lime sulfur plus oil. One to two applications of biologicals (Blossom Protect). Reapply biologicals after lime sulfur which is antimicrobial. Depending on the cultivar russet risk and the CougarBlight model risk follow with copper hydroxide/octanoate (Cueva/Previsto) every 2 to 5 days (This option is less fruit safe for russet) or Bacillus subtilis (Serenade Optimum) (most fruit safe; lower efficacy).

Pathogens of Storage Rots
In addition to the major diseases described separately, other fungal fruit infections starting in the orchard can cause storage rots. Alternaria Disease: A dark-brown to black infection caused by Alternaria alternata (and other spp.) is ubiquitous in most orchards. Infections, usually sporadic, may become frequent when sanitation is not observed or when wet conditions occur for an extended period. The fungus infects flowers at bloom but can also infect fruit through the calyx end or wounds. Floral infections can result in moldy-core disease later in storage.
Sphaeropsis Disease. A sporadic emerging disease caused by the fungus Sphaeropsis pyriputrescens infects fruits in the orchard and develops stem and calyx end rots in storage. The fungus overwinters on cankers and twig die-back. Prune diseased branches to help reduce inoculum. Pruning symptomatic crab apples is particularly important. Although this disease can be sporadic, it is still quarantined in many export countries and its identification in entry ports will result in fruit lot rejection.
Lambertella disease. This disease was recently reported in the Pacific Northwest and, therefore, is considered as quarantine pathogen. Infections are caused by the fungus L. corni-maris, which has been isolated from mummies of other fruit crops in the past but its disease cycle in apple is still unknown. The disease develops yellow mycelium that cover the fruit, but symptoms are only observed after several months of storage. Recent studies have shown that fungicides from FRAC group 1 are not effective against Lambertella, whereas fungicides from FRAC groups 7 and 11 have only moderate efficacy. Until further research has shown which other preharvest fungicides are effective, it is recommended to apply a fungicide from FRAC group 9 or 12 postharvest, as these were found to be the most effective. The fungus requires a wound on the cuticle to cause an infection, therefore, reducing damages and punctures at harvest will reduce infection risks. The possibility of infections occurring through the calyx- or stem-ends is still unknown.

Pear mildew
Apple and pear powdery mildew is caused by the same fungal species Podosphaera leucotricha which overwinters in dormant apple buds, whereas its survival in pear is still unknown. When infected buds break in spring, the fungus produces spores that are rain and wind-spread to infect freshly emerged leaves which are highly susceptible powdery mildew. Germination and infections are optimal at temperatures between 60F and 78F. Wetness plays a marginal role. The fungus then continues its multi-cycle infections through spring and early summer until the productions of new leaves and shoots cease. The fungus is slowed down by the rising temperature (above 82F) as summer progresses. Infection resumes in fall where the pathogen overwinters as ascospores (sexual form) or infected buds. Under high disease pressure and mild summer conditions, the fungus can cause russeting on fruits and therefore reduce quality. While no cultivar is immune, cultivars like Granny Smith, Honeycrisp, Idared and Crimson Crisp are highly susceptible, whereas Golden Delicious is susceptible and Fuji, Gala and Red Delicious are the least susceptible. Mildew management should start before bud break and at green tip stage (to reduce spread of new inoculum) with sulfur-based products and continue every 10 to 14 days until the production of new shoots cease. Fungicides from FRAC groups 3, 7, 11 and 19 are effective and SHOULD be ROTATED throughout the season. In growing, regions where scab is a problem, spray programs used to control the latter will control powdery mildew as well. In organic orchards, sulfur, potassium bicarbonate, and some biopesticides usually provide a good level of control.

Pear scab
Scab, caused by the fungus Venturia pyrina on pear, is major disease of pear fruit in many growing regions, especially those with high rainfall. Typical scab symptoms include gray-brown to blackish lesions on leaves and fruit. Because of the semi-arid conditions during the growing season in central Washington, scab risk is low. However, some microclimates in the north of the state can be conducive to scab and therefore, management is recommended. Pear scab can cause problems in growing regions north of Washington and in Hood River, Oregon but it is rarely seen in central and south Washington State.

Major Insects

Codling moth
Codling moth is the key pest of pome fruits in the PNW. In general, apples are more susceptible than pears, and fruits with softer flesh are more susceptible to attack. The increasing frequency of a third generation (two have been the norm historically) means that growers must be vigilant throughout the growing season, and be aware of phenology (See WSU Decision Aid system at https://decisionaid.systems). Codling moth has a long history of becoming resistant to insecticides, thus rotation of materials with different modes of action (MOA) is highly recommended. Avoid using the same MOA against consecutive generation to minimize this danger. The MOA for each material is listed in the Tables. Pheromone mating disruption was registered in 1990, and has since been widely adopted in Washington. Use of mating disruption is now considered the foundation of an IPM program. Supplementing mating disruption with insecticides may be necessary depending on pressure, and using pheromone traps for monitoring populations will prevent unnecessary applications. Detailed recommendations on pheromone placement and timing of sprays is available. Additional Details

Leafrollers (Pandemis, Obliquebanded)
Pre-bloom applications of pesticides can be effective and will also conserve natural enemies for leafroller and biological control agents of other pests, such as aphids. If treatments for leafrollers were applied at pink and/or bloom, sampling to determine the density of surviving leafrollers should be completed prior to deciding to apply additional controls at this timing. Most products listed act primarily as stomach poisons versus direct contact to residues, therefore, complete coverage is very important to achieve maximal control. Repeating an application of any product should be based on the leafroller population surviving previous treatments. Use the leafroller models on the WSU Decision Aid System (https://decisionaid.systems) for the optimum timing. Additional Details

Pear psylla
Pear psylla, Cacopsylla pyricola, is a major pest of pears in the PNW. While it is specific to pear, a portion of the population overwinters in alternative host plants such as apple and non-cultivated trees and shrubs. Pear psylla becomes active in orchards in late winter and early spring. Egg lay begins while trees are dormant or at bud swell and generally peaks between popcorn and bloom. The first generation of nymphs emerge between popcorn and petalfall. Psylla undergo 3-4 generations in a season, the 4th usually occurring during or after harvest depending on the cultivar. While many programs rely heavily on repeated broad spectrum sprays from dormant through harvest, softer programs involving the use of particle films (Surround CF or WP and diatomaceous earth) for adult repellency and soft insecticides (Esteem, Dimilin, Centaur, Neem products, Cinnerate, Rosemary oils) are encouraged for conservation of natural enemies. Predators Deraeocoris brevis, Campylomma verbasci, earwigs, anthrocorids and the parasitoid wasp Trechnites insidiosus are highly effective at controlling psylla later in the season when insecticide coverage is compromised by excessive growth. Selective materials may require more frequent applications (10-day intervals), especially from petalfall to July when psylla pressure is high. However, late season sprays will become less necessary after consecutive years in selective or organic production because natural enemies will gradually increase. Additional Details

Pear rust mite
Pear rust mite, Epitrimerus pyri, is a common pest of pears. Although similar in appearance and injury, it is not the same as Apple rust mite, Aculus schlechtendali. Pear rust mite is a very small mite that requires magnification to see. Pear rust mite becomes active as soon as buds develop. Because natural enemies will not prevent injury, control measures must be taken prior to bloom (lime sulfur before green tissue, micronized sulfur after). If left uncontrolled rust mites will injure the developing fruit, causing scaring around the calyx. Rust mites will continue to feed through the season on both the fruit and leaves, causing a light russeting over their surfaces. If rust mites reemerge in the summer, they are readily controlled by most conventional miticides. Organic products such as Cinnerate and rosemary oils also have shown efficacy against this pest. Postharvest sulfur sprays lower populations for the following season. Additional Details

San Jose scale
San Jose scale can be a minor pest if adequately controlled, or escalate into a major problem if not. It primarily infests the trunk and limbs, but scale crawlers will settle on the fruit. Damage to this season’s crop may become serious, but ultimately the infestation of wood may cause death of limbs or the entire tree. Oil plus an organophosphate in the delayed dormant spray provide control; if the organophosphate is omitted (oil only), monitor the trees carefully and add one of the listed materials if scale become numerous. Additional Details

Relative Efficacy Guide for Pears

This table is intended as a guideline to the relative efficacy of pesticides against a certain pest (see also Relative Efficacy Guide for Apple). Use it in conjunction with the Pest Control Program for Pears, which gives recommended rates and timing of sprays. The information in the table is based on research conducted at the WSU Wenatchee Tree Fruit Research and Extension Center. Tolerance or susceptibility may vary from one area to the next.

Prebloom Efficacy

Insect

CutwormsGrape mealybugPear psyllaLeafrollers (Pandemis)Leafrollers (Pandemis, Obliquebanded)San Jose scaleCodling mothGreen apple aphid
Lorsban Advanced
chlorpyrifos
4
Diazinon 50W
diazinon
33
Asana XL
esfenvalerate
1-3
DiPel DF
Bacillus thuringiensis subsp. kurstaki
33
Agri-Mek SC
abamectin
2
Rex Lime Sulfur
lime sulfur/calcium polysulfide
4
Nexter 75WSB
pyridaben
3-4
Exirel
cyantraniliprole
44
Rimon 0.83EC
novaluron
3-4
Dimilin 2L
diflubenzuron
4
Ultor 1.25L
spirotetramat
3-4
Intrepid 2F
methoxyfenozide
33
Imidan 70W
phosmet
23
Kumulus 80DF
sulfur, dry flowable
4
Esteem 35WP
pyriproxyfen
2-3413
Actara 25WDG
thiamethoxam
4
Success 2F
spinosad
3-4
Sulforix
lime sulfur/calcium polysulfide
4
Assail 70WP
acetamiprid
143-4
Proclaim 5SG
emamectin benzoate
4
Aza-Direct 1.2%L
azadirachtin
2-3
Surround WP
kaolin clay
4
Altacor 35WDG
chlorantraniliprole
44
Delegate 25WG
spinetoram
44
FujiMite XLO
fenpyroximate
3-4
Centaur 70WDG
buprofezin
2-3
Belt 4SC
flubendiamide
4
Surround CF
kaolin
4

Postbloom Efficacy

Insect

CutwormsGrape mealybugPear psyllaLeafrollers (Pandemis)Leafrollers (Pandemis, Obliquebanded)San Jose scaleCodling mothGreen apple aphid
Lorsban Advanced
chlorpyrifos
4
Diazinon 50W
diazinon
33
Asana XL
esfenvalerate
1-3
DiPel DF
Bacillus thuringiensis subsp. kurstaki
33
Agri-Mek SC
abamectin
2
Rex Lime Sulfur
lime sulfur/calcium polysulfide
4
Nexter 75WSB
pyridaben
3-4
Exirel
cyantraniliprole
44
Rimon 0.83EC
novaluron
3-4
Dimilin 2L
diflubenzuron
4
Ultor 1.25L
spirotetramat
3-4
Intrepid 2F
methoxyfenozide
33
Imidan 70W
phosmet
23
Kumulus 80DF
sulfur, dry flowable
4
Esteem 35WP
pyriproxyfen
2-3413
Actara 25WDG
thiamethoxam
4
Success 2F
spinosad
3-4
Sulforix
lime sulfur/calcium polysulfide
4
Assail 70WP
acetamiprid
143-4
Proclaim 5SG
emamectin benzoate
4
Aza-Direct 1.2%L
azadirachtin
2-3
Surround WP
kaolin clay
4
Altacor 35WDG
chlorantraniliprole
44
Delegate 25WG
spinetoram
44
FujiMite XLO
fenpyroximate
3-4
Centaur 70WDG
buprofezin
2-3
Belt 4SC
flubendiamide
4
Surround CF
kaolin

 

 

Spray Schedule

Dormant

Pear psylla

10 Product Choices

Applications and Notes » 

Delayed dormant

Cutworms

1 Product Choices

Applications and Notes » 

European red mite

1 Product Choices

Applications and Notes » 

Grape mealybug

2 Product Choices

Applications and Notes » 

Lygus bug, stink bug

1 Product Choices

Applications and Notes » 

Pear psylla

11 Product Choices

Applications and Notes » 

Pear rust mite, pearleaf blister mite

3 Product Choices

Applications and Notes » 

San Jose scale

3 Product Choices

Applications and Notes » 

Tight cluster

European red mite

1 Product Choices

Applications and Notes » 

Grape mealybug

5 Product Choices

Applications and Notes » 

Lygus bugs, stink bugs, green fruitworm

2 Product Choices

Applications and Notes » 

Pear psylla

8 Product Choices

Applications and Notes » 

San Jose scale

1 Product Choices

Applications and Notes » 

Popcorn

Pear mildew

4 Product Choices

Applications and Notes » 

Pear scab

5 Product Choices

Applications and Notes » 

Leafrollers (Pandemis)

1 Product Choices

Applications and Notes » 

Pear psylla

7 Product Choices

Applications and Notes » 

Bloom

Botrytis-Grey Mold

2 Product Choices

Applications and Notes » 

Fire blight

9 Product Choices

Applications and Notes » 

Pear psylla

1 Product Choices

Applications and Notes » 

Pear rust mite

1 Product Choices

Applications and Notes » 

First bloom

Fire blight

4 Product Choices

Applications and Notes » 

Pear mildew

3 Product Choices

Applications and Notes » 

Pear scab

5 Product Choices

Applications and Notes » 

Codling moth

1 Product Choices

Applications and Notes » 

Leafrollers (Pandemis)

1 Product Choices

Applications and Notes » 

Petal fall

Botrytis-Grey Mold

4 Product Choices

Applications and Notes » 

Bull's eye rot

1 Product Choices

Applications and Notes » 

Fire blight

8 Product Choices

Applications and Notes » 

Pathogens of Storage Rots

3 Product Choices

Applications and Notes » 

Pear mildew

9 Product Choices

Applications and Notes » 

Pear scab

5 Product Choices

Applications and Notes » 

Codling moth

1 Product Choices

Applications and Notes » 

Grape mealybug

7 Product Choices

Applications and Notes » 

Leafrollers (Pandemis, Obliquebanded)

8 Product Choices

Applications and Notes » 

Lygus bug

1 Product Choices

Applications and Notes » 

Pear psylla

14 Product Choices

Applications and Notes » 

Pear rust mite

7 Product Choices

Applications and Notes » 

14-32 days after full bloom

Codling moth

9 Product Choices

Applications and Notes » 

Pear psylla

3 Product Choices

Applications and Notes » 

Late spring and summer

Codling moth

9 Product Choices

Applications and Notes » 

Grape mealybug

6 Product Choices

Applications and Notes » 

Grasshoppers and Mormon crickets

1 Product Choices

Applications and Notes » 

Green apple aphid

2 Product Choices

Applications and Notes » 

Leafrollers (Pandemis, Obliquebanded)

7 Product Choices

Applications and Notes » 

McDaniel spider mite, twospotted spider mite, European red mite

12 Product Choices

Applications and Notes » 

Pear psylla

14 Product Choices

Applications and Notes » 

Pear rust mite

6 Product Choices

Applications and Notes » 

Pear slug

7 Product Choices

Applications and Notes » 

Pearleaf blister mite

2 Product Choices

Applications and Notes » 

San Jose scale

3 Product Choices

Applications and Notes » 

Pathogens of Storage Rots

3 Product Choices

Applications and Notes » 

Pear mildew

6 Product Choices

Applications and Notes » 

Pear scab

3 Product Choices

Applications and Notes » 

Preharvest

Botrytis-Grey Mold

1 Product Choices

Applications and Notes » 

Bull's eye rot

2 Product Choices

Applications and Notes » 

Pathogens of Storage Rots

5 Product Choices

Applications and Notes »