Pear Programs

Gray mold, caused by 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 for fungicide resistance development 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 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 has been 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 when it causes 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. Tank-mixtures of Ziram with other single-site fungicides are recommended to increase efficacy and reduced risks of fungicide resistance development. Frequent sprays may increase risk of resistance development to FRAC 1 fungicides used after harvest.

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 (2 applications). Reapply biological if lime sulfur was applied (lime sulfur is antimicrobial and reduces biological populations). Full bloom to petal fall. Watch the model. Apply materials 12-24 hours BEFORE moisture events. Sprays every 2 days may be necessary to cover opening flowers during extended high or extreme risk periods. Product used must contact the interior of the flowers in sufficient water and approved wetting agent to completely wet the interior. 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 are not effective. Organic. Prebloom: Fixed copper sanitation if fire blight was in the orchard last year. Apples Easy to Thin: Blossom Protect/ Buffer Protect early, lime sulfur (+ oil), second Blossom Protect/ Buffer Protect. Followed depending on the model and cultivar russet risk with soluble copper (Previsto 3 qt, Cueva 4 qt, or Cueva 3 qt + Serenade Opti, or Instill). Petal fall + 1-2 weeks Serenade Opti (most fruit safe) or 2% lime sulfur (red apples), essential oils (Cinnerate, Thyme Guard), peracetic acids (Oxidate 5.0, Jet-Ag). Apples Hard to Thin/Long Bloom Period: Lime sulfur (+ oil), then Blossom Protect + Buffer Protect, then a Lime sulfur (+ oil), then a Second Blossom Protect + Buffer Protect. Depending on the model and cultivar russet risk soluble copper (Previsto 3 qt, Cueva 4 qt, Cueva 3 qt + Serenade Opti, or Instill). Petal fall + 1-2 weeks Serenade Opti or 2% lime sulfur (red apples), essential oils (Cinnerate, Thyme Guard), peracetic acids (Oxidate 5.0, Jet-Ag). Apples Hard to thin varieties/ short bloom period: Lime sulfur (+ oil) 2-3 applications. Depending on the model and cultivar russet risk follow with soluble copper (Previsto 3 qt, Cueva 4 qt, Cueva 3 qt + Serenade Opti, or Instill). Petal fall + 1-2 weeks: Serenade Opti (most fruit safe) or 2% lime sulfur (red apples), essential oils (Cinnerate, Thyme Guard), peracetic acids (Oxidate 5.0, Jet Ag). Pears Easy to Mark Varieties: 2 applications of Blossom Protect + Buffer Protect during early bloom to petal fall (70-80% bloom if single treatment). Follow with Serenade Opti at petal fall to reduce russet risk from Blossom Protect yeast. Pears Marking Tolerant Varieties: 2 applications of Blossom Protect + Buffer Protect during early bloom to petal fall (70-80% bloom if single treatment). Follow with soluble copper (Cueva 4 qrt, Previsto 3 qrt, or Cueva 3 qrt + Serenade Opti) if the model indicates risk (warm/wet).

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 remains 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.

Scab, caused by the fungus Venturia pyrina on pear, is a 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 Northcentral Washington can be conducive to scab and therefore, management is recommended. In western Washington scab is common. Pear scab can cause problems in northern Washington growing regions and in Hood River, Oregon but it is rarely seen in central and south Washington State.

Several other fungal fruit infections initiated in the orchard can cause storage rots.
Alternaria rot: 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 rot: 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 twigs. 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.
Yellow-Lambertella rot: 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.

Codling moth is the key pest of pome fruits in the Pacific Northwest. 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 generations 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.

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.

Pear psylla, Cacopsylla pyricola, is a major pest of pears in the Pacific Northwest. 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 on wood while trees are dormant or at bud swell and generally peaks between popcorn and bloom on green tissues. The first generation of nymphs emerge between popcorn and petalfall. Pear psylla undergo 3–4 generations in a season, with the 3rd and 4th usually occurring during or after harvest depending on the cultivar and season. While many programs rely heavily on repeated broad-spectrum sprays from dormant through harvest, softer programs use particle films (Surround CF or WP and diatomaceous earth) for adult repellency and selective insecticides (Esteem, Dimilin, Centaur, Neem products, Cinnerate, Rosemary oils) are encouraged for conservation of natural enemies. Therefore, when possible, materials are noted as broad-spectrum when expected to disrupt some combination of predators Deraeocoris brevis, Campylomma verbasci, earwigs, anthrocorids and the parasitoid wasp Trechnites insidiosus. Selective materials are expected to conserve these natural enemies, which are highly effective at controlling psylla later in the season.

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 cinnamon and rosemary oils also have shown efficacy against this pest. Postharvest sulfur sprays lower populations for the following season.

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.