Apple Programs

Major Insects

Aphids

Natural enemies can be effective on aphids. When 20% of colonies have predators a pesticide application may be delayed or eliminated. Use of pesticides with low toxicity to predators will increase biological control. Product recommendations will be effective on apple aphid, apple grain aphid, and rosy apple aphid, but less so on woolly apple aphid.

Apple rust mite

Apple rust mite feeds on plant foliage, and in very high numbers, can cause shoots to stop growth prematurely. However, in low to moderate numbers, they are generally regarded as an important and positive part of integrated mite management. Predatory mites can eat apple rust mites when spider mites (a more damaging pest) are scarce, and sustain their populations through the season. Choose pesticides that cause minimal harm to apple rust mite unless 1) populations become very high or 2) large early season populations occur on sensitive cultivars where fruit russetting can occur, such as ‘Golden Delicious’. Additional Details about Apple rust mite

Campylomma

Campylomma is a sporadic pest of apple, and primarily a beneficial insect (pear psylla predator) on pear. It overwinters in the egg stage on the tree in the bark, and emerges just before and during apple bloom. Large populations require control as soon as they are detected; earlier sprays will do a better job of preventing fruit damage. Pay attention to label restrictions of bloom applications to protect pollinators. Petal-fall sprays will kill nymphs, but prevent little if any fruit damage. Additional Details about Campylomma

Codling moth

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. Additional Details about Codling moth

Lacanobia fruitworm

First generation control sprays should be applied by 1230-1250 degree-days, when only about 10% of the larvae are in their 4th instar. This timing represents the best opportunity to control Lacanobia subjuncta with a single insecticide application. During the second generation, 10% of 4th instar is estimated at 3050 degree-days. The best timing for an insecticide application against larvae of the second generation is at 3050 degree-days, but no later than 3150 degree-days. Additional Details about Lacanobia fruitworm

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 about Leafrollers (Pandemis, Obliquebanded)

Rosy apple aphid

Starting at pre-pink monitor 5-10 trees from each block in sensitive varieties. Treatment is justified when more than one cluster per tree is infested. Sprays become progressively less effective as the season advances and leaves curl.

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 about San Jose scale

Shothole borer

Good sanitation (removing large wood prunings, dead limbs, and woodpiles from the orchard) is the most effective management tactic. Insecticides are only effective against adults. Beetles begin flying in late April and are active through May. The second generation flight begins in late July or early August. Yellow sticky traps placed on orchard borders will detect adult beetle activity. Spraying the border trees (rows) with high water volumes will protect the remainder of the orchard in many situations where external sources are the primary problem. Additional Details about Shothole borer

Western tentiform leafminer

For best results against leafminer, use an adjuvant with abamectin and spinosad. See labels for specific adjuvant recommendations.

White apple leafhopper

Adults fly from late May until frost. Monitor nymphs on the underside of leaves. Egg parasitoid Anagrus spp. attacks overwintering and summer eggs. Only control this indirect pest when necessary. Additional Details about White apple leafhopper

Woolly apple aphid

Woolly apple aphid has proven to be one of the most difficult of the aphid pests to control in recent years. The broad-spectrum organophosphates used in previous years are no longer used, and relatively few effective materials remain. This aphid is attacked by many predators (syrphid larvae, lady beetles, lacewings, and earwigs) and a parasitoid, Aphelinus mali. These natural enemies may provide control under some circumstances, but biological control may be easily disrupted. Avoid using disruptive pesticides if possible, and if necessary, treat with one of the effective insecticides. See tables. Additional Details about Woolly apple aphid

Major Diseases

Apple 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 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 to powdery mildew. Germination and infections are optimal at temperatures between 60F and 78F. Wetness plays a marginal role. The fungus then continues with multi-cycle infections through spring and early summer until the production 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.

Apple scab

Scab, caused by the fungus Venturia inaequalis, is a major disease of pome fruit in many growing regions, especially those with high rainfall. Symptoms are gray-brown to blackish lesions on leaves and fruit. Scab risk is low under arid conditions in Central Washington. However, some microclimates in the north of the state can be conducive to scab, and therefore, management is recommended. Where scab is a problem, the fungus overwinter in fallen leaves making leaf removal/incorporation critical to reduce inoculum for the following season. Scab is effectively controlled by the same fungicides sprayed for apple powdery mildew including fungicides from FRAC groups 3, 7 and 11.

Botrytis-Gray Mold

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

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.

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 (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).

Storage Rots (Sphaeropsis, Lambertella, Alternaria)

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.

Major Fruit Protectants

Apple Sunburn

Sunburn damage costs apple growers tens of millions of dollars annually and is often the primary cause of fruit cullage for apples grown in the Pacific Northwest. Growers often lose more than 10% of their apples to sunburn unless they have used some means of protecting their fruit from sunburn damage. There are four types of apple sunburn: (i) Sunburn Necrosis, (ii) Sunburn Browning, (iii) Photo-Oxidative Sunburn, and (iv) Storage Sunburn. Apple fruit are susceptible to sunburn because they have a much higher thermal mass (the ability of a material to absorb and store heat energy) than leaves and are not able to dissipate this heat as effectively as leaves. It is important to remember that fruit temperature can be considerably higher (20 - 30°F) than the ambient air temperature.