Cause There are many storage rots caused by abiotic problems. Many of these are covered in a separate section on Apple-Storage Problems.
Bartlett Decay-If the water is warm (caused by running fruit picked on a hot day) or the SOPP concentration is too high, or the rinse is inadequate, burning at the lenticels can result.
There are also several storage rots caused by microorganisms, which are included below.
Alternaria rot-Alternaria alternata. Infection occurs through skin breaks or areas weakened by sunburn, bruising, senescence or scald.
Bull's-eye rot-Neofabraea perennans and N. vagabunda (formerly Neofabraea alba ). Infection is in the field from apple tree cankers or pear bark. Fruit can become infected any time between bloom and harvest, but susceptibility increases as the growing season progresses. The disease progresses more quickly when infection is through a wound. Rain or overtree irrigation during the growing season encourages disease spread and rot development. 'Bosc' is highly susceptible.
Blue mold-Penicillium expansum. Delays in cooling fruit after harvest can increase risk of this rot. The fungus can infect through wounds, lenticels, and bruises late in storage. High nitrogen levels and tree vigor also contribute to disease development.
Cladosporium rot-Cladosporium herbarum.
Storage scab-Venturia pyrina.
Gray mold-Botrytis cinerea. Spores from the orchard infect through wounds.
Sprinkler rot-Phytophthora cactorum. Infection is from irrigation water on fruit in the field.
Coprinus rot-Coprinopsis psychromorbida (formerly Coprinus psychromorbidus).
Mucor rot-Mucor piriformis. Spores come from soil or fallen fruit on the orchard floor.
Phacidiopycnis rot- Phacidiopycnis pyri has been found in all major pear-producing areas of the Pacific Northwest. It is associated with dead bark, cankers and twig dieback of pear trees. Spores from pycnidia are the main type of inoculum in the orchard. Infection of fruit occurs in the orchard between bloom and harvest but symptoms develop in storage. Preventing infections close to harvest is recommended.
Side rot-Cadophora malorum (formerly Phialophora malorum). 'Bosc' is very susceptible.
Sphaeropsis rot-Sphaeropsis pyriputrescens can cause a postharvest fruit rot of d'Anjou pear and several cultivars of apple. It is present in most apple and pear-producing areas of central Washington. The fungus can be found on diseases twigs, dead fruit spurs, and mummified fruit on production trees and crabapple pollinizers such as Manchurian. Infection of fruit occurs in the orchard and symptoms develop in storage.
Symptoms Bull's-eye rot-spots with light brown centers and a dark brown border. Firm, mealy texture. Rot does not spread from one fruit to another. Does not show up in the orchard but after months of storage.
Blue mold-large, light brown rots with a blue, moldy growth in the center. Rots are soft and watery.
Cladosporium rot-dark brown, water-soaked spots. Can be similar to side rot.
Storage scab-small, light brown, sunken spots.
Gray mold-large pockets of fruit rotting with a fuzzy gray moldy growth on the surface.
Sprinkler rot-lesions are light brown and soft with a pungent, phenolic odor.
Fire blight-lesions are dark brown and hard.
Coprinus rot-large depressed spots with light brown centers and a thinner, dark brown margin. A white cobweb-like growth on the surface can cause a nest or cluster of rotted fruit. Can be mistaken for bull's-eye rot.
Phacidiopycnis rot-Rot may occur on the calyx or stem end or be associated with wounds. Decayed areas appear water-soaked in the early stages of rot. As the rot develops the decayed areas turn black but the margin continues to be water-soaked. Decayed fruit eventually look like a ripe avocado. May be confused with gray mold early on but the margin of Phacidiopycnis rot appears translucent while gray mold appears brown.
Side rot-dark spots indistinguishable from Cladosporium rot.
Sphaeropsis rot-A firm, brown rot of the calyx or stem end. The fungus may form pycnidia in the decayed areas as the rot advances. The internal decayed flesh appears brown. Decay develops along the vascular tissue. Symptoms are similar to gray mold except with a strong odor.
Cultural control A combination of techniques will aid in overall control.
- Avoid use of over-tree evaporative cooling or use it in such a way that fruit is not wet for extended periods of time.
- Use low-angle sprinkler nozzles.
- Maintain good in-row weed control; mow grass between rows.
- Use foliar nutrient sprays before harvest. Calcium-based products have helped. Nutraphos-24 applied at 15 lb/A 3 weeks before harvest reduced blue mold in 'Anjou' pears by 50%. Summer applications of calcium chloride, three (3) times 2 weeks apart, help reduce both blue mold and side rot.
- Use a minimal amount of nitrogen fertilizer.
- Harvest at proper maturity, and instruct harvesters on the proper technique for removing fruit from the tree. Late harvest means increased decay.
- Clean fruit bins before filling, and keep soil off the bottom. A hot water pressure wash or steaming can help clean bins. Clean storage rooms of all debris well before filling and treat surfaces with a disinfectant.
- Harvest and cool fruit quickly. Keep bins out of sun.
- Avoid injuring fruit. This is very important. Smoothing orchard roads and driving slowly helps. Also paying pickers by the hour rather than by the bin has resulted in fewer stem punctures.
- Controlled-atmosphere storage, especially with low (1%) oxygen, reduces the incidence and severity of bull's-eye rot.
- Do not return culls back into the orchard.
- Fungicides applied during the growing season, especially before heavy rains preharvest.
- Merivon at 4 to 5.5 fl oz/A is labeled for blue and gray mold. Do not use with EC or oil-based products. May be used day of harvest. Group 7 and 11 fungicide. 12-hr reentry.
- Ph-D WDG at 6.2 oz/A for Alternaira or gray mold. May be applied on the day of harvest. Group 19 fungicide. 4-hr reentry.
- Pristine at 14.5 to 18.5 oz/A within 14 days of harvest for gray mold and blue mold. Do not use more than two (2) consecutive applications or more than four (4) times/year. Can be used day of harvest. May not be effective if used for powdery mildew or scab management during the growing season. Group 7 + 11 fungicide. 12-hr reentry.
- Topsin M WSB at 1 lb/A for pears and at 0.75 to 1 lb/A for apples. Do not use more than 4 lb/A/season or within 1 day of harvest. Do not use at any time in the orchard if your packing house uses a benzimidazole (such as Mertect or Decco Salt 19) postharvest. Group 1 fungicide. 2-day reentry.
- Ziram 76 DF at 6 lb/A for gray mold. Do not use within 14 days of harvest. May irritate the skin of people who harvest fruit. Group M3 fungicide. 48-hr reentry.
- Fruit Wraps can be used for several storage problems of pear.
- Burrows E Wrap can be used for scald control. Do not use on pears that have been treated with ethoxyquin and do not re-use wraps.
- Pear Wrap III is treated with both ethoxyquin and copper. Do not re-use wraps.
- Wash fruit in one of these solutions within 6 weeks of harvest. Make sure all fruit surfaces are covered well. Drenches tend to be better than sprays. Avoid using fungicides with the same active ingredient every year. Avoid using the same fungicide twice on the same fruit. Resistance to fungicides has been detected in Washington.
- Captan 50 WP at 2.5 lb/100 gal water. Group M4 fungicide.
- Judge 50 WDG as packing-line spray at 1 to 1.5 lb/8 to 20 gal water for 200,000 lb fruit or as a 20 to 30 second dip at 1 to 1.5 lb/100 gal water. Registered for Botrytis management. Group 17 fungicide.
- Penbotec 400 SC at 16 to 32 fl oz/100 gal water for dip (wash) tanks or drenchers. Soak for at least 30 seconds then drain fruit. Concentration should be maintained at 500 to 1000 ppm. Registered for blue and gray mold. Group 9 fungicide.
- Scholar SC at 10 to 16 fl oz/100 gal of an appropriate carrier for bin, truck or in-line dip/drench. Use at 16 to 32 fl oz/200,000 lb fruit as an in-line aqueous or fruit coating spray. Can be used twice, once before storage and again after storage. Do not expose treated fruit to sunlight. Registered for both apple and pear. Group 12 fungicide.
- Sodium hypochlorite (Agclor 310 at 1.125 to 1.5 gal/1000 gal water for apples or 1.5 to 2.25 gal/1000 gal water for pears). Filtration of the wash water will help reduce the total amount of chlorine needed.
- Sodium orthophenylphenate (Stop Mold, Steri-Seal, or Deccosol). Use Deccosol 122 at 1 gal/44 to 56 gal water. Can also be applied using thermal fogging under SLN WA-080013.
- Thiabendazole. Group 1 fungicides.
- Decco Salt No. 19 at 575 g/250 gal water.
- Decco Salt No. 38 at 575 to 1,150 g/300 gal water. Washington only.
- Mertect 340 F at 16 fl oz/100 gal water.
- Shield-Brite TBZ is also registered. See label for details.
- Bio-Save 10 LP (Pseudomonas syringae strain ESC-10) at 500 g/80 gal water. Bio-Save 11 LP (Pseudomonas syringae strain ESC-11) is also registered. Suspend in water for 10 to 30 min before use and agitate periodically. Dip or drench at least 1 min. Rated as moderately effective. O
- Botector (Aureobasidium pullulans strains DSM 14940 and 14941) at 6 to 14 oz/A depending on water volume as a preharvest application to control postharvest problems. Can be applied day of harvest. Compatible with sulfurs, oils and a few fungicides but not with many synthetic fungicides. Efficacy has been limited and inconsistent. 4-hr reentry. O
References Henriquez, J.L., Sugar, D. and Spotts, R.A. 2004. Etiology of bull's eye rot of pear caused by Neofabraea spp. In Oregon, Washington and California. Plant Disease 88:1134-1138.
Kim, Y.K., and Xiao, C.L. 2010. Resistance to pyraclostrobin and boscalid in populations of Botrytis cinerea from stored apples in Washington State. Plant Dis. 94:604-612.
Liu, Q., and Xiao, C.L. 2009. Infection of 'd'Anjou' pear fruit by Potebniamyces pyri in the orchard in relation to Phacidiopycnis rot during storage. Plant Dis. 93:1059-1064.
Sugar, D. Benbow, J.M., Powers, K.A. and Basile, S.R. 2003. Effects of sequential calcium chloride, ziram, and yeast orchard sprays on postharvest decay of pear. Plant Disease 87:1260-1262.
Xiao, C.L., Kim, Y.K., and Boal, R.J. 2014. Sources and availability of inoculum and seasonal survival of Sphaeropsis pyriputrescens in apple orchards. Plant Dis. 96:1043-1049.