Storage rots

Introduction

Fungal rots are responsible for significant losses in stored apple in most seasons. They can be divided into two broad groups:

Those causing rots primarily after harvest (store diseases)
Those that also cause rots in the orchard (orchard diseases).

Rotting in store due to the latter group mainly results from fruit infection that occurred before harvest, but remained symptomless and subsequently developed in store. The store diseases are usually wound rots which gain entry to damaged fruit at harvest.

Cox is most susceptible to rotting. Losses in other varieties such as Bramley, Braeburn, Gala or Jonagold are usually much lower, but occasionally certain fungi e.g. Phytophthora syringae, can cause significant losses in these varieties. Orchards differ considerably in actual losses due to rots and the main fungi responsible.

Information on losses in store and the rots responsible for an orchard is important if losses are to be minimised and the appropriate control measures applied. This information can be obtained from assessment of rots in the packhouse during grading.

Factors affecting fruit susceptibility to rotting

Fruit maturity: correct harvest date is important as overmature fruit are more prone to damage and rotting.

Handling: poor handling of fruit at harvest increases the risk of wound fungi such as Botrytis, Penicillium and Mucor.

Mineral composition: fruit low in calcium and high in potassium and nitrogen are more prone to rots particularly Gloeosporium in Cox. Therefore, correct mineral composition is important for varieties such as Cox and Bramley.

Weather: rainfall is the most critical factor in determining infection of apples by fungi. Wet summers and harvests usually result in high rot incidence in store.

Storage rots (orchard diseases)

Disease	Varieties	Source	Entry	Weather factors	Cultural control	Fungicides
Brown rot (Monilinia fructigena)	All varieties	Cankers, mummified fruit on orchard floor and tree	Initially by wounds. Spread by contact	Warm summer + rain	Prune out cankers Remove/collect mummies Good control of P&D Avoid fruit damage Close supervision of pickers to ensure no damaged fruit is stored	Pre-harvest spray depending on risk
Black rot (Botryosphaeria obtusa) See images below	Cox Fiesta + others	Cankers, mummified fruit, dead twigs, prunings, weeds	Direct and wounds	Warm (20ºC) + rain, humid	Prune out cankers and dead wood Remove/collect mummies Avoid piles of prunings in orchard	At present not important enough to require special measures
Gloeosporium rot (Gloeosporium spp)	Cox, Gala Jonagold Egremont Russet	Cankers, pruning snags, mummified fruits	Direct, through lenticels, eye, stalk, russet cracks	Warm weather + rain	Prune out cankers, dead stubs and die-backs Remove mummies	Pre-harvest sprays July-September
Phytophthora rot (Phytophthora syringae)	All varieties	Soil splash	Direct entry, spread by contact	Wet especially near picking	Maximum width grass strip Mulching to cover soil to reduce soil splash Removing low hanging branches Selective picking Not muddying bulk bins Encouraging earthworms to remove leaf litter	Post-harvest urea to trees to encourage leaf rot when fall Pre-harvest sprays

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Botryosphaeria rot on apple fruit in orchard showing characteristic concentric zones of rot growth

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Botryosphaeria rot around calyx end of Cox apple, associated with insect damage

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Botryosphaeria rot at eye end of Cox apple after CA storage showing characteristic purple colour

Storage rots (orchard diseases)

Disease	Varieties	Source	Entry	Weather factors	Cultural control	Fungicides
Nectria rot (Nectria galligena)	Cox, Bramley, Gala Egremont Russet	Cankers	Direct through lenticels, stalk end, eye end	Wet autumn at leaf fall. Wet spring, summer	Removing cankers and macerate with prunings	Post-harvest copper sprays to protect leaf scars, sprays at bloom and petal fall Pre-harvest sprays
Diaporthe rot (Diaporthe perniciosa) *See image below*	Cox, Bramley, Jonagold, Gala	Cankers, dead wood, mummies	Direct on mature fruit long-term stored	Warm and wet	Remove cankers, dead and weak wood during pruning	Rot usually not important enough to merit special control measures
Botrytis eye and core rot (Botrytis cinerea)	Cox	Ubiquitous especially dead plant material, e.g. flowers	Direct from dead petals to eye or to core. May require mature fruit to rot	Humid or wet	None	Possibly sprays during bloom

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Diaporthe rot on Cox

Storage rots (orchard diseases)

Disease

Varieties

Source

Entry

Weather factors

Cultural control

Fungicides

Fusarium rot

(Fusarium spp)

Cox, Bramley, Cameo

Orchard soil, plant debris, cankers, dirty bulk bins

Wounds

Core rot

Rain, warm weather

Prune out old Nectria cankers and pruning snags.

Usually not important enough to merit special attention on most varieties. On Bramley and Cameo apply fungicide sprays at blossom and petal fa

Storage rots (store diseases)

Disease	Varieties	Source	Entry	Weather factors	Cultural control	Fungicides
Botrytis rot (Botrytis cinerea)	All varieties	Plant debris, orchard soil, dirty bulk bins	Wounds. Infected stems	Store disease rapid growth at low temperatures	Careful picking to avoid wounds Good control of pest and disease Avoid muddying bulk bins and introducing debris such as leaves Clean bulk bins	Pre-harvest sprays may give some control
Blue Mould (Penicillium expansum)	All varieties especially Bramley	Plant debris, orchard soil, dirty bulk bins	Wounds, direct entry on over-mature fruit	Store disease	Careful picking and handling to avoid damage Good control of pest and disease Avoid muddying bins and introducing debris such as leaves Clean bulk bins	Post-harvest dips/drenches aggravate the problem
Mucor rot (Mucor spp)	All varieties	Orchard soil, dirty bulk bins	Wounds or through open eye in drench solution	Store disease rapid growth at low temperatures. Wet harvesting	Avoid muddying bins and introducing debris Clean bulk bins Removing fallen fruit from orchard after harvest to reduce fungus population in soil Store dry fruit	No fungicides are effective against Mucor Post-harvest dips/drenches aggravate the problem

Apple Best Practice Guide

Storage rots

Introduction

Factors affecting fruit susceptibility to rotting

Storage rots (orchard diseases)

Storage rots (orchard diseases)

Storage rots (orchard diseases)

Storage rots (store diseases)

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