Chapter 7 Fruit Disease

Section 2 Fruit Disease

苹果轮纹病

苹果炭疽病

苹果青霉病

苹果霉心病

苹果煤霉病

苹果褐腐病

梨黑星病

梨轮纹病

葡萄白腐病

葡萄黑痘病

葡萄黑腐病

柑橘青霉病

柑橘绿霉病

桃褐腐病

桃褐斑病

枣黑腐病（缩果） 枣炭疽病

1.1 Occurring and damage Brown Rot is one of the most common and

serious diseases affecting peach fruits. Field losses of nectarines can be extensive if conditions favorable for disease development occur during the blossoming or preharvest and harvest periods. Losses of peach vary with susceptibility of the cultivar.

桃褐腐病又称果腐病、菌核病，是我国南北方桃树上的重要病害。温暖潮湿地区虫害严重的果园常流行成灾。可危害桃、杏、李、樱桃等。

1. Brown Rot, 1. Brown Rot, Monilinia fructicolaMonilinia fructicola 桃褐腐病桃褐腐病

1.2 Sympotom （症状） Fruit rot starts with a small, round brown spot, whic

h expands to eventually rot the entire fruit. Infected fruit turns into a mummy on the tree. Except fruit it can also infect flower blossoms and shoots. The disease begins at bloom. Infected flowers wilt and turn brown very quickly. Shoot infections (usually from flower infections) result in small (1 to 3 inches), gummy cankers, which provide the source of infection （侵染） for fruit rot. Spores from infected flowers and cankers infect aborting fruit and healthy green fruit during long wetness periods. Infected, aborted fruit remain attached in the tree and provide an additional source of spores for more infections instead of dropping off in a normal fashion. Infections in apparently healthy green fruit remain inactive until the fruit begins to ripen （成熟） .

1.3 Pathogen

该病由子囊菌亚该病由子囊菌亚门核盘菌门核盘菌属属 monmonilinailina 和无性世代和无性世代的丛梗孢属的丛梗孢属 monimonilialia 真菌侵染所致真菌侵染所致。病菌产生子囊。病菌产生子囊盘和子囊孢子，盘和子囊孢子，并产生分生孢子并产生分生孢子。。

1. 僵果及子囊盘 2. 分生孢子梗　　分生孢子链及分生孢子

1.4 Rule of disease occurring

Disease Cycle ( 侵染循环 ) M. fructicola overwinters in orchards as mycelium on mu

mmies, fruit stems, blighted blossoms and twigs, and cankers. Sporodochia develop under cool, wet conditions during the winter and early spring. Occasionally, cup-like apothecia of M. fructicola which produce ascospores can be found on fruit mummies under the tree.

影响发病的因素 开花期低温多雨易引起花腐、叶腐或枝腐，果实成熟期温暖、

潮湿、多雨、多雾易引起果腐。贮藏期间病健接触也能传病。 果实皮薄多汁发病重。 虫害的发生程度和病害的危害轻重密切相关，虫害多发病重。 管理粗放，栽植过密、修剪不当、通风透光差病害发生重 桃、杏、李混载也有利于发病。

Disease Cycle

1.5 Prevention and Treatment

1.5.1 Cultural practices: Sanitation is essential if your orchard is to be considered a low risk for a brown rot epidemic. The practices listed below, if followed, should minimize brown rot spore populations and limit the likelihood of an epidemic when conditions are favorable for rapid disease development.

1.5.2 Chemical management Fungicides are usually required if fruit ripening o

ccurs during a period of warm, wet weather. It is important to begin spraying just before the fruit begins to ripen. Look for the first tinge of change in the yellow background color. Starting a spray program when rotten fruit is evident will result in poor disease control. Select a fungicide containing thiophanate methyl, captan, or azoxystrobin that is labeled for use on peaches. These fungicides are only effective if complete and thorough coverage of the tree(s) can be obtained. Always apply all pesticides according to directions on the label.

2 Pear scab （梨黑星病）2.1 Occurring and damage Scab is the most serious disease of apples

and pears in all country. Although it is costly to control, neglecting or wrongly applying control measures may reduce fruit yield and quality. Reduced yield is caused by the death of blossoms, shedding of immature fruit, scabbing, cracking and distortion of fruit, and loss of vigour of trees after leaf infection and subsequent partial defoliation. Scab may also develop extensively in stored fruit from infections established before harvest.

2.2 Smypotom Pear scab can invade all greens young tender organ

ization of pear, like leaf blade and petioleJ( 叶柄 ), bud, inflorescence( 花序 ), new tree top and annual branch, the leaf blade and fruit is common.

In the Henan Province mid-north, young leaf is taken bad beginning in the first ten days of May most early, occurring generally in the last 10 days of May to the first 10 days of June.

This symptom main characteristic is: the spot have black green to the black mildew, initial period sick tissue to change yellow, later dried up, sick tissue not to be rotten.

BlossomsBlack patches develop on the

flower stalks. These patches extend, and soon flower and stalk may blacken, shrivel and die.

Leaves

On the upper surface of the leaf, spots first appear as light green areas that soon turn brown, then black and velvety. The spots may be few and scattered, or so numerous that they coalesce and cover almost all the leaf surface. Infected leaves may curve inwards and become blistered and distorted. On the lower surface of the leaf, the disease may appear as a diffuse dark discolouration, tending to extend along the veins. Late in the season many small, rather angular lesions may be seen on the lower surface of the younger leaves.

Fruit Primary infection of Granny Smith apple fruit.

Infection early in the season (right), when fruit is small, results in distortion and cracking as fruit grows.

The spots on apple fruit are at first small, black and circular. They may be so numerous that as they grow they coalesce to form large scabbed areas. The central, older parts of the spots become brown and corky, and growth of the fruit in these areas is greatly restricted. Fruit infected early in the season becomes badly distorted and deep cracks may develop across the scabbed areas.

larger fruit

Spots formed on larger fruit late in the season cause much less distortion; these spots are often surrounded by a whitish band of loosened skin. Early season infection of pears can result in the formation of large corky areas on the fruit. Infection later in the season causes the formation of dark sunken spots.

Fruit before harvest Infections which occur just before

harvest can be invisible when fruit is picked, but will be apparent when fruit is removed from cool store some months later.

Twigs

Infected twigs develop a flaky appearance, when the bark becomes blistered and ruptured in places. Twig infection is rare with apples, but more common with pears.

2.3 Pathogen （病原） pear scab is caused by Venturia pirina( 梨黑星孢 )th

e fungus. The closely related fungus Venturia inaequalis causes Apple scab. The apple fungus cannot infect pears, nor can the pear fungus infect apples.

图 9-1 梨黑星病菌1．子囊孢子 2.子囊壳 2.分生孢子梗及分生孢子

2.4 Dissemination

The fungus is spread by wind and rain, and is favoured by warm, wet weather conditions.

2.5 Life cycle Throughout the growing season the scab fungus li

ves and grows on the tree, producing vast numbers of spores that spread the disease.

The fungus can live over the winter in infected areas on twigs and bud scales, but it mainly survives the dormant season within the leaves that fall in autumn. During winter it forms special structures in the dead leaf tissues, and in these structures, called perithecia, spores called ascospores are formed. By late September many perithecia are mature. When it rains they discharge their ascospores which are carried by air currents onto the trees. Most early or primary infection comes from this source.

Secondary infections Infections caused by conidia are some

times called secondary infections. They may occur from the time of the first primary lesions until the end of the season. The more spores emitted the greater the chance of infection. Consequently, in a season favourable to scab infection, the disease is easier to control in a clean orchard than in a heavily infected one.

2.6 Conditions causing disease

1. The following are necessary for infection:

mature ascospores must be present in the orchard air, or conidia must be present on lesions.

2. The leaves or fruit must remain wet long enough for the spores to germinate and for the resulting fungus growth to enter the plant tissue; this period of wetness is called the infection period.

3. Infection occurs most rapidly at temperatures between 17 and 24. The trees must remain wet for longer periods for infection to take place at temperatures outside this range.

2.7 Disease control

The two keys of Prevents and controls this disease is eliminating the germ and the chemical control in time.

2.7.1 Does well the orchard sanitation Elimination fallen leaf.

2.7.2 Chemical control

Scab control depends on spraying with protective fungicides or eradicant fungicides, or a combination of both.

Protective spraying Protective spraying keeps the susceptible pa

rts of the tree covered with fungicide. Spores lodging on these parts are killed before they can establish an infection. Frequent sprayings are necessary to keep the tree covered with fungicide, especially in October and November. At this time highly susceptible new growth is developing rapidly; ascospores are abundant and conidia may also be present. In wetter districts every apple and pear orchard should be equipped so that the entire area can be sprayed thoroughly in 2 or 3 days.

Curative spraying after infection periods

Control by protection may be supplemented by curative treatment using curative fungicide after infection periods. Some fungicides have the ability to kill the invading fungus for a limited period after infection first started. This is known as the period, and varies from 0 to 5 days, depending on the fungicide. Some of the fungicides with a long kickback action have a relatively short protective ability.

Postharvest foliage treatment

Postharvest foliage sprays are a very useful supplement to scab control, especially after a season of high scab incidence. The principle of control by treatment after harvest but before leaf-fall is to prevent the fungus surviving in the leaves over winter.