Chapter 8 Flower Disease

Study keystone of this chapter

The peony( 牡丹 ), the chrysanthemum( 菊花 ), the Chinese rosa( 月季 ), the orchid( 兰花 )and the tulip( 郁金香 )and so on, the typical flowers’s disease symptom, pathogen, the rule of occurring and controlling technology.

Section 2 Peony Disease 1. BOTRYTIS BLIGHT OF PEONY

（牡丹灰霉病）

1 Occurring and damage Botrytis blight is one of important peon

y's diseases in the world, often occurs in our country. It is more serious in Shanghai, Zhengzhou. This disease may occur in all peony's growth season, is serious to the young tender adult plant, causes seedling's damping off ( 倒伏 ) and wilt( 枯萎 ).

2. Sympotoms The Botrytis fungus grows over new shoots of peony an

d covers them with a dense velvety gray mold. Very young shoots may be blighted early on, turn black. Botrytis may also grow on developing flower parts causing bud blast and flower blight. Some buds may die without opening. Flower infections can move down into the stem causing a brown and tan target-like discoloration. Infected petals ( 花瓣 ) which drop onto leaves can result in leaf spots. Late in the season, very small, shiny black, somewhat sausage-shaped fungal structures called sclerotia ( 菌核 ) may be found just under the epidermis at the base of infected shoots.

3 Pathogen

Botrytis paeoniae Oud. ( 牡丹葡萄孢 ) ， belong to imperfect fungi ( 半知菌 ).The conidiophore erect, pale brown, septa. Conidia gathers to capitate, egg circular to the near rectangular circular; Colorless to pale brown, single , size 9-16×6-9μm . Sclerotia’s ( 菌核 ) size1-1. 5mm.

4 Condition of disease occurring

Botrytis infections are favored by cool (15oC ), rainy spring and summer weather. Gray mold can be particularly damaging when rainy, drizzly weather continues over several days.

低温、潮湿是发生 病的主要条件。春天温度较低，阴雨连绵加重幼苗的发病。该病常发生在寄主开花期后， 6 月～ 7 月为发病盛期。株丛密度大，氮肥多，有利于发病。

Disease Cycle Botrytis blight of peony infects the base of yo

ung shoots as they emerge from the ground. This disease may also infect buds or flowers a

t any stage, depending on when favorable weather conditions occur.

During wet periods, infection may spread quickly, blighting most open flowers as well as emerging buds. Severe infection may cause much of the foliage to turn brown and dieback prematurely.

In late summer, sclerotia develop in dead plant tissue, forming the overwintering stage of the fungus.

Development of Botrytis gray mold diseases.(provided by George Agrios, Plant Pathology 4th Edition)

5 Control1. sanitation The best way to manage this disease is by inspectio

n and sanitation. Remove faded or blighted flowers, blighted leaves, or entire plants infected at the base and place them in the paper bag so that they may be discarded with the trash or burned.

2. Likewise avoid overhead watering, syringing, or misting plants especially if Botrytis blight has been troublesome in the past. To promote rapid drying of plants space them to allow good air circulation.

3. Fungicide sprays may also help by protecting plants from infections.

1% 石灰等量式波尔多液， 70% 甲基托布津 1000 倍液，65% 代森锌 500 倍液，或 50% 氯硝胺 1000 倍液。每隔10 天～ 15 天喷 1 次，连续喷 2 次～ 3 次。③加强栽培管理：栽植密度要适度；雨后及时排水，株丛基部不要培湿土；重病区要实行轮作；栽植无病种苗，苗木可用 65% 代森锌 300 倍液浸泡 10 ～ 15 分钟。

When Botrytis blight of peony is a problem avoid the use of dense, wet mulches and apply the first fungicide spray in early spring just as the red shoots begin to push up out of the ground. With continuous inspection and careful sanitation gray mold can be effectively managed. Keep an eye out for the silvery-gray mold and/or tiny black sclerotia which are sure signs of this disease.

2. Phytophthora Blight

2.1 Occurring and damage The symptoms of blight caused by th

is fungus, Phytophthora cactorum, may be confused with the symptoms produced by Botrytis sp. The stems, leaves, and buds can be affected by both diseases.

2.2 Sympotoms

1. Comparing grey mildew disease with Phytophthora blight, there is no felty growth or sporulation on the plant surface when in a wet environment.

2. Infected parts become dark brown or black and somewhat leathery. The entire shoot may turn black and die.

Phytophthora blight often invades the crown and causes a wet rot.

3. Control

Because infections of this disease generally occur in the roots and lower portions of the stem, spraying with fungicides is of little value. Confirmed cases should be removed and destroyed, together with adjacent soil. Planting healthy clumps in new locations where the soil is well drained usually prevents further trouble.

3. Cankers may appear along the stems and cause them to fall over.

4. Cankers may appear along the stems and cause them to fall over. While Botrytis sp seldom invades the crown, Phytophthora sp often does, causing a wet rot to develop and destroy the entire plant.

3. White Mold3.1 Sympotoms

Mainly causes stem rot on peony as well as on many different herbaceous plants found in the garden. The entire plant or portion of the plant may wilt. The infected part of the stem turns a light tan color and may become dry and stringy. Fluffy white mycelium often appears under humid conditions, thus the name, white mold.

3.2 pathogen Sclerotinia sclerotiorum Sacc.

（小核菌） belong to imperfect fungi ( 半知菌 ).This fungi can not form conidia ( 分生孢子 ). Various sizes of irregularly shaped, hard black sclerotia( 菌核 ) may be found inside the tan area of the stem. Sclerotia are the verwintering structures for this fungus and they can survive for many years in the soil.

3.3 Control Remove and dispose of any infected

plant parts being careful to not drop the sclerotia. Sclerotinia is a soil-inhabiting fungus that is nearly impossible to remove. Replant infested areas with nonsusceptible plants. Wider spacing to improve air circulation will minimize infection by this fungus.