Download Section 3 Chinese Rose and Tulip Disease

Chapter 8
Flower Disease
Section 3 Chinese Rose and
Tulip Disease
（月季和郁金香病害）
1. Chinese Rose Black Spot （黑斑病）


Roses are an important horticultural crop in the
word，Black Spot is most familiar disease of
rose.
The disease can cause almost complete
defoliation of bushes by early fall. It produces a
weakened bush on which cane dieback, stem
canker, and winter injury can become severe.
1.1 Symptoms（症状）

Circular black spots ranging from
1/16 inch to 1/2 inch in diameter
appear generally on leaves’ upper
sides. The spots are frequently
surrounded by a yellow halo.
Infected leaves characteristically
turn yellow. They fall prematurely.
This leaf spot can be distinguished
from others by the fringed margin
and consistently black color. Cane
infection produces a reddish-purple
spot. In many varieties, pale flower
color is also indirectly caused.
1.2 pathogen
Diplocarpon rosae 放线孢属，半知菌
 Acervuli 分生孢子盘o n a leaf surface

1.3 Disease Cycle
Black spot is spread by splashing water.
Infection occurs after leaves are wet for
several hours. Therefore, the disease is
more serious during periods of rainfall.
1.4 Control
 Reduce
overwintering fungi:
 A preventive program for black
spot should begin with a thorough
cleanup in the fall.
 Diseased leaves on the ground
should be raked and destroyed. All
diseased canes should be pruned
off by cutting several inches into
good wood. These precautions
reduce overwintering fungi.
Chemical control

A fungicide program should start in the
summer just before leaves become spotted.
From then until frost, the leaves may require
a protective fungicide coating. When the
leaves are growing rapidly or during rainy
weather, it may be necessary to spray the
plants two times a week. However, if growth
is less rapid and rains are less frequent,
spraying at 7 to 10 day intervals is usually
sufficient. Proper timing is as important as
the chemical spray. （Chlorothalonil百菌清，
Captan克菌丹， Lime-Sulfur 石硫合剂）
2. Chinese rose Powdery Mildew
（月季白粉病）

This disease can cause young leaves to curl
and turn purple. Young canes may be
distorted and dwarfed. If seriously infected,
they can die. Badly infected buds do not open.

月季白粉病是世界性病害，普遍发生，玫瑰、蔷薇也受其
危害。此病一旦发生，降低切花产量及观赏价值。
2.1 Symptoms(症状)

Leaves, buds, and stems are covered
with a white powdery coating.
2.2 Pathogen

Sphaerotheca pannosa (Wallr.) Lev.(毡
毛单囊壳菌) and S. rosae(Jacz)Z.Y.
Zhao(蔷薇单囊壳) .属于子囊菌亚门单囊壳
属。附属丝菌丝状较短。闭囊壳内只有一个
子囊，椭圆形或长椭圆形，少数球形。无性
态为粉孢属（Oidium.sp）
2.3 Rule of disease occurring

The germ mainly overwinterring by the
mycelium in the bud, some areas
overwinterring on the host by the
ascocarp(子囊果). The conidia can
invade the anniversary in the
greenhouse, taking advantage of air
current dissemination directly to
invade host. If the condition is suitable,
conidia(分生孢子) can produce for many
times,and invade(侵染)many times.
2.4 Disease Cycle
 The
white fuzzy growth on the leaf
surface contains thousands of
fungal spores. Wind carries these
spores to young leaves, causing
more infection. Mildew diseases of
other plants do not infect roses.
Mildew develops rapidly during
warm, humid weather.
2.5 Control

Throughout the growing season, the infection
can be reduced through sanitation and
fungicide application. Pruning and destroying
all dead or diseased canes in the spring will
reduce the initial fungus population. During
the growing season, all diseased leaves
should be destroyed. New growth is
especially susceptible; therefore, a thorough
spray or dust coverage of canes and upper
and lower leaf surfaces (especially growing
tips) is essential. Under most conditions,
weekly applications are adequate; however,
treat more often during rapid new growth,
temperature fluctuations, and frequent rains.
3. Tulip breaking virus
(郁金香碎色花瓣病)
3.1 Symptoms
 This is the most commonly
seen virus disease in tulips. It
causes colour ‘breaking’ or
streaking of the flower colour
in pink, purple and red
flowered tulips, but white and
yellow flowered cultivars are
not affected. It is particularly
seen in late-flowering
cultivars. Mottling(斑纹) or
striping(条斑) of the leaves
also occurs. Other symptoms
include loss of vigour and
poor flower production.
While tulip breaking virus is now
known to be undesirable due to the
loss of vigour it causes, some ‘broken’
tulip flowers can look very
spectacular. In the 17th century,
when the craze for tulips was at its
peak in Holland and the cause of
flower breaking was unknown, bulbs
producing broken flowers were
extremely desirable and valuable.
3.2 Biology
 The
disease is spread by several
aphid(蚜虫) species - Myzus
persicae, Macrosiphum
euphorbiae, and Aphis fabae.
3.3 Control
 Control
using insecticides is not
very effective. Remove and
destroy infected bulbs.
 Avoid planting tulips close to
lilies, which may harbour the
virus without visible symptoms.
Cucumber mosaic virus

This disease is also seen in lateflowering cultivars. Symptoms appear
as grey-brown sunken spots or rings on
the bulb scales, which appear in
storage. These bulbs produce deformed
plants with chlorotic lesions on the
leaves and aborted or damaged flowers.
The disease is spread by aphids and
also affects many other plants.
Removal of the bulbs is the only control.