Ornamentals Powdery mildew of rose.

Ornamentals Powdery mildew of rose.
By Dr. Sarika Sangekar

1. ORNAMENTALS: A. POWDERY MILDEW OF ROSE

DR. SANGEKAR SARIKA

DEPT- BOTANY YOGESHWARI
MAHAVIDYALAYA
AMBAJOGAI

2. STUDY OF THE FOLLOWING DISEASE WITH RESPECT TO
SYMPTOMS,

CAUSAL ORGANISM,

DISEASE CYCLE AND

DISEASE MANAGEMENT

3. CAUSAL ORGANISM

4. a
=
ill!

5. INTRODUCTION

It is a common disease in the rose .
It may cause severe injury.

Powdery mildew of roses does not attack plants outside the
genus Rosa.
The disease has been reported almost from all European

countries, Asia & Australia, North & South America etc.

The causal organism was described in 1819 & is attacking all
parts of rose, more frequently leaves & young shoots.

6. SYMPTOMS :-

The first symptoms are raised, blister like areas on the young leaves, which
may become covered with a white, powdery, fungus growth.

The powdery appearance of the lesion is due to fungal spores.

Older leaves may be affected, usually with little distortion, but growing leaves
become twisted and misshapen.

Leaves Showing Yellowing.

Young growing tips are commonly completely covered by the mildew, the
result is dwarfing & curling of leaves & buds.

Buds do not open & become dwarf & finally die.

7. PODOSPHAERA PANNOSA.

The white patches on the leaves & stems, composed of slender, white threads of mycelium.
Conidiophores bear chains of egg shaped Conidia.

Conidia are disseminated with wind current & cause secondary infection.

At the end of growing season globose fruit bodies; i

tially brown & then turns black, may appear.
These are buried more or less in mycelial cushion. On leaves, thorns & canes etc.

Although winter fruit bodies, the perithecia have occur more frequently on stem they also occur on
under surface of leaf near mid vein.

Within perithecium small sac like asci containing 8 ascospores each. Winter spores are same in size to
summer spores. Ascospores mature & become ready for dissemination in the spring.

The fungus hibernate in summer stages (mycelia & conidia).

8. DISEASE CYCLE

9. DISEASE MANAGEMEN

1. Because the mildew fungus occurs externally on the rose (except the
haustoria which enter only the epidermal cells)

2. itis possible to kill it by spraying with fungicide.

3. Common fungicides include Lime — sulphur, potassium sulphide,
wettable sulphur, Bordeaux mixture, copper oxide etc.

4. Sulphur is used generally when temp is low.

5. Whenever temp gets into 90 o f. & above causes injury to rose i.e.
host.

6. Mixtures of sulphur & lead arsenate are also preferred in which 50%

sulphur is present.

7. Dusting of sulphur must be started early in the season, before infection

occurs & continued at regular intervals.