This document discusses diseases that affect gladiolus and marigold plants, including their symptoms and methods of control. It describes diseases such as Botrytis soft rot, Fusarium corm rot, Penicillium rot, wilt and stem rot caused by Phytophthora cryptogea, collar rot caused by Phytophthora and Pythium, leaf spot and blight caused by Alternaria, Cercospora and Septoria, powdery mildew caused by Oidium and Leveillula taurica, flower bud rot caused by Alternaria dianthi, and damping off caused by Pythium. Control methods include spraying fungicides, hot water treatment of corm

1. Gladiolus Diseases
&
Marigold Diseases

2. Gladiolus Diseases & its Control
The disease occurs in the cold storage when the temperature stays
below 130-150 C. The disease is characterized by the formation of
white-molded, soft, spongy corms. At early stage, the infection may
be confined to surface only, but later on, it travels to the core as
well. At high temperature, corms seal off infection, escaping further
rotting. In the field, infection is characterized by circular brown leaf
spots. The smallest spots are visible only on the upper surface of
leaf.
 Botrytis Soft Rot (Botrytis gladolorum):
Control Method :-
Leaf infection cab be controlled by spraying the plants with 0.25%
Dithane M-45, twice a week and by dusting healthy corms with
Dithane M-45, during storage.

3. The fungus is carried in corms /cormels, and the soil. Latent infection in corms
may develop into active rotting of corms/cormels during storage and also during
plant growth. Extra losses occur when plant growth is checked by poor soil
aeration, flooding or hot weather. Addition of excess nitrogen in the form of cow
dung manure results in additional casualties. The disease is characterized by rot of
corms, stunted plant growth, late blooming or blind plants, greener and smaller
buds and poor opening. The most serious loss is the reduction in number and
quality of flower spikes due to the infection.
 Fusarium Corm Rot (Fusarium oxysporum f. sp. gladioli):-
Control Method :-
Fusarium corm rot is difficult to prevent but can be controlled to some extent by
growing disease tolerant cultivars and by various control measures. Hot water
treatment of corm /cormels at a temperature of 500C for 30 minutes before
planting, use of clean soil or fumigated soil, and treatment of corms /cormels with
fungicide prevent/ control the disease. The most effective treatment is soaking
the corms in Benlate/ Bavistin 0.02% solution for half an hour before planting and
soil application of Furadan/ Thimet 10G @ 3g/square metre at the time of
planting is very helpful in preventing the incidence of this dreaded disease.

4. This is commonly known as green mold. The disease occurs when
the corms are stored in heaps after having been dug in the cold
weather. Large reddish brown lesions on the sides of the corm
characterize the disease. Sometimes lesions may be covered with
bluish green masses of fungal spores. Hot humid conditions favour
the disease.
 Penicillium Rot (Penicillium gladioli):
Control Method :-
The corms during storage should be examined periodically and
disease corms should be sorted out and discarded. Storing of the
healthy corms may prevent the occurrence of the disease. Dusting of
corms with Dithane M-45 is helpful in preventing this disease during
storage.

5. Marigold Diseases & its Control
The fungus affects the collar portions of the plants. In nursery the
infection results in damping-off and is aggravated by soil moisture. In
the field the infected plants show wilting. French marigold and
dwarf varieties are less susceptible whereas the African types are
highly susceptible to the disease.
 Wilt and Stem Rot (Phytophthora cryptogea) :-
Control Method :-
The disease may be controlled by soil treatment with Captan,
Mancozeb, Metalaxyl and Fosetyl-Al.

6. The symptoms are in the form of black lesions developed on the main stem.
Rotting at the collar regions causes death of the plant. Soil sterilization and
controlled watering help in reducing the disease incidence.
 Collar Rot (Phytophthora sp.; Pythium sp.):
 Leaf Spot and Blight (Alternaria, Cercospora and Septoria sp.):
Brown necrotic spots develop on leaves, which get enlarged at the later stage of
infection. The entire
foliage gets damaged and results in poor vegetative growth.
Control Method :-
The disease may be controlled by Spraying of fungicides is helpful in controlling
the disease.

7. The symptoms are in the form of whitish powdery growth on the aerial parts of
the plant.
 Powdery Mildew (Oidium sp.; Leveillula taurica):
Control Method :-
Spraying Sulfex (3g/litre of water) can effectively control the disease.
 Flower Bud Rot (Alternaria dianthi):
The fungus infects the young flower buds. The infected buds shrivel and become
dark brown in colour. The pathogen also infects leaves causing blight. The
infection is visible in the form of brown necrotic spots on margins and tips of older
leaves.
Control Method :-
Spraying of Mancozeb (2g/litre of water) effectively controls the flower bud and
leaf infections.

8. The disease is most prevalent at the seedling stage. Necrotic spots
and rings develop on the young seedlings causing collapse of the
seedlings. Considerable loss is sustained if seedlings are not properly
looked after.
 Damping Off (Pythium sp.):
Control Method :-
Soil sterilization by Formalin @ 2% before sowing and spraying of
Dithane Z-78 @ 2g/ litre of water are effective in controlling the
disease.