Safflower: Diseases and Symptoms
Survival and spread
- It is the most destructive disease.
- Dark necrotic lesions 2-5 mm in diameter are formed first on hypocotyls and cotyledons.
- In mature plants, small brown to dark brown concentric spots of 1-2 mm appear on leaves.
- Symptoms also appear on stem and severely infected plant gets blighted.
- Brown discolouration appears on the stem, dark brown spots with concentric rings up to 1 cm in diameter appear on the leaves which later develop into large lesions.
- Seeds also may be affected. Dark sunken lesions are produced on the testa. It may rot and damping off of seedlings occur.
- The disease is externally and internally seed borne. The pathogen survives through spores (conidia) or mycelium in diseased plant debris or weed.
- Moist (more than 70% relative humidity) and warm weather (12-25 ºC) and intermittent rains favours disease development.
Cercospora leaf spot
Survival and spread
- Safflower plants few weeks after planting or at flowering stage are commonly attacked.
- Circular to irregular brown sunken spots of 3-10 mm diameter are formed on leaves.
- Spots are surrounded by yellow halos.
- Symptoms first appear on lower leaves and spread to upper leaves.
- Stems and nodes may also be affected.
- In severe infections bracts are also affected with reddish brown spots.
- Affected flower buds turn brown and die.
- The fungus survives in seed and affected plant debris and spreads through wind borne spores.
- Warm humid weather favours the disease development.
Survival and spread
- The disease is characterized by whitish powdery growth on leaves
- Later the fungus spreads over the entire leaf. Leaves turn yellow and dry up
- The pathogen survives as oospores on the affected plant tissues and on weed hosts
- Cool (10-20ºC) and wet weather (90% RH) favours disease development
Head rot and wilt
- Plants become yellowish, turn brown and ultimately die
- Large black sclerotia of the fungus are formed on the crown inside the stem, floral heads and adjoining roots
- Shredding of the stem takes place
Transmission and favourable conditions
- In CMV infected safflower plants young leaves show irregular yellow or light patches alternating with normal green areas.
- Leaves may become blistered and distorted and infected plants are stunted.
- In few plants primary leaves are produced, forming a rosette of leaves exhibiting mosaic mottling and from the centre of this, the axis bearing secondary leaves are produced.
- The disease is transmitted in semi persistent manner by aphid Aphis gossypii.
- Aphids are more active in warm summer conditions and increased their population as well as spread the viruses more.
Ramularia leaf spot
- Round and irregular spots of 100 mm or more in diameter occur on both sides of leaves
- Whitish dense mass of conidia remain at the center which reflects light, dry spots are brown in color.
- Seedling infection causes twisting towards one side
- Chesnut brown postules are formed on hypocotyl leading to collapse of seedling
- On older plants girdling and hypertrophy of the stem base may occur
- Small powdery chesnut brown postules of 1-2 mm in size develop on leaf surface which later turn black.
- Yellowing of leaves on one side of plant starts particularly from lower leaves followed by wilting the progresses upwards
- Lesion at soil line is first symptom noticed which extends inside and affects the vascular system
- Plant starts to wilt, drooping more often
- Infected heads have aborted seed.
- Dark cortical lesions occur slightly below or at the soil level on the stem, which later extend upwards
- Lesions frequently girdle the stem
- Root development is reduced and finally seedlings die
IPM for Safflower
To know the IPM practices for Safflower, click here.
Source: NIPHM and Directorate of Plant Protection, Quarantine & Storage
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