Diseases of Chrysanthemum and their Management
Authors: Prativa Anand and Babita Singh
Division of Floriculture and Landscaping
ICAR- Indian Agricultural Research Institute, New Delhi-110012

  1. Root Rot (Pythium sp. and Phythophthora sp.)
Symptoms:

  • Rotting of stem cuttings in rooting beds in warm, moist conditions, is most common. The fungus may also enter the established plants through the wounds caused by pinching, etc.
  • The infected parts like roots, stem and leaves wilt suddenly.
Management: Sterilization of propagation media, good drainage, quick removal of infected cuttings and regular drenching with thiram are controlling measures of the disease.

  1. Stem Rot and Wilt (Fusarium oxysporum)
Symptoms:

  • Disease develops only after the appearance of flower buds or when they show colour, although infection might have occurred even in rooting beds.
  • Stem near soil becomes dark brown and dries.
  • Lower leaves turn yellow and plants wilt permanently afterwards.
Management: Soil application of Dithane M-45 (0.2%) controls the disease.

  1. Septoria Leaf Spot (Septoria obesa and Septoria chrysanthemella)
Symptoms:

  • This is the most common and serious disease of chrysanthemum.
  • Brown spots appear on leaves that grow in size and number in humid conditions.
  • Leaves turn yellow and die afterwards.
Management: Control measures include picking and destroying leaves, providing dry and airy environment and spraying bavistin (0.1%).

  1. Grey Mold (Botrytis cinerea)
Symptoms:

  • First girdling of stem takes place, which results in death of upper part.
  • Leaf infection starts from margin and proceeds towards centre and base, showing semi-circular bands.
  • Flower infection starts with brown water soaked spots on lower petals.
Management : Good aeration, adequate planting distance and spraying with bavistin (0.1%) or thiram (3g/l) provides good control.

  1. Ray Blight (Didymella ligulicola)
Symptoms :

  • It affects all above ground parts but is most severe on the shoots and on the flowers which develop reddish petal spots on light coloured cultivars and brownish spots on darker coloured types.
  • The lesions spread rapidly and the flowers collapse with the ensuing decay.
  • On shoots, the disease often begins with the rotting of terminal buds while the leaves are affected by patches of brown black decay.
Management: Destroy diseased plants promptly and avoid high humidity in greenhouse. Spray atleast three times at weekly intervals with zineb or thiram (0.2%) following the appearance of symptoms. Where the disease is suspected or prevalant, dip unrooted cuttings in benomyl suspension.

  1. Powdery Mildew (Oidium chrysanthemi)
Symptoms:

  • White powdery patches appear on the upper surface and on the tender shoots.
  • In severe cases, leaves fall off and flower production is reduced.
Management: Keeping the environment dry and spraying with wettable sulphur (0.2%) controls the disease.

  1. Rust (Puccinia chrysanthemi)
Symptoms:

  • Yellowish green spots on the upper surface and chest nut browny pustules on the lower surface of leaves.
  • Severely infected plants are stunted and do not bloom properly.
Management: Steam sterilization of soil and pots, keeping humidity below 75 percent, cutting and burning infected plants and spray of mancozeb are some of the control measures.

  1. Verticillium Wilt (Verticillium albo-atrum and Verticillium dahliae)
Symptoms:

  • Symptoms appear at the flower bud initiation and plants wilt suddenly.
Management: Selection of healthy stock plants, soil sterilization and spraying with bavistin has been recommended.

  1. Bacterial Leaf Spot ( Pseudomonas cichorii)
Symptoms:

  • Circular elliptical leaf spots appear, increase and coalesce to form large necrotic areas.
  • The disease appears first on basal leaves and progresses upwards to flower buds which turn dark and die later.
Management: Use of disease free cuttings and spraying in rainy season with copper sulphate controls the problem.

  1. Viral Diseases
Symptoms-

  • Mosaic caused by Chrysanthemum mosaic virus, Chrysanthemum virus-B, Tomato aspermy virus shows yellow mottling of leaves and breaking and distortion of flowers.
  • Tomato spotted wilt virus appears as pale mottling and necrotic spots on the leaves.
  • Chrysanthemum stunt virus shows overall reduction in plant size, pale foliage with margins failing to enlarge giving stiff appearance, flowers may open prematurely, red and bronze flowers are often bleached.
Management: Rouging and destruction of diseased plants, use of disease free cuttings, resistant varieties and insecticidal sprays to control vectors are controlling measures of the disease.




About Author / Additional Info:
Working as Scientist, Division of Floriculture and Landscaping, ICAR-Indian Agricultural Research Institute, New Delhi-110012