A number of diseases and insect pests have been found damaging chrysanthemum. If these are not controlled at right time, these can cause severe damage to the crop.
Important disease is as follows:
Diseases found in Chrysanthemum:
Black leaf spot:
It is caused by Septoria obesa and S. Chrysanthemella and is a serious disease. Greyish brown circular spots appear on the leaves. Leaves turn yellow and die. It can be controlled by spraying 0.2% Zineb or Dithane M-45.
Powdery mildew:
It is caused by a fungus (Oidium chrysanthemi). The disease is characterised by the white powdery mass on leaves and stems. To control this disease spraying with 0.5% Kerathane (40 E.C.) has been found useful.
Flower disease:
Flower rot. It is caused by grey mould (Botrytus cirterea) which appears as brown water soaked spots on the petals. The infected flowers show tan or light brown specks at the base of petals which may result complete rotting. It can be controlled by spraying 0.2% Zineb or Dithane M-45.
Insect-Pests found in Chrysanthemum:
Aphids (Myzus persicae):
Black aphids appear at the time of flowering and suck the cell sap of stem, stalk, bud, flowers, etc. Flowering is affected drastically. It can be controlled by applying Thimet in soil or by spraying Rogor 30 EC or Metasystox 25 EC @ 250 ml in 250 L of water.
Red hairy caterpillar (Amasacta moorie):
The larvae eat away the foliage leaving only the skeleton of veins. At later stages larvae migrates to other plants. It can be controlled by spraying 500 ml Thiodan or 200 ml of Nuvan in 200 L of water/acre.
Gram caterpillar (Heliothis armigera):
The caterpillar which are of green, black and yellow colour attack the flower buds and eat them away. Their presence is indicated by very fine holes. It can be controlled as in case of red hairy caterpillar.