Identification of diseases in protected agricultural crops & Floricultural plants

1. P.A.S.S. Pushpakumara | Advanced Technological Institute- Gampaha
AG 2106 - Diseases of Crops and their Management
Identification of diseases in protected agricultural crops & Floricultural
plants
Viral Diseases
1. Cucumber Mosaic Virus
Causal organism-: CMV
Symptoms: -
• Infected plants show cupping of leaves downward, severe mottling with alternating light
green and dark green patches.
• Plants are stunted, and fruits are covered with bumpy protrusions.
• Severely affected cucumber fruit may be almost entirely white.
• The virus is readily transferred by aphids and survives on a wide variety of plants.
2. Potyvirus (Tomato Brown Rugose Fruit Virus)
Causal organism-: ToBRFV
Symptoms: -
• Symptoms are expressed on leaves, calyx and fruit during the developmental
stages of a plant.
• Leaves show early symptoms of discoloration, mosaic and shoestring or fern-like
appearance, that could mimic the symptoms caused by TMV (Tobacco mosaic
virus) or ToMV (Tomato mosaic virus).
• Calyx attached to green fruit shows distinct browning of the veins and drying out
of the calyx.
• Symptoms on fruit appear as the characteristic brown wrinkled (rugose) patches
on green fruit and blotching, crinkling, and yellow to brown necrotic areas
further develop on the skin of mature fruit.
• Fruit become misshaped and may result in complete fruit abortion.
3. TYLCV (Tomato Yellow Leaf Curl Virus)
Causal organism-: TYLCV
Symptoms: -
• In tomato, symptoms are more severe when infected at an earier age and vary somewhat
among the different cultivars.
• In tomato, upward curling of leaves; mottling and often chlorotic leaf margins.
• In tomato, leaves are reduced in size.
• In tomato, plants are stunted.
• Flower abscission in tomato resulting in greatly reduced fruit set.
• No symptoms are observed in pepper
Advanced Technological Institute - Gampaha
Department of Agriculture
Year II Semester I

2. P.A.S.S. Pushpakumara | Advanced Technological Institute- Gampaha
Fungal Diseases
1. Powdery mildew
Causal organism-:
Leveillula taurica for chilli
Symptoms: -
• Disease first shows on older leaves.
• Powdery whitish spots on the under side, Necrotic, brown spots on upper leaf surface.
• later on, the whitish powdery spots may develop on the upper side.
• Leaves curl upward. Premature defoliation.
• Sun scald as a result of leaf drop.
• As the disease progress, infected parts shrivel, leaves fall off and plants might die.
Erysiphe cichoracearum for gourds
Symptoms: -
• Disease affects pumpkin, Snake gourd, Ribbed gourd, Bottle gourd, Bitter gourd and
Ash gourd.
• Whitish growth of fungus is seen on lower surface of leaves and corresponding upper
leaves show pale green areas separated by dark green areas.
• The entire leaf dries up quickly.
Sphaerotheca pannosa var. rosae for Roses
Symptoms: -
• As the name implies, the disease causes death of plants from tip downwards.
• Infection normally stems from the pruned end of the twigs and extends only a few
centimeters below the cut end.
• During severe infection, however, the disease may spread right down to the base of the
canes and subsequently the whole plant resulting in its death.
• The disease appears as slightly raised blister-like areas on the young leaves.
• Soon leaves are covered with a greyish white, powdery fungal growth, become curled and
distorted.
• On older leaves, large white patches of fungal growth appear.
• Buds may also be attacked and covered with white mildew before they open.
• Diseased buds fail to open.
• The infection spreads to the flower parts and they become discolored,
dwarfed and dried.
Oidium chrysanthemi for Chrysanthemum
• The leaves get covered with a whitish, ash-grey powdery growth on the upper surface.
• Infected leaves turn yellow and dry.
• Severely infected plants remain stunted and do not flower.
• The disease is favored by dry hot weather.
• Shade and overcrowding of plants should be avoided to reduce the disease.
2. Damping off
Refer Damping off in Solanaceae crops

3. P.A.S.S. Pushpakumara | Advanced Technological Institute- Gampaha
3. Botrytis rot
Causal organism-: Botrytis cinerea for roses
Symptoms: -
• The disease is also known as petal fire or Botrytis mold.
• Infection starts from the sepals as black-brown specks that cover the flower in due
course.
• The buds turn brown and decay.
• Sometimes partially opened buds are attacked, and the individual petals turn brown and
shrivel.
• In cool moist weather the flower is covered with greenish-grey or darkish growth of the
fungus
Bacterial Diseases
1. Bacterial wilt
Refer bacterial wilt in Brinjals.
2. Blossom end rot
Causes: -
• Fluctuating soil moisture.
• Excessive applications of fertilizer containing ammonia can also result in symptoms.
• deficiency of calcium in the soil
Symptoms of the disease
• An early symptom of blossom-end rot is a light tan patch on the blossom end of the
green fruit.
• Over time the area turns dark brown or black and may become sunken or leathery.
• Fruit which is one-third to one-half developed is most commonly affected.
• Sometimes an internal black rot will develop in the center of the fruit with little or no
external symptoms.
• Parts of the fruit not affected by blossom-end rot may be eaten.