Wilt: Fusarium solani
Economic Importance
In India it was first reported from Tamil Nadu in 1976. The disease is formed in
both air black and sandy loam soil and losses upto 80 % of plants has been reported.
Symptoms
Wilt is observed in patches. In the field the
disease is observed one month after transplanting.
Leaves of infected plants become pale and droop.
Margin of the leaves show pinkish brown
discoloration. The discoloration spreads to the
midrib in a period of 7 to 10 days. Stem portion gets
shriveled. Dark lesions are noticed on the roots
extending upto collar region which result in sloughing off the cortical tissue.
Mode of spread and Survival
Chlamydospores survive in soil and they are spread by irrigation water.
Epidemiology
Incidence is more in the presence of root lesion nematode, Pratylenchus delatrei
and Helicotylenchus dihystera.
Management
Affected plants should be pulled out and destroyed to reduce the disease. The
nematode can be controlled by soil application of Phorate at the rate of 1 g/plant on 10th
day of transplanting. Soil drenching with Carbendazim 0.1 per cent or Copper
oxychloride 0.25 per cent on 30 days interval controls the disease. The treatment may be
repeated after 3 to 4 weeks if needed.
Stem rot: Rhizoctonia solani
The pathogen also causes pre-emergence damping off, Brown to black lesions
develop on stem just above soil level and result in girdling of the stem. The lesions
extend to the upper part of the stem. The lesions extend to the upper part of the stem and
result in collapse of seedlings. The roots are also rotted.
Management
Drenching with Fosesty1-A1 has been found effective in the control of the
disease.
Leaf blight: Colletotrichum crossandrae
Symptoms
The symptoms of leaves consist of the development of brownish, depressed
necrotic areas surrounded by reddish and slightly raised margins. Initially the spots
appear as brownish specks but become darker as they expand. The lesions are more
prominent on lower leaves and confined to the margins. Infected leaves roll up, shrivel
and drop off, leaving a barren stem with a whorl of young leaves at the top.
Management
Spraying with benomyl 0.1% (or) Mancozeb 0.2% (or) Carbendazim 0.1%
Alternaria leaf spot: Alternaria amaranthi var. crossandrae
Symptoms
This disease was first reported from Tamil Nadu during 1972. Infected leaves
show small, circular or irregular yellow spots on the upper surface. They soon enlarge
turn brown and develop dark brown concentric rings. Infected leaves become yellow and
drop off prematurely.
Management
Spraying with Benomyl 0.1% (or) Mancozeb 0.2% (or) Carbendazim 0.1%.
