DISEASE OF FIELD CROPS

1. Brown spot of paddy
A.Nitha Reddy
111718012002
DAG-A

2. Brownspot:
 PATHOGEN: Bipolaris oryzae (breda de hann)
shoemaker ( syn.Helminthosporium oryzae)
 This disease was considered to be the major
factor contributing to the “Great Bengal
Famine”in 1942.
 It is used by USA as biological weapon in JAPAN
during WORLD WAR II

3. SYMPTOMS:
• The symptoms of disease
appear on the coleoptile,the
leaves,leaf sheath and also the
glumes.
• Small circular to oval reddish-
brown spots with gray center
surrounded by a dark to
reddish-brown margin.
• The fungus may also infect
glumes,causing dark brown to
black oval spots and may also
infect the grain,causing a black
discoloration.

4. ETIOLOGY:
 Greyish brown to dark brown septate mycelium.
 Conidiophore may arise singly or small group.
 They are striaght or geniculate(curved)-pale to
brown.
 Conidia are curved with a bulge in centre &
tappering towards end
 Olive green to golden brown,6-14 septate.
 Sexual fruiting body in sexual stage: perithecia
with asci

5. DISEASECYCLE:
• Externally seed borne
disease.
• Primary infection is
through seed.
• Disseminated by air
currents.
• Collateral host :
Digitaria
sanguinalis,Echinocloa
colonum.

6. FAVOURABLECONDITION:
 Temperature ranging from 25°c-30°c.
 Water stress and high humidity(80-100%).
 Poorly drained or abnormal soils, which are deficient in
nutrient elements.
 Leaves which are wet for 8-24 hrs are prone to infection.

7. MANAGEMENT: use of disease free seeds.
 Use of resistant varieties.
 Avoid excess use of N application
 Use of silicon fertilizers(eg.calcium silicate slag).
 Hot water seed treatmemt (54-54°c)for 10-12min.
 Seed treatment with captan,thiram or carbendazim.
 Spray Mancozeb@0.2% after flowering and milky stage.