SHEATH BLIGHT DAMAGING ON RICE
(Jul 23, 2014)
M.Sc Huynh Kim Ngoc
Sheath blight , in some places known as cancer disease is common and important disease
on rice after blast disease. Although the disease is easy to identify and has specific product ,
but if not detected and treated promptly without proper treatment, yield can reduce significantly.
Unlike the leaf blight (blast disease) damaging in the hot weather, alternating cold, cloudy sky,
a lot of fog, so often appear and damage in Winter - Spring. Sheath blight disease favorite hot- humid weather,
high humidity from and less light, so that disease often appear in Summer-Autumn crop, Monsoon crop.
Damage causing agent
Sheath blight disease caused by soil-inhabiting fungus: Rhizoctonia solani, besides rice fungus is harmful
to vegetables, beans, corn, gourd, squash, melons, carrots, red peppers ... germs spread by irrigation ,
soil borne germs and residues of diseased plant from the previous crop .On rice, if using the short-term variety ,
high yield, seeded field , close transplanting , light lacking , fertilizing excessive nitrogen, applying nitrogen late,
unbalanced application on NPK , the field moisture is too high , fields in previous crop got sheath blight diseased ,
not clean up straw, ratoon rice , weeds ... sheath blight easily occurs in subsequent crop.
Unlike the leaf blight disease, can occur at all stages of growth and damage on all parts of the rice plant ,
on the other hand : visible lesions so easy timely prevention and treatment. Sheath blight disease, in contrast,
usually occurs in maximally tillering , booting , flowering stages (about 35 to 70 DAS),
the disease progresses silently sheath where being adjacent to the water level,
if it will not detect disease until disease developed on flag leaf ( upwards ) , prevention was too late.
Symptoms of sheath blight is easy in identification, the disease initially appeared in sheath adjacent to the water level ,
lesions are patchy spots like leopard skin, gray green , brown edges, soaked water ,
slowly eating lession into the sheath to make it become brown ,gradual dry dying,
while disease eating also spread upwards, once the disease spreads to flag leaf (upwards ),
the yield can be reduced to 50%, grain not beautiful, unfilled rice seed, easy to break when grinding .
If observing lesions, closely on the old leaves , we will find the small gray brown hard sclerotium .
These are sclerotes , they will fall in water spreadingthe next rice hill or lie down under ground ,
in the straw keep waiting , will continue harming the subsequent crop.
Sheath blight disease often happen in clusters on the field but where rice grown too thick,
so good (in the middle of the field near water inlet sluice , so when visiting the fields ,
farmers should note these places first
Prevention and treatment
To prevent and treat sheath blight , it needs to apply integrated measures such as:
(1) Clear straw, ratoon rice , weeds, plant residues after harvest.
(2) Not seeding, transplanting too thick, fertilizer NPK balancedly , not applying excessive nitrogen fertilizer,
fertilizing nitrogen late, should increase fertilizing K, has increased disease resistance as well as limited lodging.
(3)Do not let the field too be wet, deeply submerged
(4) Visit the field often , especially at booting-flowering stages , pay attention to too food field
, the rice grow too densely ,it needs to separate rice to observe at the foot to see whether there is disease . If any ,
stop using N fertilizer immediately , spraying nitrogenous foliar feed and it should spray fungicide immediately
(5) Using one of the following specific products
* Vanicide 3SL, 5SL: 1.5 L dose (1.0 L) / ha.
* Saizole 5SC: 1.0 L / ha
Note: When spraying ,it should be well sprayed , it needs to spray enough water as recommended on the label.