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.