Find It Here
Twitter update
Subscribe

Subscribe to Post Updates from Arkansas Row Crops


 

RSS AgNews
Quick Links
Agricultural Programs
19
Jun
2015
Rice leaf blast now reported in four Arkansas counties
Author: Yeshi Wamishe, Extension Rice Plant Pathologist

— and Jarrod Hardke, Extension Rice Agronomist

The concerns for blast disease have increased the last three years with wet and cold early spring conditions and as planting dates have been pushed later. This year southern Louisiana has reported blast early in the season, Texas reported in three counties, and Arkansas has reported in four counties (Desha, Prairie, Arkansas, and Greene) this week on fields planted with Jupiter (Figure 1) and CL151 (Figure 2). Blast this year is reported about a week earlier than last year. Last year, almost all rice-producing counties in Arkansas reported blast disease on several rice varieties including Jupiter, CL151, CL261, Roy J, and Francis. However, the extent of damage depended on the adequacy of the response by producers. Timely action with flood depth and fungicide application at recommended rates and timings paid off.

Fig. 1. Blast on Jupiter in Prairie County that started on shallow flood area

Fig. 1. Blast on Jupiter in Prairie County that started on shallow flood area

Fig. 2. Blast on CL151 in Prairie County that started in non-flooded field.

Fig. 2. Blast on CL151 in Prairie County that started in non-flooded field.

Blast is one of the most devastating diseases of rice. The blast pathogen is air, seed, or residue-borne. Seed and air-borne pathogens can easily move long distances. Air-borne spores usually infect young leaves. Spores from young leaves may infect collars, nodes, and panicles of rice. Sometimes when the first infected leaves dry and die back, blast tends to “disappear” and may not be a problem later in the season. However, when present, it can cause dramatic yield loss on susceptible rice under favorable conditions. Although severe damage occurs when the fungus attacks the nodes, leaf blast can also do considerable damage to leaves. Moreover, leaf blast can provide inoculum for neck and panicle blast later in the season. Note that we still have some rice varieties in production that are susceptible to blast disease. Even if we know a variety is resistant, it does not fully exclude risk of blast disease since the blast pathogen race may change with time. New races can change the resistance of a variety to susceptible. See the reaction of some of the commercial varieties summarized last year.

Variety
Blast
Antonio
S
LaKast
S
Arize 1003
No info
Bengal
S
Caffey
No info
Catahoula
R
Cheniere
VS
Variety
Blast
Francis
VS
Jazzman
S
Jazzman-2
S
Jes
R
Jupiter
S
Mermentau
S
Neptune
R
Variety
Blast
CL142 AR
S
CL181 AR
MS
CL151
VS
CL152
VS
CL162
VS
CL261
VS
Cocodrie
S
Variety
Blast
RT CL XL729
R
RT CL XL745
R
RT CLXP756
No info
RT XL723
R
RT XP 753
No info
RT XP 754
No info
Taggart
MS
Variety
Blast
CL111
MS
CL131
MS
Rex
S
Roy J
S
Colorado
VS
Della-2
No info
Templeton
R

Early detection of blast disease helps us to act early with deep flooding. Early blast disease in susceptible varieties can be well suppressed with deep flood management. Dry fields provide aerobic conditions and promote blast disease development. Fungicide application may not be needed for early blast disease unless the field has a history and conditions are favorable.

Blast can occur in an open area at the edge of the field where flood depth is shallow or in no flood conditions (Figure 2). Hot spots could largely be at the field edges where the dew period is long due to the shade from trees or in denser spots where nitrogen fertilizer is abundant. In all the fields visited distinct old and young lesions have developed. Older lesions are lens-shaped/spindle shaped, typical symptoms for identification (Figure 3). Young lesions can be confused with brown spot or chemical injury to unfamiliar eyes (Figure 4). As a result, laboratory diagnosis may be needed to confirm blast in the absence of older lesions. Some lesions may be confused with some other physical damage (Figure. 5).

Fig. 3. Blast lesions with the typical spindle-shape useful for field diagnosis

Fig. 3. Blast lesions with the typical spindle-shape useful for field diagnosis.

Fig. 4. Blast lesions without the typical spindle shape. The ashy center with reddish boundary tells it is blast.

Fig. 4. Blast lesions without the typical spindle shape. The ashy center with reddish boundary tells it is blast.

Fig. 5. Blast lesion on the leaf edge may be confused with chemical, insect of any other physical damage

Fig. 5. Blast lesion on the leaf edge may be confused with chemical, insect of any other physical damage.

Mild temperatures, extended free moisture periods on the leaves, foggy or cloudy conditions, frequent rain, and slow wind promote disease development and spread. Once a flood is established, maintenance of a deep flood of four inches or more throughout the season is highly recommended. Excess nitrogen fertilization also worsens blast disease. To read more on blast and conditions that favor the disease go to http://www.arkansas-crops.com/2015/06/02/reported-louisiana-arkansas/.

Check out these answers by Cartwright and Wamishe to questions on blast in 2013. They are provided below in case similar situations happen.

  1.  If I see leaf blast early in the season and treat the field with Quadris, do I need to spray twice later in the season to control neck blast?
  2.  You should keep the permanent flood to at least 4 inches.  A deep flood is 4 inches in the shallowest part of the paddy.  The effective fungicides work best if applied twice for blast.  The first application should be made at late boot to beginning of panicle tip emergence and the second when panicles are 50-75% out of the boot on most of the main tillers.  Higher rates are best.
  3.  Do I need to worry about blast when I hear reports of its occurrence in LA, TX, or even in AR?
  4.  No.  But scouting of fields historically prone to blast is always warranted.  Leaf blast should be scouted for during June or early July.  We recommend integrated disease management practices including deep flood, clean and high quality seed, resistant varieties, proper N and K fertilizer management, and disease scouting and fungicide applications when needed.  Staying alert and on top of irrigation is really necessary for blast control in areas prone to the disease.
  5.  If there is no blast in my field but I know my variety is susceptible to blast; do I need to spray fungicide for protection?
  6.  Depends.  If there is truly no blast in the field, why would we spray?  Accurate scouting pays off with this disease.  Any blast history in the field is a good indicator of potential disease problems, so these fields should be monitored accordingly.  Leaf blast and neck blast occur at different times during the season, and leaf blast tends to dry up or “disappear” after midseason in many fields.  While preventative applications to all acres of susceptible varieties are simple, they are not as economical or as sustainable as IPM applications based on monitoring and field to field judgment.

Save pagePDF pageEmail pagePrint page
«
»