Controlling Blast


Last year, when I was writing about disease management for the 2012 rice-growing season, I concentrated on what I thought was going to be the major issue of the year – resistant sheath blight. At the time, I was concerned about the possible section 18 label for Sercadis fungicide, which had not, at that writing, been granted. Little did I know that would soon change.

On May 1 of last year, I was called to look at a field and discovered severe blast on CL261. This was the beginning of the worst blast epidemic in southwest Louisiana that any of the scientists working with rice in Louisiana have encountered. In March, Dr. Groth checked stubble in the same field and found active blast.

Aside from the use of fungicides, the primary cultural practices recommended to reduce the incidence and severity of blast in rice are to select resistant varieties, plant early, do not over-fertilize with nitrogen, maintain a good flood and keep plant populations within the recommended level.

Of these, the most common problem associated with heavy blast pressure has been the failure to maintain a four- to six-inch flood depth on the field.

According to seed dealers and others, there has been a significant shift away from CL151 because of its susceptibility to blast and an increase in other varieties that performed well under the blast pressure we had last year. I have always recommended planting several varieties to avoid this type of situation. The lure of the exceptional yield potential of CL151 and the long absence of severe blast lulled our vigilance, and we paid for it.

There has also been more early planted rice this year than last. In 2012, March was abnormally warm. In spite of that, a lot of rice did not get planted early because many farmers had intended to drill or broadcast seed on dry ground.

Remember, March of 2012 was also wet and that delayed planting and forced some farmers to abandon their original plans, flood up fields and water-seed.

This year, March started out cool as it usually does, but most of us thought that was temporary. We were wrong. Farmers started planting and, at the first signs of a wet weather pattern, flooded up fields and water-seeded.

It stayed cold all through March and April, and, at this writing, we are expecting record cold for the first week of May. So we have a lot of rice that, based on planting date, is 60 days old, but looks like it is 30 days old. Without sunshine and warmer temperatures, it just will not grow.

I have no idea if this will translate into the effect of late planting, but I would assume it will and hope it does not. If you plant a susceptible variety and plan to use a fungicide to control blast, follow Dr. Groth’s recommendations in his Rice Disease Newsletter this year. It details all of the current recommendations and any changes that might have occurred since last year on labels. All of the fungicide labels indicate the need for TWO applications to effectively control blast. Read the labels.

The resistant sheath blight issue has not gone away and will not in the foreseeable future. One good thing is the news that we received recently from Bobby Simoneaux of the Louisiana Department of Agriculture and Forestry that the EPA has granted a section 18 for Sercadis for 2013.

Check Dr. Groth’s newsletters for details.


Reading is fundamental

UCCE Rice Farming Systems Advisor

Early planted rice is often in jeopardy of struggling through cool temperatures, which slow germination and seedling emergence. Under these conditions, plants are predisposed to seedling diseases that may be caused by several organisms and produce symptoms of seedling rot or seedling blight under water-seeded conditions.

When considering the use of a disease management product, consider a few factors prior to making a decision. First, if the product makes claims of disease management, make sure it is registered by the California Department of Pesticide Regulation (CDPR) for use on rice in California. Even if the material is marketed as organic, it must be registered by CDPR for use on rice in order to be legally used for pest management in California.

Second, seek out independent product evaluation data to determine if these products are effective at managing your target rice disease. Not all products are effective against all rice pathogens so you should read the product label and any other product information to ensure that we are not comparing apples to oranges. For example, you don’t gain much knowledge of a product when you are shown data demonstrating how great the product works on reducing sheath blight disease since this is not a significant disease in California. While sheath blight disease is related to the aggregate sheath spot disease that occurs in California, it is not guaranteed that product performance will be the same.

Finally, if you choose to use one of these newer fungicide products for the first time, consider treating a portion of a field or fields and evaluating product performance by measuring disease incidence and severity at the end of the season. This will provide you with a much better product evaluation than if you were to treat a whole field and try to compare the results with a neighboring field or performance in a previous year.

It is my opinion that your best management tool is a dedicated scouting plan. There is no substitute for field scouting when deciding if action needs to be taken in the form of field drainage for seedling diseases or a fungicide application for diseases such as aggregate sheath spot and rice blast. Inspect your crop weekly throughout the season for disease symptoms. Once the damage is visible from the pickup truck, it might be too late to take appropriate action to minimize economic damage.


Seed treatments are good insurance

Rice Research Entomologist

This month’s topic is disease management, which is timely for Texas rice farmers. Southeast Texas is experiencing a very cold spring. In fact, weather forecasters are predicting record lows in southeast Texas during the first week of May. This means rice is off to a slow start and much rice remains susceptible to seedling diseases. Thus, fungicidal seed treatments are good insurance against seedling diseases caused by the likes of Pythium, Achlya, Fusarium, Curvularia, Rhizoctonia and Sclerotium.

When soil and air temperatures are unseasonably cool, these soilborne fungi attack seeds and seedlings to reduce stands and retard growth. In addition, I recently observed increased phytotoxicity in my own plots caused by a combination of cool weather and herbicide damage. I think the cold temperatures are slowing rice growth and metabolism, allowing the symptoms of phytotoxicity (leaf burn and yellowing) to persist. But getting back to fungicidal seed treatments – as you probably know, the seed treatment CruiserMaxx Rice contains an insecticide and three fungicides (Dynasty, Maxim and Apron). The seed treatment NipsIt INSIDE, which contains the insecticide clothianidin, now can be purchased with two fungicides. The name of this seed treatment is NipsIt SUITE Rice, and the fungicides are fludioxonil (Spirato 480) and metalaxyl (Sebring 318). Fludioxonil is a broad-spectrum fungicide giving protection against decay, damping- off and seedling blight. Metalaxyl protects against Pythium. In addition, Release LC (gibberellins) can be added for enhancement of seedling emergence and stand establishment. Basically, the quicker you can get your seedlings out of the ground, the better.

I want to discuss the importance of scouting for disease management. I have not observed many farmers using the “T-tool” to scout for disease. But, this is tried and true technology that can save you money and/or increase yields and quality. Why apply expensive fungicides when your crop does not need them? On the other hand, you definitely do not want to miss an application of fungicide when needed. Here is the link to the Texas Rice Production Guidelines, which describes the scouting method for sheath blight in the Disease Management section:

Scouting also can alert you to other problems in your fields such as stalk borers, nitrogen deficiency, armyworms, other diseases and irrigation problems. Don’t just “windshield inspect.” Get out of your pickup and walk your fields. Don’t rely totally on your water manager to tell you what is going on in your fields.

Finally, I want to mention the passing of Raymond Franz who farmed rice many years west of Houston. Raymond was a stalwart in the Texas rice industry and was a big supporter of research and Extension. My heart goes out to Raymond and family.

Integrated approach

Rice Extension Agronomist
University of Arkansas,
Division of Agriculture

There are a number of general practices that can help rice growers manage disease each year. Dr. Yeshi Wamishe, Extension rice plant pathologist, recommends using an integrated approach for disease management.

Disease prevention begins well before planting with crop residue management. A number of rice disease pathogens can survive on residue while waiting for favorable hosts such as your rice crop. Prior to planting, it is also important to consider proper fertilization. Ensuring adequate potassium fertilization will help to promote good overall health of the rice crop and is known to help directly manage brown spot and stem rot diseases of rice. Dr. Wamishe notes that brown spot is an indicator for some kinds of stress, including potassium deficiency.

In addition, proper nitrogen fertilization can help reduce disease incidence later in the season. Applying too much nitrogen at preflood can increase the risk of sheath blight, blast and bacterial panicle blight, among others.

Once it is finally time to plant, it is best to do so early. For most Arkansas rice farmers, that has not been an option this year, which means that there is already an increased risk for disease development in the 2013 crop. Selection of resistant or tolerant cultivars plays a major role in managing diseases. No single cultivar is best against all major diseases. In fields with a history of a particular disease problem, it is always advisable to plant a cultivar more tolerant to that specific disease. Timely irrigation and adequate flood depth is important in maintaining plant health and can directly help limit blast disease development. The use of fungicides to suppress disease development should be based on field history. Dr. Wamishe recommends that for diseases such as sheath blight and blast, scouting the disease of concern is encouraged before fungicide application to minimize the risk of fungicide resistance development.

With half of the rice planted in May this year, kernel smut and false smut, as well as bacterial panicle blight, should be of primary concern for growers. Kernel smut and false smut may be a concern if the season continues to be wet. Bacterial panicle blight may be a concern if we experience high nighttime temperatures in July and early August as in 2010 and 2011.

For fields with a history of smut problems, fungicides should be used as preventative treatments. It is important to note that current fungicides can suppress these diseases but do not provide 100 percent control. Bacterial panicle blight is largely seed-borne. The bacteria also survive in soil on residue. Among the current cultivars, most of the commercial varieties are susceptible, but Jupiter and hybrids are moderately resistant.

For fields with a history of bacterial panicle blight, it is recommended that hybrid rice or Jupiter be planted. In previous years, fields with adequate nitrogen and potassium fertilizer, appropriate seeding rate and good water management had lower bacterial disease pressure. Currently, there are no chemical management options available to be used in the United States for this disease.

For more information on rice disease management in Arkansas, please refer to the MP154 – Arkansas Plant Disease Control Products Guide – 2013.

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