Use preventive, cultural, chemical methods and crop rotation to control red rice.
By Dr. Garry McCauley
Texas AgriLife Research & Extension Center
Controlling red rice requires a program approach that uses good management – a combination of preventive, cultural and chemical methods in conjunction with crop rotation. Preventive measures include planting high-quality rice seed and using clean equipment and machinery in farm operations. Use of high-quality rice seed free of red rice is extremely important in preventing the introduction of red rice into a field.
After working a field infested with red rice, whether during field preparation or harvesting, clean machinery before moving to the next field to prevent introducing red rice seed into other fields. Mud and other debris that cling to tractors and cultivating equipment can contain red rice seed that can be moved into a red rice-free field.
Cultural Methods
During seedbed preparation, destroy all red rice plants in the field before planting. Because red rice is more vigorous and grows faster than commercial rice, give commercial rice an opportunity to compete effectively with red rice by planting it at the suggested (or at a slightly higher) seeding rate. Red rice tillering and seed production is decreased when competition from commercial rice is high.
Use proper water management to suppress red rice effectively. Permitting soil to dry out and re-wet encourages the germination of weed and red rice seed. Water-seeding in combination with good water management helps suppress red rice. Two suggested techniques are continuous flood culture and the pinpoint flood system. In these systems, it is important to flood immediately after seedbed preparation. Delayed flooding allows red rice seed to germinate and get established, resulting in a loss of red rice suppression.
Post-harvest management is critical in red rice management. High moisture red rice seed incorporated in the soil may remain dormant for many years. Red rice seed left on the soil surface over winter will lose dormancy. These seed will germinate by March and can be killed by cultivation. Red rice will lose its dormancy through a series of wetting and drying cycles. A winter with alternating dry and wet periods most likely will result in severe red rice pressure in the following season. A wet winter generally results in lower red rice pressure the next season.
Herbicide Use
Although continuous and pinpoint flood cultures suppress red rice, they may not provide adequate control. To improve control, use herbicides in combination with specific water management techniques.
Newpath can be applied only to CLEARFIELD rice varieties and provides very effective control of red rice. Two applications are critical for control. The first application can be applied preplant and incorporated or at spiking to one-leaf rice or red rice. The later application has proven to provide better red rice control. The second application should be applied at four-leaf rice or red rice. Applications made later (five- to six-leaf) may reduce control. It is important that the herbicide be activated immediately after application with a flush or rainfall. The best control is obtained when the flood is applied no later than seven days after the last application.
Field selection is critical. Non-CLEARFIELD rice fields and other crops are extremely sensitive to drift. Escapes can occur in either of these chemical management systems. In the CLEARFIELD/Newpath system, Beyond at 5 oz/acre can be used to control escapes. Beyond can be applied between late tillering and panicle initiation. Beyond can be applied only following two applications of Newpath. It is strongly recommended that escapes be rougued from fields before heading.
Stale Seedbed Technique
Another method of red rice control is to use the fall or spring stale seedbed cultural management system. Keep it idle or stale to allow germination and growth of red rice. If necessary, fields may be flushed to maximize red rice seed germination. When red rice is actively growing and 4 inches tall or less, apply 1 quart of 4 lb a.i./gal glyphosate. When applying by air, apply 3 to 5 gallons of water per acre. Application to red rice growing in saturated soils is not as effective as in moist soils. Normal production practices are then followed. For the most effective control of red rice, wait at least six days but not more than nine days after application to flood and plant using the water-seeded method.
The most practical and economical way to control red rice is to rotate grain sorghum and soybeans with rice. Two suggested threeyear crop rotations are soybeans/soybeans/rice or grain sorghum/soybeans/ rice. When growing soybeans in these rotations, use a herbicide such as Frontier, Lasso, Dual or Treflan at recommended label rates. Planting grain sorghum in the rotation and using atrazine is also effective. Although red rice can be controlled with these herbicides, early cultivation and application of a selective post-emergence soybean herbicide such as Poast, Select, Fusion, Assure II or Fusilade DX are necessary to control any red rice that escapes the soil-applied herbicide. It is important to plant alternate crops for at least two years before rice to achieve satisfactory control of red rice.
Contact McCauley at (979) 234-3578 or gmccaule@sbcglobal.net.