Arkansas rice farmers battled tremendous numbers of rice stink bugs in 2001. Some mills estimated losses in excess of $20 million directly or indirectly related to rice stink bug feeding.
In 2002, information about the risks of the rice stink bug and the importance of careful scouting and treatment when necessary was provided growers. As a result, stink bug damage to rice was reduced substantially.
As the 2003 rice crop begins to head, farmers shouldn't lose the ground that was gained in 2002. A few reports of rice stink bugs are beginning to come in on the earliest-headed rice, and indications are that the pressure could be high again.
Louisiana is reporting severe infestations of rice stink bugs. In addition, the spring weather has created a rather “grassy” crop. Therefore, you should scout fields carefully to insure that your crop is protected from this insect. This is particularly important in fields with escaped grass.
Rice fields should be scouted weekly for four weeks after heading for rice stink bugs. Using a 15-inch sweep net, stink bugs found in excess of five bugs per 10 sweeps during the first two weeks after heading should be treated. If stink bugs are found in excess of 10 bugs per 10 sweeps during the second two-week period, treatment is needed.
Product options include methyl parathion, Karate Z, Mustang Max, Sevin, or malathion. Methyl parathion provides a quick kill but has no residual activity. Karate Z and Mustang Max are pyrethroids that provide good control and provide some residual control. Sevin has probably the longest residual effects, but it has the slowest “knock-down” and is typically the most costly.
Fields that have grass escapes should be watched closely. Rice stink bugs feed on almost any grass species, including wheat, grain sorghum, barnyardgrass, johnsongrass and rice, and fields that have higher grass present will likely have more rice stink bugs.
Grass around field borders should be mowed throughout the season. However, mowing the grass for the first time next to heading rice will also likely move the stink bugs into the rice fields. Also, pay particularly close attention to rice fields located next to grain sorghum when the grain sorghum is harvested.
Rice stink bugs cause both yield and quality losses. During the early heading stages, stink bugs feeding on panicles can cause blanking or malformation of the kernel. The first two-week period after heading is when the majority of yield loss occurs.
Feeding during the milk and soft dough stages results in removal of all or part of the grain contents, which can reduce grain yield. Pathogens are also introduced into the kernel by rice stink bug feeding during this stage, which results in discoloration and weakening of the kernel. This discoloration and weakened kernel results in pecky rice.
As the amount of pecky rice increases, quality and value of the crop are reduced.
Although stink bugs contribute to the total amount of discolored grains, they are not the sole cause. Other pathogens, such as that responsible for kernel smut, cause grain discoloration. However, adequate control of rice stink bugs during heading can improve rice grade, quality, and selling price.
Significant amounts of pecky rice may result in significant dockage at the mill. Therefore, it's important to treat whenever rice stink bugs exceed the thresholds established for heading rice.
Charles E. Wilson Jr. is the Extension rice agronomist at the University of Arkansas Rice Research and Extension Center in Stuttgart. e-mail [email protected].