Rice Stink Bug
Jaley Pearson - Faulkner County Extension Intern
As rice starts to head something you need to be increasingly on the lookout for is rice sink bugs. Rice stink bugs, scientific name Oebalus pugnax, is known as the key pest of heading rice in Arkansas. Adult rice stink bugs are straw-colored, 3/8 to 1/2- inch long, somewhat elongated and flattened with forward pointing spines on the shield-like segment behind the head (pronotum).
Adults emerging in the spring feed almost exclusively on developing seeds on wild grass species. Adults migrate from wild grasses to rice when plants begin to develop kernels or develop in and around fields on wild host plants. Wild host plants can include barnyard grass and field corn. The rice stink bug has been of concern to Arkansas rice producers for many years. Its feeding causes yield reduction and decrease of rice quality or pecky rice. Reproduction begins soon after feeding starts. The ability of the rice stink bug to feed and reproduce on a wide range of wild grasses plays a significant role in its status as an economic pest. Feeding on early grasses in the spring enables the rice stink bug to reproduce and increase significantly in number.
Rice stink bug adults and nymphs have piercing sucking mouthparts. When feeding, the bug inserts the mouthpart into the developing seed and begins to inject saliva and other secretions to aid in digestion of plant materials. The salivated plant materials are ingested by the bug and subsequently digested. The saliva hardens when it comes in contact with air, forming a feed sheath on the exterior of the plant. Stink bug feeding on developing seeds causes several different types of damage to rice. Early feeding from pre-fertilization through early milk stages causes the heads to blank or abort. Feeding during the milk to soft dough stages results in kernel shrinkage or slight discoloration. During the hard dough through the hard kernel stages, feeding seldom causes shrinkage or discoloration but does create an entry site for fungi and bacterial organisms that may cause discoloration. Pecky rice is created by a combination of the bug’s injection of saliva and the creation of an entry site by the feeding hole in the seed. Fungi enter the feeding site either on the mouthparts or post-feeding. These fungi cause discoloration and dark spots typically associated with pecky rice. Pecky rice is also subject to breaking easily and causing shattered kernels. Significant populations of rice stink bug result in yield reductions and decline in quality or grade.
Recently when we were out walking a corn field that was adjacent to a rice field, we noticed a large population of rice sink bugs. Because of this, in the following weeks it will be important be on the lookout for rice stink bugs in your rice crop, for they can affect yield greatly.
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