What is the red-shouldered stink bug (RSSB)?
The RSSB referred to at this Web site is Piezodorus guildinii. RSSB is actually a misnomer, because this stink bug does not have an accepted common name. Piezodorus guildinii acquired this name (RSSB) because it was originally thought to be a different stink bug species when it was first noticed in south Louisiana.
Is the RSSB (Piezodorus guildinii) a new pest of soybeans?
The RSSB is an emerging, major pest of Louisiana soybeans, but it is not a new pest in the United States. It was documented in the southern United States as a pest of soybeans in the early 1980s. It has been a major pest in South America since the 1970s.
The RSSB was first observed in Louisiana at the St. Gabriel Research Station in 2000. Populations increased gradually until a major epidemic occurred in southern Louisiana during the 2004 season.
How do you identify the RSSB (Piezodorus guildinii) in the field?
The adult RSSB is light green and approximately 7/16 inch in length, or about ¾ the size of an adult southern green stink bug. The distinguishing characteristic for field identification is the reddish line or band that runs across the back near the head. The color of this band may vary in the field (possibly because of the age of the adult) and will at times appear yellow, pink or orange.
The immature stage of the RSSB is a nymph that looks similar to the adult but is wingless and smaller. There are five development stages for the nymphs, but the identifying characteristics for each stage have not yet been clearly defined. Newly hatched nymphs appear dark reddish-brown, and the older nymphs range from light green to light brown. Older nymphs have a broad, dark band that runs down the middle of the abdomen.
How do you identify RSSB (Piezodorus guildinii) eggs in the field?
The RSSB lays eggs in masses that average about 15 eggs each. Rather than circular egg masses, RSSB masses are usually made up of two long rows of eggs. The eggs are very dark and somewhat barrel shaped. Research indicates that most egg masses are laid on the pods, but they can be on other plant parts.
How does the life cycle of the RSSB (Piezodorus guildinii) compare to other stink bug pests?
The RSSB life cycle is similar to other stink bugs, but it does not appear to have a reproductive advantage. That is, compared to the southern green stink bug, the RSSB lays fewer eggs and takes more time to complete its life cycle. From a freshly laid egg to a newly emerged adult, the RSSB requires about 39 days to complete a generation.
How does the RSSB (Piezodorus guildinii) damage soybeans?
The RSSB appears to damage soybeans in a manner similar to other common stink bug pests in Louisiana. Adults and nymphs use their piercing-sucking mouthparts to feed on pods and thus damage the seed. This can result in a decrease in yield and crop quality, and possibly a delay in maturity.
How does RSSB (Piezodorus guildinii) damage compare to other common stink bug pests of soybeans?
According to research from South America, the RSSB appears to cause more seed damage than do the southern green stink bug and Euschistus heros, a brown stink bug species native to Brazil.
What caused the RSSB (Piezodorus guildinii) epidemic in 2004?
RSSB populations had gradually increased in south Louisiana since 2000, but the reasons for this increase are not entirely clear. Favorable environmental conditions and favorable cropping practices are possible explanations. Also, there is documentation from Georgia that RSSB population increases may be cyclical. What is known, however, is that RSSB is more tolerant to insecticides, especially those commonly used for the major stink bug pests in the United States. This has been confirmed by reports from South America as well as LSU AgCenter research in 2003 and 2004.
In 2004, heavy RSSB infestations became established in soybeans early and the problem became more severe as the season progressed because of lack of effective control.
When and where did the RSSB (Piezodorus guildinii) epidemic occur in 2004?
Control problems with RSSB were first reported to the LSU AgCenter in early August. They occurred in an area of south Louisiana (commonly referred to as the Cane Belt) where soybeans are grown in the vicinity of sugarcane,. Control problems were the most severe in this area. Many fields required multiple insecticide applications because of mediocre control and rapid pest resurgence following treatment. In a few cases, fields were abandoned (control efforts were ceased) because of the lack of a cost-effective treatment.
RSSB spread westward and northward from the Cane Belt. By the end of the season, this stink bug was present in southwest Louisiana and as far north as Franklin Parish in the northeast. There is also evidence to suggest that this stink bug was present in parts of the Red River Valley.
Which insecticides performed best in 2004 for the RSSB (Piezodorus guildinii)?
LSU AgCenter research and production field reports indicate that acephate was the most effective insecticide for RSSB control.
Which insecticides will be recommended in 2005 for RSSB (Piezodorus guildinii) ?
Acephate will be recommended for control of RSSB at 0.75 to 1.0 pound active ingredient per acre. Baythroid will be recommended for suppression of RSSB at 0.044 pound active ingredient per acre.
LSU soybean insect researchers conducted six small plot, replicated trials and one non-replicated, large plot trial in 2004. Numerous insecticides and insecticide tank mixes were tested. Some materials appeared promising, but further research will be required before additional recommendations can be made.
How do you sample a field for RSSB (Piezodorus guildinii)?
The sweep net appears to be an effective sampling method based on previous field and research experience in Louisiana. The shake cloth could probably also be used, since thresholds in South America are based on the number of bugs per row meter. There is no data to verify the relationship between the two methods for this particular stink bug.
What will be the economic threshold or time to treat for RSSB (Piezodorus guildinii) in 2005?
The economic threshold for RSSB has been lowered to 24 bugs per 100 sweeps. The previous threshold for all stink bugs was 36 bugs per 100 sweeps. This change is based on LSU AgCenter research, field reports from production soybeans and research previously conducted in South America.
Are there control options other than insecticides for the RSSB (Piezodorus guildinii)?
There are no cultural, biological or other non-chemical control methods available for effective control of RSSB. This is not to say that none will be found or developed, but data and experience are lacking.
Does the RSSB (Piezodorus guildinii) feed on other host plants or crops?
The RSSB can be found on a wide variety of alternate host plants, although it appears to prefer legumes. Research from Florida indicates that hairy indigo and lanceleaf crotolaria are important wild hosts. In the spring of 2005, RSSB were found on hairy vetch and black medic in south Louisiana.
What is the 2005 forecast for RSSB (Peizodorus guildinii) in Louisiana?
RSSB problems could be equally severe and more widespread in 2005. This pest greatly expanded its geographic range in Louisiana in 2004. Also, RSSB were easily found in wild host plants in February and March, which indicates that they survived the winter.