Matthew E. Baur, Baldwin, Jack L. | 8/16/2005 11:29:23 PM
First described in 1837, Piezodorus guildinii (the redbanded stink bug) has been reported throughout the Americas. In Brazil, it is one of the principal pentatomid pests of soybean and has been common since 1970. In North America, it occurs in the southeast, as far north as Arkansas, as far east as South Carolina, Georgia and Florida, and as far west as New Mexico. In the early 1980s, about 20% of the stink bugs collected from Georgia and Florida soybeans were redbanded stink bugs (RBSB). From 1987-1991, redbanded stink bug populations declined to very low numbers in the Southeast. In 2000, low numbers of redbandedstink bug were collected in Louisiana soybeans, and in 2003, populations of RBSB were a concern in Louisiana and Texas soybeans. Piezodorus guildinii is distributed in southern Louisiana, population densities can be high (often exceeding 3-4 times economic threshold levels), and can be difficult to control with insecticides.
Three aspects of the ecology of RBSB are important to consider when attempting to control their populations:
Redbanded stink bug populations increase more slowly than populations of southern green stink bug because female RBSB lay fewer eggs (an average of 50 eggs compared to over 100 for southern green stink bug) and RBSB nymphs take longer to develop. Despite the slower population growth, it has been estimated that five to eight generations of Piezodorus guildinii may occur in a single growing season. Because so many generations may occur within a single season, generations begin to overlap (i.e., adults, nymphs, and eggs may be present simultaneously in the same field) by mid July. When all life stages are present, chemical control measures may be less effective if some of the life stages are not susceptible to the control measure. For instance, eggs and small nymphs reside predominantly in the middle third of the soybean canopy on leaves, stems and pods; insecticide coverage in the middle and lower third of the plant canopy may be difficult to achieve. In addition, eggs are often unaffected by insecticides. Redbanded stink bug feed on a variety of cultivated and uncultivated plants including: soybean, lentil, kidney bean, peanut, pigweed, poison ivy, catalpa, cactus, sunflower, castor bean, wheat, cotton, pokeweed, strawberry, fennel, violets, many types of clover, alfalfa, medic, vetch, crotalaria and indigo. Because their host plant range is broad, populations of RBSB could develop to high levels on weedy plants. In addition, adults are highly agile and therefore, populations developing on weedy hosts could move into soybean fields readily. In addition, because of the "flightiness" of adults, individuals may avoid insecticide exposure by fleeing fields that have been treated.
First described in 1837, Piezodorus guildinii (the redbanded stink bug) has been reported throughout the Americas. In Brazil, it is one of the principal pentatomid pests of soybean and has been common since 1970. In North America, it occurs in the southeast, as far north as Arkansas, as far east as South Carolina, Georgia and Florida, and as far west as New Mexico. In the early 1980s about 20% of the stink bugs collected from Georgia and Florida soybeans were redbanded stink bugs (RBSB). From 1987-1991, redbanded stink bug populations declined to very low numbers in the Southeast. In 2000, low numbers of redbandedstink bug were collected in Louisiana soybeans, and in 2003, populations of RBSB were a concern in Louisiana and Texas soybeans. Piezodorus guildinii is distributed in southern Louisiana, population densities can be high (often exceeding 3-4 times economic threshold levels), and can be difficult to control with insecticides.
In Louisiana, researchers and consultants have been using the economic threshold for southern green and brown stink bugs for the redbanded stink bug (1 stink bug per row ft or 36 stink bugs in a sweep sample of 100 sweeps). However, all of the research on the economic threshold for redbanded stink bug has been conducted in Brazil. Economic thresholds used in Brasil for RBSB range from two to four stink bugs per row meter. The stink bug threshold used in Louisiana would be similar to the higher threshold (four per row meter). There is evidence to suggest that the amount of damage caused by RBSB is higher than that caused by either southern green or brown stink bugs.
Redbanded stink bugs caged on plants for 15 days at four adults per row meter (about one per row foot) during pod fill (late R5 to beginning R6) in the field damaged about 19% of the seeds, whereas southern green and brown stink bugs (at the same infestation levels) damaged less than 4% of the seeds. No significant differences in yield were observed; however, plots infested with RBSB yielded about 10% less than control plots, and this was in line with the loss observed with southern green stink bug (11% loss). In a greenhouse experiment where 2 adults were infested on caged plants for 15 days during the pod-filling period (late R5 to early R6), the number of fully filled pods dropped by 40% on plants infested with RBSB compared to a 20% drop on plants infested with southern green stink bug. The number of deflated (flat) pods with no observable seeds increased significantly as a result in both plants infested with RBSB and southern green stink bug. High populations (up to eight stink bugs per row meter) of RBSB that persist for an extended period (20-30d) during the pod fill period of soybean development can reduce yields by up to 30%. Lower populations (less than four stink bugs per row meter) that persist for up to 15 days will cause less than 10% yield loss.
Several research questions need to be answered about the general biology and ecology of this species in the United States in an effort to provide consultants and producers with solutions to this problem. These include, but are not limited to the following. Researchers need to determine what host plants, besides soybean, redbanded stink bug populations use to increase their numbers. These host plants could be destroyed, thereby limiting the buildup of populations on alternate hosts. For instance, it has been observed in 2004 that redbanded stink bugs were present in high numbers on medic, clovers and vetch along rights-of-way, ditches and field margins early in the spring. Destruction of this habitat may give some control. Researchers need to determine if the threshold currently used for other species is valid for redbanded stink bug. Researchers also need to determine the cause for the control failures observed in south Louisiana in 2004. For instance, does the agility of adults explain some of the lack of control? Or, does coverage matter more when trying to control RBSB because of the presence of overlapping generations? In addition, researchers need to determine how susceptible these insects are to insecticides in the laboratory. Finally, researchers need to determine how other insect species may affect populations of redbanded stink bug. For instance, how much competition occurs between this stink bug species and southern green stink bug? Do any of the current natural enemies (insect parasites attacking the eggs and adult stink bugs) use redbanded stink bug as a host, and does this affect any control?