Evaluating Behavioral Responses of Selected Stink Bugs (Hemiptera: Pentatomidae) to Spinosad

Southern green stink bug, Nezara viridula (L.) and redbanded stink bug, Piezodorus guildinii (Westwood) are two of the most important seed sucking pests affecting Louisiana soybean production and rice stink bug, Oebalus pugnax (F.) is an important late season pest in Louisiana rice. Exploration of chemicals that exhibit attraction or repellent activities toward major stink bug species would be beneficial in developing push–pull strategies. Spinosad is a commercially available natural insecticide that may have arrestant, attractant, or phagostimulant properties against stink bugs. To test this, a series of laboratory experiments were conducted to investigate the tactile, olfactory, and feeding responses of these stink bugs toward two commercial spinosad products (Entrust and Tracer) and technical grade spinosad. In tactile assays, female and male redbanded stink bug were arrested by Entrust, Tracer, and technical grade spinosad, whereas only rice stink bug and southern green stink bug males were arrested by Entrust. Y-tube assays revealed no attraction to any of the products by either male or female rice stink bug, redbanded stink bug, or southern green stink bug. In paired (treated or untreated soybean seed) feeding preference experiments, southern green stink bug showed no preference for any treatment, whereas redbanded stink bug fed more on Entrust- and Tracer-treated seed. From these results, spinosad appears to have an arrestant and phagostimulant effect on redbanded stink bug in the laboratory.

Reexamination of the Influence of Oebalus pugnax (Hemiptera: Pentatomidae) Infestations on Rice Yield and Quality

The rice stink bug, Oebalus pugnax (F.), is the most important pest of headed rice, Oryza sativa L., in the United States. Numerous studies have attempted to quantify the impact of O. pugnax feeding on rice yield and grain quality, but these studies have often produced conflicting results. Across mid-south U.S. rice, thresholds based on sweep net sampling are used to determine the need for insecticide applications, but few studies have related sweep net captures to rice quality parameters. Field trials were conducted in Louisiana in 2015 and 2016 that used different rates of insecticides to establish rice plots with mean O. pugnax infestations ranging from 0.8 to 24.6 insects per 10 sweeps. Insecticide applications improved panicle weight and head yields as well as decreased percentage peck. A series of linear regressions examined relationships between O. pugnax captures and rice yield and quality parameters, including panicle weight, head yield (% whole kernels), and peck (discolored grains). Mean O. pugnax sweep net captures across all sampling dates in both years were significantly and negatively correlated to panicle weight and head yield and positively correlated to percentage peck. Peck was negatively correlated with head yield. Results from sampling at different maturity stages indicate sweep net captures at grain fill and soft dough stages had the greatest influence on rice yield and quality parameters, respectively. Further research into impacts of milling quality reductions on farm revenue and the influence of cumulative infestations over grain development is needed to improve economic thresholds for O. pugnax in rice.

Relative Abundance of the Stink Bug (Hemiptera: Pentatomidae) Complex Infesting Rice in the Everglades Agricultural Area of Florida

Florida’s rice stink bug complex comprises three species; Oebalus pugnax (F.), O. insularis (Stal), and O. ypsilongriseus (DeGeer), the latter two of which are invasive and exclusive to Florida within the United States. A series of surveys were conducted in 2017 and 2018 to determine the relative abundance of the three species throughout Florida’s rice growing region within the Everglades Agricultural Area, in addition to comparing their seasonality within crop and noncrop habitats. Sampling occurred in commercial rice fields and adjacent transects of graminaceous noncrop hosts using sweep nets. Oebalus pugnax (52.7%) and O. insularis (61.7%) were the most abundant species in 2017 and 2018, respectively. Both species were more prevalent in rice fields compared to transects of noncrop hosts. Oebalus ypsilongriseus remained in low abundance relative to O. pugnax and O. insularis, and did not differ in numbers collected among rice and noncrop hosts. Of the noncrop hosts in transects, Panicum dichotomiflorum (fall panicum) was the most abundant across both years. This study is the first report of Oebalus species feeding on Echinochloa crus-galli (common barnyardgrass) in Florida. This study shows that the invasive O. insularis continues to increase in abundance, and has surpassed O. pugnax in terms of regional populations. These results emphasize the need for additional studies to assess the interactions among O. insularis and other Oebalus species in addition to its feeding behavior in Florida rice.

Susceptibility of Rice to Oebalus pugnax (F.) (Hemiptera: Pentatomidae) Feeding at Different Levels of Grain Maturity and Impacts on Insecticide Termination

The stages of rice, Oryza sativa L. (Poales: Poaceae), grain maturity that are most susceptible to rice stink bug, Oebalus pugnax (F.), damage have been identified; however, the stage at which they are no longer capable of causing appreciable damage during grain maturity is unclear. The objective of this study was to determine the susceptibility of rice to rice stink bug feeding at different levels of grain maturity and determine an insecticide termination timing. Rice stink bug damage was examined using five levels of grain maturity described as percent of kernels reaching mature straw coloration referred to as hard dough (20, 40, 60, 80, and 100%) across a range of infestation levels using single panicle sleeve cages and large cages. Hybrid and conventional cultivar rice panicles at 20, 40, and 60% hard dough were found to be susceptible to indirect yield loss, as two rice stink bugs per panicle resulted in over 7% peck. In large cage trials, 25 rice stink bugs caused 0.7–1% peck to hybrid and conventional rice plots at 20% hard dough. Much less damage was observed once rice reached 60% hard dough, where peck averages only reached 0.4%. Decreased damage at 60% hard dough was validated using uncaged trials where 0.4% additional peck was observed in unsprayed plots. These data indicate that rice in the early stages of hard dough is susceptible to large levels of indirect yield loss, but unless significant densities of rice stink bug are present at 60% hard dough, no more sampling or applications are necessary.

Influence of Sweep Length on Rice Stink Bug (Hemiptera: Pentatomidae) Capture and Reliability of Population Density Estimates

The rice stink bug, Oebalus pugnax (F.), is a key pest of heading rice, Oryza sativa L. (Poales: Poaceae), in the southern United States. Sweep net sampling is the recommended method for sampling rice stink bug in rice, but there currently exists no specific recommendation for sweep length, and a large amount of variation likely exists amongst samplers. The objectives of this study were to determine the role that sweep length plays in sampling accuracy and determine the feasibility of using sweep lengths smaller than 180°. When monitoring sweep lengths by consultants, producers, and researchers, a large amount of variation in sweep length and a significant linear relationship between sweep length and rice stink bug catch per 10 sweeps was observed. Sweep length was then controlled at three levels (0.8, 1.8, and 3.5 m) and a change from 0.8 to 1.8 m in sweep length led to an increase on average of 2.28 rice stink bugs per 10 sweeps. These data suggest knowledge of sweep length is vital, and paired with large amounts of observed variation in sweep length, recommending a specific sweep length is ideal. Using Taylor’s values, it was determined that 1.8 m sweeps resulted in density estimates that were as reliable as 3.5 m (180°) sweeps, suggesting a longer sweep length was not necessary. A 1.8 m sweep length recommendation would create an easier sampling regimen that is still reliable, which could lead to more accurate action threshold decisions being made for rice stink bug if it increases adoption in consultants and producers.

Populations of Stink Bugs (Heteroptera: Pentatomidae) and their Natural Enemies in Peanuts

The objective of this on-farm study was to determine if peanuts harbor populations of stink bugs (Heteroptera: Pentatomidae) and their natural enemies in Georgia. Eight species of phytophagous stink bugs were found in peanuts over the 5-yr study. The predominant stink bug species were Nezara viridula (L.), Euschistus servus (Say), Euschistus quadrator (Rolston), and Oebalus pugnax pugnax (F.). The remaining 4 species, Acrosternum hilare (Say), Euschistus tristigmus (Say), Euschistus ictericus (L.), and Thyanta custator accerra McAtee, were found in relatively low numbers. All developmental stages of N. viridula, E. servus, E. quadrator, A. hilare, and O. p. pugnax were collected at various times in the study indicating that these 5 species of stink bugs were developing on this crop. Seasonal abundance of N. viridula and E. servus nymphs and adults provided further support that these 2 species of stink bugs developed on peanuts. At least 1 generation of N. viridula and E. servus occurred in peanuts each year, and generally some of the adults that developed on peanuts oviposited on peanuts producing another generation of nymphs in this crop. Because only adults of T. c. accerra, E. tristigmus, and E. ictericus were found in peanuts, these 3 stink bug species probably were not developing on this crop. Adult stink bugs were parasitized by the tachinid parasitoids Trichopoda pennipes (F.) and Cylindromyia spp. Stink bug eggs were parasitized by the scelionids, Trissolcus basalis (Wollaston), Trissolcus thyantae Ashmead, Trissolcus brochymenae (Ashmead), Telenomus podisi Ashmead, and Gryon obesum Masner, and an unknown encyrtid species. Geocoris punctipes (Say), Geocoris uliginosus (Say), Orius insidiosus (Say), Podisus maculiventris (Say), and Oxyopes salticus Hentz preyed on stink bugs in peanuts. Peanuts harbor populations of stink bugs and their natural enemies, and thus the role peanuts play in landscape ecology of stink bugs needs to be ascertained to better understand how to manage stink bug populations in landscapes in which peanuts are associated with other crops.