The Journal of Cotton Science 24:27–33 (2020) 27 http://journal.cotton.org, © The Cotton Foundation 2020 ARTHROPOD MANAGEMENT AND APPLIED ECOLOGY Comparisons of Cotton Boll Injury Caused by Four Species of Boll-Feeding Insects (Hemiptera: Pentatomidae and Miridae) James P. Glover* and Michael J. Brewer ABSTRACT grandis Boheman (Coleoptera: Curculionidae), have substantially decreased the use of broad-spectrum Field experiments with individually caged nonselective pesticides (Allen et al., 2009). As a result, cotton bolls were conducted in 2013 and 2014 stink bugs (Hemiptera: Pentatomidae) and plant bugs to characterize boll injury from a species com- (Hemiptera: Miridae) have been released from indirect plex of boll-feeding insects represented by the control and their pest status has increased (Glover et verde plant bug, Creontiades signatus (Distant) al., 2019; Lu ., al 2010). Stink bugs and plant bugs (Hemiptera: Miridae); redbanded stink bug, have become recognized as major pests in cotton Piezodorus guildinii (Westwood); brown stink during the last two decades (Greene et al., 2001) in bug, Euschistus servus (Say); and green stink bug, the southern U.S. (Luttrell et al., 2015) and elsewhere Chinavia hilaris (Say) (Hemiptera: Pentatomidae). (Lu et al., 2010; Soria et al., 2017). Field-collected adult bugs were used individually The sucking-insect complex that feeds on cotton to infest single cotton bolls of several ages (0-7 bolls in South Texas is composed of three stink bugs days post-anthesis) previously maintained free [green stink bug, Chinavia hilaris (Say); brown stink of insect injury. Individual cotton bolls were bug, Euschistus servus (Say); and redbanded stink infested at mid-bloom for seven days with one bug, Piezodorus guildinii (Westwood) (Hemiptera: bug per boll for each species, and an uninfested Pentatomidae)] and one mirid species [verde plant control was included. Species and boll age varied bug, Creontiades signatus (Distant) (Hemiptera: across years, allowing selective within-year com- Miridae)]. These boll-feeding stink bugs also occur parisons. Response to feeding resulted in reduced at other locations in the southern U.S. (Greene et boll retention, increased boll injury in the form of al., 2001; Suh et al., 2013). Injury from the green reduced lint, and increased frequency of boll rot. stink bug and brown stink bug cause decreased boll Results showed that verde plant bugs readily fed retention, lint loss, and seed loss (Greene et al., 2001). on comparatively less mature bolls and feeding Yield loss can be further magnified when bacteria decreased boll retention. In contrast, stink bugs or fungi that cause boll rot are introduced during fed on larger bolls and caused significant injury. probing and feeding activity from stink bugs and Variation in boll retention, boll injury, cotton the verde plant bug (Glover et al., 2019; Medrano boll rot, and yield were associated primarily with et al., 2015). The ability to breach the carpel wall is species differences and secondarily with boll age associated with mouthpart morphology (Esquivel, from 0 to 7 days old. Boll injury was apparent 2019; Esquivel and Hinze, 2019; Esquivel et al., across species and subsequent yield reduction 2019) and possibly other factors, such as boll wall attributed to insect feeding was detected for all thickness (Esquivel and Hinze, 2019). Variablity species, except the redbanded stink bug. associated with boll rot disease transmission is less studied, limited primarily to the southern green stink he advent and widespread adoption of transgenic bug, Nezara viridula (L.) (Hemiptera: Pentatomidae), TBt (Bacillus thuringiensis) cotton, Gossypium and the brown stink bug (Medrano et al., 2009, 2016). hirsutum L. (Malvaceae: Malvales), and area-wide Soybeans, Glycine max (L.) Merr. (Fabales: Faba- eradication of the boll weevil, Anthonomus grandis ceae), grown along the Texas Gulf Coast harbor the redbanded stink bug (Vyavhare et al., 2014), which can move into developing cotton as soybean pods begin to senesce (Bundy and McPherson, 2000). J.P. Glover* and M.J. Brewer, Department of Entomology, Historically, the southern green stink bug, green stink Texas A&M AgriLife Research & Extension Center, 10345 State Hwy 44, Corpus Christi, TX 78406. bug, and brown stink bug are known to be economic *Corresponding author: [email protected] pests of cotton (McPherson and McPherson, 2000). GLOVER AND BREWER: COTTON BOLL INSECT INJURY COMPARISONS 28 The verde plant bug is a significant cotton pest in adults with all appendages were used for infesting South Texas. Armstrong et al. (2013) demonstrated the caged cotton bolls. that the verde plant bug readily injured bolls < 12 The experiment was conducted in 2013 and 2014 d old from the first day of bloom (white flower), at the Texas A&M AgriLife Research and Extension whereas older bolls incurred little or no injury in a Center farm at Corpus Christi, TX. PHY 367 WRF no-choice test. When given a choice of varied-age (PhytoGen Cottonseed, Dow AgroSciences, India- squares and bolls on a branch, Brewer et al. (2012a) napolis, IN) cottonseed was planted in early May on found that older squares and young bolls were pre- 91-m length rows and 96-cm row centers at a field site ferred, which decreased boll retention and increased of ≈0.4 ha, resulting in a plant stand of ≈77,800 plants subsequent yield decline. Verde plant bug was also per ha (31,500 plants per acre). Cotton plots were associated with cotton boll rot (Brewer et al., 2012b; grown without irrigation in 2013 when 235 mm of Glover et al., 2020). A related species, Creontiades rainfall occurred from 15 April to 1 August (National distant (Stal) (Hemiptera: Miridae), also has been Weather Service, 2019). Supplemental irrigation was shown to injure pre-bloom and early-bloom cotton provided by a drip system in 2014 (drought year) to in Australia (Khan et al., 2006). attain a total of 241 mm of water inputs from 15 April Glover et al. (2019) compared several species to 1 August (Glover et al., 2019). Thiamethoxam in- of stink bugs and the verde plant bug to generate secticide (Centric 40WG, Syngenta Crop Protection, economic injury levels using whole-plant caging Greensboro, NC) was applied at labelled rates every experiments. They found severity of boll injury and 10 d to maintain plots free of pests before and after yield decline was greater when cotton was infested at infestation. Thiamethoxam application was discontin- mid-bloom compared with late-bloom. Differences ued 14 d prior to infesting with experimental insects, in injury and yield decline were observed among and applications resumed at the conclusion of the in- insect species, but these differences were less ap- festation period. Cages were thoroughly examined for parent. The objectives of this study were to compare any remaining live experimental insects and removed boll retention, boll injury, boll rot, and yield decline when found. Other agronomic practices were normal as a result of feeding activity by the green stink bug, for the region (Morgan, 2018). brown stink bug, redbanded stink bug, and verde Insect Infestation and Experimental Design. plant bug on individual bolls varying in age. Individual insects were released into individually caged cotton bolls for a 1-wk period to characterize MATERIALS AND METHODS the effects of insect species and boll age on boll re- tention, cotton boll injury, cotton boll rot, and yield. Insect Collection and Cotton Management. Treatments were comprised of a species (including Adult insects used for infesting caged, single cotton a no-insect control) by boll age factorial. In 2013, bolls were collected from wild and cultivated host available species included verde plant bug, red- plants, including cotton, sorghum, Sorghum bicolor banded stink bug, brown stink bug, and green stink (L.) Moench (Cyperales: Poaceae), soybean, and bug; boll ages were 0- and 3-d post-anthesis. In 2014, several seepweeds, Suaeda spp. (Caryophyllales:C species available included verde plant bug, brown henopodiaceae). Insects were collected using a KISS stink bug, and green stink bug; boll ages were 3-, (keep it simple) sampler (Beerwinkle et al., 1997); 5-, and 7-d-old post-anthesis. In 2014, the boll age the sampler is a modified leaf blower that aspirates range was modified to eliminate the 0-d interval and insects from vegetation and transfers them into an increase the age ranges based on first year data that inflatable sock that fits on the opposite end of the showed a large amount of boll abscission for 0-d-old blower’s fanned nozzle. Verde plant bugs were col- bolls. Treatment combinations of species and boll lected from a mixture of cotton, seepweeds, and ages were replicated 12 times in 2013 and 14 times grain sorghum from milk through hard dough stages. in 2014; replications were set out in randomized All stink bug species were collected from cotton blocks in uniform cotton planting. and various pod-filling stages of soybean. Follow- Prior to experimental infestation, the bolls were ing collection, all insects were held individually in enclosed as white blooms within small organza plastic portion cups (model S-20778, Uline, Pleasant fabric cages (12 by 13 cm, ~240 µ mesh, JoAnn’s Prairie, WI) for a 24-h fasting period. Individuals that Fabrics, Hudson, OH) that protected them from feed- survived the fasting period were inspected and only ing by any naturally occurring insects (Armstrong JOURNAL OF COTTON SCIENCE, Volume 24, Issue 1, 2020 29 et al., 2005). At this time, the cotton was in the damaged locule count (Brewer et al., 2013; Glover second week of bloom and was characterized as 10 et al., 2019). Next, the boll interior was thoroughly to 12 nodes above white flower (Kerby et al., 2010). inspected for symptoms of cotton boll rot (Medrano Four days before each infestation, plants were hand et al., 2009).