Economic Injury Level of the Neotropical Brown Stink Bug Euschistus Heros (F.) on Cotton Plants
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Neotrop Entomol (2017) 46:324–335 DOI 10.1007/s13744-016-0454-2 PEST MANAGEMENT Economic Injury Level of the Neotropical Brown Stink Bug Euschistus heros (F.) on Cotton Plants 1 1 2 3 MF SORIA ,PEDEGRANDE ,ARPANIZZI ,MDTOEWS 1Lab of Applied Entomology and Biotechnology, Graduate Program in Agronomy, School of Agricultural Sciences, Federal Univ of Grande Dourados, Dourados, MS, Brasil 2Lab of Entomology, Embrapa National Wheat Research Center, Passo Fundo, RS, Brasil 3Dept of Entomology, Univ of Georgia, Tifton, GA, USA Keywords Abstract Pentatomidae, sucking pest, attack, injury, In Brazil, the Neotropical brown stink bug, Euschistus heros (F.) damage, treatment threshold (Hemiptera: Pentatomidae), commonly disperses from soybeans to Correspondence cotton fields. The establishment of an economic treatment threshold MF Soria, Lab of Applied Entomology and for this pest on cotton crops is required. Infestation levels of adults of Biotechnology, Graduate Program in Agronomy, School of Agricultural Sciences, E. heros were evaluated on cotton plants at preflowering, early Federal Univ of Grande Dourados, flowering, boll filling, and full maturity by assessing external and Dourados, MS, Brasil; miguelagro@gmail. internal symptoms of injury on bolls, seed cotton/lint production, com and fiber quality parameters. A completely randomized experiment Edited by Jorge B Torres – UFRPE was designed to infest cotton plants in a greenhouse with 0, 2, 4, 6, and 8 bugs/plant, except at the full-maturity stage in which only Received 13 March 2016 and accepted 13 October 2016 infestation with 8 bugs/plant and uninfested plants were evaluated. Published online: 14 November 2016 Results indicated that the preflowering, early-flowering, and full- maturity stages were not affected by E. heros. A linear regression * Sociedade Entomológica do Brasil 2016 model showed a significant increase in the number of internal punc- tures and warts in the boll-filling stage as the population of bugs increased. The average number of loci with mottled immature fibers was significantly higher at 4, 6, and8bugscomparedwithuninfested plants with data following a quadratic regression model. The seed andlintcottonwasreducedby18and25%atthemaximumlevel of infestation (ca. 8 bugs/plant) in the boll-filling stage. The micronaire and yellowing indexes were, respectively, reduced and increased with the increase of the infestation levels. The economic injury level of E. heros on cotton plants at the boll-filling stage was determined as 0.5 adult/plant. Based on that, a treatment threshold of 0.1 adult/plant can be recommended to avoid economic losses. Introduction Bt varieties by growers (Soria et al 2009, 2010a, Thomazoni et al 2010). A similar phenomenon occurred The importance of stink bugs (Heteroptera: in the Southeast and Mid-South regions of the USA in the Pentatomidae) as pests of cotton in Brazil has increased mid-1990s (Greene et al 1999,Haneyet al 2009,Olson in recent years due to the reduced use of broad-spectrum et al 2011), in which these two factors resulted in the rise insecticides on the crop—a result from the success of of pentatomid pests, such as Euschistus servus (Say), regional suppression programs of the boll weevil Nezara viridula (L.), and Acrosternum (Chinavia) hilare (Anthonomus grandis Boh.) and widespread adoption of (Say) to the status of key pests of cotton. Brown Stink Bug Damage to Cotton 325 In Brazil, among the three species of stink bugs— Nevertheless, studies have been conducted to improve the Euschistus heros (F.), Edessa meditabunda (F.), and determination of the treatment threshold using the assess- N. viridula, that infest cotton fields in the Cerrado region— ment of symptoms of injury inside bolls of different sizes/ the first species is the most prevalent and of greater impor- ages in the USA (Reay-Jones et al 2009,Toewset al 2009, tance, as it is capable of causing significant damage to soy- Bacheler et al 2010). bean and cotton (Soria et al 2009, 2010a, b, Thomazoni et al In contrast, in Australia, control of stink bugs and plant 2010). In the Brazilian Cerrado, cotton crops are grown in bugs [Creontiades dilutus (Stål) and Creontiades pacificus close proximity to soybean, and E. heros is the main (Stal) (Hemiptera: Miridae), N. viridula,andPiezodorus pentatomid pest that infests soybean. Due to its ability of hybneri (Gmelin) (Hemiptera: Pentatomidae)] is implement- adapting to environmental conditions of the main row crop ed when an average of 0.5 bugs is found/m2 (Ward 2005), production regions and disperse from one host plant to an- showing the variability in recommendations depending on other, regardless of whether the plants are cultivated or not the country/location, environmental and farming conditions, (Panizzi 1997, 2000, Degrande & Vivan 2008), this pest can as well as pest species. be considered a threat to cotton crops in the Cerrado. Although preliminary studies in Brazil have detected the The dispersal ability of pentatomids in search of improving ability of Piezodorus guildinii (Westwood), N. viridula, and conditions for shelter, food, and reproduction (Panizzi & Silva E. heros (Cruz-Júnior 2004,Soriaet al 2009, 2010a)tocause 2009) results in infestations of E. heros in Brazilian cotton injury and damage to cotton bolls, no study has determined fields. Long-cycle cotton varieties planted as a first crop or the treatment threshold level of control and/or economic short/medium-cycle cotton varieties planted as a second damage caused by these insects in Brazilian cotton. crop just after soybean cultivation favor the dispersal of Specifically, E. heros, the main species of stink bugs found E. heros adults from maturing soybean crops to neighboring in the Brazilian Cerrado, should be closely investigated. Some cotton crops (Soria et al 2009, 2010a). Some growers have treatment threshold recommendations, without a scientific reported extended infestations of cotton crops by stink bugs basis, have been implemented, and this could result in un- for a period lasting 30–40 days (FK, Mato Grosso Cotton necessary applications of insecticides, especially of organo- Institute personal communication to MFS). phosphates and pyrethroids, or in a late chemical treatment Normally, when a soybean crop enters the maturation/ to avoid yield losses already occurring. Therefore, the pres- harvesting stage, the adjacent cotton crops are in full bloom ent study reports, for the first time, the effects of different (boll-filling phase) and, therefore, susceptible to stink bugs E. heros adult population levels on cotton. Seed and cotton (Willrich et al 2004a,Musseret al 2008). In the Southeastern lint production as well as fiber quality of Bt cotton plants USA, the 3rd through the 5th week is the most susceptible (Bollgard®) (Cry1Ac) in different phenological stages was period for injury from stink bugs (Bacheler et al 2010); during assessed, providing an economic injury level (EIL) for this this period, >70% of the bolls are <25 days old (days after pentatomid on cotton crops in Brazil. anthesis) or ≤25 mm in diameter, which is considered the size/age of bolls most susceptible to feeding injury from stink bugs (Herbert et al 2009). Material and Methods When bolls suffer feeding injury and no abscission of these structures occurs, they develop cellular calluses Study location (“warts”) and show internal punctures in the mesocarp and, often, dark marks on the external exocarp (Wene & The study was conducted using potted growth cotton plants Sheets 1964, Greene et al 1999,Toewset al 2009, cultivated in a greenhouse,fromOctober04,2009,to Medrano et al 2011). Infestation by E. heros canresultina May 19, 2010, at the Laboratory of Applied Entomology and significant reduction (60%) in the production of seed cotton Biotechnology (22°11'50.20"S, 54°55'58.90"W at 459 m of and lint (Soria et al 2010b). altitude), School of Agricultural Sciences of Universidade In the major cotton-producing regions of the USA, control Federal da Grande Dourados (UFGD), Dourados, MS, Brazil. of stink bugs in cotton is generally recommended when 1 bug/ 6 ft is found using the beat sheet sampling method or when Plant cultivation conditions (on average) 20% of bolls, ±2.5 cm in diameter, exhibit signs of internal damage (Greene et al 1999, 2001, 2006). However, Plants of the Bt variety NuOpal® Bollgard® that express the recently, a dynamic treatment threshold, based on week of Cry1Ac protein (Monsanto do Brasil Ltda., São Paulo, SP) flowering, was established in which the percentage of bolls were grown in pots with a 15-L substrate capacity. Initially, with a mean diameter of 2.5 cm showing any symptoms of soil from the layer 60–80 cm in depth (Distroferric Red internal injury is assessed has been widely adopted by North Latosol—“Latossolo Vermelho distroférrico—Lvdf”)was American cotton producers (Bacheler et al 2010). sieved with a 2-mm sieve-mash and subsequently mixed with 326 Soria et al soil conditioner (Ribumin®, Technes Agrícola, Cabreúva, SP) plastic containers (20 × 30 × 10 cm) with a perforated lid cov- at a ratio of 10:1. In each pot, 11 kg of substrate (sieved soil ered with voile-type fabric and a base lined with filter paper. and soil conditioner) was combined with 18 g of limestone- Sexing of adults was performed at 1–7 days of age, and bugs type filler, and the mixture was incubated for 40 days to were kept in groups of 20–25 couples to allow mating. promote the reaction of limestone with the soil that corrects Adult bugs received a diet of green beans (Phaseolus the pH and Al toxicity before planting. vulgaris L.) and fruits of privet [(Ligustrum lucidum (Ait.)], One day before sowing, 4 g of fertilizer formula 02-20-18 supplemented with dried seeds from soybeans [Glycine (N-P-K + Ca = 9.0% and S = 5%) was added to each pot and max (L.)], peanuts (Arachis hypogaea L.), and sunflowers homogenized with a gardening trowel.