Published August 16, 2017 RESEARCH Tolerance in St. Augustinegrass Germplasm against Blissus insularis Barber (Hemiptera: Blissidae) Susana R. Milla-Lewis,* Katharine M. Youngs, Consuelo Arrellano, and Yasmin J. Cardoza S.R. Milla-Lewis, Dep. of Crop and Soil Sciences, North Carolina ABSTRACT State Univ., Raleigh, NC 27695-7620; K.M. Youngs and Y.J. Cardoza, St. Augustinegrass [Stenotaphrum secundatum Dep. of Entomology and Plant Pathology, North Carolina State Univ., (Walt.) Kuntze] is a widely used lawn grass Raleigh, NC 27695-7613; C. Arrellano, Dep. of Statistics, North in the southern United States due to its Carolina State Univ., Raleigh, NC 27695-8203. Received 20 May stoloniferous growth habit and shade tolerance. 2016. Accepted 1 Dec. 2016. *Corresponding author (susana_milla- However, St. Augustinegrass is prone to [email protected]). Assigned to Associate Editor Ambika Chandra. thatch accumulation, which is conducive to Abbreviations: FPLI, functional plant loss index; PI, plant introduction; pest problems, with the southern chinch bug SCB, southern chinch bug. (Blissus insularis Barber, SCB) being the most economically important one. Previous work to identify additional sources of SCB resistance t. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] reported genotypes with comparatively high Sis widely used as a lawn grass in warm, tropical, and sub- numbers of recovered insects but low damage tropical regions of the world (Sauer, 1972). It is a popular choice ratings. This study was conducted (i) to evaluate for lawns in the southern United States due to its aesthetically the performance of these materials in response pleasing appearance and shade tolerance (Busey and Davis, 1991; to varying SCB feeding densities, and (ii) Trenholm and Nagata, 2005). However, St. Augustinegrass is to determine feeding and oviposition under prone to thatch accumulation (Horn et al., 1973), which is con- no-choice scenarios. Genotypes exposed to 0, 10, or 30 adult SCBs were evaluated after 4 ducive to insect and disease problems (Haygood and Martin, wk for damage and insect survival. Significant 1990). The southern chinch bug (SCB, Blissus insularis Barber) is differences were observed among genotypes. the most economically important insect pest of St. Augustinegrass Across infestation levels, while recovered insect and is found throughout the Gulf States, from Texas to Florida numbers for susceptible check ‘Seville’ and and further north into Georgia and North Carolina (Henry and plant introductions 509038 and 509039 were Froeschner, 1988; Sweet, 2000). Southern chinch bugs have not significantly different, damage ratings were piercing-sucking mouthparts and feed on the phloem of grass significantly lower for the latter, indicating that plants within meristematic tissues (Painter, 1928). In doing so, these materials were tolerant to SCB feeding. SCB deposit their salivary sheaths in the plant tissue at the site In the no-choice experiments, survival levels of feeding (Backus, 1988). These insects normally reside in the of both males and females on week 4 were thatch area of the turfgrass stand and prefer to feed on the lower significantly lower for resistant check ‘FX10’, PI leaf sheaths and crown area of the plant (Anderson et al., 2006). 365031, and PI 289729. These genotypes, along with PIs 291594, 300129, and 647924, showed Affected areas turn yellow, then brown, and ultimately die. As significantly lower SCB oviposition and feeding the season progresses, these areas can coalesce into large areas or compared with Seville. Our study was able to entire lawns of dead grass (Reinert et al., 1995). confirm that two PIs display tolerance to SCB feeding, and five additional PIs have antibiosis Published in Crop Sci. 57:S-26–S-36 (2017). activity against adult SCB (likely antibiosis), doi: 10.2135/cropsci2016.05.0361 representing sources of SCB resistance for future St. Augustinegrass breeding efforts. © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). S-26 WWW.CROPS.ORG CROP SCIENCE, VOL. 57, JULY–AUGUST 2017 Historically, management of the SCB has been In a previous study looking at new sources of resistance achieved through insecticide applications (Watson and to SCB, complete antixenosis was not detected among a set Bratley, 1929; Kelsheimer, 1952; Wolfenbarger, 1953; of plant introductions (PIs) of St. Augustinegrass (Youngs Kerr, 1956). However, heavy reliance on chemical con- et al., 2014). Nonetheless, a number of PIs within the tested trol and lack of proper rotation of chemical formulations group exhibited damage ratings that were not significantly (Cherry and Nagata, 2005; Vázquez et al., 2011), com- different from those of the resistant checks. Further evalu- bined with more generations per year of SCB living in ation of these materials for neonate development identified warm climates, have led to development of resistance to nine PIs with low survival and slower development of SCB organophosphates and organochlorines (Kerr, 1958, 1961; compared with susceptible checks (Youngs et al., 2014). Reinert, 1982; Reinert and Niemczyk, 1982; Reinert and Four of the genotypes identified as having antibiosis- Portier, 1983) and to bifenthrin in Florida (Cherry and based resistance (PI 509038, PI 509039, PI 600734, and PI Nagata, 2005) and permethrin (Vázquez et al., 2011) in 647924) are diploid, which facilitates their use for transfer Florida. Currently, clothianidin (Arena, Valent Profes- of resistance into commercial cultivars. sional Products, Walnut Creek, CA) is the best insecticide In the research described here, we furthered our in the market for chemical control of resistant chinch bug efforts to assess potential tolerance in selected genotypes populations in Florida. and reference cultivars of St. Augustinegrass. Our objec- Host-plant resistance can provide a feasible alterna- tives were: (i) to evaluate the performance of selected PIs tive to chemical SCB management. Host-plant resistance in response to feeding by varying densities of SCB, and (ii) encompasses a range of adaptations evolved by plants, to assess potential adult feeding or oviposition deterrence. which reduce the impact of pests and diseases, improving plant survival and reproduction (Hayes, 1935; Fleschner, MATERIALS AND METHODS 1952; Price, 1986). Traditionally, host-plant resistance has St. Augustinegrass Maintenance been the most successful approach for controlling SCB in and Experimental Propagation St. Augustinegrass (Horn et al., 1973, Reinert and Dudeck, A total of five cultivars and 11 PIs of St. Augustinegrass were 1974; Crocker et al., 1982, 1989; Busey and Zaenker, 1992). used in this study (Table 1). Additionally, two accessions of There are three clearly delineated categories of host-plant pembagrass (Stenotaphrum dimidatum), a close relative of St. resistance: antixenosis, antibiosis, and tolerance. Anti- Augustinegrass, were included. The cultivars were chosen to xenosis includes any plant characteristic that leads to the serve as points of reference for ascribing tolerance–susceptibil- pest’s nonpreference for a resistant plant when compared ity scores to the uncharacterized accessions. The group included with a susceptible plant (Painter, 1951; Kogan and Ortman, SCB-resistant ‘FX-10’ (Busey, 1990), ‘Captiva’ (Nagata and 1978). Antibiosis is due to chemical plant properties that Cherry, 2003), and ‘Raleigh’ (Anderson et al., 2006; Chong can negatively affect the life history of the pest, leading to et al., 2009; Youngs et al., 2014) and SCB-susceptible Flora- increased mortality, decreased fecundity, or reduced lon- tam (Busey and Center, 1987; Nagata and Cherry, 2003) and ‘Seville’ (Crocker et al., 1989). Plant introductions were chosen gevity (Painter, 1951). A plant exhibiting tolerance, on according to the results of Youngs et al. (2014), who reported the other hand, is an acceptable and adequate host for the genotypes with comparatively high numbers of recovered pest, but it can withstand large infestations and can com- insects but low damage ratings. Cultivars and PIs were obtained pensate for any damage caused by the noxious organism from the North Carolina State University (Raleigh, NC) turf- (Painter, 1958). Southern chinch bugs have been able to grass breeding program’s germplasm collection. consistently overcome management strategies ranging from All plant materials were propagated and maintained accord- chemical to host-plant resistance. For example, ‘Floratam’ ing to Youngs et al. (2014) and grown at the North Carolina State St. Augustinegrass, which was released in 1973 (Horn et University greenhouse complex (Raleigh, NC) at 28 ± 5°C and al., 1973) and subsequently planted throughout the south- under natural light with an approximate 14:10-h light:dark cycle. ern United States (Reinert and Dudeck, 1974; Crocker et al., 1982, 1989), exhibited a high level of SCB antibiosis Blissus insularis Colonies (Reinert and Dudeck, 1974). However, resistance-breaking All SCB used in this study were offspring from adult SCB col- SCB populations in Floratam fields were reported in Flor- lected from infested residential lawns in Wilmington, NC. ida by 1985 (Busey and Center, 1987) and have continued Southern chinch bug colonies were maintained by transferring 40 to 70 SCB adults into new flats (15.25 ´ 20.32 cm) of SCB- to spread since then (Cherry and Nagata, 1997; Reinert, susceptible