Symptoms, Distribution and Abundance of the Stem-Boring Caterpillar, Blastobasis repartella (Dietz), in Switchgrass

A potential pest of switchgrass, Panicum virgatum L., was first detected in South Dakota in 2004, where death of partially emerged leaves was noted in a small proportion of tillers. Similar “dead heart” symptoms were observed in switchgrass in Illinois during 2008 and adults of a stem-boring caterpillar were collected and identified as Blastobasis repartella (Dietz). In 2009, a survey of the central United States was used to estimate the distribution and abundance of this insect. In eight northern states, B. repartella was consistently found in both cultivated plots and natural stands of switchgrass. In four southern states, B. repartella was not detected. However, because symptoms are conspicuous for a short period of time, failure to collect stem-borers on one survey date for each southern location does not necessarily define the limit of distribution for B. repartella. Sampling in four northern states showed the proportion of tillers damaged by B. repartella ranged from 1.0–7.2%. Unlike some caterpillars that feed on native grasses, it appears that the egg-laying behavior of adult moths may preclude the use of prescribed burns as an effective method to suppress this stem-boring caterpillar. As a potential pest of switchgrass planted for biomass production, near-term research needs include refining the geographic distribution of B. repartella, quantifying potential losses of switchgrass biomass, and determining whether switchgrass may be bred for resistance this and other stem-boring insects

Biomass Yield of Switchgrass Cultivars under High- versus Low-Input Conditions

Switchgrass (Panicum virgatum L.) is undergoing development as a biomass crop to support conversion of cellulosic biomass to energy. To avoid the competition of biomass with food or feed crops, most commercialization proposals suggest that switchgrass should be grown exclusively on marginal lands that are not fit for food or feed production. The objective of this study was to investigate the potential for cultivar x environment interactions that would affect the methods and approaches for breeding and evaluating switchgrass cultivars, including both upland and lowland types, for high-input versus low-input types of environments. Biomass yield was measured on 14 cultivars that were present in 28 replicated field experiments representing seven regions, ranging from 75 to 100° W and spanning USDA Hardiness Zones 4 through 7. Region was the most important environmental factor interacting with cultivars, supporting the idea that the north-central and northeastern United States should have independent switchgrass breeding programs. Cultivars interacted with soil phosphorus concentration in New Jersey and with depth of the A and B horizons in New York and showed mild interactions with rate of nitrogen fertilizer at several locations. Cultivar rank correlation coefficients between the two rates of nitrogen fertilization (100 vs. 0 kg N ha−1) ranged from 0.23 to 0.88, suggesting a possible benefit to breeding and selection without applied nitrogen fertilizer

Establishment and Persistence of Yellow-Flowered Alfalfa No-Till Interseeded into Crested Wheatgrass Stands

Crested wheatgrass [Agropyron cristatum (L.) Gaertn., A. desertorum (Fisch. ex Link) Schult., and related taxa] often exists in near monoculture stands in the northern Great Plains. Introducing locally adapted yellow-flowered alfalfa [Medicago sativa L. subsp. falcata (L.) Arcang.] would complement crested wheatgrass. Our objective was to evaluate effects of seeding date, clethodim {(E) -2-[1-[[(3-chloro-2-propenyl)oxy]imino] propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} sod suppression, and seeding rate on initial establishment and stand persistence of Falcata, a predominantly yellow-flowered alfalfa, no-till interseeded into crested wheatgrass. Research was initiated in August 2008 at Newcastle, WY; Hettinger, ND; Fruitdale, SD; and Buffalo, SD. Effects of treatment factors on plant frequency during initial establishment were influenced by site environments. Late summer and spring were suitable seeding dates. Clethodim sod suppression increased seedling frequency in most cases. Seedling frequency increased as seeding rate increased from 0.56 to 7.84 kg pure live seed (PLS) ha–1. Specific seeding dates, clethodim sod suppression, and high seeding rates did not greatly improve initial establishment when site environments were poor. Residual effects of seeding date and sod suppression post establishment were not significant at most locations, but seeding rate effects were evident. Initial establishment and persistence of Falcata alfalfa was successful at Newcastle, indicating that interseeding in late summer or spring using low seeding rates (≤3.36 kg PLS ha–1) without clethodim can be effective. Assessing grass canopy cover, soil texture, and management (e.g., haying) is necessary to determine the suitability of crested wheatgrass sites for interseeding

Nitrogen Demand Associated with Increased Biomass Yield of Switchgrass and Big Bluestem: Implications for Future Breeding Strategies

Development of perennial biomass cropping systems is focused on maximizing biomass yield with minimum inputs, particularly nitrogen (N) fertilizer. Historical breeding efforts have focused on increasing biomass yield but have ignored N-use efficiency. The purpose of this study was to quantify the increased N demand associated with realized gains in biomass yield from big bluestem (Andropogon gerardii Vitman) and switchgrass (Panicum virgatum L.) breeding programs. Nitrogen demand was highly variable across locations and years, ranging from − 1.7 to + 6.8 kg N Mg−1 DM, with an average of 2.2 kg N Mg−1 DM. Increases in N demand were closely associated with realized gains in biomass yield and were observed for all types of switchgrass (upland, lowland, and hybrid) as well as for big bluestem. Attenuation of these responses will require alternative breeding schemes that are focused on evaluation of switchgrass genotypes and progeny under low-N conditions and include a highthroughput tissue N analysis as a component of future selection criteria, designed to develop new cultivars with high biomass yield and low tissue N

The genetic basis for panicle trait variation in switchgrass (Panicum virgatum)

Key message: We investigate the genetic basis of panicle architecture in switchgrass in two mapping populations across a latitudinal gradient, and find many stable, repeatable genetic effects and limited genetic interactions with the environment. Abstract: Grass species exhibit large diversity in panicle architecture influenced by genes, the environment, and their interaction. The genetic study of panicle architecture in perennial grasses is limited. In this study, we evaluate the genetic basis of panicle architecture including panicle length, primary branching number, and secondary branching number in an outcrossed switchgrass QTL population grown across ten field sites in the central USA through multi-environment mixed QTL analysis. We also evaluate genetic effects in a diversity panel of switchgrass grown at three of the ten field sites using genome-wide association (GWAS) and multivariate adaptive shrinkage. Furthermore, we search for candidate genes underlying panicle traits in both of these independent mapping populations. Overall, 18 QTL were detected in the QTL mapping population for the three panicle traits, and 146 unlinked genomic regions in the diversity panel affected one or more panicle trait. Twelve of the QTL exhibited consistent effects (i.e., no QTL by environment interactions or no QTL × E), and most (four of six) of the effects with QTL × E exhibited site-specific effects. Most (59.3%) significant partially linked diversity panel SNPs had significant effects in all panicle traits and all field sites and showed pervasive pleiotropy and limited environment interactions. Panicle QTL co-localized with significant SNPs found using GWAS, providing additional power to distinguish between true and false associations in the diversity panel

A generalist–specialist trade-off between switchgrass cytotypes impacts climate adaptation and geographic range

Polyploidy results from whole-genome duplication and is a unique form of heritable variation with pronounced evolutionary implications. Different ploidy levels, or cytotypes, can exist within a single species, and such systems provide an opportunity to assess how ploidy variation alters phenotypic novelty, adaptability, and fitness, which can, in turn, drive the development of unique ecological niches that promote the coexistence of multiple cytotypes. Switchgrass, Panicum virgatum, is a widespread, perennial C4 grass in North America with multiple naturally occurring cytotypes, primarily tetraploids (4×) and octoploids (8×). Using a combination of genomic, quantitative genetic, landscape, and niche modeling approaches, we detect divergent levels of genetic admixture, evidence of niche differentiation, and differential environmental sensitivity between switchgrass cytotypes. Taken together, these findings support a generalist (8×)–specialist (4×) trade-off. Our results indicate that the 8× represent a unique combination of genetic variation that has allowed the expansion of switchgrass’ ecological niche and thus putatively represents a valuable breeding resource

Symptoms, Distribution and Abundance of the Stem-Boring Caterpillar, \u3ci\u3eBlastobasis repartella\u3c/i\u3e (Dietz), in Switchgrass

A potential pest of switchgrass, Panicum virgatum L., was first detected in South Dakota in 2004, where death of partially emerged leaves was noted in a small proportion of tillers. Similar “dead heart” symptoms were observed in switchgrass in Illinois during 2008 and adults of a stem-boring caterpillar were collected and identified as Blastobasis repartella (Dietz). In 2009, a survey of the central United States was used to estimate the distribution and abundance of this insect. In eight northern states, B. repartella was consistently found in both cultivated plots and natural stands of switchgrass. In four southern states, B. repartella was not detected. However, because symptoms are conspicuous for a short period of time, failure to collect stem-borers on one survey date for each southern location does not necessarily define the limit of distribution for B. repartella. Sampling in four northern states showed the proportion of tillers damaged by B. repartella ranged from 1.0–7.2%. Unlike some caterpillars that feed on native grasses, it appears that the egg-laying behavior of adult moths may preclude the use of prescribed burns as an effective method to suppress this stem-boring caterpillar. As a potential pest of switchgrass planted for biomass production, near-term research needs include refining the geographic distribution of B. repartella, quantifying potential losses of switchgrass biomass, and determining whether switchgrass may be bred for resistance this and other stemboring insects

Acanthocaudus Smith

<i>Acanthocaudus</i> Smith <p>(Figs 1–7)</p> <p> <i>Acanthocaudus</i> Smith 1944: 96 [as subgenus of <i>Trioxys</i> Haliday]. Type species: <i>Trioxys</i> (<i>Acanthocaudus</i>) <i>tissoti</i> Smith [by original designation; USNM, examined].</p> <p> <i>Acanthocaudus</i>: Mackauer 1960: 138 [status revised to genus].</p> <p> <b>Diagnosis.</b> <i>Acanthocaudus</i> can be differentiated from other genera of Aphidiinae with species in the Nearctic Region using data in the key to New World genera of Aphidiinae in van Achterberg (1997): forewing without marginal and submarginal cells, tergum 1 and sternum 1 fused basally at least to level of spiracles, hypopygium of female with prongs, hypopygium of female with accessory prongs at base of hypopygial prongs, and female with at least terga 6–7 with subapical row of pegs or spines.</p> <p> <b>Distribution.</b> CANADA: British Columbia (Schlinger & Hall 1960); CUBA: Guantánamo (as Oriente), Pinar del Río (Starý 1981); USA: Florida (Smith 1944), Indiana *, South Dakota (Assefa <i>et al</i>. 2015), Wisconsin (Smith 1944), and Washington (Pike <i>et al.</i> 2000).</p> <p> <b>Hosts.</b> <i>Aphis gossypii</i> Glover, <i>Uroleucon</i> (<i>Uroleucon</i>) <i>ambrosiae</i>, <i>Uroleucon bradburyi</i> (Olive) *, <i>Uroleucon</i> (<i>Lambersius</i>) <i>erigeronense</i>, <i>Uroleucon</i> (<i>Lambersius</i>) <i>gravicorne</i>, <i>Uroleucon</i> (<i>Uroleucon</i>) <i>rudbeckiae</i>, and <i>Uroleucon</i> (<i>Uroleucon</i>) <i>russellae</i> (see host sections for each species below for references to rearing records).</p>Published as part of <i>Kula, Robert R., Johnson, Paul J., Heidel-Baker, Thelma T. & Boe, Arvid, 2017, A new species of Acanthocaudus Smith (Braconidae: Aphidiinae), with a key to species and new host and distribution records for aphidiines associated with Silphium perfoliatum L. (Asterales: Asteraceae), pp. 543-552 in Zootaxa 4236 (3)</i> on page 546, DOI: 10.11646/zootaxa.4236.3.8, <a href="http://zenodo.org/record/322303">http://zenodo.org/record/322303</a&gt

Acanthocaudus tissoti Smith

<i>Acanthocaudus tissoti</i> (Smith) <p>(Figs 3–4, 6–7)</p> <p> <i>Trioxys</i> (<i>Acanthocaudus</i>) <i>tissoti</i> Smith, 1944: 96 [USNM, examined].</p> <p> <i>Acanthocaudus tissoti</i>: Mackauer 1960: 138 [revised combination].</p> <p> <i>Trioxys</i> (<i>Acanthocaudus</i>) <i>schlingeri</i> Muesebeck, 1958: 144 [USNM, examined]. <b>New synonym.</b> <i>Acanthocaudus schlingeri</i>: Mackauer 1960: 138 [revised combination].</p> <p> <b>Diagnosis.</b> The mesosoma is mottled yellow and brown or entirely brown in <i>A</i>. <i>tissoti</i>; it is entirely yellow in <i>A</i>. <i>caudacanthus</i> <i>.</i> The head is entirely brown or brown dorsally and gradually transitioning to yellow ventrally in <i>A</i>. <i>tissoti</i>; it is yellow with ocellar triangle entirely brown to black or yellow with brown to black markings around periphery of each ocellus in <i>A</i>. <i>bicolor</i>.</p> <p> <b>Distribution.</b> CANADA: British Columbia (Schlinger & Hall 1960); CUBA: Guantánamo (as Oriente), Pinar del Río (Starý 1981); USA: Florida (Smith 1944), Indiana *, South Dakota (Assefa <i>et al</i>. 2015).</p> <p> <b>Hosts.</b> <i>Uroleucon</i> (<i>Uroleucon</i>) <i>ambrosiae</i> (Muesebeck 1958) ex <i>Baccharis</i> sp. (Schlinger & Hall 1960) and <i>Parthenium hysterophorus</i> (Starý 1981), <i>Uroleucon</i> (<i>Uroleucon</i>) <i>rudbeckiae</i> (Smith 1944) ex <i>Silphium perfoliatum</i>, <i>Uroleucon</i> (<i>Uroleucon</i>) <i>russellae</i> (Marsh 1979).</p> <p> <b>Specimens reared.</b> All USA. INDIANA: 1 ♀ Tippecanoe Co., Lily Wildlife Area, 40°23'15.26"N 86°56'11.30"W, 2.vii.2007, T.T. Heidel, ex undet. aphids on <i>Silphium perfoliatum</i>, 07-254; 1 ♀ same data as previous except 07-296; SOUTH DAKOTA: 3 ♀ 21 ♂ Brookings Co., Brookings, South Dakota State University, Campus Agronomy Farm, 1.viii.2001, P. Loewe & A. Boe, ex aphids on <i>Silphium perfoliatum</i>; 15 ♀ 12 ♂ 5 indet. same data as previous except Felt Farm, 4 mi N of Brookings, 44°22'08"N 96°47'39"W, 1693' elevation, coll. 28.vii.2013, A. Boe, em. 28.vii.–2.viii.2013, ex <i>Uroleucon</i> cf. <i>rudbeckiae</i> on <i>Silphium perfoliatum</i>; 20 ♀ 20 ♂ 1 indet. same data as previous except coll. 3.viii.2013, P. J. Johnson, em. 3–4.viii.2013; 1 ♀ same data as previous except coll. 15.viii.2013, em. 17–20.viii.2013 (1 ♀ PURC, 10 ♀ 10 ♂ SDSU, 30 ♀ 43 ♂ 6 indet. USNM).</p> <p> <b>Discussion.</b> Muesebeck (1958) differentiated <i>A</i>. <i>schlingeri</i> (Figs 4, 7) from <i>A</i>. <i>tissoti</i> (Figs 3, 6) based on the absence of a distinct carina mediobasally on the propodeum and the eyes more convergent ventrally in the former compared to the later. Analysis of 31 female specimens from South Dakota regarded as <i>A</i>. <i>tissoti</i> by the first author revealed that the carina mediobasally on the propodeum varies from present to absent within this species. Also, FW was 1.40–1.67X FH for 26 of the female specimens from South Dakota regarded as <i>A</i>. <i>tissoti</i>. The FW:FH ratio for the holotypes of <i>A</i>. <i>tissoti</i> and <i>A</i>. <i>schlingeri</i> are 1.42 and 1.43, respectively, and thus, both fall within that range. Therefore, <i>Acanthocaudus schlingeri</i> Muesebeck, 1958 is synonymized with <i>Acanthocaudus tissoti</i> (Smith, 1944) given the intraspecific variation observed for the features used to distinguish those species.</p>Published as part of <i>Kula, Robert R., Johnson, Paul J., Heidel-Baker, Thelma T. & Boe, Arvid, 2017, A new species of Acanthocaudus Smith (Braconidae: Aphidiinae), with a key to species and new host and distribution records for aphidiines associated with Silphium perfoliatum L. (Asterales: Asteraceae), pp. 543-552 in Zootaxa 4236 (3)</i> on pages 548-550, DOI: 10.11646/zootaxa.4236.3.8, <a href="http://zenodo.org/record/322303">http://zenodo.org/record/322303</a&gt

Acanthocaudus

Key to the species of <i>Acanthocaudus</i> (based on females) <p> 1. Mesosoma and metasoma entirely yellow (Figs 2, 5)............................ <i>Acanthocaudus caudacanthus</i> (Smith)</p> <p>- Mesosoma and metasoma with at least some brown coloration (Figs 1, 3–4, 6–7)...................................2</p> <p> 2. Mesosoma yellow except mesonotum brown (Fig. 1); head either yellow with ocellar triangle entirely brown to black (50%) or yellow with brown to black markings around periphery of each ocellus (50%)..... <i>Acanthocaudus bicolor</i> Kula, new species</p> <p> - Mesosoma mottled yellow and brown (Fig. 6) or entirely brown (Fig. 7), propleuron, pronotum, mesoscutum peripherally, mesopleuron peripherally, metapleuron, and propodeum with varying extent of yellow when mesosoma is mottled; head entirely brown or brown dorsally and gradually transitioning to yellow ventrally.............. <i>Acanthocaudus tissoti</i> Smith</p>Published as part of <i>Kula, Robert R., Johnson, Paul J., Heidel-Baker, Thelma T. & Boe, Arvid, 2017, A new species of Acanthocaudus Smith (Braconidae: Aphidiinae), with a key to species and new host and distribution records for aphidiines associated with Silphium perfoliatum L. (Asterales: Asteraceae), pp. 543-552 in Zootaxa 4236 (3)</i> on page 550, DOI: 10.11646/zootaxa.4236.3.8, <a href="http://zenodo.org/record/322303">http://zenodo.org/record/322303</a&gt