M. C. Engelke

Interploid St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) hybrids recovered by embryo rescue

St. Augustinegrass is one of the most important warm season turfgrasses in the southern United States because of its shade tolerance. Most cultivars are diploids (2n = 2x = 18) and are susceptible to various diseases and insects. Polyploid cultivars in the species have some resistance to pests, but most lack cold tolerance. In this study, eight polyploid genotypes were crossed with six diploid cultivars to transfer pest resistance to the diploids. Because interploid crosses often result in aborted seed, it was necessary to use in vitro techniques. Using embryo rescue, 268 plants were recovered from 2,463 emasculated and pollinated florets (10.88% crossability). Because of the heterogeneous nature of the species, these purported hybrids could not be verified by phenotype. DNA markers were used for hybrid identification. A subset of 25 plants from crosses between the aneuploid cultivar Floratam (2n = 4x = 32) and five diploid cultivars were analyzed using 144 expressed sequence tags–simple sequence repeats (EST-SSRs) developed from buffelgrass cDNA sequence data. Chi-square tests for paternal-specific markers revealed that all analyzed progeny were true F1 hybrids and none originated from self-fertilization or unintended outcrossing. In addition to identifying DNA polymorphism, the EST-SSRs revealed that genetic variation exists among all analyzed cultivars and is not partitioned between ploidy levels. The findings demonstrate that these embryo rescue techniques will enable the entire spectrum of St. Augustinegrass genetic variation to be better used through the recovery of interploid hybrids.

Susceptibility of Genera and Cultivars of Turfgrass to Southern Chinch Bug Blissus Insularis (Hemiptera: Blissidae)

ABSTRACT The southern chinch bug (Blissus insularis Barber) is the most damaging insect pest of St. Augustinegrass (Stenotaphrum secundatum Walt. Kuntze), across the southern U.S.A. Susceptibility to the southern chinch bug and reproductive potential of the bugs on 24 cultivars from 7 genera in 8 turfgrasses were evaluated under greenhouse conditions. Stenotaphrum secundatum (‘Raleigh’, ‘Texas Common’, and ‘Captiva’) cultivars were the most susceptible among all the turfgrass genera and each produced populations ≥97.5 bugs per 15-cm diameter plant within the 11-week test period from Jul to Sep 2008. Substantial populations also developed on zoysiagrass (Zoysia spp.) (‘Emerald’, ‘Empire’, ‘Palisades’, and ‘Zorro’) cultivars and on ‘609’ buffalograss (Buchloë dactyloides (Nutt.) Engelm.). Low population development was recorded on cultivars of bermudagrass (Cynodon spp.), centipedegrass (Eremochloa ophiuroides (Munro) Hack.), seashore paspalum (Paspalum vaginatum Swartz), bahiagrass (Paspalum notatum Flugge), and tall fescue (Festuca arundinacea Schreb.).

The Differential Grasshopper (Orthoptera: Acrididae)—Its Impact on Turfgrass and Landscape Plants in Urban Environs

ABSTRACT The differential grasshopper, Melanoplus differentialis (Thomas) (Orthoptera: Acrididae), frequently migrates from highway rights-of-way, pastures, and harvested fields to feed in urban/suburban landscapes and retail/wholesale nurseries across the southern and southwestern U.S.A., as these areas dry down during hot dry summers. Nine selected turfgrasses and 15 species of landscape plants were evaluated for their susceptibility or resistance to this grasshopper. Grasshoppers were collected from stands of Johnsongrass, Sorghum halepense, which was used as a standard host for comparison in both experiments. Based on feeding damage, number of grasshopper fecal pellets produced, and their dry weight, Zoysia matrella cv. ‘Cavalier’ was the least preferred grass followed by Buchloe dactyloides cv. ‘Prairie’ and Z. japonica cv. ‘Meyer’. Festuca arundinacea was significantly the most preferred host and sustained the most feeding damage, followed by Poa pratensis × P. arachnifera cv. ‘Reveille’ and 2 Cynodon spp. cultivars, ‘Tifway’ and ‘Common’. Among the landscape plants, Hibiscus moscheutos cv. ‘Flare’, Petunia violacea cv. ‘VIP’, Phlox paniculata cv. ‘John Fanick’, Tecoma stans cv. ‘Gold Star’, and Campsis grandiflora were the least damaged or most resistant. Plumbago auriculata cv. ‘Hullabaloo’, Glandularia hybrid cv. ‘Blue Princess’, Canna × generalis, Johnsongrass, and Cortaderia selloana cv. ‘Pumila’ sustained the most damage. Based on the number of fecal pellets produced and their weights, Canna × generalis and Glandularia hybrid cv. ‘Blue Princess’ were the most preferred landscape plants tested.

Recovery growth of Meyer and experimental zoysiagrass progeny after sod harvest.

Information is limited on the recovery growth of zoysiagrass (Zoysia spp. Willd.) after sod harvest. ‘Meyer’ and DALZ 0102 (both Z. japonica Steud.) and eighteen zoysiagrass progeny originating from crosses between a Z. matrella (L.) Merr. × Z. japonica or ‘Emerald’ (Z. matrella × Z. pacifica Goudsw.) × Z. japonica were evaluated for sod recovery growth after harvest in Manhattan in 2008 and 2009, and in Olathe, KS, in 2009 and 2010. Sod pieces (51 cm wide × 102 cm long × 5 cm thick) were harvested on 9 July 2008 at Manhattan and on 8 July 2009 at Olathe using a mechanical sod cutter. Sod recovery growth in areas of harvested strips was determined by taking an overhead digital image of a 40- by 35-cm area to determine percentage green coverage. At 60 days after harvest in Manhattan, coverage ranged from 17% to 97%; a progeny from Z. matrella × Meyer (97% coverage) demonstrated superior recovery growth to Meyer (38% coverage). Recovery growth was slower in Olathe where irrigation was applied less frequently, and all progeny were similar to Meyer until 15 July of the summer following harvest, when individual progeny from ‘Cavalier’ × Chinese Common and Emerald × Meyer were superior to Meyer. The potential for faster recovery after harvest compared to Meyer may be attractive to sod producers seeking to maximize the number of harvests from a zoysiagrass sward.

RESISTANCE IN ZOYSIAGRASS ( ZOYSIA SPP.) TO THE FALL ARMYWORM ( SPODOPTERA FRUGIPERDA ) (LEPIDOPTERA: NOCTUIDAE)

ABSTRACT The fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a pest of most turfgrass species in the United States. Twelve cultivars and genotypes of zoysiagrass (Zoysia spp.) were evaluated for resistance to both neonate and 4-d-old fall armyworm larvae. Three cultivars, ‘Cavalier’, ‘Emerald’, and ‘Belair’, were the most resistant to feeding by neonate larvae with less than 5% of the larvae survived beyond 4-d of feeding. After 10 d, 10% or less of the confined larvae were alive on these 3 cultivars along with ‘Meyer’, ‘Korean Common’, ‘El Toro’ and DALZ8501. When most of the same genotypes were exposed to 4-d-old larvae that had developed on a susceptible host, ca. 20% of the mortality was eliminated. Survivorship for 7-d-old larvae (after 3 d feeding) was 40% or greater on all genotypes except for Cavalier. Only Cavalier, DALZ8501, and Korean Common exceeded 85% mortality after 13 d of feeding. Meyer produced 97.6% mortality of neonate larvae, but only 46.7% of larvae that had first fed on a susceptible host. The 4-d-old larval that fed on the resistant genotypes usually weighed less than half the weight of those fed on susceptible Palisades and DALZ8516. Also, days-to-pupation and days-to-adult emergence were shortest on the 2 most susceptible genotypes. No fall armyworm larvae were able to survive more than 17 d on Cavalier. Several other cultivars were identified with resistance.

RESIDUAL CHEMICAL CONTROL FOR MELANOPLUS DIFFERENTIALIS (ORTHOPTERA: ACRIDIDAE) IN URBAN LANDSCAPES

Melanoplus differentialis (Thomas) (Orthoptera: Acrididae) and several other species of grasshoppers invade urban/suburban landscapes and retail/wholesale nurseries during the hot, dry summers in the southern United States to consume the foliage of many species of landscape plants and turfgrass. Two experiments were conducted to determine which insecticides could be used to safely provide residual control for the continual daily migration of grasshoppers in urban landscapes and nurseries. Leaves from treated Hibiscus moscheutos were harvested sequentially in time at 1-, 5-, and 11-days posttreatment and adult differential grasshoppers were confined on them for 24-, 48- and 72-hr exposures. Treatments with two synthetic pyrethroids, bifenthrin 0.66F (0.782 ml/liter) and lambda-cyhalothrin 9.52 WP (0.748 g/liter), provided 94 and 83%, mortality respectively, with 24-hr exposure to the 1-day-old treated leaves. Both chemicals provided 100% control of the grasshoppers during 72-hr exposure. The half rate (0.391 ml/liter) of bifenthrin also provided 89% control within the 72-hr evaluation. Treatments with diazinon AG600 (4.25 ml/liter) also provided 80-85% control with 72-hr exposure on the 1-day-old treated leaves. Acephate 75% S (0.803 g/liter) provided 33-39% control on the 1-day-old residues. Lambda-cyhalothrin provided 84% control with 72-hr exposure to the 5-day-old treated leaves. Residual control was also provided at 5 days by bifenthrin and acephate (53% and 46-50%, respectively). Most materials evaluated failed to provide any protection at all and none of the treatments provided residual control when grasshoppers were exposed to 11-day-old residues. No phytotoxicity to hibiscus was observed due to any of the treatments.