Increasing use of sustainable plants in production and landscape design

Literally hundreds of ornamental and turfgrass taxa were evaluated for their resistance characteristics to traditional or newly invasive pests. Highlights of the projects are profiled below:

Japanese Beetle on Crapemyrtle
The Japanese beetle, Popillia japonica Newman, is recognized as the most widespread and destructive pest of turf, landscape and nursery crops in the eastern United States. Forty-one crape myrtle cultivars representing a range of flower color and heights were planted on 15 foot centers at the University of Georgia Mountain Station in Blairsville. The cultivars that showed significantly lower percent leaf damage on three or more sample dates were ‘Centennial’, ‘Chickasaw’, ‘Choctaw’, ‘Lipan’, ‘Pecos’, ‘Potomac’, ‘Raspberry Sundae’, ‘Tonto’, ‘Wichita’ and ‘Tuscarora’. The cultivars that consistently had significantly fewer or no beetles on two or more sample dates were ‘Apalachee’, ‘Chickasaw’, ‘Hardy Lavender’, ‘Lipan’ ‘Pocomoke’, ‘Potomac’, ‘Raspberry Sundae’, ‘Tonto’, ‘Tuscarora’, and ‘Wichita’. The cultivars that were among the most damaged on three or more sample dates were ‘Biloxi’, ‘Byer’s Wonderful White’, ‘Comanche’, ‘Dynamite’, ‘Hopi’, ‘Miami, ‘Natchez’, ‘Regal Red’, ‘Sioux’ and ‘Zuni’; and the cultivars that consistently had significantly higher numbers of beetles on two or more sample dates were ‘Byer’s Wonderful White’, ‘Catawba’, ‘Comanche’, ‘Hopi’, ‘Miami’, ‘Natchez’, ‘Osage’, ‘Regal Red’, ‘Sioux’, and ‘Zuni’.

Lesser canna leafroller and Japanese beetle on Canna
Twenty-two cultivars of canna lilies, Canna x generalis, were evaluated for potential resistance to the lesser canna lily leafroller, Geshna cannalis, and the Japanese beetle, Popillia japonica. Both of these pests cause defoliation of the plants resulting in reduced plant fitness and aesthetic injury. Cultivars sustaining the most damage by leafrollers were ‘Richard Wallace’, ‘Firebird’, and ‘Black Knight’. While Japanese beetle injury varied, cultivars most consistently damaged by beetles were ‘Lenape’, ‘Scarlet Wave’, ‘Dawn Pink’, and ‘Crimson Beauty’. While all plants sustained at least some injury, cultivars that consistently had the least amount of damage by leafrollers were ‘Maudie Malcolm’, ‘Striped Beauty’, and ‘Journey’s End’. ‘Maudie Malcolm’ and ‘Striped Beauty’ were similarly avoided by Japanese beetles, while ‘Journey’s End’ sustained moderate injury from this pest. Tall cultivars with red or orange flowers and some red in their foliage were especially vulnerable to infestation by the lesser canna leafroller.

Lace bugs on Pennisetum ornamental grasses
Leptodictya plana Heidemann is an emerging pest on ornamental grasses in the southern United States. Thirty-two selections of commercially available ornamental grasses and sedges and five trial accessions of Pennisetum purpureum were evaluated for susceptibility to L. plana feeding and oviposition. No- choice studies were conducted in a greenhouse by securing four lace bugs to leaf blades of each plant using clip cages. Lace bugs stayed attached for five days. Damage and number eggs were recorded. Choice studies were conducted in the laboratory by placing leaf blades from each genus of plant species into a large petri dish in a spoke pattern. There were no plants tested that consistently received zero percent damage in either trial. Plants that sustained the least damage included Acorus spp., Cordyline spp., and Panicum spp. Pennisetum spp. entries exhibited the highest overall percent damage and were the only genera of plants that supported oviposition.

Lace bugs on Pieris
Stephanitis takeyai Drake and Maa (Hemiptera: Tingidae), the Andromeda lace bug, is an important pest of Pieris D. Don spp., a popular landscape plant. Cultivated Pieris taxa have not been evaluated for their pest resistance and this information would be useful to growers as well as breeders. The azalea lace bug, S. pyrioides was included in the study because of its importance as the major economic and cosmopolitan tingid species which is also known to infest other ericaceous hosts. Both lace bugs are Asian indigenes as are most cultivated Pieris currently in production. Over 60 Pieris taxa were evaluated for their susceptibility to the two species of lace bugs based on leaf damage, adult survival on leaves and emergence of nymphs using no-choice Petri dish assays. The taxa P. phillyreifolia and P. japonica ‘Variegata’ were consistently resistant to both species of lace bugs while P. japonica ‘Cavatine’ was consistently susceptible to both. P. japonica ‘Temple Bells’ and was notable in being highly susceptible to S. takeyai, but resistant to S. pyrioides. Oviposition was noted only with S. takeyai on some Pieris taxa, whereas S. pyrioides did not oviposit on any of the Pieris taxa. Choice assays (with 10 Pieris taxa) and whole plant assays (with 5 Pieris taxa) using S. takeyai alone were also conducted, confirming the resistance of P. phillyreifolia and susceptibility of P. japonica ‘Temple Bells’.
Wide variability in leaf shape, size, texture, color and growth habit exists among Pieris taxa, even among taxa within the same species. Screening of Pieris taxa for their reaction to Stephanitis lace bugs (Hemiptera: Tingidae) revealed gradients in susceptibility to the lace bugs. This study also examined some of the potential mechanisms of resistance in selected Pieris taxa to S. takeyai, based on their differences in lace bug susceptibility and also the possible role of leaf parameters in plant resistance. Experiments with extracts of leaf-surface lipids revealed that Pieris leaf wax does not have a role in resistance. Leaf wax extracts from the resistant species P. phillyreifolia applied on leaves of the susceptible cultivar P. japonica ‘Temple Bells’ did not affect feeding, oviposition or survival of S. takeyai, and neither did the reverse affect the resistance of P. phillyreifolia. Leaf penetrometer measurements indicated significantly higher force was required to puncture P. phillyreifolia leaves. This species also had higher fiber, lignin and cellulose content and lower leaf moisture content. Ultrastructural studies on leaves of selected Pieris taxa revealed significant differences in the number and size of stomata. P. phillyreifolia leaves had the highest number of stomata per unit area but they were the smallest in size, whereas P. japonica ‘Temple Bells’ leaves had a lower number but the largest stomata. Resistance in Pieris taxa to S. takeyai may be attributed to a combination of different factors among which leaf toughness, moisture and stomatal characters may have a significant role.

Hemlock wooly adelgid and their predators on hemlock
Understanding how fertilization affects host resistance to hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae), is important since fertilizers are often used to grow resistant selections to a suitable size for testing. We evaluated four hemlock species under three different fertilizer regimes to assess whether or not fertility affected resistance to the adelgid and to determine if feeding preferences of the predators Laricobius nigrinus Fender and Sasajiscymnus tsugae (Sasaji & McClure) based on eggs obtained from adelgids raised on plants fertilized or not. Treatments were long-term fertility (June 2008 to June 2009), short-term fertility (March to June 2009), and no fertilizer. Plants were fertilized with 240 ppm N using water soluble fertilizer (NPK: 20-20-20) in a biweekly interval. Plants (> 1-yr old) were artificially infested with adelgids on 31 March 2009. Among unfertilized hemlocks (n = 10/species), foliar N content was highest in Tsuga mertensiana (Bong.) Carrière, and lowest in T. chinensis (Franch.) E. Pritz. Significantly more progredien ovisacs or sisten eggs were present on T. mertensiana than on the other hemlock species with none on unfertilized T. chinensis. Fertilizing T. heterophylla (Raf.) Sarg. had no effect on adult A. tsugae feeding. However, densities of developing A. tsugae nymphs, were higher on unfertilized T. heterophylla than on fertilized T. heterophylla regardless of fertilizer. Both L. nigrinus and S. tsugae consumed more adelgid eggs that developed on fertilized T. canadensis than from unfertilized ones. This predatory preference was not noted on T. heterophylla or T. mertensiana.

Dogwood Sawfly on Cornus spp.
Dogwood sawfly (Macremphytus tarsatus Say) is a native, phytophagous
insect that relies on Cornus sp. host plants for larval development.
Feeding injury by dogwood sawflies is primarily aesthetic and seldom
results in host plant death. Still, native and non-native dogwoods have
not been evaluated for susceptibility to larval feeding by this
aesthetically damaging wasp. Ten species or cultivars of dogwoods that
are either naturalized native plants or economically significant
landscape plants were assayed for host suitability to dogwood sawfly
larvae in no-choice and choice experiments. Flowering, kousa and
cornelian cherry dogwoods were consistently ranked among the least
susceptible host plants while 'Sibirica' tatarian, gray, and
'Flaviramea' golden-twig dogwoods were highly preferred hosts.
Preliminary GC/MS comparisons of foliar metabolite extracts from all 10
species have identified five peaks of interest that varied between
resistant and susceptible hosts. These results suggest that certain
chemical constituents in foliage of dogwood species may be important
predictors of host palatability. More research is needed to confirm
this hypothesis before crossbreeding for sawfly resistance can proceed.

Florida wax scale on Hollies
33 taxa of potted hollies were represented by six plants (replications). Plant taxa were selected to provide varieties within four landscape use groups; trees, large shrubs, medium shrubs, and small shrubs. The intended purpose of the groupings was for easier incorporation into the plant use database, also an objective of this project. For example, if this research determines that Ilex crenata ‘Hoogendorn’ (small shrub group) is more susceptible to this scale, then a resistant variety in the same use group would be suggested by the software as a substitute.
In mid-May 2009 and 2010, potted plants were infested with Florida wax scale (FWS), Ceroplastes floridensis . Stems were tethered into each potted plant using parafilm. Foliage was sampled to determine nitrogen and water content, leaf thickness and toughness, and an assessment of crawler density was also taken. All varieties hosted crawlers but crawler density showed significant variation among cultivars and species. Among use groups, the tree had the most significant variation in crawler density. Data also suggest thickness and toughness are significant factors in wax scale crawler density. In fall 2010, gravid females were sampled from each plant to determine the number of offspring (eggs or crawlers) on each respective cultivar.

Based on 2009 data, crawlers will settle on all varieties of holly in this trial. Fecundity evaluated in 2010 explained the rapid buildup on populations on certain hollies in the field. These differences have been previously reported without fully understanding how these population outbreaks occur. This should provide landscape architects and growers with the needed information to select less susceptible cultivars within each use group for production or planting designs.

Rose evaluations
Sales and use of shrub roses has increased dramatically but information on performance in Florida and the SE is lacking, especially under low maintenance conditions. An evaluation of 12 shrub rose cultivars was conducted at 3 sites in Florida. After 40 weeks, Knock Out received the highest average cumulative visual quality ratings in north and central Florida, and Knock Out and Home Run had the highest ratings in south Florida. The largest average cumulative flowering occurred with Knock Out in south Florida, Knock Out, Home Run and 'Bailey Red' in central Florida, and Knock Out and Home Run in north Florida. Ratings in central Florida declined in late summer and fall in association with damage from chilli thrips (Scirtothrips dorsalis). Peak flowering of most cultivars occurred in July in south and central Florida and Aug. through Nov. in north Florida.

Chinch bugs on St. Augustine
Field and greenhouse studies were conducted in Georgia and South Carolina to determine the tolerance and antibiosis effects of 15 St. Augustinegrass genotypes against the southern chinch bug. ‘Floratam’ and ‘Floralawn’ cultivars were highly resistant to southern chinch bug populations in South Carolina and Georgia. When southern chinch bugs were caged on Floratam for 37 days in a greenhouse study, both survivorship and adult reproduction were either stopped or significantly reduced. Color and quality ratings of heavily infested field plantings of ‘Raleigh’ were not significantly reduced even though this cultivar had the highest chinch bug density. Color and quality ratings for ‘Amerishade’ were significantly lower than all other cultivars. The data suggested that the St. Augustinegrass cultivars exhibited different levels of tolerance to infestation by southern chinch bug. The results called into question the established treatment threshold of 20-25 chinch bugs 0.1 m-2, which does not consider the tolerance levels among St. Augustinegrass cultivars. Numbers of the predator Lasiochilus palidulus also varied by genotype and were least abundant in the resistant cultivars and most abundant in ‘Winchester’.

Grubs on Paspalum
Ten cultivars of seashore paspalum, Paspalum vaginatum Swartz, were compared for their response to Japanese beetle, Popillia japonica Newman, larval root feeding. Cultivars of bermudagrass, Cynodon sp. and zoysiagrass, Zoysia sp. were also included for comparison. Turf grown in pots in the greenhouse was infested with second and third instar larvae in this two year study. Grub survival and weight gain, foliar growth and root loss were compared among turfgrass species and cultivars. Few species related differences were identified. Differences in grub tolerance were however, observed to be a function of turfgrass cultivar. Some turf types demonstrating tolerance to grub feeding had rapid root growth and high root mass in control pots, but this was not consistent for all cultivars showing enhanced ability to maintain foliar growth despite grub feeding. The paspalum cultivars that appeared most tolerant of grub feeding were 561-79, Sea Isle 2000, Durban, HI-10, Kim-1, Sea Dwarf and Sea Spray.

Fall armyworms on Paspalum
Eight of 10 turfgrass species and cultivars evaluated supported growth and development of the fall armyworm in this study. Larval and pupal weights and days to develop to pupal stage were significantly influenced by turfgrass selection. Paspalum selections with the lowest larval weights, suggesting some degree of antibiosis, included PI-422024 (P. notatum var. saurae) and PI-462298 (P. quadrifarium). The lowest pupal weights were observed among Paspalum spp. accessions, including PI-286486 (P. thunbergii), PI-310146 (P. notatum). Extended days to develop to pupal stage were observed for PI-422024 (P. notatum var. saurae) and PI-310146 (P. notatum). All initial 30 neonate larvae failed to survive to 8d on ‘Cavalier’ zoysiagrass.
Larvae failed to survive to 8d on 1 of the 10 Paspalum spp. accessions, this was. PI-404449 (P. ionanthum). The grass with highest survival was P. vaginatum 03-539-31 (83.34%). Larvae failed to survive to the pupal stage on 1 Paspalum spp. accession; this was PI-404449 (P. ionanthum). Survival of initial 30 neonate larvae to 8d ranged from 30% on PI-422024 (P. notatum var. saurae) to 83.34% on P. vaginatum 03-539-31.
Among Paspalum spp. accessions evaluated, P. vaginatum 03-539-31.and P. vaginatum 03-525-22 were the most suitable (susceptible) hosts, as measured by larval and pupal weights and days to develop to pupal stage. The least suitable (resistant) hosts among Paspalum spp. accessions were PI-404449 (P. ionanthum), PI-422024 (P. notatum var. saurae), PI-310146 (P. notatum) and PI-286486 (P. thunbergii).

Two lined spittlebugs on centipedegrass
Warm season turf selections of centipedegrass, bermudagrass, St. Augustinegrass, and zoysiagrass were evaluated for tolerance to adult two lined spittlebug (Prosapia bicincta Say) feeding in choice and no- choice experiments, and for their ability to support nymphal development (antibiosis potential). Among 133 selections evaluated for response to the two lined spittlebug, several showed evidence of potential antibiosis and/or improved tolerance over commercially available cultivars. Most of the centipedegrass germplasm evaluated was susceptible to the spittlebug. Some potential antibiosis among Chinese centipedegrass introductions was identified, and there was a gradient in the ability of the different grasses to tolerate spittlebug feeding. Among the centipedegrasses evaluated, fewest nymphs developed on TC 341, TC 379, TC 399, TC 422 and E. cilliaris. The bermudagrasses 00-23 and 00-28 and the St. Augustinegrasses T638 and Mercedes failed to support development in either of the two developmental trials conducted. In a laboratory trial, the fewest nymphs developed on St. Augustinegrass. Among centipedegrasses, the least damage was visible on TC 441, TC 341, TC 358, TC 342, TC 344, TC 390, TC 438, TC 362, TC 347 and TC 346 in no- choice trials. In choice trials, however, the least damaged centipedgrasses were TC 324, 325, 326 and 338 and TC 358 and 359. The most tolerant bermudagrasses were 00-23, 03-14, and 03-15.

Survey results
Although lawn care and landscape maintenance professionals appear increasingly willing to use Integrated Pest Management (IPM) strategies and adopt nonchemical pest management alternatives into management practices, the opinions of landscape management professionals have not been assessed regarding anticipated influences of increased use of insect- and disease-resistant ornamental plants on grounds management activities, client satisfaction, or business profitability. Lawn care and landscape professionals are well positioned to implement many IPM practices into landscape use and to educate their consumer clients about ecologically sustainable landscape designs and beneficial management techniques. Conversely, if some of these professionals are unwilling to advocate installation of ornamental host plants that are resistant to certain pests or diseases, market success of such plants can be limited. To better understand perceptions of green industry professionals relat ed to these issues, we surveyed lawn care and landscape business owners and employees to categorize their perceptions about insect- or disease-resistant ornamental plants and qualified their beliefs in relation to both personal and firm demographics. A total of 391 completed surveys were received from Tennessee, Florida, and Georgia participants. Data analyses revealed that lawn care and landscape maintenance professionals largely believe that insect- and disease- resistant plants will benefit their businesses and should result in increased client satisfaction. Only ’4% of respondents stated concern that business would incur at least some negative effect if pest-resistant plants were made more available or used in greater numbers in client landscapes. Among all respondents, there was an average expectation that 60% or more of plants within a given client’s landscape would have to be resistant to insect pests or plant diseases to result in a decrease in company profits. If insect- and disease-resistant ornamental plants were used more widely in client landscapes, respondents expected that the required number of site visits to client landscapes would remain unchanged and that moderate reductions in insecticide and fungicide use would result.

GardenSource
GardenSource is designed as a web application to reach the largest possible audience of agents, homeowners and growers. Easily expandable and adaptable to allow for any changes necessary to the content or how it's organized. Everything about the plants in the database is searchable and can be used to organize your results. Putting it on the web allows for unlimited growth and cooperation with interest groups at any point. Setting up a multiuser website let's us have multiple contributors and future collaboration with growers and industry professionals.
A broad selection of plants is needed to provide adequate diversity of data. Once the list is prepared a fieldset representative of the whole can be selected. Once a sample set of plants are entered into the database a series of "views" can be constructed to assess the most desirable ways to search for and view the information. Additional sections of the site can be built as new needs are determined.

• final report with images