Survival of SSG, an Endophytic Burkholderia Biocontrol Agent, on the Boxwood Leaf Surface

Survival of Burkholderia cepacia complex (Bcc)-based biocontrol agents (BCA) has been associated with their field performance for foliage disease control. SSG, a strain of boxwood endophytic Bcc, suppresses a broad spectrum of plant foliage diseases, including boxwood blight, but the control efficacy declines over time. Factors affecting SSG survival on leaf surfaces were investigated to promote the application of the BCA for boxwood blight management. ‘Justin Brouwers' boxwood plants were treated with SSG cells at 107 to 108 colony-forming unit (CFU)·ml−1, maintained in a moist chamber at 10, 20, or 30 C (50, 68, 86 F), and sampled after the inoculum was blow-dried at 0, 3, 6, 12, and 24 h after treatment. The retained cells per leaf at 0 hours was 105 to 106 CFU, but only less than 10% of the cells survived 24 h after application, irrespective of the wet period and temperature. A wet condition of 12 and 24 h at 20 and 30 C facilitated SSG survival on the second day. Further survival of SSG was affected by temperature but not wetness. Damp conditions and pleasant temperatures can improve bacteria survival and stability and are keys to promoting BCA field applications. Index words: Biocontrol agent, endophyte, survival on plant surfaces, temperature, wetness. Species used in this study: Bacterium strain, SSG (Burkholderia sp);Plant species: Buxus sempervirens L. ‘Justin Brouwers'.

Nursery Management of Two Major Below-Ground Feeding Plant Pests: Root Mealybug, Rhizoecus sp. and Rice Root Aphid, Rhopalosiphum rufiabdominalis (Sasaki) (Hemiptera: Pseudococcidae and Aphididae)

Root mealybug (Rhizoecus sp.) and rice root aphid (Rhopalosiphum rufibdominalis) are below-ground feeding insects that are difficult to control and have become major pests as production of their host plants has grown. Field trials were designed to investigate the impact new insecticides and biopesticides have on root mealybugs and rice root aphids. In our first three trials, we investigated the effects of biopesticides, entomopathogenic nematodes or fungi on reflexed stonecrop (Sedum rupestre) and stonecrop (S. montanum) against root mealybug. We found that flupyradifurone (Altus), flonicamid (Aria), chlorantraniliprole (Acelepryn), pymetrozine (Endeavor), Beauveria bassiana (Mycotrol), Chromobacterium subtsugae (Grandevo), Burkholderia spp. strain A396 (Venerate), cyantraniliprole (Mainspring) and Steinernema carpocapsae (Millenium) significantly reduced root mealybug populations compared to nontreated controls when applied as drenches in a curative manner. In our fourth trial, we evaluated biopesticides and Beauveria bassiana, on rice root aphid feeding on common rush (Juncus effusus) roots. Results showed pymetrozine significantly reduced populations as early as 14 days after treatment and continued to reduce their population throughout the remainder of the trial. However, chlorantraniliprole, cyantraniliprole, Beauveria bassiana, M-306 and MBI-203 did not significantly reduce rice root aphid populations until 28 days after initial application. Predator activity on root balls of Juncus effusus plants was also noted during the trials and may provide an integrated pest management (IPM) approach in controlling populations. Index words: reflexed stonecrop, Sedum rupestre L, stonecrop, Sedum montanum Song. & Perr, common rush, Juncus effuses L, Beauveria bassiana, Mycotrol, Steinernema carpocapsae, Millenium, reduced-risk pesticides, Chromobacterium subtsugae (Grandevo), flupyradifurone, Altus, flonicamid, Aria, chlorantraniliprole, Acelepryn, pymetrozine, Endeavor, Burkholderia spp. strain A396, Venerate, cyantraniliprole, Mainspring, M-306, MBI-203. Chemicals used in this study: flupyradifurone (Altus); flonicamid (Aria); chlorantraniliprole (Acelepryn); cyantraniliprole (Mainspring); pyrometrozine (Endeavor); Burkholderia spp. strain 396 (Venerate); Chromobacterium subtsugae (Grandevo); Beauveria bassiana (Mycotrol); AMBI-203 WDG – 30% Chromobacterium subtsugae strain PRAA4-1T cells and spent fermentation media. EPA registration number 84059-27; MBI-206 EP – 94.46% Heat-killed Burkholderia spp. strain A396 cells and spent fermentation media. EPA registration number 84059-14; MBI-203 SC2 – 98% Chromobacterium subtsugae strain PRAA4-1T cells and spent fermentation media. Experimental; MBI-306 SC1 - 94.46% non-viable Burkholderia spp. strain A396 cells and spent fermentation media. Experimental. Species used in this study: Root mealybug, Rhizoecus sp; Rice root aphid, Rhopalosiphum rufiabdominalis (Sasaki); reflexed stonecrop, Sedum rupestre; stonecrop, Sedum montanum; common rush, Juncus effusus.

Versatile Native Grasses and a Turf-Alternative Groundcover for the Arid Southwest United States

Water use limitations offers new opportunities for utilization of low-input native grasses and groundcovers for the landscapes of southwest USA. Two field studies were conducted with eleven plant species for two years in Scottsdale and Sun City West, AZ to evaluate rate of emergence, ground surface coverage, plant height, and overall plant quality. In the laboratory, Eragrostis tef at 86% and Eragrostis intermedia at 85% were showing higher percentage of germination compared to other species. Within eight weeks, ten species exhibited an average of 81% emergence at Scottsdale while nine species showed only 58% emergence at Sun City West. Sporobolus cryptandrus grew to greater than 76 cm (30 in) in height while kurapia (Lippia nodiflora) grew to about 5 cm (2 in). The performances of the groundcover kurapia and the native grasses tested demonstrated excellent potential in the low desert southwest U.S., with low rates of water use, applying fertilizer only at planting, and less frequent mowing requirements. Lippia nodiflora, Sporobolus airoides, Bouteloua gracilis, Eragrostis intermedia, and Muhlenbergia asperifolia remained green throughout the year when mowed twice a year. Lippia nodiflora, Hilaria rigida, and Bouteloua gracilis exhibited the highest ground surface coverage and uniformity in growth. Index words: groundcover, landscape, low input, native grasses, plant species. Species used in this study: Blue grama, Bouteloua gracilis (Kunth) Lag. ex Griffiths; bufflograss, Buchloe dactyloides (Nutt.) Engelm.; plains lovegrass, Eragrostis intermedia A.S. Hitchc.; teff, Eragrostis tef (Zucc) Trotter; big galleta, Hilaria rigida (Thurb); Kurapia, Lippia nodiflora (L.) Greene; alkali muhly, Muhlenbergia asperifolia (Nees & Meyen ex Trin.) Parodi; alkali sacaton, Sporobolus airoides (Torr.) Torr.; spike dropseed, Sporobolus contractus A.S. Hitchc.; sand dropseed, Sporobolus cryptandrus (Torr.) A. Gray; and desert zinnia, Zinnia acerosa (DC.) A. Gray.

Adventitious Rooting of Lavandula x intermedia Cuttings

Due to challenges associated with lavender propagation, Texas hybrid lavender (lavandin) growers require revised propagation information. Therefore, experiments investigated effects of media and plant growth regulators (PGR) on rooting of three different lavandin (Lavandula x intermedia) cultivars. PGRs applied to cuttings were naphthaleneacetic acid (NAA), or indole-3-butyric acid (IBA) at three concentrations. In addition, four rooting media were examined. Cuttings exposed to a peat moss/sand medium had the greatest mean overall rooting percentage, number of roots, and regardless of cultivar, cuttings exposed to the peat moss/sand medium had the longest roots. In general, mean rooting data were also greatest for cuttings dipped in NAA at 0.5 and 1.0 g·L−1 (500 and 1000 ppm, respectively). Overall, across all media and PGR treatments ‘Grosso' cuttings tended to have the greatest rooting percentage and longest roots. In addition, compared to the no PGR treatment, ‘Provence' and ‘Hidcote Giant' cuttings exposed to the peat moss/sand medium and greater PGR concentrations produced cuttings with an increased mean rooting percentage and longer roots. When rooting lavandin cultivars, results indicate correct media selection, PGR formulation, and PGR concentration determine propagation success. Index words: lavandin, Lavandula x intermedia Emeric ex Loisel, peat moss, perlite, rooting percentage, root quality, sand. Chemicals used in this study: indole-3-butyric acid (IBA; 0.5, 1.0, and 1.5 g.L−1); naphthaleneacetic acid (NAA; 0.5, 1.0, and 1.5 g.L−1). Species used in this study: ‘Grosso', ‘Provence', and ‘Hidcote Giant' lavandin (Lavandula x intermedia Emeric ex Loisel.).

Factors Influencing Honeybee (Apis mellifera L.) Visits to Crepe Myrtle (Lagerstroemia sp.)

Honeybees (Apis mellifera L.) are important pollinators and will selectively forage on crepe myrtle (CM) during the summer months. Unfortunately, CM pollen can become contaminated with pesticides used to control insects, especially crepe myrtle bark scale (Acanthococcus lagerstroemiae Kuwana). An experiment was conducted in July and August of 2019 and 2020 to compare honeybee visits to CM among four cultivars (‘Natchez', ‘Tuscarora', ‘Ebony Fire', and ‘Pocomoke') at an isolated location, and within a single cultivar series (Ebony) near other pollinator-friendly plants. ‘Natchez' had the most honeybee visits per tree, averaging 1.4 visits per 75 seconds per tree per day in 2019 and 1.2 visits per 75 seconds per tree per day in 2020, followed by ‘Tuscarora' with 0.8 and 0.4 honeybee visits per 75 seconds per tree per day, in 2019 and 2020, respectively. In 2020, there was a significant, moderate correlation (P< 0.001, r = 0.51) between bloom number and honeybee visits, with ‘Natchez' (158.9) and ‘Tuscarora' (148.2) having more average blooms per tree than ‘Ebony Fire' (35.6) and ‘Pocomoke' (35.7). Landscape environment and proximity to pollinator-friendly plants did not affect honeybee visits. CM are an important foraging resource for honeybees in the summer, and honeybees have a strong preference for cultivars with large, productive bloom clusters. Index words: pollinators, crepe myrtle bark scale, Acanthococcus lagerstroemiae, crepe myrtle Species used in this study: Crepe myrtle, Lagerstroemia indica L.; Lagerstroemia × faurei; Honeybee, Apis mellifera L.; American bumblebee, Bombus pensylvanicus De Geer.

Changes in Production Practices by Green Industry Growers from 2009 to 2019

As a result of the latest economic recession (2007 to 2009), the U.S. green industry suffered significant economic losses, leading to major industry structural changes. To be competitive and effectively manage risk, nursery and greenhouse operators need reliable and up-to-date information. However, the availability of such data from federal government sources has become limited. This report summarizes the state of the industry, focusing on trends in production-related characteristics from the 2009, 2014, and 2019 survey years. As firm size increased, the percent of annual sales attributed to large plant species (e.g., deciduous trees) increased, while herbaceous (e.g., perennials) and specialty (e.g., Christmas tree) plants made up a larger percentage of annual sales for small- and medium-sized firms. The majority of respondents (73.3%) indicated a proportion of their sales came from container-grown plants. The most frequently used integrated pest management (IPM) practice was removal of infested plants (81%), followed by cultivation/hand weeding. As firm size increased, participation in IPM strategies increased. Interestingly, statistical differences between small- and medium-sized firms were infrequent, indicating similar levels of use; however, most of the IPM strategies used were more frequently employed by large-sized firms when compared to small- or medium-sized firms. Index words: Container-grown, greenhouse, integrated pest management (IPM), nursery, ornamental plants.

A Comparison of the Attributes of Pine Straw from Southern Pine Species

Longleaf pine (Pinus palustris Mill.), and slash pine (Pinus elliottii Engelm.) are two southern pine species that are popular for producing pine straw for landscaping. The objective of this research was to determine the response of soil properties and weed growth to the application of pine straw. Longleaf pine, slash pine, and two non-mulched controls (with and without chemical weed control) were tested. Volumetric soil water content, soil nutrients, soil temperature, weed biomass, and seedling growth were measured. Compared to non-mulched controls, both longleaf and slash pine plots had a greater soil moisture during extended periods without rainfall in the full sun environment. When soil temperatures increased, mulched plots had lower soil temperature relative to non-mulched plots. Soil pH and soil nutrients were generally similar between pine straw types with few significant differences in measured variables. Both pine straw treatments reduced weed growth and longleaf pine maintained a greater straw depth over the study period compared to slash pine, but no differences were observed for decomposition. These results indicate that longleaf pine straw and slash pine straw perform equally as well in terms of increasing soil moisture, moderating soil temperature, and reducing weed growth compared to not using mulch. Index words: Pinus elliottii, Pinus palustris, organic mulch, soil properties, landscaping. Species used in this study: Shumard oak, Quercus shumardii Buckl., Eastern redbud, Cercis canadensis L.

Analyzing the Structural Shifts in U.S. Boxwood Production Due to Boxwood Blight

The purpose of this study is to examine the changes in the sales of boxwood (Buxus spp.) that have occurred in boxwood production states. We theorize that some of the shifts in production areas over the period from 2009 to 2019 have been impacted by the introduction of boxwood blight into the United States. Boxwood blight (Calonectria pseudonaviculata) was first observed in the U.S. in 2011 by plant pathologists in 8 states: Connecticut, Maryland, Massachusetts, New York, North Carolina, Oregon, Rhode Island, and Virginia. The disease has now been seen in 30 states plus the District of Columbia. The data used for this analysis is from the Census of Horticultural Specialties (CHS), a survey administered by the United States Department of Agriculture, National Agricultural Statistics Service (USDA-NASS) every five years. The findings from this analysis of the Census of Horticultural Specialties data from 2009 to 2019 indicate that there were already shifts occurring in boxwood markets prior to the introduction of boxwood blight. However, boxwood blight has exacerbated the supply chain challenges for green industry participants by limiting production in certain areas of the country, increasing the costs of producing boxwood compared to other evergreen shrubs, and perhaps dampening the demand from what might have been without the existence of the blight. Index words: economics, horticulture, nursery, landscaping, ornamental, woody plants, sales. Species used in this study: Boxwood (Buxus spp.), Boxwood Blight [Calonectria pseudonaviculata (Crous, J.Z. Groenew. & C.F. Hill) L. Lombard, M. J. Wingf. & Crous].

Factors affecting boxwood blight spread under landscape conditions

We investigated the spread of boxwood blight in a simulated landscape under conducive natural conditions from 2017 to 2019. We used strict sanitation to greatly reduce or eliminate spread by contact. Movement of the pathogen from an infected source plant was limited to one plant, likely spread by means of water splash. Plants were mulched with composted hardwood chips and mulching likely was primarily responsible for limiting spread to only the adjacent plant. Boxwood (Buxus spp.) cultivar susceptibility and fungicide spray programs influenced the incidence of spread and severity of disease; in 2018 and 2019 the more susceptible cultivar had higher disease incidence and severity, respectively, than less susceptible cultivars. Fungicide application only caused a small reduction in disease incidence in 2018. We also demonstrated that spores in clumps could survive extended dry conditions, indicating the importance of sanitation procedures on reducing spread. This experiment demonstrates that boxwood blight can be controlled in a landscape by following best management practices including cultural, sanitation, host susceptibility and fungicide application tactics. Index words: epidemiology, fungicide management, Buxus, chemical disease management, mulch, resistance. Chemicals used in this study: chlorothalonil (Daconil WeatherStik 54.0% F), fludioxonil plus cyprodinil (Palladium 25% and 37.5% WDG), mancozeb (Manzate 80% WP), metconazole (Tourney 50% WDG), propiconazole (ProCon-Z 14.3 L), pyraclostrobin (Insignia 20 WG), pyraclostrobin plus fluxapyroxad (Orkestra Intrinsic 21.26 SC), tebuconazole (Torque 38.7 SC), thiophanate-methyl (Spectro90 50% WP). Species used in this study: boxwood (Buxus L.), boxwood blight (Calonectria pseudonaviculata (Crous, J.Z. Groenew. & C.F. Hill) L. Lombard, M. J. Wingf. & Crous.