Wayne A. Mackay

Micropropagation of Mexican redbud, Cercis canadensis var. mexicana

Mexican redbud (Cercis canadensis var. mexicana) shoot cultures were initiated from explants taken from both mature and juvenile stock plants. Culture conditions affecting shoot growth and proliferation and rooting of three clones were investigated. Shoot growth was best on media supplemented with 0.25% activated charcoal and solidified with 0.2% Gelrite. Four commercially available salt formulations (Andersons rhododendron medium, WPM, MS, DKW) were tested for growth of shoot cultures, and Andersons rhododendron basal salt mixture was superior. Axillary shoots grew from explants cultured media supplemented with a wide range of concentrations of benzyladenine and thidiazuron. Benzyladenine at 5.6–22.2 μM supported the best combination of shoot quality and number. Rooting of microshoots in vitro was best on half-strength WPM containing 6.71 μM naphthaleneacetic acid and 0.1% activated charcoal.

RESISTANCE AMONG LANTANA CULTIVARS TO THE LANTANA LACE BUG, TELEONEMIA SCRUPULOSA (HEMIPTERA: TINGIDAE)

Abstract Lantana lace bug, Teleonemia scrupulosa Stål, (Hemiptera: Tingidae) is a primary insect pest of lantana, a landscape plant commonly grown across the southern United States. Twenty-eight cultivars of lantana were evaluated for resistance to lantana lace bug in replicated field plantings. Natural infestations of lantana lace bugs developed in mid-Jul, and were dispersed across all the replicates within 30 d in Dallas, TX. Populations of nymphs and adults were sampled bi-weekly from Sep-Nov 1996. Highest mean populations were present on ‘Patriot Desert Sunset’ (40.3 nymphs and adults/3-leaf sample/plant), ‘Pink Frolic’ (20.6) and ‘Patriot Sunburst’ (19.4). Nineteen of the cultivars exceeded 4 lace bugs per 3-leaf sample. Lace bugs were never detected on 3 cultivars, ‘Weeping White’, ‘White Lightning’ and ‘Weeping Lavender’ during the test period, and ‘Imperial Purple’, ‘Patriot Rainbow’ and ‘Denholm Dwarf White’ had seasonal means of only 0.1 total lace bugs per sample. Cultivars of L. montevidensis (K. Spreng.) Briq. (mean of 0.02 lace bugs/3 leaf sample) were highly resistant, whereas many cultivars of L. camara L. and L. hybrida hort (6.73 and 9.54 lace bugs/3 leaf sample, respectively) were susceptible. Cultivars with gold, red, purple, and white flowers had far fewer lace bugs than did cultivars with either orange/red, yellow, or bicolors of yellow with another color. These results indicate that within most flower colors or bicolors, there exists a range of resistance among the cultivars and usually at least 1 cultivar per color form with resistance to the lantana lace bug.

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.

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.

Moisture and Nutrient Storage Capacity of Calcined Expanded Shale

Expanded shale (EXSH) is an important and increasingly popular soil conditioner with several horticultural applications, including its use as a soil amendment for clay textured soils (Sloan et al., 2002), as an ingredient in plant growing media (Sloan et al., 2010) or green roof substrates (Ampim et al., 2010 ). It is a lightweight material produced by firing mined lumps of shale at high temperatures in a rotary kiln in a process similar to that of clay ceramics. The resulting product can be screened to create various size fractions depending on the intended use. For example, Texas Industries (TXI) of North Texas, USA produces five size fractions of expanded shale that includes the following ranges, from smallest to largest, 0.07 to 0.60 mm, 0.60 to 2.0 mm, 2.0 to 4.8 mm, 4.8 to 6.4 mm, 6.4 to 9.5 mm, 9.5 to 12.7mm, 12.7 to 15.9 mm Expanded shale aggregates are suitable as components of planting media and soil amendments because, unlike most minerals, they are porous, stable, and resistant to decomposition (Ferguson, 2005). Expanded shale is believed to beneficially modify growth media properties by enhancing overall aeration, improving water and nutrient holding and release capacities, and promoting optimum plant growth (Blunt, 1988; Dunnett and Kingsbury, 2008). Sloan et al. (2002) found that expanded shale consistently improved overall plant performance better than quartz sand, sphagnum peatmoss and cottonseed hull when they were used as amendments for poorly-drained Austin silty clay soils suggesting its superiority as a soil conditioner for the production of horticultural crops on soils with poor tillage characteristics. In a similar way, Nash et al. (1990) found that a potting medium comprising a mixture of peat moss and expanded shale increased the growth and quality of petunia and impatiens. Smalley et al. (1993) also found that amending soils with products containing expanded shale did not hamper plant performance. Though growth index and plant dry weight of Salvia (Salvia splendens) and Vinca (Catharanthus roseus) increased with increasing fertilizer levels for all their treatments, the greatest performance of these plants were observed for treatments amended with the product containing expanded shale, granite sand and composted poultry litter. In another application, Forbes et al. (2004 and 2005) discovered that expanded shale is a potential sorbent for phosphorus in subsurface flow

MICROPROPAGATION SYSTEMS FOR THE MEXICAN REDBUD (CERCIS CANADENSIS VAR. MEXICANA L.) AND OTHER WOODY PLANTS OF THE CHIHUAHUAN DESERT

SummaryThere are many Chihuahuan desert species that have potential as landscape plants for the arid communities of the southwestern United States [agarita, Berberis trifoliata Moric.; Mexican buckeye, Ungnadia speciosa Endl.; Texas madrone, Arbutus xalapensis var. texana (Buckl.). A. Gray]. Within these plant populations, there are superior genotypes that offer even greater interest for the landscape. However, it is difficult to clonally propagate many of these species with conventional techniques, and the seed-derived populations often do not breed true. Therefore, selection of superior genotypes in wild populations coupled with clonal propagation through tissue culture may offer an attractive option. It is relatively easy to achieve disinfestation of explants from desert plants due to a general lack of natural surface contamination by fungi and bacteria, even though interference from numerous trichomes can impede good contact with disinfesting agents. However, there is only a narrow window of time that is ideal for explant collection, because of the brief, periodic flushes of growth that characterize this unusual plant group. There may be years when, due to the harsh environment, the amount of suitable explant material is severely limited. Phenolics and exudates are also problematic in this group of plants, and acclimatization of ex vitro plantlets to the harsh desert environment is a particular challenge. For these reasons, specific adaptations and modifications were necessary to achieve success with micropropagation of desert plant species such as Mexican redbud (Cercis canadensis var. mexicana L.).