Indications of Susceptibility to Calonectria pseudonaviculata in Some Common Groundcovers and Boxwood Companion Plants

Knowing the host range of a pathogen is critical to developing and implementing effective disease management programs. Calonectria pseudonaviculata (Cps) is known to attack a number of species, varieties, and cultivars in the genus Buxus as well as three Pachysandra species (Pachysandra terminalis, Pachysandra procumbens, and Pachysandra axillaris) and several Sarcococca species, all in the Buxaceae family. The objective of this study was to evaluate non-Buxaceae groundcovers and companion plants commonly associated with boxwood plantings for their susceptibility to Cps. Twenty-seven plant species belonging to 21 families were exposed to different levels of inoculum: 50 to 300 conidia per drop for detached leaf assays and 30,000 to 120,000 conidia per 1 ml for whole-plant assays. Inoculated plants were incubated in humid environments for at least 48 h to facilitate infection. Cps infection and sporulation were observed on 12 plant species: Alchemilla mollis, Arctostaphylos uva-ursi, Brunnera macrophylla, Epimedium × youngianum, Galium odoratum, Geranium sanguineum, Phlox subulata, Tiarella cordifolia, Callirhoe involucrata, Iberis sempervirens, Mazus reptans, and Vinca minor. These results suggest that there may be more hosts of Cps commonly grown in nurseries and landscapes. If corroborated by observations of natural infection, these findings have implications for the Boxwood Blight Cleanliness Program instituted by the National Plant Board and for planning disease mitigation at production and in the landscape.

Calonectria pseudonaviculata can Cause Leaf Spot and Stem Blight of Pachysandra procumbens

The authors' objective in this study was to determine the susceptibility of P. procumbens to C. pseudonaviculata. This is the first report of C. pseudonaviculatum causing a leaf spot and stem lesion disease on P. procumbens. Accepted for publication 14 January 2012. Published 26 February 2013.

Plant Introductions from the Mt. Cuba Center

Over the past 7 years, eight plants have been introduced from the Mt. Cuba Center for the Study of Piedmont Flora—two woody and six herbaceous ornamentals—which will be illustrated and described. Cornus sericea `Silver and Gold', 1988, is a sport of and similar to `Flaviramea' with white variegated leaves. Aster novae-angliae `Purple Dome', 1989, is a widely known and compact form (50 cm tall) of the species. Heuchera americana `Garnet', 1989, has shiny green foliage of the species mottled garnet-red. Solidago sphacelata `Golden Fleece', 1989, is a compact (50 cm) form of the species with semi-evergreen basal foliage, winning the ISU outstanding plant award in Switzerland in 1994. Leucothoe axillaris `Greensprite', 1991, is easy to propagate and quick to grow, with solid green, narrow leaves with undulating edges and attenuated tips. Pachysandra procumbens `Forest Green', 1992, has larger leaf whorls and a more smoothly undulating surface than the species. Trillium grandiflorum `Quicksilver', 1992, is similar to the species only with 1-year doubling time. Aster laevis `Bluebird', 1995, is similar to the species but has so far been free from foliage diseases.

UPDATE ON MICROPROPAGATION OF PACHYSANDRA PROCUMBENS MICHX.

Pachysandra procumbens, the Allegheny spurge, is a native herbaceous perennial. Microcuttings were maintained in liquid MS medium in Magenta boxes with membrane rafts. A preliminary study looked at 1,2.5,5, and 10 mg BA/liter and 0 and 1 mg NAA/liter. Shootscultured with 5 or 10 mg BA/liter and no NAA produced significantly more axillary shoots. When shoots were cultured on media containing 5,10, 15, 20, or 25 mg BA/liter, trend analysis indicated significant linear and quadratic trends. Shoots proliferated similarly when cultured with 5 to 20 mg BA/liter. Non-fully expanded shoots proliferated significantly better compared to fully expanded shoots. After 6 weeks, microcuttings dipped in 500 or 1000 ppm IBA (50% ethanol) had produced significantly more roots of greater length compared to the control. Sixteen weeks after potting, rooted microcuttings potted in MetroMix 500, Promix BX, or a nursery mix (60% pine bark, 20% peat, 20% stone dust) had initiated significantly more shoots.

MICROPROPAGATION OF PACHYSANDRA PROCUMBENS

Pachysandra procumbens, the Allegheny pachysandra, is very rare to rare throughout most of its native range. Winter color, growth habit and ease of maintenance all recommend this perennial as an alternative ground cover for shady habitats. Development of micropropagation protocols may allow for its mass distribution. Non-wild collected shoots were disinfested using conventional procedures and were cultured and maintained in an MS based stock medium. Shoots proliferated equally well on an MS, a modified MS or a DKW based medium. Shoots had significantly more swelled buds when cultured in medium gelled with Gelrite or in liquid medium on membrane rafts compared to vermiculite. Microcuttings with or without a basal node rooted equally well. Microcuttings with or without an apical bud rooted equally well; however, microcuttings with an apical bud produced significantly longer roots.