Browsing by Author "Wills, Wirt H."
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- Boxwood in the landscapeRelf, Diane; Appleton, Bonnie L.; Weidhaas, John A.; Wills, Wirt H. (Virginia Cooperative Extension Service, 1989)Describes boxwood and its use in landscaping. Also discusses maintenance, diseases and pests of boxwood.
- The Genesis and Dissolution of William Preston's SmithfieldWills, Wirt H. (Montgomery County Branch Association for the Preservation of Virginia Antiquities, 2004)An article tracing many of the land transactions over the 230-year period of Preston family involvement.
- Inoculum densities of Thielaviopsis basicola in tobacco fields in Virginia, and the relationship of inoculum density to the severity of black root rot and growth of tobaccoSpecht, Lawrence P. (Virginia Polytechnic Institute and State University, 1985)A new selective medium (TB-CEN) was developed for isolating Thielaviopsis basicola, cause of black root rot of tobacco, from soil. TB-CEN medium contains etridiazol and nystatin to inhibit the growth of undesired fungi, and unautoclaved extract from carrot to selectively enhance for the growth of T. basicola. Inoculum and/or population densities of T. basicola in five burley tobacco fields were 74-166 propagules per g of soil, and 0-12 propagules per g of soil in three other burley fields. Inoculum and/or population densities of T. basicola in 12 flue-cured and 2 sun-cured tobacco fields were 0-26 propagules per g of soil, and 101 and 402 propagules per g of soil in two other flue-cured fields. Environmental factors apparently had a strong effect on black root rot development, since root rot and plant stunting were severe in two burley fields that had 148 and 158 propagules per g of soil, but were not severe in the two flue-cured fields that had 101 and 402 propagules per g of soil. All of the cultivars planted in the four fields were susceptible. Black root rot was the major disease associated with the stunting of tobacco plants in the burley region of Virginia, but not in the flue- and sun-cured regions. No evidence was found to indicate that endomycorrhizae were involved in tobacco stunting in Virginia. T basicola inoculum density-disease severity studies were conducted both in soil-temperature tanks and in the field. Tobacco seedlings were grown in temperature tanks (20-23 C) for 30-31 days in naturally infested field soil (pH 6.5). For all cultivars tested (Burley 21, NC95, and Va Gold), the mean percent of roots that were rotted increased significantly (P=0.001) as inoculum density increased (R² range for regressions=0.93-0.97). Severe levels of root rot occurred at inoculum densities of 50-200 propagules per g of soil. Significant (P=0.01) reductions in plant growth occurred at inoculum densities as low as 5-10 propagules per g of soil. In a study conducted on a commercial burley tobacco (cv. B21-Ky10) field, inoculum densities of 150 and 683 propagules per g of soil were associated with moderate and severe levels of black root rot, respectively. Differences between soil-temperature tank and field studies appeared to be due to variations in environmental- and host-related factors. In another burley field study, the fungicide imazalil, which completely inhibited the growth of T. basicola when amended into agar media at a concentration of 1.0 μg a.i./ml, failed to control black root rot when it was added to transplanting water (50 ml/plant) at concentrations as high as 1,500 μg a.i./ml.
- John Floyd, Kentucky Hero, and Three Generations of Floyds and Prestons of VirginiaFloyd, Letitia Preston; Wills, Wirt H.; Stubbs, June (Montgomery County Branch Association for the Preservation of Virginia Antiquities, 1998)A vivid account of 18th century frontier life in southwest Virginia and Kentucky.
- The major diseases of boxwoodLambe, Robert C.; Wills, Wirt H. (Virginia Cooperative Extension Service, 1980-04)Boxwood diseases including phytophthora parasitica, macrophoma leaf spot, volutella stem blight, and keys to proper use of pesticides
- The Owners of the Historic Smithfield Manor HouseWills, Wirt H. (Montgomery County Branch Association for the Preservation of Virginia Antiquities, 2003)In a brief note, Wirt Wills traces the owners of the stately old manor house from the time of its construction until 1959 when it was given to the APVA.
- The Phoenix Caper — A Frontiersman Goes to SeaWills, Wirt H. (Montgomery County Branch Association for the Preservation of Virginia Antiquities, 2006)An analysis of several accounts of John Floyd's foreign exploits.
- Recollections of 18th Century Virginia Frontier LifeFloyd, Letitia Preston; Wills, Wirt H.; Stubbs, Jane (Montgomery County Branch Association for the Preservation of Virginia Antiquities, 1997-05)Written a century and a half ago, Floyd reminiscences about her childhood in Smithfield, but also writes of horrific tales of Indian fighting.
- Survival and chemical control of Cylindrocladium spp. inciting root rot of black walnut seedlingsRoth, Don Allen (Virginia Tech, 1978)Air drying of naturally infested soils (0.12 to 0.38% water or about -2,000 bars) resulted in no recovery of Cylindrocladium crotalariae microsclerotia, but rewetting soils to near field capacity for 1 to 4 wk before assay resulted in partial recovery from the air drying-induced decreased germinability. Numbers of germinable C. crotalariae microsclerotia (assayed at 26 C) decreased progressively over 4 wk when naturally infested soils were incubated at 6 C. No germinable microsclerotia were recovered when soils were incubated at -10 C. When soils incubated at -10 C and at 6 C were transferred to 26 C for 4 wk, the low-temperature effect was partially reversed. Incubation of naturally infested soils under field conditions over the winter months (November-February) indicated that a similar low-temperature phenomenon exists in nature. Germinability of axenic, laboratory-grown microsclerotia of C. crotalariae, C. floridanum, and C. scoparium incubated 4 wk at 6 C ranged from 0 to 91.3% (mean = 37.7%) of the initial germinability. Partial recovery of laboratory-grown microsclerotia from the lowtemperature effect, by incubation at 26 C, was demonstrated. Conductivity measurements of solutions bathing microsclerotia incubated at 6 C and 26 C for 4 wk indicated that chilling injury may account, in part, for decreased germinability of microsclerotia. Direct observation of washed conidia of C. scoparium on rewetted, non-sterile soils at 26 C indicated that peak germination (33-58%) occurred after 24 h incubation. Peak germination on continually moist soils was somewhat lower (18-26%) than on rewetted soils. Conidia did not germinate on continually moist soils at 6 C. Conidia germinated at a high level (93-95%) in axenic culture in the absence of exogenous carbon and nitrogen substrates. The inhibition of conidium germination on soils was due, in part, to the presence of fungistatic soil volatiles. Addition of low levels of carbon and nitrogen substrates nullified the inhibitory effect of soil volatiles. Germinability of C. scoparium, C. crotalariae, and C. floridanum conidia in artificially infested soils (assayed on a selective medium at 26 C) decreased progressively during incubation at 26 C from 1 wk to 4 mo. No germinable conidia were recovered after incubation of soils at 6 C for 4 wk. Control of Cylindrocladium root rot of black wainut seedlings with sodium azide at 224 kg/ha applied by the plowdown method was comparable to MC-33 at 504 kg/ha. Sodium azide at 67 kg/ha was only marginally effective in disease control. Reduction of Cylindrocladium microsclerotium populations, qualitatively assayed by the azalea leaftrap method, was found in soil samples from plots fumigated with sodium azide and MC-33. A small-spored Cylindrocladium sp. with clavate to papillate vesicles, identified as C. parvum, was consistently recovered from diseased roots and soil samples from a Virginia forest nursery. Percentage recovery from necrotic roots and soil samples collected from root zones of necrotic black walnut seedlings was appreciably higher for C. parvum than for C. floridanum or C. scoparium. In greenhouse tests, limited pathogenicity of C. parvum on black walnut seedlings was demonstrated.