Search Results

You are looking at 31 - 36 of 36 items for

  • Author or Editor: Kimberly A. Williams x
Clear All Modify Search

In three experiments, damage caused by twospotted spider mite (TSSM; Tetranychus urticae Koch) was correlated with the quality of ivy geranium [Pelargonium peltatum (L.) L'Her ex Aiton], and the action threshold for TSSM on ivy geranium was developed. Ivy geranium quality was measured as overall plant quality—plant size and form, and leaf greenness and glossiness—leaf browning, and leaf distortion. Young plants with high initial TSSM numbers (30 TSSM/plant) exhibited the greatest damage, suggesting that monitoring for TSSM early in the plant production cycle is necessary to prevent extensive damage. The leaf distortion index and overall plant quality were correlated with cumulative TSSM density and marketability in 4-week-old plants infested with 30 TSSM, whereas leaf browning was not correlated with either. Thus, either leaf distortion or overall plant quality can be used to measure economic damage resulting from TSSM. The action threshold for TSSM on ivy geranium was determined using overall plant quality. When the predatory mite, Phytoseiulus persimilis Athias-Henriot, is used to control TSSM, the action threshold was found to be 2 TSSM/leaf. Results also showed that fertilizer combinations of 8 or 24 mm nitrogen and 0.32, 0.64, or 1.28 mm phosphorus had no effect on cumulative TSSM density. When P. persimilis was released at predator: prey ratios of 1:60, 1:20, and 1:4, TSSM damage, measured as both leaf distortion and overall plant quality, was significantly reduced at 1:4 and 1:20, but not at 1:60. A 1:4 rate resulted in the most marketable plants. These results suggest that P. persimilis should be released at a rate of 1:4 when the TSSM action threshold is reached.

Free access

Many plant species are prone to physiological disorders in which lesions develop on the leaf tissue. Nomenclature for such lesions has included intumescences, excrescences, neoplasms, galls, genetic tumors, enations, and oedemata. Interchangeably using these terms causes confusion as to whether these names refer to the same or different disorders. Two of the most commonly used names are oedema and intumescence. The objective of this research was to characterize the development of lesions on ornamental sweetpotato (Ipomoea batatas ‘Blackie’), tomato (Solanum lycopersicum ‘Maxifort’), interspecific hybrid geranium (Pelargonium × ‘Caliente Coral’), and bat-faced cuphea (Cuphea llavea ‘Tiny Mice’) to determine similarities and differences in morphology and nomenclature among these physiological disorders. Light microscopy was used to characterize differences in cross-sectional height, width, and area of lesions on each species. Additionally, leaf tissue samples were embedded in paraffin, and 10-μm cross-sections were stained with Toluidine blue O and observed using light microscopy to identify specific cell layers involved with lesion development. Field emission scanning electron microscopy (SEM) and digital photography were used to observe the microscopic and macroscopic stages of lesion development, respectively, on each species. The lesions observed on ornamental sweetpotato were significantly greater in height and area than on the other three species, whereas tomato lesions were significantly greater in width. Lesions on ornamental sweetpotato and bat-faced cuphea occurred predominantly on the adaxial surface of the leaf, whereas lesions on geranium and tomato occurred predominantly on the abaxial surface. With lesions on tomato, ornamental sweetpotato, and bat-faced cuphea, the epidermis was often subjected to the same hypertrophy apparent in the underlying parenchyma cells, ultimately allowing for greater cell expansion. However, in geranium, the epidermis resisted the expansion of the underlying cells, resulting in the eventual tearing of this tissue layer. Previous research indicates that lesion development on geranium is closely related to water status within the plant and may result in a wound response or provide a means of facilitated gas exchange. On the contrary, development of lesions on ornamental sweetpotato and tomato is believed to involve light quality. Based on these results and observations, two disorders occur across these species. The term “intumescence” should be used when referring to abnormal lesions on ornamental sweetpotato and tomato, and the term “oedema” should be used when referring to lesions on geranium. The term “intumescence” should also be used when referring to bat-faced cuphea lesions resulting from the morphological and anatomical aspects of these lesions closely resembling development on ornamental sweetpotato and tomato. Future research should investigate the role of light quality regarding development on this species.

Free access

Two greenhouse studies were conducted to examine effects of nitrogen source on primary and secondary metabolism of pac choi (Brassica rapa L. subsp. chinensis cv. Mei Qing Choi) and diamondback moth (Plutella xylostella L.) consumption, development, survival, and body weight. Applications of a liquid organic source of nitrogen (fish hydrolysate fertilizer) were compared with a conventional fertilizer to determine whether nitrogen source directly impacts pac choi chemistry (elemental composition and phenolics) and biomass and indirectly affects diamondback moth fitness parameters. There was no significant effect of fertility treatment on pac choi chemistry or biomass with the exception of percent leaf phosphorus, which was significantly higher in the conventional fertility treatment, and p-coumarin, which was significantly higher in the organic fertility treatment. Diamondback moth also affected plant chemistry. Both calcium (Ca) and magnesium (Mg) were significantly higher in plants infested with larvae compared with uninfested plants. Fertilizer affected diamondback moth fitness with percent survival and cohort development significantly reduced on pac choi associated with the organic fertilizer. However, pac choi receiving the organic treatment was similar in regard to primary nutrients and secondary compounds compared with plants that received a conventional fertilizer.

Free access

Preparing faculty to conduct quality teaching is critical to maximize student learning and the educational experience. As increased attention to faculty effectiveness and effect of their teaching program is observed, the more important it becomes for faculty to engage in the scholarship of teaching and learning (SoTL). The workshop “Developing a scholarship of teaching and learning portfolio in applied horticulture” was conducted at the 2022 American Society for Horticultural Science conference in Chicago, IL, USA, and featured a panel of teaching scholars who provided insight and guidance for developing, enhancing, evaluating, and promoting SoTL for both traditional classroom teachers and extension educators.

Open Access

High tunnels are becoming an increasingly important production tool for vegetable, small fruit, and cut flower growers in many parts of the United States. They provide a protected environment relative to the open field, allowing for earlier or later production of many crops, and they typically improve yield and quality as well as disease and pest management. Producers, ranging from small-scale market gardens to larger scale farms, are using high tunnels of various forms to produce for early markets, schedule production through extended seasons, grow specialty crops that require some environmental modification, and capture premium prices. The rapid ongoing adoption of high tunnels has resulted in numerous grower innovations and increased university research and extension programming to serve grower needs. An informal survey of extension specialists was conducted in 2007 to estimate numbers (area) of high tunnels and crops being grown in them by state, and to identify current research and extension efforts. Results of this survey provide an indication of the increasing importance of these structures for horticultural crop production across the country.

Free access