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Summary Goals: Bunch grape production in the southeastern United States is limited by the endemic bacterium Xylella fastidiosa, causal agent of Pierce’s disease (PD). University of California, Davis-bred PD-resistant 87.5% Vitis vinifera L. winegrape selections represent a new technology that can help sustain the viticulture industry in the southeastern U.S. by reducing pesticide inputs and diversifying grape production. PD-resistant vines were planted to determine viticultural performance and survival in central Alabama. We anticipated our results would indicate whether regional growers could feasibly grow PD-resistant, predominantly V. vinifera winegrapes under humid southeastern U.S. viticulture conditions. Key Findings: All evaluated selections grew vigorously under humid southeastern conditions. U0501-12 produced the highest pruning weight during the 2015 to 2016 period of study. U0502-10 was the most productive selection, as measured by total yield per vine, and had the largest clusters. Harvest soluble solids content was highest for selection U0501-12, while titratable acidity was lowest for U0502-01. All selections broke bud prior to historical late-spring frost-risk dates, although no injury was experienced in the years evaluated. U0502-10 began veraison between one and two months earlier compared to the other selections in both years. U0502-10 was also harvested 70 and 22 days prior to the next selection in 2015 and 2016, respectively. The experimental vines neither exhibited symptoms nor tested positive for PD during vine establishment. Under regional commercial management practices, no vine losses resulted from other pathogens. However, an aggressive disease management strategy will be mandatory to produce consistently clean fruit in the humid southeastern U.S. Impact and Significance: These results indicate grapevines with predominantly V. vinifera background can survive under humid viticulture conditions in central Alabama with the incorporation of alleles for PD resistance. Further research is necessary to refine management practices enabling sustainable production in the southeastern U.S. as PD-resistant grapevine cultivars become commercially available to regional producers.

The total phenolic content and jasmonic acid (JA) content of foliage from gerbera (Gerbera jamesonii ‘Festival Salmon’) subjected to low and high fertilization rates were measured to determine effects of fertilization on phytochemicals implicated in defense of insect pests. Gerbera seedlings were fertilized with low (only supplied with initial fertilizer charge present in professional growing media) or high (200 mg·liter−1 N; recommended rate) fertilization rates. Since JA is induced in response to wounding, treatments consisted of ± mechanical wounding with a hemostat to one physiologically mature leaf and the subsequent harvest of that leaf at specified time intervals (0, 0.5, 1, 3, and 10 h) for JA quantification. Total phenolic content was measured in mature and newly formed leaves. Plants receiving low fertility had reduced aboveground dry mass, were deficient in nitrogen and phosphorous, and had approximately a 9-fold higher concentration of total phenolics in mature leaf tissue compared to high fertility plants. Newly formed leaves had greater concentrations of phenolics than mature leaves in low fertility plants. In response to wounding, JA accumulation was more rapid and higher concentrations of JA were sustained longer in low fertility plants than in high fertility plants. These results show that altering fertilization does affect phytochemicals implicated in defense against insect pests, and these chemical defenses are increased in the foliage of low fertility gerberas.

This study evaluated the influence of insecticides on gas exchange, chlorophyll content, vegetative and floral development, and plant quality of gerbera (Gerbera jamesonii Bolus `Festival Salmon'). Insecticides from five chemical classes were applied weekly at 1× or 4× their respective recommended concentration. The insecticides used were abamectin (Avid), acephate (Orthene), bifenthrin (Talstar), clarified hydrophobic extract of neem oil (Triact), and spinosad (Conserve). Photosynthesis and stomatal conductance were reduced in plants treated with neem oil. Plants treated with neem oil flowered later—and at 4× the recommended label concentration had reduced growth, based on lower vegetative dry mass (DM) and total aboveground DM, reduced leaf area, thicker leaves (lower specific leaf area), higher chlorophyll content (basal leaves), and reduced flower production. Plants treated with acephate at 4× the recommended label concentration were of the lowest quality due to extensive phytotoxicity (leaf chlorosis). Plants treated with 1× or 4× abamectin or spinosad were of the highest quality due to no phytotoxicity and no thrips damage (thrips naturally migrated into the greenhouse). The control plants and plants treated with 1× bifenthrin had reduced quality because of thrips feeding damage; however gas exchange was not negatively affected.

This research focused on the influence of insecticides on gas exchange, chlorophyll content, vegetative and floral development, and overall plant quality of gerbera (Gerbera jamesonii var. `Festival Salmon'). Insecticides from five chemical classes were applied weekly at 1× and 4× the recommended concentrations. Insecticides used were: abamectin (Avid® 0.15 EC), acephate (Orthene® Turf, Tree & Ornamental Spray 97), bifenthrin (Talstar® Nursery Flowable), clarified hydrophobic extract of neem oil (Triact® 70), and spinosad (Conserve® SC). Phytotoxicity occurred in the form of leaf chlorosis on all acephate treatments, with the greatest damage occurring at the 4× concentration. Photosynthesis and stomatal conductance were significantly reduced in plants treated with neem oil extract. Plants treated with the neem oil extract (1× and 4×) flowered later and had reduced growth [lower shoot dry mass (DM) and total DM]. Plants that received 4× the recommended concentration of neem oil extract had reduced leaf area, thicker leaves (lower specific leaf area), higher leaf chlorophyll content, and reduced flower production, as determined by flower number and flower DM. Plants treated with acephate 4× concentration were the lowest quality plants due to extensive phytotoxicity (leaf burn), which also reduced photosynthesis. The highest quality plants were treated with spinosad and abamectin due to zero phytotoxicity and/or no thrips damage (thrips naturally migrated into the greenhouse). The control plants and plants treated with bifenthrin 1× were not marketable due to thrips damage; however, plant growth characteristics and gas exchange were not statistically different.

This research focused on the influence of insecticides on plant growth, gas exchange, rate of flowering, and chlorophyll content of chrysanthemum (Dendranthema grandiflora Tzvelev cv. Charm) grown according to recommended procedures for pot plant production. Five insecticides were applied at recommended concentrations at three different frequencies: weekly (7 days), bi-weekly (14 days), or monthly (28 days). A separate treatment was applied weekly at 4× the recommended concentration. Insecticides used were: acephate (Orthene®) Turf, Tree & Ornamental Spray 97), bifenthrin (Talstar®) Flowable), endosulfan (Thiodan®) 50 WP), imidacloprid (Marathon®) II), and spinosad (Conserve®) SC). Phytotoxicity occurred in the form of leaf burn on all acephate treatments, with the greatest damage occurring at the 4× concentration. Photosynthesis and stomatal conductance were influenced primarily by the degree of aphid and/or spider mite infestation—except for acephate and endosulfan treatments (weekly and 4×), which had reduced photosynthesis with minimal insect infestations. Plants receiving imadacloprid monthly had the greatest leaf dry mass (DM). Plants treated with acephate had lower leaf and stem DM with bi-weekly and 4× treatments. Spinosad treatments at recommended concentrations had reduced stem DM, in part due to aphid infestations. The flower DM was not significantly different among treatments. There were treatment differences in chlorophyll content as measured with a SPAD-502 portable chlorophyll meter.