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M.D. Boyette, D.F. Ritchie, S.J. Carballo, S.M. Blankenship, and D.C. Sanders

A significant portion of harvested produce never reaches the consumer due to, postharvest diseases. Various chemicals have been used to reduce the incidence of postharvest diseases. Many of these materials have been removed from the market in recent years due to economic, environmental, or health concerns. Although somewhat limited in the range of diseases controlled, chlorination is effective when combined with proper postharvest handling practices. Additionally, it is a relatively inexpensive postharvest disease control method that poses little threat to health or the environment. The proper use of chlorination in the management of postharvest diseases in fresh fruits and vegetables is discussed.

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Ronald K. Jones, Ann R. Chase, Melvin P. Garber, William G. Hudson, Jeffrey G. Norcini, and Kane Bondari

A national survey of the commercial ornamental industry was conducted to determine the current status of pest control including chemical and nonchemical disease control practices. The fungicides thiophanate methyl, chlorothalonil, mancozeb, and metalaxyl were used in the greatest quantity and by the largest percentage of growers. Metalaxyl was used in greenhouse and field operations by the highest percentage of growers, primarily to control root diseases but many growers reported using metalaxyl to control foliar disease. Overall, more fungicides were used in the field for foliar diseases, whereas almost equal amounts of fungicides were used for foliar and root diseases in the greenhouse.

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J.B. Magee, B.J. Smith, and Agnes Rimando

Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality fresh-market berries. In a systematic disease control spray program, four fungicides registered for grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest to five muscadine cultivars. Objectives of the study were to: 1) determine the effects of the spray schedule on foliage and berry diseases; and 2) study the relationship between disease incidence and resveratrol content of the berries. Resveratrol, a phytoalexin, has shown potential value in prevention and treatment of cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by fungicide treatments. Resveratrol was determined separately on berry skins, seed and pulp/juice by gas chromatography/mass spectroscopy (GC/MS). Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship between resveratrol concentration in skins and total disease score or scores of specific diseases was not established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Resveratrol concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.

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Iva Suzanne Wilson, George Ray McEachern, and J Dan Hanna

Canopy management experiments of hedging and/or leaf pruning, were conducted in 1988 and 1989 to examine their effect on yield, quality and disease control of `Chenin Blanc ' grapes in Southeast Texas. Vines hedged and/or leaf pruned in May reduced bunch rot. In 1988 all three treatments had a significant lower juice pH at harvest than the control. The combination treatment also had a higher yield.

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Iva Suzanne Wilson, George Ray McEachern, and J Dan Hanna

Gibberellic acid and fungicide experiments were conducted in 1988 and 1989 to examine their effect on yield, quality and disease control of 'Chenin Blanc' grapes in Southeast Texas. Gibberellic acid applied 7 and 14 days prior to bloom at 2.5 and 5.0 ppm reduced the number of berries per cluster in 1988 and 1989. The 2.5 ppm rate reduced berries and increased yield. The GA treatments also reduced bunch rot at harvest. Benomyl + Manzate fungicide treatments were superior to Nova and control in reducing bunch rot.

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Mark A. Bennett, Nancy W. Callan, and Vincent A. Fritz

Disease management is an important step in any crop establishment system. Emergence of field-seeded crops may take several weeks for many species and represents a vulnerable stage of plant growth. This paper considers various biological, chemical, and physical seed treatments for improved seed performance. The role of seed quality and cultural practices in seedling establishment also is reviewed. Multidisciplinary approaches to improving horticultural crop establishment are promising.

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Thomas M. Sjulin

techniques ( Parikka and Lemmetty, 2004 ) will require even higher levels of disease control in the nursery fields. The defining characteristic of a day-neutral cultivar is the ability to produce flowers following lengthy cold storage on the mother plant

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R. I. Hamilton

Abstract

The practice of using plant viruses in the control of virus diseases, originally demonstrated in 1933 by Salaman (56), arose from observations made over 50 years ago by McKinney (41), Thung (64), and others who reported plants, preinoculated with mild strains of some viruses, and later inoculated with related severe strains, often failed to show symptoms of the severe strains. The phenomenon has been termed “cross protection” (22, 32, 66). The general observation, failure of the severe strain to cause symptoms, is valid but the principles underlying the phenomenon are not understood. For example, 2 strains may exhibit reciprocal protection, but others may not (23, 24, 39). Moreover, evidence is accumulating in some experimental systems that, even though the severe strain may not induce symptoms, it does replicate in the protected plant (7, 17), so that the failure to express symptoms may not necessarily mean failure of the severe strain to infect and replicate. On the other hand, Dodds (16) provided evidence that cross protection between 2 strains of cucumber mosaic virus appears to operate by preventing infection by the challenge strain.

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Sephra N. Rampersad

pathosystem exists and methods of disease control remain largely uninformed. Microclimate factors, including temperature, source, and availability of nutrients and soil pH can influence growth and susceptibility of the host, growth of the pathogen, and the

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Nicolas Tremblay, Tarif Charbaji, Francois Fournier, and Odile Carisse

Scientific literature contains several examples of disease development influenced by fertilization practices. A set of data collected by the «Scouting and Research Network, South of Montreal Area» and consisting of disease and tissue analysis data on carrot and onion crops was made available for principal component analysis. It was hypothesized from the analysis that high N tissue levels would reduce Cercospora carotae and Botrytis squamosa importance on carrot and onion leaves, respectively. In a controlled environment study, Cercospora spots were inversely related to urea levels sprayed on carrot leaves although urea had no influence on plant growth. In a field study with onion, however, urea sprayed at 10 kg/ha, alone or in combination with a fungicide, had no effect either on Botrytis or on maturation or yield. With these mixed results, more research seems needed to assess the potential of nutrient sprays in reducing pesticide use.