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Barbara J. Smith

loses due to this disease. This is environmentally sound because it results in reduced use of fungicides. CONCLUSIONS As our knowledge of the anthracnose pathogens and the epidemiology of anthracnose diseases has increased, so has our ability to

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Dale E. Kester, Tom Gradziel, and Karen Pelletreau

A model for the epidemiology of noninfectious bud-failure (Fenton, et al., 1988) predicts that BF-potcntial is universally present within specific almond cultivars with variation existing in the rate and pattern of development of BF phenotypes. Orchard surveys of Carmel in 1990 and 1991 involving four nursery sources showed a trend of 2 per cent of affected trees after one year in the orchard, increasing to 4 per cent in the second, with prospects for gradual increase with time. All four sources produced some BF trees with significant differences among sources. A study has been started to identify the source and pattern of BF-potential within the entire Carmel cultivar. It has two parts. A pedigree analysis of propagation sources from eleven commercial nurseries traces their genealogy from the original seedling plant first discovered in 1947. A propagation test of approximately 3000 individual trees representative of the propagation sources of all eleven commercial nurseries has been established. The origin of each progeny tree has been maintained in respect to source, tree, budstick and individual bud location on the stick. Expression of bud-failure symptoms in individual trees will identify the source and pattern of BF-potential within the cultivar.

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Christopher P. Ryan, Peter H. Dernoeden, and Arvydas P. Grybauskas

of the epidemiology of dollar spot is thus warranted given the economic importance of this disease. Furthermore, it is unknown if steps in dollar spot epidemics vary in their incidence based on cultivar grown. Thus, the primary objective of this study

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Leah L. Granke, Layla E. Crawford, and Mary K. Hausbeck

. 61 OT010 Jarvis, W.R. Gubler, W.D. Grove, G.G. 2002 Epidemiology in agricultural pathosystems, p. 169–199. In: Belanger, R., W. Bushnell, A. Dik, and T. Carver (eds.). The powdery mildews: A comprehensive treatise. APS Press, St. Paul, MN Kerssies, A

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Richard Smith, Bob Mullen, and Tim Hartz

Pepper stip is a physiological disorder manifested as gray-brown to greenish spots occurring on fruit of bell, pimento, Anaheim, and other types of peppers, most noticeably on red fruit produced under fall conditions. The spots, ≈0.5 cm in diameter, occur singly or in groups; marketability for either fresh market or processing use is severely affected. The factors controlling the occurrence or severity of the disorder are not well understood; to date, control has been achieved primarily by the use of resistant cultivars. In 1995 replicated plots of susceptible (`Yolo Wonder L' and `Grande Rio') and resistant (`Galaxy' and `King Arthur') cultivars were grown in seven commercial fields in central California. `Galaxy' and `King Arthur' were essentially free of symptoms, while `Yolo Wonder L' and `Grande Rio' showed significant damage at all sites, with 23% to 88% of fruits affected at the mature-red stage. Petiole tissue analysis showed that resistant cultivars consistently had lower N and K, and higher Ca concentrations than susceptible cultivars; the same trend was apparent in fruit tissue. Stip was most severe at sites with low soil Ca and/or very high N and K fertilization rates. It is hypothesized that Ca nutrition significantly influences stip expression.

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E. Barclay Poling

by Adam Dale, Dan Legard, Tom Sjulin, and myself to proceed with the organization of a workshop for the ASHS Annual Conference in July 2004 in Austin, TX. The 4-h workshop on 18 July 2004, was divided into two parts: 1) Etiology, Epidemiology, and

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Richard Smith, Robert Mullen, and Tim Hartz

Pepper stip is a physiological disorder manifested as gray-brown to greenish spots occurring on the fruit of bell, pimento, Anaheim, and other types of peppers, most noticeably on red fruit that mature under fall conditions. Most hybrid bell cultivars are resistant to the malady; the problem is most severe for pepper growers reliant on less-expensive, open-pollinated cultivars. In 1995, we initiated studies to evaluate the possible link between mineral nutrition and this disorder. Two susceptible open-pollinated cultivars and two resistant hybrid cultivars were grown in randomized plots at seven sites. Significant correlations were seen between the levels of potassium (r = 0.59) and calcium (r = -0.37) in whole leaves and the incidence of stip (P = 0.05). The stip-resistant cultivars also maintained less total nitrogen in the whole leaves than susceptible cultivars (P = 0.05). In 1996 and 1997, we undertook field studies to evaluate the effects of varying calcium and nitrogen application rates. Inconsistent results were observed with calcium applications. Moderate reductions in stip incidence was observed at some sites and no reduction at others following foliar calcium applications. Nitrogen nutrition had no effect on stip severity. In 1998, evaluation of a large number of open-pollinated cultivars was undertaken; `Gusto' showed excellent tolerance to pepper stip, followed by `Taurus' and `Cal Wonder 300'. We conclude that growers that are reliant on open-pollinated cultivars can utilize these cultivars to minimize the incidence of pepper stip.

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Arcenio Gutierrez-Estrada, Emma Zavaleta-Mejl̀a, and Gustavo Mora-Aguilera

Viruses associated to eight Alstroemeria varieties and the relationship of thrips density and environmental factors with Tomato Spotted Wilt (TSW) intensity as well as the TSW effect on yield were studied in `Rosario' in Central Mèxico. Using hosts range the viruses detected were Tomato Spotted Wilt Tospovirus (TSWV), Impatiens Necrotic Spot Tospovirus (INSV), Alstroemeria Mosaic Potyvirus (AlMV), Alstroemeria Streak Potyvirus (ASV), Arabis Mosaic Nepovirus (ArMV), and Cucumber Mosaic Cucumovirus (CMV). With serology it was confirmed the presence of TSWV in `Jubilee', `Rosario', and `Regina' varieties; INSV in `Anabel', `Jubilee', and `Red Sunset'; and AlMV in `Rosario', `Red Sunset', `Rosita', `Yellow King', `Jubilee'. and `Rojo Sangria'. TSWV and AlMV were found coinfecting `Rosario' plants. Five percent of plants were serologically positive to TSWV in the first flower harvest (25 Jan.-5 Apr.), 10% in the second (12 Ap.-21 June), and third (5 July-13 Sept.), and 18% in the last harvest (23 Sept.-6 Dec.). The highest peak density of thrips (520 to 630 individuals per sticky trap) were registered when the maximum temperature was higher than 35 °C and the relative humidity was between 40% to 60%. However, such peak density was not correlated with a significant increase of TSW incidence. Number and quality of inflorescences and the stem growth rate were significantly higher (P = 0.05) in plots with asymptomatic plants than that with plants showing putative symptoms of TSW.

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B. Reyes-Gonzalez, G. Mora-Aguilera, S. Osada, D. Tèliz, and U. Diaz

The temporal progress of postbloom fruit drop was characterized in North Veracruz, Mexico, in two commercial orchards with low and high management technology. A total of 200 flowers per orchard were assessed for disease incidence every 2 days during the flowering season. Colletotrichum isolates, putatively similar to C. acutatum, were obtained from diseased flowers and inoculated to Citrus sinensis and Citrus latifolia completing the Koch's postulates. The average Area Under Disease Progress Curve (AUDPC) (625 vs. 688 days, %) and final disease incidence (Yf) (68% vs. 67%) were statistically similar (P = 0.05) to both orchards. Epidemic rates were in the range of 0.05 to 0.16 units, with the highest variability in the high technology orchard. The total epidemic duration was 15 and 18 days for the high and low technology orchards, respectively. The highest absolute increase of disease occurred at 13 days after the beginning of flowering during the full bloom stage. The absolute increase of disease was not correlated (P = 0.05) with nonlagged values of relative humidity (%), maximum temperature (°C) and the number of Colletotrichum spores captured on a Burkard like trap. However, 5-day lagged values of spore numbers were apparently correlated with the highest absolute increase of disease. Similarly, 3- to 5-day lagged values of number of days with at least 85% relative humidity was needed to explain the main spore peaks.

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Arcenio Gutièrrez-Estrada, Emma Zavaleta-Mejl̀a, and Gustavo Mora-Aguilera

Viruses associated to eight Alstroemeria varieties and the relationship of thrips density and environmental factors with Tomato Spotted Wilt (TSW) intensity as well as the TSW effect on yield were studied in `Rosario' in Central Mexico. Using hosts range the viruses detected were Tomato Spotted Wilt Tospovirus (TSWV), Impatiens Necrotic Spot Tospovirus (INSV), Alstroemeria Mosaic Potyvirus (AlMV), Alstroemeria Streak Potyvirus (ASV), Arabis Mosaic Nepovirus (ArMV) and Cucumber Mosaic Cucumovirus (CMV). With serology, the presence of TSWV was confirmed in `Jubilee', `Rosario', and `Regina'; INSV in `Anabel', `Jubilee', and `Red Sunset'; and AlMV in `Rosario', `Red Sunset', `Rosita', `Yellow King', `Jubilee', and `Rojo Sangria'. TSWV and AlMV were found coinfecting `Rosario' plants. Five percent of plants were serologically positive to TSWV in the first flower harvest (25 Jan.-5 Apr.), 10% in the second (12 Apr.-21 June), and third (5 July-13 Sept.) and 18% in the last harvest (24 Sept.-6 Dec.). The highest peak density of thrips (520 to 630 individuals per sticky trap) were registered when the maximum temperature was higher than 35 °C and the relative humidity was between 40% to 60%. However, such peak density was not correlated with a significant increase of TSW incidence. Number and quality of inflorescences and the stem growth rate were significantly higher (P = 0.05) in plots with asymptomatic plants than that with plants showing putative symptoms of TSW.