scholarly journals Inoculation Method, Temperature, and Relative Humidity Affect Leaf and Neck Anthracnose, a New Onion Disease in Michigan

2018 ◽  
Vol 19 (1) ◽  
pp. 64-68
Author(s):  
Lina M. Rodriguez-Salamanca ◽  
Rachel P. Naegele ◽  
Lina M. Quesada-Ocampo ◽  
Mary K. Hausbeck
Keyword(s):  
Relative Humidity ◽  
Disease Severity ◽  
Colletotrichum Coccodes ◽  
Conidial Suspension ◽  
New Disease ◽  
Inoculation Method ◽  
Millet Seed ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies

Leaf and neck anthracnose caused by Colletotrichum coccodes is a new disease of onion in Michigan. To test the effect of inoculation method, Prince onion seedlings were grown in the greenhouse and inoculated with either a conidial suspension of C. coccodes (alone or with an abrasive agent) or infested millet seed (dry or wet, 2 or 5 g). Foliar disease severity was greater when a conidial suspension (>39%) was used compared with infested millet seed (≤24.3%). Growth chamber studies were conducted using Infinity onion seedlings that were inoculated with a conidial suspension spray to determine the effects of temperature (15, 20, 25, or 30°C) and duration (0, 12, 24, 48, or 72 h) of high (95 ± 5%) relative humidity (RH) on disease severity (percentage of leaf area with C. coccodes lesions). Significant differences and interactions among temperature and RH were observed. The combination of high temperature (≥25°C) and extended (≥24 h) high RH resulted in >20% disease severity 28 days postinoculation. Results suggest that onion leaf and neck anthracnose symptoms are likely to be more severe when the environmental conditions are ≥25°C with ≥24 h of high RH.

Environmental Effects on MSMA Phytotoxicity to Wild-Type and Arsenical Herbicide-Resistant Common Cocklebur (Xanthium strumarium)

1996 ◽  
Vol 10 (4) ◽  
pp. 809-814 ◽  
Author(s):  
Chandrashekhar I. Nimbal ◽  
David R. Shaw ◽  
Gene D. Wills ◽  
Stephen O. Duke
Keyword(s):  
Relative Humidity ◽  
Xanthium Strumarium ◽  
Wild Type ◽  
Fresh Weight ◽  
Low Light ◽  
Herbicide Resistant ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Weed Resistance

Effects of temperature, relative humidity, and light on MSMA phytotoxicity to wild-type and arsenical herbicide-resistant biotypes of common cocklebur grown from seed collected in Mississippi were evaluated. In growth chamber studies, 20-d-old plants were sprayed with 0.5 kg ai/ha of MSMA, and after 7 d, fresh weight and chlorophyll content were measured to estimate phytotoxicity. All three environmental factors influenced the level of weed resistance. In studies with day/night temperatures of 30/25 C and 500 μmol/m2/s PPFD light with a 14-h photoperiod, phytotoxicity of MSMA at 40% relative humidity was minimal, but was significantly greater at 60 and 90% relative humidities. The resistant (R) biotype was affected less than the susceptible (S) biotype at the higher relative humidities. The level of resistance estimated by fresh weight reduction was greatest at 30/25 C, but was most pronounced at 35/30 C using chlorophyll measurements. Resistance was lowest at 25/20 C by either measurement. MSMA phytotoxicity occurred at light intensities of 75, 500, and 750 μmol/m2/s PPFD; however, biotypic response was greatest at 500, followed by 750 μmol/m2/s PPFD. Resistance of the (R) biotype to MSMA was not significant at 75 μmol/m2/s, suggesting that differentiation between the biotypes for MSMA sensitivity would be difficult under low light.

Anthracnose of Florida Beggarweed (Desmodium tortuosum) Caused byColletotrichum truncatum

Weed Science ◽  
1988 ◽  
Vol 36 (3) ◽  
pp. 329-334 ◽  
Author(s):  
John Gardina ◽  
Robert H. Littrell ◽  
Richard T. Hanlin
Keyword(s):  
Relative Humidity ◽  
Host Specificity ◽  
Plant Species ◽  
Fungal Pathogen ◽  
Disease Development ◽  
Colletotrichum Truncatum ◽  
Optimum Conditions ◽  
Cotyledon Stage ◽  
Chamber Studies ◽  
Growth Chamber Studies

Greenhouse and growth chamber studies were conducted to determine conditions for infection of the fungal pathogenColletotrichum truncatum(Schw.) Andrus and Moore on Florida beggarweed (Desmodium tortuosum(Sw.) DC. # DEDTO and to determine the host specificity of this fungus. Optimum conditions for disease development were 14 to 16 h incubation in 100% relative humidity (RH) at 24 to 29 C. Control of Florida beggarweed with 105to 107C. truncatumspores/ml was greatest in the cotyledon stage and decreased with plant age. Ten of 18Desmodiumspecies tested were susceptible to the Florida beggarweed isolate ofC. truncatumbut 13 other plant species and varieties were resistant and 61 were immune.

scholarly journals A Method to Induce Stem Cankers by Inoculating Nonwounded Populus Clones with Septoria musiva Spore Suspensions

Plant Disease ◽  
2010 ◽  
Vol 94 (10) ◽  
pp. 1238-1242 ◽  
Author(s):  
Jared M. LeBoldus ◽  
Peter V. Blenis ◽  
Barb R. Thomas
Keyword(s):  
Disease Severity ◽  
Hybrid Poplar ◽  
Field Studies ◽  
Conidial Suspension ◽  
Populus Balsamifera ◽  
Inoculation Method ◽  
Spray Inoculation ◽  
Septoria Musiva ◽  
Artificial Inoculations ◽  
Canker Development

Most artificial inoculations of Populus spp. stems with Septoria musiva have required host wounding to induce canker development; in the absence of wounds, frequencies of cankers have been low. Three greenhouse inoculation experiments were conducted to demonstrate the reliability and repeatability of an inoculation method that did not require wounding. In the first, 16 clones of hybrid poplar were inoculated with three isolates of S. musiva to compare responses following wounding and inoculation with mycelium (wound inoculation) with responses following inoculation of nonwounded trees by spraying with a conidial suspension (spray inoculation). Stem disease severity among clones following spray inoculation was correlated with stem disease severity following wound inoculation. A significant clone–isolate interaction was detected with spray inoculation but not wound inoculation. In the other two greenhouse experiments, 29 clones of hybrid poplar and 69 clones of Populus balsamifera were inoculated with a spore suspension mixture of three isolates. In both cases, the experimental error was similar to that obtained in previous experiments, in which trees were wound inoculated, and was adequately small to permit detection of differences in responses among clones. Ultimately, field studies will be needed to determine the best inoculation method for predicting stem responses to this pathogen under field conditions. However, relative to wound inoculation, spray inoculation of nonwounded trees has the advantage of yielding faster results, permitting inoculation with a mixture of isolates, and not circumventing potential mechanisms for resisting penetration. The ability to infect stems without wounding creates opportunities for numerous types of epidemiological and disease control studies that are difficult to conduct with wound inoculation.

scholarly journals Influence of Temperature, Relative Humidity, Ascospore Concentration, and Length of Drying of Colonized Dry Bean Flowers on White Mold Development

Plant Disease ◽  
2006 ◽  
Vol 90 (7) ◽  
pp. 946-950 ◽  
Author(s):  
R. Harikrishnan ◽  
L. E. del Río
Keyword(s):  
Relative Humidity ◽  
Linear Increase ◽  
White Mold ◽  
Post Inoculation ◽  
Disease Development ◽  
Dry Bean ◽  
Influence Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Inoculum Type

Growth chamber studies were conducted using rehydrated dry bean (Phaseolus vulgaris) flowers (RDBF) to assess the influence of temperature (18 and 22°C), relative humidity (RH; 25 and 90%), and ascospore concentrations (102, 103, and 104 ascospores/ml) on white mold incidence in dry bean. Additional studies were carried out to determine the influence of inoculum type (ascospore and mycelium) and to estimate the effect of duration of drying of colonized RDBF on viability of Sclerotinia sclerotiorum and white mold incidence. There was a linear increase in white mold incidence with increase in ascospore concentration but neither temperature nor RH levels significantly affected disease development. In the inoculum type study, both temperature and RH levels significantly affected white mold incidence; however, neither ascospore nor mycelial inocula had a significant effect on white mold incidence. Drying colonized RDBF for up to 96 h did not affect S. sclerotiorum viability; but the amount of white mold incidence depended more on post-inoculation RH and drying duration than on the temperatures tested. Colonized RDBF dried for 96 h took approximately three times longer to achieve 100% white mold incidence compared with colonized RDBF dried for 24 h. These results suggest the potential for greater white mold development with higher ascospore availability and the potential of dry S. sclerotiorum-colonized dry bean flowers as a viable inoculum source.

scholarly journals Effects of Temperature, Humidity, and Wounding on Development of Phytophthora Rot of Cucumber Fruit

Plant Disease ◽  
2010 ◽  
Vol 94 (12) ◽  
pp. 1417-1424 ◽  
Author(s):  
L. L. Granke ◽  
M. K. Hausbeck
Keyword(s):  
Relative Humidity ◽  
Phytophthora Capsici ◽  
Fruit Size ◽  
Fruit Rot ◽  
Age Related ◽  
Cucumber Fruit ◽  
Wide Range ◽  
Pickling Cucumbers ◽  
Effects Of Temperature ◽  
Growth Chamber Studies

The effects of temperature (10, 15, 20, 25, 30, and 35°C) and relative humidity (~35, 60, 70, 80, and 100%) on development of Phytophthora fruit rot, caused by Phytophthora capsici, of pickling cucumber (Cucumis sativus) were investigated in controlled growth chamber studies. The effect of wounding on disease development was characterized for small (2.0 to 2.5 cm diameter × 8 to 9 cm long), medium (3.0 to 4.0 cm diameter × 12.0 to 13.0 cm long), and large (>4.5 cm diameter × >14 cm long) pickling cucumbers. Lesions developed on cucumbers incubated at all temperatures tested except 10 and 35°C. Disease severity was greatest on cucumbers incubated at 25°C at 4 days postinoculation (dpi). Lesions formed on cucumbers incubated at all relative humidities tested. The diameter of water-soaking and pathogen growth increased as the incubation relative humidity increased. Wounding lessened age-related resistance in pickling cucumbers. The diameter of water-soaking was similar for all wounded cucumbers at 4 dpi regardless of fruit size. Sporangial production was greater on small and medium fruits than on large fruits. These results indicate that P. capsici is capable of infecting cucumbers over a wide range of temperature and relative humidity conditions. Wounding increases the susceptibility of pickling cucumbers to P. capsici.

scholarly journals Comparison of Whole Plant and Detached Leaf Screening Techniques for Identifying Anthracnose Resistance in Strawberry Plants

Plant Disease ◽  
2018 ◽  
Vol 102 (11) ◽  
pp. 2112-2119
Author(s):  
Melinda A. Miller-Butler ◽  
Barbara J. Smith ◽  
Ebrahiem M. Babiker ◽  
Brian R. Kreiser ◽  
Eugene K. Blythe
Keyword(s):  
Relative Humidity ◽  
Disease Severity ◽  
Conidial Suspension ◽  
Severity Rating ◽  
Detached Leaf ◽  
Whole Plant ◽  
Germplasm Line ◽  
Detached Leaves ◽  
Whole Plants ◽  
Leaf Symptoms

Anthracnose is a destructive disease of strawberry caused by several Colletotrichum species including C. acutatum, C. fragariae, and C. gloeosporioides. Identification of anthracnose resistant strawberry germplasm has commonly relied on inoculation of whole plants with isolates of these pathogens. In this study, whole plants and detached leaves from 81 germplasm lines were inoculated with a conidial suspension of isolates of C. acutatum, C. fragariae, and C. gloeosporioides, incubated in the dark at 30°C, 100% relative humidity, for 48 h, and assessed for disease severity based on symptoms on inoculated petioles and leaves. The correlation between the disease severity ratings of the whole plants rated 30 days after inoculation and detached leaves rated 5 days after inoculation was determined. Based on leaf symptoms and petiole lesions, the association between the whole plant leaf disease severity rating (DSR) and detached leaf DSR was positive (rp = 0.70), and the association between the whole plant DSR and the detached leaf DSR was also positive (rp = 0.66). Whole plant and detached leaf DSRs were used to assign each germplasm line to a resistance category, and a posthoc Tukey’s test showed that the whole plant DSR means and the detached leaf DSR means for each resistance category differed significantly at p < 0.05. This research was used to develop a strawberry detached leaf assay which can reliably and quickly determine the degree of resistance of strawberry germplasm to anthracnose.

The Influence of Environmental Factors on Oryzalin Activity

Weed Science ◽  
1983 ◽  
Vol 31 (5) ◽  
pp. 752-758 ◽  
Author(s):  
James E. Nelson ◽  
William F. Meggitt ◽  
Donald Penner ◽  
James S. Ladlie
Keyword(s):  
Environmental Factors ◽  
Foxtail Millet ◽  
Grain Sorghum ◽  
Amaranthus Retroflexus ◽  
Surface Irrigation ◽  
Setaria Verticillata ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Smooth Pigweed

Effects of temperature, sunlight, soil incorporation and surface irrigation on the phytotoxicity of oryzalin (3,5-dinitro-N4,N4-dipropylsulfanilamide) were studied. The activity of oryzalin applied 4 to 6 weeks prior to planting was enhanced by covering the soil with plastic as measured by the inhibition of grain sorghum [Sorghum bicolor(L.) Moench. 'Sexauer G-701′] root growth. Growth chamber studies demonstrated that oryzalin phytotoxicity to grain sorghum was greater at 20 and 25 C than at 30C. The control of foxtail millet[Setaria italica(L.) Beauv. #5SETIT] bristly foxtail[Setaria verticillata(L.) Beauv. # SETVE], redroot pigweed (Amaranthus retroflexusL. # AMARE), and smooth pigweed (Amarantbus hybridusL.), and injury to grain sorghum increased as the thoroughness of mechanical incorporation of oryzalin into soil increased. The phytotoxicity of surface-applied oryzalin increased with increasing amounts of irrigation water until it equaled the level of a preplant-incorporated treatment.

Mineral Nutrition and the Parasite-Host Relationship of Witchweed

Weed Science ◽  
1971 ◽  
Vol 19 (5) ◽  
pp. 528-533 ◽  
Author(s):  
G. H. Egley
Keyword(s):  
Relative Humidity ◽  
Mineral Nutrition ◽  
Mineral Nutrients ◽  
High Relative Humidity ◽  
Nutrient Level ◽  
Sorghum Vulgare ◽  
Nutrient Levels ◽  
Chamber Studies ◽  
Growth Chamber Studies ◽  
Relationship Of

The influence of mineral nutrition on the parasite-host relationship of witchweed (Striga luteaLour.) and sorghum (Sorghum vulgarePers. ‘Texas Bighead’) was investigated in greenhouse and growth chamber studies. Sorghum was grown in Eustis loamy sand, either infested or not infested with witchweed, and treated with one of three levels of mineral nutrients. Witchweed reduced host-shoot yields by about 70% at the low nutrient levels and by about 45% at the highest nutrient level. Witchweed produced seed at all nutrient levels, whereas the host produced seed at the highest level only. Increased nutrition also increased witchweed yields. Regardless of nutrient level, an early attack by witchweed was more destructive to the host than a late attack. Growth of witchweed in soil also was studied after the parasite was detached from the host or the host shoot was removed. When only the host shoot was removed, (a) witchweed growth was inhibited; (b) feeding of sucrose to witchweed did not restore parasite growth; (c) mineral nutrients were toxic to the parasite; and (d) high relative humidity around witchweed protected it from the nutrient toxicity. High relative humidity enhanced survival of the detached parasite but markedly inhibited growth of witchweed in the intact parasite-host relationship.

Seed Germination and Seedling Emergence of Scotch Broom (Cytisus scoparius)

Weed Science ◽  
2009 ◽  
Vol 57 (6) ◽  
pp. 620-626 ◽  
Author(s):  
Timothy B. Harrington
Keyword(s):  
Seed Germination ◽  
Temperature Regime ◽  
Root Biomass ◽  
Seedling Emergence ◽  
Soil Drought ◽  
Dark Light ◽  
Scotch Broom ◽  
Effects Of Temperature ◽  
Chamber Studies ◽  
Growth Chamber Studies

Scotch broom is a large, leguminous shrub that has invaded 27 U.S. states. The species produces seeds with a hard coat that remain viable in the soil for years. Growth-chamber studies were conducted to determine effects of temperature regime and cold-stratification period on seed germination. Seedling emergence, mortality, and biomass also were studied in response to sulfometuron and metsulfuron herbicides and variation in soil texture and watering regime. Germination was greatest for a dark/light temperature regime of 15/20 C. Initial rates of germination increased as stratification period was varied from 0 to 60 d, but final germination after 90 d did not differ significantly among periods. Applied alone or in combination, sulfometuron and metsulfuron decreased biomass and increased mortality of seedlings. Mortality from simulated soil drought was greater in the presence versus absence of sulfometuron (20 and 6% mortality, respectively) probably because the herbicide reduced root biomass by 58 to 95%. Invasiveness of Scotch broom is facilitated by a prolonged period of germination across a broad temperature range. Increased control of Scotch broom seedlings with sulfometuron is likely if application is timed to expose recently emerged seedlings to developing conditions of soil drought.

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