scholarly journals Effectiveness of Fungicide on Soybean Rust in the Southeastern United States: A Meta-Analysis

2018 ◽  
Vol 10 (6) ◽  
pp. 1784 ◽  
Author(s):  
Mary Delaney ◽  
Althea ArchMiller ◽  
Dennis Delaney ◽  
Alan Wilson ◽  
Edward Sikora
Keyword(s):  
United States ◽  
Meta Analysis ◽  
Southeastern United States ◽  
Soybean Rust

scholarly journals Quantitative Aspects of the Spread of Asian Soybean Rust in the Southeastern United States, 2005 to 2006

2007 ◽  
Vol 97 (11) ◽  
pp. 1428-1433 ◽  
Author(s):  
R. S. C. Christiano ◽  
H. Scherm
Keyword(s):  
United States ◽  
South Carolina ◽  
Average Rate ◽  
Southeastern United States ◽  
Monitoring Program ◽  
Early Summer ◽  
Soybean Rust ◽  
Initial Inoculum ◽  
Disease Progress ◽  
Short Period

The regional dynamics of soybean rust, caused by Phakopsora pachyrhizi, in six southeastern states (Florida, Georgia, Alabama, South Carolina, North Carolina, and Virginia) in 2005 and 2006 were analyzed based on disease records collected as part of U.S. Department of Agriculture's soybean rust surveillance and monitoring program. The season-long rate of temporal disease progress averaged ≈0.5 new cases day–1 and was higher in nonsentinel soybean (Glycine max) plots than in sentinel soybean plots and kudzu (Pueraria lobata) plots. Despite the early detection of rust on kudzu in January and/or February each year (representing the final phase of the previous year's epidemic), the disease developed slowly during the spring and early summer on this host species and did not enter its exponential phase until late August, more than 1 month after it did so on soybean. On soybean, cases occurred very sporadically before the beginning of July, after which their number increased rapidly. Thus, while kudzu likely provides the initial inoculum for epidemics on soybean, the rapid increase in disease prevalence on kudzu toward the end of the season appears to be driven by inoculum produced on soybean. Of 112 soybean cases with growth stage data, only one occurred during vegetative crop development while ≈75% occurred at stage R6 (full seed) or higher. The median nearest-neighbor distance of spread among cases was ≈70 km in both years, with 10% of the distances each being below ≈30 km and above ≈200 km. Considering only the epidemic on soybean, the disease expanded at an average rate of 8.8 and 10.4 km day–1 in 2005 and 2006, respectively. These rates are at the lower range of those reported for the annual spread of tobacco blue mold from the Caribbean Basin through the southeastern United States. Regional spread of soybean rust may be limited by the slow disease progress on kudzu during the first half of the year combined with the short period available for disease establishment on soybean during the vulnerable phase of host reproductive development, although low inoculum availability in 2005 and dry conditions in 2006 also may have reduced epidemic potential.

scholarly journals Epidemiology of Soybean Rust in Soybean Sentinel Plots in Florida

Plant Disease ◽  
2011 ◽  
Vol 95 (6) ◽  
pp. 744-750 ◽  
Author(s):  
Heather M. Young ◽  
James J. Marois ◽  
David L. Wright ◽  
Dario F. Narváez ◽  
G. Kelly O'Brien
Keyword(s):  
United States ◽  
Growth Stage ◽  
Disease Incidence ◽  
Southeastern United States ◽  
Tropical Storm ◽  
Environmental Data ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Maturity Group ◽  
Rain Events

Since its discovery in the southeastern United States in 2004, soybean rust (SBR) has been variable from year to year. Caused by Phakopsora pachyrhizi, SBR epidemics in Florida are important to understand, as they may serve as an inoculum source for other areas of the country. This study examined the first disease detection date, incidence, and severity of SBR in relation to environmental data, growth stage, and maturity group (MG3, MG5, MG7) in soybean sentinel plots (225 m2) across north Florida from 2005 through 2008. The majority (91%) of the initial infections were observed in MG5 and MG7 soybeans, with plots not becoming infected until growth stage R4 or later. Precipitation was the principle factor affecting disease progress, where disease increased rapidly after rain events and was suppressed during dry periods. On average, plots became infected 30 days earlier in 2008 than 2005. In 2008, there was a significant increase in disease incidence and severity associated with the occurrence of Tropical Storm Fay, which deposited up to 380 mm of rainfall in north Florida. The results of this study indicate that climatic and environmental factors are important in determining the development of SBR in north Florida.

scholarly journals Comparative Susceptibility of Kudzu Accessions from the Southeastern United States to Infection by Phakopsora pachyrhizi

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 593-598 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
W. F. Moore ◽  
T. W. Allen
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Average Diameter ◽  
Economic Loss ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Wide Range ◽  
The Individual ◽  
A Site

Soybean rust, caused by Phakopsora pachyrhizi, was first discovered in the continental United States in the fall of 2004. The potential for economic loss in the United States hinges largely on whether or not the pathogen can survive winters in the absence of soybean. Kudzu (Pueraria lobata) is known to be a host for P. pachyrhizi in Asia and South America and is widely distributed in the southern United States. This study examined reactions of kudzu collected from several areas of the southeastern United States to three isolates of P. pachyrhizi, one each from Alabama, Louisiana, and Brazil. Susceptible tan (TAN) lesions, resistant reddish-brown (RB) lesions, and immune (IM) response, previously described on soybean, were produced on kudzu based on the evaluation of 125 plants. However, in contrast to soybean, the RB response on kudzu was common, with approximately 50% frequency. IM responses to at least one isolate were observed on five individual plants, and two plants were immune to all three pathogen isolates used in the test. TAN lesions averaged 3.2 uredinia per lesion with an average diameter per uredinium of 121 μm. In contrast, RB lesions had an average of 0.3 uredinia per lesion with an average uredinial diameter of 77 μm. In 25 of 39 (64%) instances in which multiple plants were tested from a site, each reacted the same to the individual pathogen isolates. This suggested a tendency for plants at specific sites to be genetically identical with respect to rust reaction. Only 19 of 125 (15%) individual plants produced a different reaction to one isolate than to the other two isolates. When four kudzu plants previously shown to produce only TAN lesions to P. pachyrhizi isolates Alabama 04-1, Brazil 01-1, and Louisiana 04-1 were inoculated with eight additional isolates from several areas of the world, all 11 isolates produced only TAN lesions. Likewise, when five other plants previously shown to produce only RB lesions when inoculated with the three isolates were inoculated with the 11 isolates, all produced only RB lesions. These results suggest that susceptibility or resistance to P. pachyrhizi in individual kudzu plants often is broad, extending over a wide range of P. pachyrhizi isolates.

scholarly journals Effects of Daily Temperature Highs on Development of Phakopsora pachyrhizi on Soybean

2012 ◽  
Vol 102 (8) ◽  
pp. 761-768 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner
Keyword(s):  
United States ◽  
Southeastern United States ◽  
The United States ◽  
Daily Temperature ◽  
Soybean Rust ◽  
Limiting Factor ◽  
Climatic Data ◽  
Phakopsora Pachyrhizi ◽  
Diurnal Temperature ◽  
National Climatic Data Center

Although considerable information exists regarding the importance of moisture in the development of soybean rust, little is known about the influence of temperature. The purpose of our study was to determine whether temperature might be a significant limiting factor in the development of soybean rust in the southeastern United States. Soybean plants infected with Phakopsora pachyrhizi were incubated in temperature-controlled growth chambers simulating day and night diurnal temperature patterns representative of the southeastern United States during the growing season. At 3-day intervals beginning 12 days after inoculation, urediniospores were collected from each plant and counted. The highest numbers of urediniospores were produced when day temperatures peaked at 21 or 25°C and night temperatures dipped to 8 or 12°C. When day temperatures peaked at 29, 33, or 37°C for a minimum of 1 h/day, urediniospore production was reduced to 36, 19, and 0%, respectively, compared with urediniospore production at the optimum diurnal temperature conditions. Essentially, no lesions developed when the daily temperature high was 37°C or above. Temperature data obtained from the National Climatic Data Center showed that temperature highs during July and August in several southeastern states were too high for significant urediniospore production on 55 to 77% of days. The inhibition of temperature highs on soybean rust development in southeastern states not only limits disease locally but also has implications pertaining to spread of soybean rust into and development of disease in the major soybean-producing regions of the Midwestern and northern states. We concluded from our results that temperature highs common to southeastern states are a factor in the delay or absence of soybean rust in much of the United States.

scholarly journals Effects of Frequency of “Extreme” Temperature Highs on Development of Soybean Rust

2013 ◽  
Vol 103 (7) ◽  
pp. 708-716 ◽  
Author(s):  
M. R. Bonde ◽  
S. E. Nester ◽  
D. K. Berner
Keyword(s):  
United States ◽  
Southeastern United States ◽  
Extreme Temperature ◽  
The United States ◽  
Major Effect ◽  
Soybean Rust ◽  
Temperature Pattern ◽  
Extreme Temperatures ◽  
Diurnal Temperature ◽  
Soybean Industry

Previously, we hypothesized that summer “extreme” diurnal temperature highs in the southeastern United States were responsible for the yearly absence or delay of soybean rust development until fall. Utilizing temperature-controlled growth chambers, a diurnal temperature pattern of 33°C high and 20°C low reduced urediniospore production by 81%. However, that study did not consider the influence of frequency of extreme temperatures on soybean rust. We now report that a temperature high of 35°C for 1 h on three consecutive days, initiated 15 days after inoculation, when lesions had formed, reduced urediniospore production by 50% and required 9 to 12 days for sporulation to resume once the extreme temperature highs ceased. Furthermore, three consecutive days in which the temperature high was 37°C, beginning immediately after inoculation and subsequent dew period, reduced lesion numbers by 60%. The combined effects of reduced numbers of lesions and urediniospores per lesion caused by extreme temperature highs can account for observed absence or delay of soybean rust development in the southeastern United States until fall. A comparison of frequency of extreme temperature highs with numbers of counties reporting presence of soybean rust from 2005 to 2012 verified that extreme temperature highs may be largely responsible for absence or delay of soybean rust development. This is the first report showing the effect of frequency of extreme temperature highs on development of soybean rust. Because the south-to-north progression of soybean rust is required for the disease to occur in the major soybean-production regions of the United States, temperatures in the southeastern United States have a major effect on the entire U.S. soybean industry.

scholarly journals Multiyear Regional Evaluation of Foliar Fungicide Applications for Cotton Target Spot Management in the Southeastern United States

Plant Disease ◽  
2020 ◽  
Vol 104 (2) ◽  
pp. 438-447
Author(s):  
H. L. Mehl ◽  
N. S. Dufault ◽  
T. W. Allen ◽  
A. K. Hagan ◽  
P. Price ◽  
...  
Keyword(s):  
United States ◽  
Production Systems ◽  
Meta Analysis ◽  
Block Design ◽  
Southeastern United States ◽  
Disease Onset ◽  
Cotton Production ◽  
Target Spot ◽  
Single Well ◽  
Foliar Fungicide

Fungicide programs for managing target spot of cotton caused by Corynespora cassiicola were evaluated over 15 site-years in the southeastern United States between 2014 and 2016. Two cultivars, hypothesized to vary in target spot susceptibility, PhytoGen 499WRF (PHY499) and Deltapine 1137B2RF (DPL1137), and four fungicides (azoxystrobin, flutriafol, pyraclostrobin, pyraclostrobin + fluxapyroxad) plus nontreated control, were compared. Fungicide programs consisted of 1) a single application at first flower or disease onset and 2) the first application followed by a second 14 days later. Treatments were applied in a factorial, randomized complete block design. Target spot onset and severity varied among site-years. Except when severity was low, target spot-associated defoliation was greater on PHY499 than on DP1137. Fungicides delayed disease development and defoliation, but application number had little impact. Based on a meta-analysis of 15 site-years, pyraclostrobin-based applications resulted in a 4 to 6% yield preservation, and yield preservation was greater at site-years with early disease onset and >40% target spot associated defoliation. Results suggest a single well-timed application of a pyraclostrobin-based fungicide reduces defoliation and protects cotton yield at locations with high target spot severity. Additional research is needed to identify risk factors for target spot-associated yield losses in cotton production systems.

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