Stage of detection and number of sprays for controlling soybean rust

During winter extension meetings, three of the most common questions asked about Asian soybean rust were: when will soybean rust show up in the northern United States; how early should a spray application be made; and how many sprays would be needed. It is incorrect that once soybean rust outbreaks occur in coastal regions of the Gulf of Mexico, the disease can be airborne to Iowa within 2 to 3 days and defoliate soybeans in a week or two if no chemical is applied immediately after the spores arrive. Another recent question is whether spraying at the vegetative growth stage is needed. To address all these questions, we need to know the most likely stage of soybean rust when it appears in the United States

Update: Outbreak prediction for Asian soybean rust in Iowa

Last year, Asian soybean rust moved slowly and did not show up in Iowa. Because of the dry weather conditions that prevailed during the 2005 growing season, one cannot draw a meaningful conclusion. Therefore, soybean rust remains a major concern for soybean producers in the northern regions. A common question asked this winter has been: what is the risk of a soybean rust outbreak in the upcoming season

Soybean rust update - May 2, 2005

Based on our experience with corn rusts, we suspected that disease outbreaks occurring in Florida and southern Texas in March and April would be an indication that rust spores would likely be available to move to Gulf Coast states. The earlier an outbreak occurs in the South, the higher the risk for northern soybean production regions. Since the first detection in kudzu in central Florida in late February, no outbreak was observed in the last two months. The first detection outside Florida on volunteer soybeans was confirmed in southern Georgia

Models and applications for risk assessment and prediction of Asian soybean rust epidemics

Asian rust of soybean [Glycine max (L.) Merril] is one of the most important fungal diseases of this crop worldwide. The recent introduction of Phakopsora pachyrhiziSyd. & P. Syd in the Americas represents a major threat to soybean production in the main growing regions, and significant losses have already been reported. P. pachyrhizi is extremely aggressive under favorable weather conditions, causing rapid plant defoliation. Epidemiological studies, under both controlled and natural environmental conditions, have been done for several decades with the aim of elucidating factors that affect the disease cycle as a basis for disease modeling. The recent spread of Asian soybean rust to major production regions in the world has promoted new development, testing and application of mathematical models to assess the risk and predict the disease. These efforts have included the integration of new data, epidemiological knowledge, statistical methods, and advances in computer simulation to develop models and systems with different spatial and temporal scales, objectives and audience. In this review, we present a comprehensive discussion on the models and systems that have been tested to predict and assess the risk of Asian soybean rust. Limitations, uncertainties and challenges for modelers are also discussed

Models and applications for risk assessment and prediction of Asian soybean rust epidemics.

Asian rust of soybean [Glycine max (L.) Merril] is one of the most important fungal diseases of this crop worldwide. The recent introduction of Phakopsora pachyrhizi Syd. & P. Syd in the Americas represents a major threat to soybean production in the main growing regions, and significant losses have already been reported. P. pachyrhizi is extremely aggressive under favorable weather conditions, causing rapid plant defoliation. Epidemiological studies, under both controlled and natural environmental conditions, have been done for several decades with the aim of elucidating factors that affect the disease cycle as a basis for disease modeling. The recent spread of Asian soybean rust to major production regions in the world has promoted new development, testing and application of mathematical models to assess the risk and predict the disease. These efforts have included the integration of new data, epidemiological knowledge, statistical methods, and advances in computer simulation to develop models and systems with different spatial and temporal scales, objectives and audience. In this review, we present a comprehensive discussion on the models and systems that have been tested to predict and assess the risk of Asian soybean rust. Limitations, uncertainties and challenges for modelers are also discussed

Development of Glomerella leaf spot is enhanced in virus-infected Maxi Gala apples.

Apples are commercially grown in Brazil in a subtropical environment that favors the development of fungal diseases such as Glomerella leaf spot (GLS) caused mainly by Glomerella cingulata (anamorph Colletotrichum gloeosporioides). The main objective of this work was to evaluate the effect of mixed infections by Apple stem grooving virus (ASGV) and Apple stem pitting virus (ASPV) on the infection and the colonization processes of C. gloeosporiodes in cv. Maxi Gala plants. Leaves of 16-month-old potted plants were spray-inoculated and both the disease incidence and lesion count were monitored over time and leaf severity was assessed in the final evaluation using an image analysis tool. Results showed that initial infection estimated from a monomolecular model fitted to progress of lesion count was higher and the incubation period (time to reach 50% incidence) was on average 10 h shorter in virus-infected plants compared to non-infected plants. It is hypothesized that initial events such as conidial germination and fungal penetration into plant cells were facilitated by the presence of viral infection. Also, final GLS severity was significantly higher in the virus-infected plants. Mixed infections by ASGV/ASPV seemed to make apple leaves more susceptible to the initial infection and colonization by C. gloeosporioides

Soybean rust outlook--July 18, 2005

During the past week, soybean rust was found for the first time infecting a commercial soybean field in southern Alabama, 1 mile northwest of a sentinel plot that was found to be infected three weeks earlier. Earlier this week, it was confirmed in a sentinel plot in George County, southeastern Mississippi, at very low levels. In the Alabama field, the disease level was also at very low levels, and the farmer has sprayed the field during the past weekend. The disease was also found in a second sentinel plot in Georgia

Soybean rust weekly outlook- May 23

No other detection has been reported during the past three weeks. The volunteer soybeans found infected in Seminole County of southern Georgia were removed. Sustained, coordinated, and quality monitoring activities have been carried out in southern states, according to southern region coordinator Don Hershman, extension plant pathologist at the University of Kentucky. Soybeans in sentinel plots in Florida are at flowering stage, but no rust has been reported in soybean plants there

Sentinel plots for controlling soybean rust

Timely application of fungicides is the only way to effectively and efficiently protect soybean crops from soybean rust infections. Because we do not know when and where the disease outbreaks will occur in the coming season, early detection of soybean rust during the growing season is key for timely applications. Over the past few years in other countries, sentinel plots have been effective in detecting the disease early and guiding producers in making better spray decisions

Soybean rust outlook - June 13

This year\u27s hurricane season started early and the arrival of Tropical Storm Arlene has raised some concerns regarding the risk of soybean rust (SBR) this season. The early start of the hurricane season reflects some similarities between the soybean rust situation and the southern corn leaf blight epidemic in 1970. In that epidemic, one major condition was an unusual tropical storm that occurred in June, which facilitated the spread of the southern corn leaf blight (SCL) pathogen from southern Mississippi and Alabama to the northern Corn Belt