What's Cropping Up? Blog

Articles from the bi-monthly Cornell Field Crops newsletter

February 22, 2017
by Cornell Field Crops
Comments Off on A New Soybean Disease Resource Available for NY Growers

A New Soybean Disease Resource Available for NY Growers

Jaime A. Cummings and Gary C. Bergstrom
School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University

Figure 1. An example of one of the diseases identified for the first time in NY as a result of the survey.

Surveys of soybean diseases in New York were initiated in 2012 with support by the Northern New York Agricultural Development Program (2013-2016) and the New York State Corn and Soybean Growers Association (2013-2015). Prior to 2012, no systematic assessment of soybean diseases was made in NY in recent decades and was long overdue. The survey was coordinated by Cornell University’s Field Crops Pathology program under the direction of Dr. Gary Bergstrom and Research Support Specialist Jaime Cummings in collaboration with numerous Cornell Cooperative Extension Educators and countless soybean growers throughout the state.  The purpose of the surveys was to gain a better understanding of the occurrence and distribution of soybean diseases affecting NY growers and to document and monitor the expansion of diseases to new areas.  All distribution maps are based on a positive laboratory diagnosis of the causal microorganism associated with observed symptoms.  Actual ranges of disease occurrence may be wider than appears on these maps but have not yet been confirmed through vigorous laboratory diagnoses. The results of this ongoing survey are now available in the soybean disease section of Cornell’s fieldcrops.org extension website https://fieldcrops.cals.cornell.edu/soybeans/diseases-soybeans/soybean-disease-survey.

Through the efforts of this survey, a total of seven diseases previously undocumented in NY were discovered and confirmed.  These diseases included charcoal rot, Fusarium wilt, sudden death syndrome, brown stem rot, northern stem canker, bacterial wilt and powdery mildew.  The soilborne diseases identified are of particular concern to growers.  Knowing where these diseases have been confirmed will aid growers in making decisions on selecting varieties with resistance and other management options for diseases of potential importance in their areas.  Multiyear surveys better capture the reality of disease occurrences in the region due to the variation in weather from year to year, because each disease may be favored by specific weather conditions.  We will continue the soybean disease survey in 2017 to expand our database and knowledge of which soybean diseases occur throughout NY.

The website, updated annually, outlines the progress of the survey, including the locations included in the survey, the number of samples diagnosed and the primary diseases identified each year.  New York soybean growers can use this new tool to find information on which diseases have been identified in their respective counties, along with information on each disease including epidemiology, diagnostic characteristics for in-field identification, and management options and recommendations (Fig. 1).

Save

Save

December 5, 2014
by Cornell Field Crops
Comments Off on What’s Cropping Up? Vol. 24, No. 6 – November/December – Full Version

What’s Cropping Up? Vol. 24, No. 6 – November/December – Full Version

WCUVol24No6The full version of What’s Cropping Up? Volume 24, No. 6 is available as a downloadable PDF.  Individual articles are available below:

December 5, 2014
by Cornell Field Crops
Comments Off on Resistance to Brown Stem Rot May Be Needed in Future Soybean Varieties for New York State

Resistance to Brown Stem Rot May Be Needed in Future Soybean Varieties for New York State

Jaime A. Cummings and Gary C. Bergstrom, School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University

A potentially yield-reducing disease called ‘brown stem rot’ (BSR) was confirmed for the first time in New York soybean fields in 2013, and was found again in 2014.  It showed up in some plants from soybean fields in Cayuga, Herkimer, Niagara, and Yates Counties collected by Cornell Cooperative Extension Educators Kevin Ganoe, Keith Severson, Michael Stanyard, and Bill Verbeten, with support from the New York Soybean Check-off Program.  The disease was diagnosed in the Field Crops Pathology Laboratory at Cornell based on characteristic symptoms and the laboratory isolation of the causal fungus and confirmation of a portion of its signature DNA sequence. So far, BSR has not been detected outside of the four counties mentioned above.  It is noteworthy that BSR was not detected in soybean fields in northern New York scouted in 2013 and 2014 by CCE Educators Michael Hunter and Kitty O’Neil, with support from the Northern New York Agricultural Development Program.

Brown stem rot is caused by the fungus Cadophora gregata (syn. Phialophora gregata) and occurs in most soybean production regions of the US, but this is, to our knowledge, the first confirmation in New York or the northeastern U.S.  Reported yield losses in the Midwest have ranged from minor to in excess of 25%, so the presence of the pathogen is considered a significant factor for soybean production. Yield loss is often a function of the relative susceptibility of varieties that are planted; varieties vary from susceptible to resistant.  BSR is a disease of priority to soybean seed companies.  Resistant varieties are widely available, and most seed catalogs provide resistance ratings for BSR.  If BSR becomes more prevalent in New York, selection of resistant varieties may become more important for New York producers.

The foliar symptoms of BSR are similar to those of other soilborne diseases that restrict the movement of water and nutrients to the leaves.  So BSR can be confused with northern stem canker and sudden death syndrome, all of which result first in yellowing and then browning of leaf tissues between the veins during pod-filling stages.  However, not all soybean varieties exhibit foliar symptoms when infected with the BSR fungus.  What is distinctive about BSR is the browning of the internal tissues of infected plants (Figure 1).  This discoloration is often most obvious near the nodes when stems are split lengthwise.  Dead leaves may remain attached to the plant. Stem discoloration symptoms may be confused with those caused by white mold, northern stem canker, or Phytophthora stem rot.

Figure 1.  Foliar symptoms and browning of internal stem tissues caused by brown stem rot.  (Photo courtesy of Iowa State University http://www.ipm.iastate.edu/ipm/icm/2006/9-18/sds.html )

Figure 1. Foliar symptoms and browning of internal stem tissues caused by brown stem rot. (Photo courtesy of Iowa State University http://www.ipm.iastate.edu/ipm/icm/2006/9-18/sds.html )

Infection by the fungus occurs early in the season, through the roots, from where the fungus continues to grow throughout the plant’s water-conducting tissues.  Temperature has the greatest impact on disease development, and is favored by temperatures between 60 – 80F.  But, temperatures above 80F may halt BSR development and spread.  Because infection occurs at early stages (around the three leaf stage) of the crop, foliar fungicides applied during flowering and pod-filling stages will not be effective in suppressing BSR.

The fungus survives on soy residues and in the soil in the field for many years. Luckily, the pathogen survives on few other plant species, and in severely infested fields, a rotation of at least 3 years out of soybean and deep plowing of infected soybean residues would reduce the incidence of BSR in a subsequent soybean crop.

The most important thing that a New York soybean producer can do at this time is to learn to recognize the symptoms of BSR and other soilborne diseases and to get a diagnosis of problems that they observe in their fields.  If BSR or other soilborne diseases are confirmed, producers should talk to their seed supplier and order soybean varieties with appropriate levels of resistance for the soilborne diseases observed on their farm.

Acknowledgements: This research received financial support from the New York Soybean Check-off Research Program, the Northern New York Agricultural Development Program, and Cornell University Hatch Project NYC153473.

October 6, 2014
by Cornell Field Crops
Comments Off on What’s Cropping Up? Vol. 24, No. 5 – September/October – Full Version

What’s Cropping Up? Vol. 24, No. 5 – September/October – Full Version

WCUVol24No5The full version of What’s Cropping Up? Volume 24, No. 5 is available as a downloadable PDF.  Individual articles are available below:

September 19, 2014
by Cornell Field Crops
Comments Off on Northern Stem Canker: A New Challenge for New York Soybean Producers

Northern Stem Canker: A New Challenge for New York Soybean Producers

Jaime A. Cummings and Gary C. Bergstrom – School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section – Cornell University

Figure 1.  Canker on stem, and inter-veinal discoloration of leaves above the canker caused by northern stem canker. Photo by Jaime Cummings.

Figure 1. Canker on stem, and inter-veinal discoloration of leaves above the canker caused by northern stem canker. Photo by Jaime Cummings.

As part of 2014 research projects supported by the New York Soybean Check-off Program and the Northern New York Agricultural Development Program, participating Cornell Cooperative Extension Educators have been scouting soybean production fields, recording observations on diseases, and sending plant samples to the Field Crop Pathology Laboratory at Cornell University for positive diagnosis of disease problems.  A serious disease called ‘northern stem canker’ was confirmed for the first time in New York soybean fields.  It showed up in samples from soybean fields in Jefferson, Livingston, Niagara, Ontario, Orleans, Seneca, and Wayne Counties collected by CCE Educators Mike Hunter, Mike Stanyard and Bill Verbeten.  The disease was diagnosed at Cornell based on characteristic symptoms and the laboratory isolation of the causal fungus and confirmation of a portion of its DNA sequence.  Soybeans are also being scouted in other areas of New York in 2014, but so far this disease has not been detected outside of the seven counties mentioned above.

Northern stem canker (NSC) is caused by the fungus Diaporthe phaseolorum var. caulivora and differs from a related fungus, Diaporthe phaseolorum var. meridionalis, that causes southern stem canker throughout the southern U.S.  NSC occurs in most Midwestern states and in Ontario, but this is, to our knowledge, the first confirmation in New York or the northeastern U.S.  Reported yield losses in the Midwest have ranged from minor to in excess of 50%, so the presence of the pathogen is considered a significant factor for soybean production. Yield loss is often a function of the relative susceptibility of varieties that are planted; varieties vary from susceptible to resistant.  If NSC becomes more prevalent in New York, selection of resistant varieties may become more important for New York producers.

Figure 2. Internal and external stem symptoms caused by northern stem canker. Photo by Jaime Cummings.

Figure 2. Internal and external stem symptoms caused by northern stem canker. Photo by Jaime Cummings.

The foliar symptoms of NSC are similar to those of other soilborne diseases that restrict the movement of water and nutrients to the leaves.  So NSC can be confused with brown stem rot and sudden death syndrome, all of which result first in yellowing and then browning of leaf tissues between the veins during pod-filling stages.  What is distinctive about NSC is the stem lesions called cankers that form near nodes and often girdle the stem, resulting in wilting and necrosis above the canker (Figure 1).  Dead leaves remain attached to the plant and turn blackish.  Cankers often have a reddish margin and gray center (Figures 1 & 2).  Symptoms in the interior stem initiate as a slight browning at the nodes and then may progress to complete browning and deterioration of the pith, while the roots remain symptomless (Figure 2). Necrotic stem symptoms may be confused with those caused by white mold or Phytophthora stem rot.

Infection by the fungus occurs early in the season, from spores splashed by rain from the soil to the stems; rainfall and warm temperatures favor epidemics. Because infection occurs at early stages (around the three leaf stage) of the crop, foliar fungicides applied during flowering and pod-filling stages will not be effective in suppressing NSC.

The fungus survives on soy residues in the field for many years, and produces its infective spores on these residues. Some research suggests that other legume crops such as alfalfa and a number of weed species can harbor the fungus between soybean crops though the importance of these associations is not well established. Deep plowing of infected soybean residues and multiple year rotations with corn or small grains may reduce the potential of NSC in a subsequent soybean crop. The pathogen can also survive in and be transmitted by infected seed, such that fungicidal seed treatment can reduce the chances for introducing the pathogen into new fields.

The most important thing that a New York soybean producer can do at this time is to learn to recognize the symptoms of NSC and other soilborne diseases and to get a diagnosis of problems that they observe in their fields.  If NSC or other soilborne diseases are confirmed, producers should talk to their seed supplier and order soybean varieties with appropriate levels of resistance for the soilborne diseases observed on their farm.

Acknowledgements: This research received financial support from the New York Soybean Check-off Research Program, the Northern New York Agricultural Development Program, and Cornell University Hatch Project NYC153473.

 

 

Subscribe

Follow this blog

Get a weekly email of all new posts.

Skip to toolbar