New Field Crops Plant Pathology Webpage

Recently, we went live with a new Field Crops Plant Pathology webpage that can be found at the following address:

http://www.uwex.edu/ces/croppathology

At this website, we will have updated information regarding diseases of wheat, corn, alfalfa, and soybean. Specifically, it is our long range goal to have one page fact sheets for the major diseases of each crop. This will be a work in progress, so please excuse the construction.

We also link to "CoolBean.info", "Soyhealth", and "Forage Resources" to provide the most comprehensive information on diseases affecting field, small grain, and forage crops for producers in Wisconsin and elsewhere.

Some of the key components of the new Field Crops Plant Pathology webpage include the ability to ask specific questions about diseases affecting field, small grain, and forage crops. This can be found under the link, "Ask about Crop Diseases".

We will continually work to update this webpage and will keep people notified of changes on the main page. We also welcome any feedback about this site via the "Contact" link.

On-Farm Research Conference in Iowa in December

On-Farm Research Conference - Designing Scientifically Valid Crop Production Research

Dec. 18-19, Knapp-Storms Dining Complex, Iowa State University, Ames, IA

If you are interested in learning more about conducting scientifically valid in-farm research, I will be participating in a conference on December 18 and 19 in Ames, IA. This workshop includes topics on the following:

1. Introduction to on-farm research
2. Data Collection for agronomic, plant disease, insect, and soil and plant fertility
3. Statistics for on-farm research
4. Breakout sessions on: technology for collecting data, what to do with the results, how does economics fit in research, and a consulting session

Speakers include a diverse mix from the fields of plant pathology, statistics, agronomy, meteorology, and economics. Continuing education credit is offered for this workshop.

For more information, please contact me via email at pde@plantpath.wisc.edu, or see the website for more information.

Preliminary Soybean Yields

The 2008 soybean harvest is just getting under way. For most of the growing season, the soybean crop has been about 150 to 200 GDU's behind the 5-year average. Fortunately for WI soybean growers, the unseasonably warm weather we have been enjoying over the last 10 days has quickly advanced our crop towards maturity. However, unfortunately for our growers, preliminary yield estimates are variable. Most of the soybeans that were harvested over the weekend were early maturity group soybeans that were adversely affected by the dry conditions we experienced in August. As growers begin to harvest their later maturity group soybeans, yields will likely be higher due to the late rainfalls that aided seed-fill and the higher yield potential that full season soybeans generally exhibit. The preliminary yield reports from Jefferson (Joe Bollman), Iowa (Rhonda Gildersleeve), Dodge (Matt Hanson), and Green Lake (Carla Hargrave) counties show soybean yields ranging from the low 20's to about 50 bu per acre. Yields generally improve as we move from west to east (Iowa to Dodge County). Regardless of yield variability, if you saw a combine rolling this weekend you likely also saw a drill nearby as growers try to get their wheat crop planted in time to take full advantage of the warm weather and any crop insurance restrictions.

Check Combine Settings to Minimize Soybean Harvest Loss

Growers should take extraordinary precautions this year to check combine settings throughout the harvest day especially if they switch soybean maturity groups. Much of the rainfall that occurred in the dry areas of WI occurred too late to aid early maturity group soybeans (these soybeans were physiologically mature-R7 growth stage prior to rain); however many late maturity group varieties were still in the R6 (grain-fill) growth stage and may have benefited from the late August/early September rainfall. As growers proceed in harvest a quick in-field estimate can be preformed to assess where yield losses are occurring. The three areas of concern are pre-harvest loss (standing soybean), header loss (harvested swath in front of combine), and machine loss (harvested swath behind combine) (Images 1). In each area of interest count the number of beans per 10 ft2. Remember 40 seeds per 10 ft2 equal ~1 bushel per acre yield loss (Image 2).

For more information please see the following article.

Measuring and Reducing Soybean Harvest Losses

Image 1. Fall volunteer soybean in winter wheat caused by machine loss.

Image 2. Two bushel per acre yield loss

Charcoal Rot Showing up in Drought Stressed Beans

Phytophthora root rot is being blamed for much of the late season death we are experiencing in our soybean fields. However if you have experienced any droughty conditions charcoal rot may be the culprit. Charcoal rot is caused by the fungus Macrophomina phaseolina and is root disease of soybean. The development of charcoal rot this year has coincided with the very dry conditions we have seen since flowering. An early indicator of charcoal rot could have been seen around flowering with any premature yellowing of the upper canopy (i.e., yellowing of the top leaves) with eventual leaf drop of those leaves. This can often be mistaken for normal plant senescence. Also, at this point in the growing season, a diagnostic sign of the pathogen can be seen on the lower stem or root tissue of soybean and this is termed microsclerotia (Images 1 and 2). These are tiny, dark fungal structures that can seen with the naked eye after scraping the outer tissues. In terms of yield, the plants in the driest part of field may have unfilled upper pods and low plant vigor. The charcoal rot pathogen survives as these microsclerotia in the soil and in plant tissue and can be long-lived. At this point in the season, management for charcoal rot is not an option. Management for charcoal rot includes the following: (i) reduction of plant stress, (ii) variety selection, and (iii) rotation.

Images 1 and 2. Charcoal rot microsclerotia on lower soybean stems.

For more information on charcoal rot please click here

Stress on R6 Soybean

I have logged many miles across Southern WI the past week and have noticed several pockets of soybean that could use some rain. The U.S. Drought Monitor service verifies my wind shield scouting as it places most of southern WI in the abnormally dry category (Image 1). Across southern and central WI the average soybean field I have been in is at the R5.5 to R6 growth stage (full seed). In WI the R6 growth stage on average lasts ~18 days but will range from 9 to 30 days depending upon the weather. Soybean in this stage use about 1/4 to 1/3 inches of water per day. Lack of sufficient water during this growth stage can cause young pods and developing seed to abort reducing the number of seeds per plant (Images 2 &3).

Image 1.

Images 2 & 3. Stress induced seed and pod abortion at R6 soybean.

Soybean plants can reduce the size of their leaf pore openings to reduce the loss of water vapor. This also reduces the intake of carbon dioxide and the manufacturing of photosynthates which slows plant growth. When normal soil moisture returns, normal growth is resumed. This ability to reduce metabolic activity allows plants to tolerate dry spells without dying or harming their ability to resume growth when normal moisture returns.

If stress has severely affected pod set and seed fill, and if livestock feed is needed, soybeans can be harvested as a forage for ensiling. Highest protein and yields are obtained from soybean harvested at the R6 to R7 growth stage. Harvesting soybeans for forage between the R1 and R5 stage will result in a very high quality silage, but dry matter yields will be reduced significantly. Forage quality will be reduced from R5 soybean forward if a conditioning process is used during harvest. Conditioning will cause significant seed shattering.