CMEG Crop Management Extension Group

Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

July 26, 2006    Vol. 06:13

IN THIS ISSUE:

Status of Soybean Diseases in Pennsylvania — Erick De Wolf, Plant Pathology

Soybeans in most parts of the state are now moving through the early reproductive stages of growth.  The central and western counties are reporting that the crop is in full bloom (R2), and agents in the southeast indicate they their fields range from R2-R3.  Based on samples from the Pennsylvania sentinel plots it appears that three diseases are becoming common in PA: septoria brown spot, downy mildew, and frogeye leaf spot.  These diseases can be found in most areas of the state, but the intensity of each disease differs with variety and production practices.  In most years these diseases do not result in significant yield losses under Pennsylvania conditions.  Our evaluation of the various fungicides here in PA suggests that it is possible to reduce disease pressure, but that these lower disease levels may not translate into yield.

Phytophthora stem rot has also been reported in a number of production fields.  The disease is often associated with wet soils and I suspect that many of our problems with Phytophothora stem began during our extended period of rainy weather in mid-May.  Plants with Phytophthora stem rot develop a characteristic brown lesion that extends upward from the base of the plant.  As the lesion expands the entire plant will wilt and die prematurely.  Producers that are finding significant levels of Phytophthora in their fields should consider selecting varieties with at least one single gene for resistance (effective against limited races of the organism), and use partial resistance (effective against all races) where possible. Our colleague Anne Dorrance at Ohio State University does a great job of evaluating soybean varieties for resistance to Phytophthora.  She posts her results in the OSU soybean performance tests.  You can find this information on line at: http://www.oardc.ohio-state.edu/soy2001/  This would be a good place to start looking for varieties that will help limit future damage from this disease in PA.

As soybeans move through flowering and the early reproductive stages of growth in Pennsylvania, some producers may begin to ask interesting questions about the use of fungicides on soybeans.  The following article is intended to provide some information about a number of factors related to fungicide application to soybeans including the risk of soybean rust in Pennsylvania and using fungicides for “plant health”.

Soybean rust: The risk of soybean rust for Pennsylvania is very low.  At this time, rust remains limited to the deep south.  To date most of the reports of rust have been on in FL, GA, and AL.  This past week Louisiana reported rust on kudzu in three locations (parishes) in that state.  Our colleagues there report that the fungus is reproducing at these sites; however, they have not fund rust in soybean.  The weather there has been hot and dry in these areas so it will likely take a significant amount of time for the rust to reach high levels.  Soybean producers should continue with their normal management plans, but should carefully watch rust in the deep south. If the rust gets out of control in the South we may need to be ready for action. I would suggest you check the USDA. website frequently for updates. I post comments about the rust situation in the U.S. and its implications to Pennsylvania each week. Interested parities can find the site at: http://www.sbrusa.net/

Canola Trial Update — Greg Roth, Grain Crop Management

We recently completed our first winter canola trial as part of the National Winter Canola Testing Program ( http://www.oznet.ksu.edu/library/crpsl2/samplers/SRP954.asp).  Our objective was to gather some experience and performance data on canola under our conditions here in Pennsylvania.  Canola is a potential biofuel crop that averages about 40% oil compared to 22% oil in soybeans.  We are still analyzing the data, but entries averaged from about 50 to 65 bushels per acre, which we were pleased with.  In comparison our wheat variety trial yields have been in the 80 bushel per acre range.

We seeded the canola in September at a rate of about 6 pounds of seed per acre following a pre plant incorporated Treflan herbicide program.  Establishment was a bit spotty due to the dry conditions in the fall and some plots only had about a 50% stand.  The canola compensated very well, however, and some of the thin stands had very good yields.  Weed control in the trial was good.  Winterkill was minimal and we topdressed in the spring with 100–0–0–20.  We noticed some bird feeding activity late in the season, we did not experience heavy losses due to the birds.  We harvested on July 7, just before our wheat was ready.  We were concerned about grain losses due to shattering before and during combining and inevitably had some, but they were not severe.  We were able to set our small grain combine up to do a reasonable job cleaning the grain with a minimum of effort.

Overall I consider our first canola trial a success and now look to work on doing some economic analysis to compare the potential profitability to other crops like wheat and soybeans.  We will also be harvesting a spring planted canola and mustard trial this week which also looks very good.

Fall Legume Cover Crops for Nitrogen Fixation and Soil Improvement — Sjoerd Duiker, Soil Management Specialist and Bill Curran, Weed Scientist

In last week’s issue, Joel Hunter prodded us to try out some fall cover crops for their many benefits, such as erosion control, nitrogen contribution and improved soil quality. Two fall-established leguminous cover crops that offer good potential for nitrogen fixation, erosion control and soil quality improvement are crimson clover and hairy vetch.

Crimson clover can supply up to 130 lbs/A N fertilizer equivalent to the following crop, whereas hairy vetch can contribute 160 lbs/A N. The amount of N depends on how much biomass the cover crops accumulate, much of which depends on how late they are planted and when they are killed. Hairy vetch accumulates biomass primarily in April and May, whereas crimson clover is a little (1–2 weeks) earlier in putting on biomass. For maximum N contribution one would have to wait until either the middle of May (crimson clover) or the beginning of June (vetch) in central PA or a week earlier for southern PA. If one terminates the cover crops earlier the N-contribution will be lower, and N may have to be supplemented in fertilizer or manure for maximum crop yields.

In the literature, crimson clover is reported to be winter-hardy in USDA. Hardiness Zone 8, whereas hairy vetch is listed as being winter-hardy in hardiness zone 6. This suggests that crimson clover would not over winter dependably in Pennsylvania, whereas hairy vetch would over winter in the southern portion of our state only. However, in Penn State evaluations in southeastern Pennsylvania, crimson clover survived the winter consistently from 2002-2005, similar to hairy vetch. The key is to establish these cover crops in mid-September in the southeast, or by the 1st of September in central PA. Reports from the northwest suggest that hairy vetch established by the 1st of September has survived the winters there too. There are reports that if these legumes are established with a cereal cover crop, they will survive the winter better than if they are planted alone.  However, unless global warming really starts to provide more mild winters, we do not recommend trying crimson clover except in the most southern regions of PA.

Both crimson clover and hairy vetch do best on well-drained soils and prefer a soil pH between 6.0 and 7.0. They are adapted to high soil fertility status (phosphorus, potassium and sulfur). There are good options to mix these legumes with a cereal for added cover crop benefits. Mixing hairy vetch with oats is one good option: the oats give quick cover in the fall but winterkill, whereas the hairy vetch grows slowly in the fall, but puts most biomass on in the spring. Another option is mixing hairy vetch with wheat or rye. In this case the cereals survive the winter with the hairy vetch. This has not been found to adversely affect nitrogen fixation by the vetch. The cereal residue is more resistant to decomposition and the mixture will therefore provide a longer-lasting mulch than hairy vetch alone. Mixing these cereals with crimson clover is also possible. In this case a little more competition can be expected between the cereal and the clover because clover tends to grow faster in the fall whereas it does not climb up into the cereal like vetch does.

Make sure the legumes are inoculated with the proper rhizobium strain, and plan on terminating them with more than only glyphosate. A mix of glyphosate and 2,4-D is a full-proof method of terminating these cover crops. Be prepared to plant through a thick mat of residue in the spring, which can be a little intimidating. Chisel plowing or disking are not recommended to manage heavy cover crops: one either has to moldboard plow it under (ouch) or no-till into the heavy residue. In the latter case, hair-pinning is an issue one has to be prepared to deal with. If a good stand of corn is established, one has a beautiful mulch and great satisfaction with a job well done. The difference in soil quality due to the covers is tremendous and the nitrogen benefits can pay for the cover crop seed. We had excellent results this past year with planting corn into hairy vetch (we are counting on 120 lbs/A of N for the corn and decided not to put any additional N-fertilizer on besides starter fertilizer).

Seeding rates for crimson are 15 (drilled) to 30 (broadcast) lbs/A, or 20 (drilled) to 40 (broadcast) lbs/A for hairy vetch. If they are grown in mixtures, add 1 bu/A of rye or wheat, or 1.5 bu/A of oats, but don’t reduce the seeding rate of the legume.

Finally, consider the previous herbicide program before establishing a cover crop.  In particular, corn herbicides and legume cover crops may pose the greatest risk — a number of corn herbicides carry an 10 to 18 month restriction before you can successfully establish a legume or grass forage.  This may be because of both the potential for illegal herbicide residues in the forage as well as concern of carryover injury.  Unsuccessful establishment of the cover crop due to carryover residues is certainly more of a concern for cover crops than illegal herbicide residues which may pose a risk for meat or milk products.- they not really valid for non food or livestock feed crops.  A few generalizations can be made.  In general, carryover injury can be a concern for atrazine (apply less 1.0lb active per acre to corn if seeding late summer legumes or no more than 1.25 lb active before cereal grains like rye).  In addition, some of the ALS-type herbicides such prosulfuron (Spirit or Exceed), the herbicide clopyralid (Stinger and Hornet), and mesotrione, (Callisto, Lumax, and Lexar) can also be problematic for legume cover crops. In addition, if some of the more residual soybean herbicides are used like Pursuit, Scepter, Classic or Canopy, these will also potentially injure susceptible legume cover crops.  The bottom line, is to check the herbicide label prior to planting a cover crop rotation — this is a good conservative rule to follow to ensure successful cover crop establishment.

Results from the Penn State Barley Performance Trials — Erick De Wolf, Dave Johnson, & Greg Roth

Growing conditions for barley were nearly ideal in many parts of Pennsylvania this year, and growers are reporting above average yields and high test weights.  As you know, barley fits well with our production systems here in PA providing valuable cover crop in the fall and early spring. The grain and straw can also be useful sources of feed, bedding and income for some operations.   Penn State researchers including Dave Johnson, Greg Roth and Erick De Wolf conduct an annual evaluation of barley varieties in Pennsylvania.  Results from this year are now available at Penn State Small Grain Management Web site.

Contributors: State Specialists:  Erick De Wolf, Greg Roth, Bill Curran, Sjoerd Duiker, Marvin Hall, and Doug Beegle.  Extension Educators:  Mena Hautau (Berks), Joel Hunter (Crawford), Kevin Fry (Armstrong), Mark Madden (Sullivan), Dwane Miller (Schuykill), Jeff Graybill (Lancaster), and Dave Messersmith (Wayne).

Editor: Kevin Fry

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Calendar of Events: http://www.events.psu.edu/cgi-bin/cal/webevent.cgi?cmd=opencal&cal=cal209&

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