Alfalfa Weevil Activity and Scouting

We have accumulated enough Growing Degree Days that small alfalfa weevil larvae should be active in fields. Generally this pest does not develop into a problem but there have been a couple of years out of the last 20 where a spray to control would be warranted. Alfalfa feeding should be focused at the growing tip of the crop. At this point the larvae will be very small with a black head as they develop the size and amount of feeding increase.

To sample for alfalfa weevil, gather 10 stems per area and shake the stem into a bucket dislodging the larvae and counting the number of larvae in the bottom of the bucket. The number of larvae are then compared to the height of the stem to determine if treatment is warranted using the chart below:











A fact sheet reference with more detail can be found at: http://ohioline.osu.edu/ent-fact/pdf/0032.pdf

Wheat is in Growth Stage 6 to 7-Jointing

Wheat is in Growth Stage 6 to 7 which is jointing. This is a crucial stage for management decisions.

First, by now we should have applied topdress nitrogen. From this point on delays in adding N will decrease yield. The majority of the wheat appears to have been topdressed but if any fields remain make them a priority.

Second, any herbicides used from this point on require a careful label review. Some herbicides will cause crop injury when applied after jointing. The 2009-7 CORN Newsletter has an article the topic. If weeds need to be controlled from this point on you can refer to the Ohio/Indiana Weed Control Guide Bulletin 789. Page 141 of this publication shows growth stages and herbicide products graphically.

Third, scouting for diseases should happen in the next couple weeks. A priority would be varieties that are susceptible to powdery mildew, Septoria blotch and Stagonospora blotch. Bulletin 785 has more information on yield loss by suceptibility that is a useful scouting guide. A handy reference on fungicides is also available.

Do not Just Look at the Herbicide Trade Name Look at the Active Ingredient

In recent years there has tended to more remixing of current active ingredients in new premixes rather than the introduction of new chemistry due to the competitive nature of today's herbicide market. Thus from year to year a product with a simliar trade name may have a very different mix of active ingredients and/or concentrations that could change there use and precautions.

An article in The Bulletin from the University of Illinois by Aaron Hager highlight the active ingredients from several common herbicides. He made the following observation:

A brief examination of names of herbicides currently on the market demonstrates that several active ingredients are marketed under more than one trade name/formulation. For example, the active ingredient isoxaflutole is marketed as Balance Pro and Balance Flexx. Even though the active ingredient in the two products is identical and the trade names are very similar, several important differences between the products mean that their use patterns are not necessarily interchangeable.

Other differences among the various products also become apparent. Resolve DF and Resolve SG are different formulations of rimsulfuron that contain the same amount of active ingredient per unit of formulated product, so application rates are identical. However, while Resolve Q also contains rimsulfuron, it has thifensulfuron as well. Both Flexstar and Flexstar GT can be applied postemergence to glyphosate-resistant soybean varieties, but only Flexstar can be applied to non-GMO soybean varieties.

The full article can be found at http://www.ipm.uiuc.edu/bulletin/article.php?id=1095 provides a table of product formulations and active ingredients applied at label rates.

Does Early Planting = Higher Soybean Yields?

D.B. Egli and P.L. Cornelius from the University of Kentucky recently took a number of planting date studies from across the US, including Ohio. and did an analysis of maximizing yield by planting date. What they found is that there was no consistent advantage to early planting. The study divided out results by region, midwest, upper south and deep south. They found very similar responses to planting data regardless of region. Planting dates from mid-April to late May resulted in similar yield averages. What the data did show was a definate yield loss when planting date was delayed past May 30 in the Midwest (0.7 % per day), June 7 in the upper south(1.1% per day) and May 27 in the deep south(1.2% per day).

The authors reasoned that the steady decline from late planting could be a response to changes in the plant or changes in the plant's environment or some combination of these factors. The discuss photosynthesis, temperature, reproductive versus vegetative among other issues that explain this response.

Their conclusion was if the soil is ready in late April farmers should start planting but realize it may not necessarily increase yields.

The full article can be found http://agron.scijournals.org/content/vol101/issue2/ under 'Production Agriculture'

Four Steps to Better Bean Yields

"We use to see 40 bushel beans in the 1940's when we first started growing soybeans and last year I was still growing 40 bushels beans" was a question from the hallway last Friday with a couple area farmers. Their question has been on my mind. I do not have all the answers but a few things that could lead to better bean yields if the proper attention has not been given to these areas. I assume the first question of are we picking high yielding genetics has already been answered and is the starting point.

1. What soil borne problems do you have? Probably the two biggest things we need to consider is phytohpthora root rot, pythium and soybean cyst nematode. If we are not accounting for the presence of these diseases in our production we are losing yield. Phytothora needs to be looked at in a total management way with use of genetic resistance, variety tolerance and seed treatments in a total package to control this critical disease. Pythium likewise needs to be controlled with seed treatment and the treatments are similar to phythothora. An detailed article for more reference Soybeans :When to use a seed treatment and which seed treatment to use? was in a recent CORN Newsletter article. The other consideration from a soil standpoint is soybean cyst nematode. This is a silent yield robber resulting in stunted plants that could be from any number of other things. If you have have not checked field for this problem it can make a significant difference. More information can be found in SCN Factsheet.
2. Soil Compaction is another concern. Soybeans have a tap root and compaction layers can substantially alter the root system. Last summer I watched a field that had a compacted area that seemed to be behind all year long. The root system went down about 4 inches and made a 90 degree turn. The plants got growth to them late season and it would have been easy to just write it off as just wet area but the yield was substantially lower.
3. If you are letting weeds get more than 6 inches tall before controlling them in May and June you are losing yield. Post emergence applications should be planned to assure these first weed flushes do not get ahead of the crop. By 9 inches tall you have lost 6% or 3.6 bushels on 60 bushel beans or at 12 inches 10% or 6 bushels. A good article on weed competition and yield loss in beans is Benefits of Pre Herbicides in Roundup Ready Management Systems.
4. Don’t forget the inoculant! For a number of years, Dr. Jim Beuerlein has evaluated these and they have provided a return on investment. If you are applying inoculant at the same time as the seed treatment be sure that it is a safe combination. 2007 data from these studies can be found at http://agcrops.osu.edu/soybean/documents/12007INOCFINALREPORT.pdf
   

Before You Destory a Wheat Field...

If you have a field that will be destroyed and planted to corn or soybeans you do need to visited with Farm Service Agency and file some paperwork. They will need you to fill out a failed crop report and need some information from you about the planting being destroyed. If you have crop insurance you will want to contact your agent as well before destroying the crop.

Wet feet affects wheat

The wet weather since mid march has taken wheat back in some areas of fields and in a few cases nearly entire fields. Just a few reminders on evaluating wheat stands.

1. Plant stand for good yields. We look for a minimum stand of 12 tillers per foot of row, but we like to see 20 or more per foot of row.
2. Evaluated plant health. If there are low-lying areas in the field or areas with unhealthy-looking plants, remove a few plants from those areas and observe the roots and crowns for discoloration. Gently remove (preferentially by washing) the dirt from the roots, and look for darkish areas or lesions. Healthy roots and crowns typically have a milky-white color, compared to the dark discoloration usually seen on infected roots. Remember, it is not uncommon for the older, lower leaves of the plant to die at this time of the year.
3. What nitrogen rate should I use. Studies over the last five years have shown that yields were the same or slightly better when a single application occurred at Feekes 6 (first node visible of early stem elongation) compared to initial greenup. To determine N rates consider yield potential N rate = 40 + [1.75 x (yield potential – 50)]
   
   Based on the equation above and deducting 20 lb from a fall application, we would recommend a spring application of
   - 110 lb N per acre for a yield potential of 100 bu,
   - 90 for 90 bu potential;
   - 70 for a 80 bu potential and
   - 40 lb N per acre for a 60 bu potential.
   

For more information on nitrogen rates refer to http://corn.osu.edu/story.php?setissueID=283&storyID=1684