Field Crop News

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

April 1, 2005    Vol. 05:01

IN THIS ISSUE:

Mark Your Calendar

Weather Outlook

Production

Pest Management

Editorial

Welcome to the first edition of Field Crop News in 2005! The Penn State Crop Management Extension Group (CMEG) is committed to offer you timely information about the full range of crop management issues, including variety selection, tillage, planting, equipment choices, liming and fertilization, weed, pest and disease management, soil management, manure handling, harvesting and storage and more. This first issue does not have reports from the regions. Those will appear in future issues of FCN. We hope this will be a great year for everyone and look forward to hearing from you! Short letters to the editor (max 100 words) can be directed to me (swd10@psu.edu) for inclusion in FCN.

Many greetings,

Sjoerd W. Duiker
FCN Editor, 2005/06
Soil Management Specialist

WEATHER OUTLOOK

After a few spring-like days, expect a more wintry feel to the atmosphere as a very cool air mass spreads over the state this first weekend of April. Wet snow may accumulate a few inches in the western mountains later Saturday. The chill will moderate on Sunday, though with an active breeze and clouds giving way to sunshine. The first full week of April will bring a warming trend which should culminate at mid-week with readings in the 60's and low 70's. No rain is expected from April 3-6. A complex front will approach the state late in the week with another round of showers and perhaps a few thunderstorms. Rainfall will be generous, between a half and one and half inches, though not uniform.

The second week of April (7-15) will start cool and cloudy with gusty winds and scattered showers. Expect moderate to near seasonal levels by mid-month, but no prolonged warm periods before the third week of April.

Overall precipitation is expected to average above to much above normal in April and temperatures below normal. The initial outlook for the summer period (Jun-Aug) favors a cooler than average summer with at least one month with well above normal rainfall.

Paul Knight, pgk2@psu.edu
Pennsylvania State Climatologist

PRODUCTION

Is Your Planter Ready?

Newly planted corn

The quality of your corn stand will largely depend on planter performance. An irregular stand can easily cost you 10% of your yield. Planter performance is especially critical in no-till because of high penetration resistance, crop residue at the soil surface, and a rough soil surface. Inadequate planting will result in uneven seed depth and plant spacing. Hairpinning is common if coulters and row cleaners don't work properly. Although it is getting late, you still have a chance to get your planter maintenance done. Here are some tips to prepare your planter for the new season.

  1. Level planter. By placing a level on the toolbar you can easily check if it is horizontally aligned. If you notice that the unit is either hanging back- or forwards, you need to lift or lower the hook-up to the tractor. This is essential to get accurate seed depth placement.
  2. Planter unit alignment. Look across your planter units from the side. Are they all at the same height? If one unit is either up or down compared to the others, it needs some work. A common problem is that some bolts are loose. You should not be able to easily lift up your unit.
  3. Diameter of seed opener disks. Check operator manual to determine acceptable disk diameter. Stick two business cards between the openers and move them as close together as possible. The space between them should be 3" or more, depending on your planter type. If opener disks are worn too much you will get a "W" shaped seed slot instead of the desired "V" slot.
  4. Diameter of coulters. Check the diameter of the coulters, and replace them if needed. You should adjust the depth of worn coulters that are still usable.
  5. Pressure on firming wheels. Check the pressure on the firming wheels. The downward pressure should be adequate, but not too high (check operator manual).
  6. Depth wheels. Depth wheels should run tight. Change washers from in- to outside (or vice versa) of depth wheel if necessary.
  7. Depth of seed placement. Place the planter on a concrete floor to measure the difference between the bottom of the depth wheels and slot opener, and adjust to the desired depth. The front coulter should be set at the appropriate depth (no deeper than the seed slot openers).
  8. Alignment of individual components. Take a rope and pull it straight from the front coulter to the back press wheels. The firming wheels, slot openers, and coulters should all be in line.
  9. Wear on chains and sprockets. Check the chains that drive meters and their sprockets. If they are worn too much they need to be replaced. Excessive wearing of these parts will cause skips and doubles.
  10. Clean metering units. Take metering units apart. Remove dirt and clean the hood with soapy water (no kerosene, diesel or oil should ever be used in metering units!). Check for broken fingers in a finger-pickup meter, check the brush that wipes of excess seeds, and see if a groove has formed in the chromium house of the metering unit. If the groove becomes large, and if brushes wear, you have a greater likelihood of doubles. Brushes need to be replaced at least every other year.
  11. Elevator belt in metering unit. The belt (in finger pick-up meters) should be flexible, not have cracks in it, and should be clean. Clean with soapy water and let it dry before putting it back in. Put the metering unit back together. The rubber belt should be placed back in the right direction, or your meter will malfunction. You can lubricate with graphite (NO OIL or WD-40).
  12. Calibrate meter. It is highly recommended to take your finger pick-up metering unit to the dealer to have it calibrated. Take a bag of your own seed with you, and give him the correct speed at which you'll be driving.
  13. Vacuum/air units. If you have a vacuum or air meter, check for leaks and appropriate vacuum or air pressure.
  14. Check your fertilizer unit. Hang a bucket below the tube of the unit, and do a test run of 175 feet in the field. Weigh the fertilizer in the bucket, multiply by 100, and you have the fertilizer you'll put on in pounds per acre (at 30" row spacing). Adjust as needed.

Sjoerd Duiker, swd10@psu.edu
Soil Management, Crop and Soil Sciences

SMALL GRAINS FIELD DAY

We are planning our 2005 Small Grains Field Day on June 7 from 10 am to 3 pm at the Agronomy Research Farm at the Russell Larson Research Center. This will be a good opportunity to review wheat and barley varieties in our trials, view hulless barley, spelt and hard wheat lines, and review disease and crop management issues. We also plan to address topics on seed testing and milling industry issues as well. Cost will be $10 which will include lunch. More details will be available on our website http://smallgrains.psu.edu/ soon.

Greg Roth, gwr@psu.edu
Grains Crop Management, Crop and Soil Sciences

AGRONOMIC ASPECTS OF SOYBEAN MANAGEMENT AND SBR

In general, it is too early to make many recommendations regarding the impact of cultural practices on soybean rust. It is uncertain how the rust will interact with the environment and our existing cultural practices and whether any change in management would be warranted.

For example, delaying soybean planting into late May or even later may increase disease severity because the earlier planted crops may have some potential to avoid a late infestation of soybean rust. However, soybeans flower primarily based on photoperiod, so often flowering dates are not greatly impacted by planting date. Double cropped soybeans may be at more risk in our environment because of the delayed planting issue. However, this effect could vary depending on when the rust arrives and the weather conditions during disease development.

There seems to be some uncertainty regarding the potential of wider rows in managing soybean rust. Most soybeans in Brazil are planted in 18 inch rows and they are managing the rust well with this spacing. Wide rows (>14 inches) allow for more penetration of the fungicide into the canopy, less opportunity for wheel track damage and more opportunity for rapid drying of the lower canopy. But given that we are unsure that we will even see soybean rust this year, we would be hesitant to make any row spacing changes that might impact yields without the rust.

Another potential issue of concern is the effect of wheel track damage on soybean yields. In studies that have examined this effect, wheel track damage is dependent on the stage, tire width and other factors. Jim Beurlein, agronomist at Ohio State has estimated that a late August spray application with a 60 foot boom and ten inch tires in drilled soybeans could result in a yield loss of about 2.1%, or just over a bushel in 50 bushel per acre soybeans. These losses can be reduced and some saving in seed costs can be achieved by using a skip row pattern where rows in the sprayer tracks are not planted.

One effect often noticed in strobilurin fungicide applications to soybeans is a delay in maturity of the crop. Eventually, we may find that we need to adjust our maturity recommendations for soybeans if fungicide applications become common.

Another agronomic issue is whether other applications of insecticides or fertilizer can be added to fungicide applications to provide an additional increase in yields. If compatible, there may be an opportunity to reduce application costs and hence increase the probability of a response to these inputs, but they should be based on sound science and pest management principles. In general, soybean responses to foliar fertilizers have been small and inconsistent.

In summary, there may be some agronomic changes to soybean management that may be necessary as a result of soybean rust, but it is generally too early to consider substantial changes in management at this point.

Greg Roth, gwr@psu.edu
Grains Crop Management, Crop and Soil Sciences
Erick DeWolf, edd10@psu.edu
Corn Management, Plant Pathology

ALFALFA FROST HEAVING: ASSESSING THE DAMAGE

Alfalfa frost heaving, where the repeated freezing and thawing of the soil causes the alfalfa crown to be pushed above the soil surface, is common throughout Pennsylvania. Here are some answers to commonly asked questions about frost heaving of alfalfa.

Is there anything that can be done to push the crown back into the soil?
No. While many people have tried cultipackers or lawn rollers to push the heaved alfalfa crown and root back into the soil, there is no data suggesting that any of these techniques are beneficial.

How much frost heaving is needed to justify rotating an alfalfa field into another crop?
The answer to this question depends on the severity of the heaving. Consequently a complete evaluation of the stand is needed. Depending on when the crowns were elevated above the soil, all of the crown buds could have been frozen and the plant is essentially dead. Look for green growth coming from the crown and count the number of these crowns per square foot. If, on average, there are five or more live crowns per square foot then the stand is probably worth keeping at least through the first harvest.

Will the alfalfa that is still alive remain productive throughout the season?
Frequently, alfalfa plants that have heaved only a small amount (one inch or less) still have their tap root intact and can remain productive. Caution must be used to insure that the crown is not removed when cutting the alfalfa during harvest. These crowns will also receive additional damage from wheel traffic with each harvest which kills additional crown buds and exposes the crown to more diseases.

Fields in which alfalfa crowns have heaved a lot (greater than 1 inch) are strong candidates for rotation into another crop. However, if there are more than five live plants per square foot then it may be best to take an early first harvest prior to rotating. Plants with their crowns elevated to this height generally have their tap root broken and will be more susceptible to drought stress (low production) this summer. In addition, crowns at this height can be cut off during the first harvest leaving the root with no growing points for herbage regrowth.

How can I tell if the alfalfa is worth keeping after the first harvest?
As mentioned earlier, the number of crowns per square foot is one method for determining alfalfa stand productivity. However, better than the number of live crown is the number of stems per square foot. As the stem number declines to 40 stems or less per square foot alfalfa fields begin to loose profitability and should be rotated out of alfalfa.

Will the heaved alfalfa survive another winter?
Unfortunately, the crown buds (from which spring growth comes from) of heaved alfalfa plants will be exposed to colder temperatures next winter because the crowns will not be insulated by the soil. Exposure to freezing temperatures next winter may kill the crown buds. If an alfalfa field with heaving this spring is kept until next spring it should be monitored very closely with anticipation that it should be planted to another crop.

Marvin H. Hall, mhh2@psu.edu
Forage Management, Crop and Soil Sciences

DEPTH AND CONTACT CRUCIAL IN FORAGE ESTABLISHMENT

More failures in forage establishment are the result of improper seeding depth than any other cause! If seeding depth isnÕt correct then you might as well not bother to plant. A forage seed has a very small supply of stored energy to support the seedling until it emerges and begin making its own energy. Seeds placed too deep are not likely to emerge. Seeds placed on the surface or in a loose or cloddy seedbed often do not have adequate seed-soil contact. In those cases, dry soil conditions following seeding usually result in desiccation and death of the seedlings. Optimum seeding depth varies with soil type (sandy, clay, or loam), soil moisture, time of seeding, and firmness of seedbed but generally is not more than 1/4 inch deep.

Ensuring that seeds are placed at the proper depth requires a firm seedbed. It is extremely difficult to accurately regulate seeding depth if the soil is soft and fluffy. Here is a rule-of-thumb regarding soil firmness "On properly firmed soil, an adultÕs footprint should not be deeper than 1/4 inch". Forage seeds should be covered with enough soil to provide moist conditions for germination but not so deep that the shoot cannot reach the surface.

Forage seeds need to absorb at least their own weight in water before germination begins. Unless the seed has been planted in saturated soils, the water generally moves into the seed from surrounding soil. Adequate seed-to-soil contact ensures maximum water movement into the seed in the shortest time. Field situations (cloddy or loose soil) that do not promote good seed-to-soil contact generally result in extended germination periods and sporadic emergence. The use of press wheels on a grain drill or culti-packing after seeding can improve seed-to-soil contact.

Marvin H. Hall, mhh2@psu.edu
Forage Management, Crop and Soil Sciences

PEST MANAGEMENT

2004 FIELD TRIALS RESEARCH REPORT AVAILABLE ON-LINE

The 2004 Field Trials Research Report is available for viewing as a pdf document at www.weeds.psu.edu/research.html#report,/a>. The report contains a summary of the herbicide evaluation trial results for corn, soybean, and forage weed control trials.

HERBICIDE RESISTANT WEED UPDATE

Herbicide resistant weed problems continue to increase both in Pennsylvania and across the Midwest. I attended a meeting last week in Indianapolis where my extension colleagues reported some updates on existing problems or new resistant weeds.

glyphosate resistant horseweed

Glyphosate-resistant horseweed. Of course glyphosate-resistant horseweed/marestail continues to be on the forefront in terms concern and also acres impacted. The region of impact extends from the East Coast to the state of Missouri. The occurrence of the resistant biotype is increasing particularly in the eastern Corn Belt and ALS-resistance is also present in some of these populations. Bill Johnson and his colleagues at Purdue University as well as Mark Loux and Jeff Stachler at Ohio State University are doing a great job monitoring the situation in Indiana and Ohio and trying to get a handle on control and management. Purdue University has a website that focuses on the latest information available for horseweed management viewable at www.btny.purdue.edu/weedscience/marestail/index.htm. In addition, Purdue, Ohio, and Illinois weed scientists recently published a new fact sheet titled "Biology and Management of Horseweed (Extension Pub ID-323) which provides some good background on biology and management. It's available in hard copy from Purdue University or on-line at http://www.btny.purdue.edu/weedscience/marestail/ID-323%20HorseWeed.pdf

Closer to home, the problem continues to spread into new areas on the Delmarva and in Pennsylvania. We identified our first occurrence in Chester County, PA from a control failure in 2003 (Field Crop News Vol. 04:08) and have not had the kind of rapid spread or evolution that has been seen in some other states. Certainly, our more diverse crop rotations have helped because we know that continuous no-till Roundup Ready soybeans or cotton acreage is a driving factor. Still, we had several reports of suspected resistant horseweed last summer particularly in the Southeastern part of the state. We are finishing up a greenhouse assay where we tested populations from two separate farms in Lehigh County with up to 3X rates of glyphosate. Both populations survived the 3X rate, so the resistant weed biotype is most certainly in Pennsylvania, but it spreads or evolves more slowly than in states to the South or West. Early spring application with 2,4-D, including cloransulam (FirstRate) in the program (watch out for ALS resistance) or other fall or spring applied residuals (Valor, Python, Canopy EX, etc.), spring tillage, and crop rotation are all considered as possible control options. The weed science group at Penn State University as well scientists at other institutions are studying various aspects of glyphosate resistant horseweed management, so discovery of new knowledge focused on biology and management alternatives will be provided as it becomes available.

glyphosate resistant common ragweed

Common ragweed. Another glyphosate-resistant weed recently identified in Missouri is common ragweed. It was officially reported back in December, 2004 by Reid Smeda from the University of Missouri. Thus far, it has only been identified in a single field that was no-till for 13 years in a soybean-wheat-double crop soybean rotation with reliance on glyphosate for weed control. The resistant biotype displays about a 10X level of resistance to glyphosate. Although not confirmed, another incidence of glyphosate-resistant common ragweed has been reported in Arkansas. In addition, ALS and triazine-resistant common ragweed have been reported in other states. Expect to hear more about this resistant weed problem in the future.

Common lambsquarters. Finally, erratic common lambsquarters control with glyphosate appears to be on the rise. Several states including Delaware and Virginia have reported lambsquarters control problems, particularly in soybean. Although no one has yet declared officially that they have a glyphosate resistant biotype, colleagues at Ohio State University are fairly certain they have the problem. Ohio State's Jeff Stachler reported last week that lambsquarters populations in at least six counties are suspected to be glyphosate resistant and that farmers should not rely on glyphosate alone for post weed control in soybeans. Mark Loux and Jeff Stachler discussed the situation in Ohio State University's 2005-01 C.O.R.N Newsletter (http://agcrops.osu.edu/). At the very least, ensure that a sufficient rate of glyphosate (0.75 lb ae/acre) is POST-applied to common lambsquarters with an appropriate adjuvant system (NIS plus AMS) at a time when lambsquarters is generally easily controlled (less than 6 inches tall).

Glyphosate stewardship to avoid or limit herbicide resistance continues to be an issue for university weed scientists and the users of glyphosate. The potential increase in Roundup Ready corn adoption as well as the introduction of other Roundup Ready crops such as alfalfa will certainly increase the potential for glyphosate resistant weeds. Management guidelines based on IPM principles (i.e. multiple tactics) can certainly slow or maybe even prevent the evolution of glyphosate or other resistant weeds. At the extension specialist meeting last week, it was decided that we would produce a series of regional educational materials providing management guidelines for glyphosate resistance and management for potential problem weeds. Stay tuned for the completion of those materials.

ALS-resistant weeds. Finally, ALS-resistant weeds continue to increase in Pennsylvania and elsewhere. ALS herbicides include Accent, Harmony GT, Option, Permit, Pursuit, Raptor, Steadfast and others and are frequently used in most of our major field crops in the Northeast. We have reported the presence of ALS-resistant smooth pigweed and shattercane in Pennsylvania in previous newsletters. New cases of ALS-resistant pigweed are being reported and we are particularly concerned about ALS-resistant shattercane in corn, where alternative chemical control strategies are limited. Last summer, we encountered a giant foxtail control problem in Lancaster County where POST ALS control programs had been used for several years in corn. We are currently running a greenhouse assay on the foxtail population and preliminary evidence suggests that we may have our first case of ALS-resistance in Pennsylvania in this species. I'll provide more information once we are certain.

In summary, herbicide resistant weeds are on the rise. In planning your weed management program this year remember that frequent use of any herbicide class or family can lead to resistance. Herbicide families or classes of greatest concern in the Northeast include the triazines, ALS, ACCase, and now glyphosate. Primary management strategies include rotation of herbicides with alternative modes of action, use of effective tank-mixtures targeting problem weeds, and incorporating effective cultural and mechanical control strategies in the weed management program. Consider herbicide-resistance in your weed management program.

Bill Curran, wcurran@psu.edu
Weed Science, Crop and Soil Sciences

WHAT'S NEW FOR AGRONOMIC WEED CONTROL - 2005

Labeled Products - CORN

Lexar 3.7SC (Syngenta) is a premix that contains mesotrione (Callisto), s-metolachlor (Dual II Magnum) and atrazine. It is similar to Lumax, but has a higher rate of atrazine and a lower rate of s-metolachlor. The typical use rate in soils with less than 3% organic matter and regardless of the tillage system is 3 qt/A Lexar. (This rate would be equivalent to 1.38 pt/A Dual II Magnum, 5.4 fl oz/A Callisto, and 1.3 lb atrazine.) If soils have greater than 3% organic matter, use 3.5 qt/A. Like Lumax, Lexar is primarily a soil-applied (or early post) herbicide that controls a number of common broadleaf and grassy weeds including lambsquarters and pigweed (both triazine- and ALS-resistant), velvetleaf, ragweed, smartweed, foxtails, crabgrass, fall panicum, and yellow nutsedge. The additional atrazine in Lexar, compared to Lumax, improves control of cocklebur, annual morningglory, prickly sida, and giant ragweed. Do not apply this product more than 14 days prior to planting, or to field corn greater than 12 inches tall and before grassy weeds emerge. There are no insecticide restrictions when applied preemergence, but be cautious of restrictions with early post-applied Lexar if OP or carbamate insecticides are used. Corn, soybeans, small grains, and sorghum may be planted the spring following application of Lexar. Alfalfa and all other crops may be planted after 18 months.

Callisto and sweet corn. Syngenta is still waiting for EPA to approve mesotrione for use in sweet corn. It was hoped that Callisto would have a label for sweet corn during 2004, but that did not happen. If EPA grants an approval soon, applications of Callisto to sweet corn may be allowed during the 2005 growing season. If Callisto is labeled for use in sweet corn, Syngenta hopes to have Lumax and Lexar approved as well. Once approved, these newer herbicide options could be a good fit for helping to manage weeds in sweet corn in our region.

Other Notes - ATRAZINE UPDATE

Atrazine was recently re-registered by the EPA after a 10-year review. For the most part, only a few changes will affect producers in our area, including some updates regarding personal protective equipment (PPE) requirements and an increase in time between atrazine application and harvest. For field corn, do not graze or harvest for forage within 60 days of application and do not harvest sorghum as a forage within 60 days if applied pre and 45 days if applied post. All manufactures and sellers must attach a special sticker to atrazine-containing products that alerts the buyer to use the product in accordance with the new supplemental labeling standards.

Labeled Products - SOYBEAN

Canopy EX 29.5WDG (DuPont) is a premix of chlorimuron (Classic) and tribenuron (Express). It will be primarily used for fall or early spring burndown and some residual control of common winter annual weeds prior to planting soybeans in no-till or conservation tillage fields. Classic EX can be applied from 1.1 to 3.3 oz/A and the spray solution must include either COC or NIS. For best burndown results, the addition of 2,4-D ester is recommended. It will provide control of numerous winter weeds including common chickweed, purple deadnettle, henbit, shepherdspurse, yellow rocket, pepperweed, bittercress, speedwell, and dandelion. For fall treatments, apply anytime after early October while weeds are still actively growing but before ground becomes frozen. Do not apply Canopy EX within 45 days of soybean planting. Be cautious of crop rotation restrictions Ð 3 months for small grains and pasture grasses, 9 months for field corn and sorghum, 12 months for alfalfa and clovers, and 18 months for sweet corn. With the introduction of Canopy EX, it is expected that DuPont will phase out Canopy XL [chlorimuron + sulfentrazone (Authority)]. Canopy XL has been an effective herbicide for soybeans and its loss will leave several holes. Unlike Canopy XL, which contains two herbicide modes of action (ALS + PPO), Canopy EX contains two ALS inhibitors. ALS resistant weeds continue to increase in prevalence and new soybean products are few in number. Hopefully, other effective multiple mode of action products will enter the market place in the future.

Select Max 0.97EC (Valent) is a new clethodim product which has some new adjuvants in the formulation which improve grass control compared to the old Select formulation. Although it controls many annual and perennial grasses, its primary use will be in Roundup Ready soybeans to control volunteer Roundup Ready corn varieties. Use 8 to 12 fl oz/A for volunteer corn from 4 to 24 inches tall. No additional surfactants are needed if it is tank-mixed with a glyphosate product that is already fully loaded with adjuvants. Select Max will initially be marketed in the Midwest, however some may eventually be here in the Northeast.

Labeled Products - SMALL GRAINS

Osprey 4.5WDG (Bayer CropScience) Osprey is a new ALS-inhibitor herbicide that contains mesosulfuron. Osprey is labeled for use in wheat and in our region it will primarily target annual ryegrass control, including Hoelon (ACCase) resistant biotypes. It does have activity on annual bluegrass and will suppress common chickweed, henbit, and pigweed. The Osprey use rate is 4.75 oz/A. Always include MSO (methylated seed oil) at 1.5 pt/A or a Òbasic blendÓ type adjuvant (NIS or MSO plus an ammonium nitrogen fertilizer source) at 0.8-1.6 pt/A. Applications should be made when weeds are young and actively growing at the 1-leaf to 2-tiller stage. To broaden weed control spectrum, Osprey may be tank-mixed with other herbicides including, Harmony Extra, Harmony GT, MCPA, Buctril, and Stinger. Soybeans can be planted after 90 days of application, corn after 12 months, and alfalfa after 10 months. Side note: Aside from Osprey, Achieve and Hoelon are other herbicide options to consider for annual ryegrass control. Hoelon has been labeled for use in wheat and barley to control annual ryegrass and other weedy grasses, but is not effective on downy brome or cheat. Hoelon may be applied pre or post in wheat, but only pre in barley. Achieve provides good control (90%) but must be applied early, before annual ryegrass reaches 1 inch tall. Applications made after this time provided poorer control. Hoelon and Achieve will not control ACCase-resistant ryegrass, which has been a problem in Maryland and Virginia.

Glyphosate and Roundup Ready issues

Glyphosate-containing products continue to be produced by many companies. There are over 50 glyphosate-containing products on the market and about 25 are considered generic brands. Some common products include Roundup, Touchdown, Glyphomax, Credit, Buccaneer, ClearOut 41, Gly Star and Extreme. Most companies offer two glyphosate products, one fully loaded with adjuvants and the other that requires some additional surfactants to improve performance. Monsanto, Syngenta, Dow AgroSciences, Nufarm, Albaugh/AgriStar, Tenkoz, Griffin, CPT, Cheminova, FarmSaver.com, are just some of the companies now labeling glyphosate. Because there are so many choices, be cautious of different formulations and use restrictions. When comparing glyphosate products and their activity always compare the pounds of glyphosate acid (or acid equivalent, ae), not just the total pounds of glyphosate (active ingredient, ai) which includes the amount of inactive salts used to formulate the product. For example, Roundup WeatherMax is formulated as a 5.5 lb ai/gallon product that contains 4.5 lb ae/gallon, whereas the new Glyphomax XRT is a 5.4 lb ai and contains 4 lb ae of glyphosate acid. Most of the generic glyphosate brands are 4 lb ai, and 3 lb ae of glyphosate acid. The glyphosate acid equivalent, the amount of adjuvant in the product, and the service guarantees are key factors that should be considered when comparing the rates and costs of various glyphosate products.

Glyphomax XRT and Durango (Dow AgroSciences) are new formulations of glyphosate that contain 4 lb ae/gallon (5.4 lb ai) and have a fully loaded adjuvant system. Both products are the same formulation, but Glyphomax XRT will be marketed as the ÒserviceÓ brand, while Durango will be the Òno serviceÓ brand. Glyphomax XRT will cost slightly more than Durango since the service policy provides greater performance assurances. A typical use rate will be 24 fl oz/A. Glyphomax XRT and Durango can be applied to Roundup Ready crops in addition to other uses. The original Glyphomax and Glyphomax Plus formulations will be phased out soon.

Touchdown Total (4.17 lb ae/gallon) and Touchdown HiTech (5.1 lb ae) are SyngentaÕs new higher load potassium salt formulations of glyphosate. Touchdown Total is more concentrated than Touchdown IQ and is fully loaded with all the necessary adjuvants; the typical use rate will be 24 fl oz/A. Touchdown HiTech does not contain adjuvants, so they must be included in the spray mixture; the typical HiTech use rate will be 1.2 pt/A. Touchdown Total and HiTech can be applied to Roundup Ready crops, with many other uses as well.

Roundup Ready alfalfa varieties are in the final stages of development and will allow over-the-top applications of glyphosate. USDA registration of RR alfalfa is expected sometime in 2005. Seed supplies will be limited initially, but there should be some fall dormancy 3 and 4 varieties for our area. The seed cost has yet to be determined, but will likely be about double the cost of a normal bag of seed and producers will need to sign a Technology Agreement. Yield and quality data are being tested at universities and other industries. Penn State is currently testing RR alfalfa for performance, yield, and other considerations such as opportunities in no-till and potential use in mixed stands.

Roundup Ready wheat. Monsanto announced it is deferring all further efforts to introduce RR wheat, until such time that other wheat biotechnology traits are introduced. Control of volunteer RR wheat and potential gene flow to a wild weedy relative helped prompt this decision. In lieu of wheat, Monsanto will invest more research and development efforts toward new and improved traits in corn, cotton, and oilseeds.

Roundup Ready crops continue to receive approval for use in other countries. The European Union recently approved Roundup Ready Corn 2 for use in food products. However, this does not mean that EU farmers can grow RR Corn 2 yet, that approval is still pending. Other countries such as Japan and Argentina are allowing the use of RR Corn 2 in food and feed products and/or for planting. Growers should contact local grain handlers regarding handling and buying policies of this grain. Worldwide, there has been over 170 million acres planted to RR crops in more than 15 countries/regions.

Glyphosate stewardship policies are being suggested and discussed by university scientists and others in the scientific community and agricultural sector. These discussions focus on preserving the future usefulness of glyphosate. Certain management practices are being recommended to avoid the selection for glyphosate resistant or tolerant weed populations. Some recommendations include: rotating glyphosate with non-glyphosate herbicides; if possible, not using more than two applications of a glyphosate-based herbicide in a field over a two-year period; using tank mixtures or alternative herbicides for burndown in RR crops that require more than one over-the-top glyphosate application; planting conventional rotational crops following RR crops and using non-glyphosate herbicides; and following good crop management practices to ensure competitive crops and including non-chemical weed control tactics when possible. As a result of the concern for weed shifts and resistance, Monsanto has changed some of its glyphosate use recommendations and Syngenta and Dow AgroSciences have both added glyphosate stewardship statements to their glyphosate containing products.

Dwight Lingenfelter, dxl18@psu.edu
Bill Curran, wcurran@psu.edu
Weed Science, Crop and Soil Sciences