May, 2000

Volume 16, No. 1

MARYLAND WEED REPORTER

The rains have stopped and the sun is out! Growers are out tilling ground and planting corn. Spring is here! With that will come our usual compliment of questions and problems. What are some of the things we can anticipate?

Corn

With the wet weather we've had and growers anxious to get on their land, compaction seems to be a yearly issue we're faced with. In particular, side-wall compaction appears more often than not. Here, the corn plant will set roots in the slot opened by the front coultar. Because the soil is somewhat wet and compacted, the plants' roots have a hard time penetrating the hard soil around it and only sets roots in the furrow. Thus, you end up with a weakened plant with a limited root system. If the press wheel on the planter didn't adequately close the furrow, it leaves the seed exposed to chemical exposure from herbicide applications made after planting. Materials such as Prowl, Basis and Python (Python is in Bicep Magnum TR, Broadstrike/Dual, and Hornet) can get down in the furrow, and create injury problems as the seed germinates. Even products such as Dual, Frontier, Harness/Surpass, etc., can get down in the furrow and cause the typical buggy-whipping associated with this chemistry.

Soybeans

I have also seen the side-wall compaction issues discussed above in soybean plantings. With a limited root structure, soybeans are susceptible to injury problems as well from preemergence herbicide applications. Another injury problem I have seen in soybeans concerns soil pH. In areas of the state where lime-amended sludge has been applied, the soil pH may exceed 7.0 or higher. Some of the preemergence herbicides such as Canopy or Canopy XL are slowly broken down under these conditions. Because of this, they are much more available for plant uptake, resulting in injury. In soybeans, you may see root pruning, a shortening of the internodes, and purpling of the soybean leaves. Sometimes, carryover to corn may occur resulting in similar problems.

These are just a couple of the issues that I commonly see this time of the year. I'll address a few more below as I review some of the newer products and techniques you should be aware of.

Small Grains - What's New

Wheat - Ryegrass

Hoelon is still our only choice for control of annual ryegrass in barley and wheat. We are looking at a number of other options that we hope to get labeled in the near future. They are as follows:

Wheat - Annual Bluegrass

Annual bluegrass continues to become a problem in small grains. Rough stalk bluegrass is becoming more widespread as well. While we haven't examined any preemergence applications for annual bluegrass control in wheat or barley, we have examined some postemergence applications and their ratings are as follows:

Postemergence

Finesse - poor

Glean - poor

Maverick - good

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Wheat - Bulbous Oatgrass

Bulbous oatgrass continues to spread across areas of the state and creat havoc in small grains. The only product we've had success with in the control of bulbous oatgrass in wheat is Maverick.

Postemergence

Maverick - good

Maverick

Maverick is not yet labeled for use in Maryland. Unfortunately, the current label states,

"Do not plant any crops other than fall or spring wheat for a period of one year following Maverick herbicide application." Maverick is a sulfonylurea herbicide and carryover to double-crop soybeans is a concern. We have planted STS soybeans after fall and spring applications of Maverick and observed no carryover effects. Hopefully we'll have this product for use in control of these above mentioned grassy weeds in the near future. While I haven't mentioned it, Maverick also provides good postemergnece control of a variety of brome grass species as well.

No-till corn

With the wet weather we've had coupled with the lateness of the season, it would appear that we will see more no-till corn this year. When tackling the above grasses, keep the following in mind the following:

When no-tilling into annual ryegrass you will need at least 1.5 qt/A of Roundup to kill it. Gramoxone is ineffective. Accent will control it postemergence in standing corn.

When no-tilling into bulbous oatgrass, you will need at least 1.0 qt/A of Roundup or 2 to 2.5 pt/A of Gramoxone to kill it.

Corn - What's New

While we're on the subject of no-till corn and Roundup, let's review some of the different formulations and companies marketing glyphosate.

The Magnum's

Dual II and Bicep II are being replaced by Dual II Magnum and Bicep II Magnum. What was in the original Dual was a mixture of two isomers. The more active isomer was isolated and became Dual II Magnum. This same isomer is in Bicep II Magnum. BASF is in the process of doing the same thing with Frontier. Frontier is actually made up of two different isomers. The more active isomer has been isolated and will be the next generation of Frontier. At this point, all Frontier (and Guardsman) products will be sold off in the 2000 cropping season. Starting in 2001, Frontier will be replaced with its more active isomer under the trade name Outlook. Since DuPont also sells Frontier as the package-mix with atrazine under the trade name Leadoff, expect to see some name changes in the DuPont product line as well.

New names in corn - preemergence

Axiom AT - Axiom (flufenacet + metribuzin) + atrazine.

Balance - a new preemergence broadleaf and grass herbicide labeled last year in areas outside of the mid-Atlantic region. It is a bleaching-type herbicide.

Degree - Degree contains the same active ingredient as Harness but is a new encapsulated formulation of acetochlor designed to extend soil residual control of annual grass species. Monsanto claims the release of acetochlor from the encapsulation is triggered primarily by soil temperature. As the soil temperature warms up, the product becomes available to control weeds, while under cold conditions, it remains unavailable.

Degree Xtra - is a premix of Degree and atrazine.

Epic and Epic Lite - Balance + flufenacet.

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New names in corn - postemergence

Accent Gold - Accent + Matrix + Python. One rate - 2.9 ounces per acre. Targeted for areas outside of the Delmarva region.

Aim - labeled last year for postemergence broadleaf control in corn. One rate - 1/3 ounce per acre with a cost of about $2.50 to $3.00 per acre. Works on small annual broadleaf weeds like lambsquarters, pigweed, morningglory, nightshade and velvetleaf. Also looking at it as a burndown additive in no-till.

Basis Gold - this one has been out awhile, but I thought I'd mention it once again. It's a mixture of Accent + Matrix + atrazine. You need to add 2 to 4 ounces of Banvel/Clarity per acre if you're going after triazine-resistant broadleaf weeds. Labeled at 14 ounces per acre up to 12 inch corn. A lot of interest in this product this year!

Celebrity Plus - Accent + the sodium salt of dicamba (same one in Distinct). One rate - 4.8 ounces per acre; labeled from 4 to 24 inch tall corn.

Distinct - labeled last year for postemergence broadleaf control in corn - annuals and perennials.

Apply up to 6 ounces per acre from 4 to 10 inch corn; 4 ounces per acre from 10 to 24 inch tall corn.

Liberty and Liberty ATZ - for use only on Liberty-Link or GR corn. Liberty ATZ is a blend of Liberty + atrazine.

Lightning - excellent postemergence control of honey-vine milkweed. Use only on IMI corn, now called Clearfield or Clearfield production system.

NorthStar - Beacon + the sodium salt of dicamba (same one in Distinct). Labeled from 4 to 20 inch corn; directed spray up to 36 inch corn. One rate - 5 ounces per acre.

Pinnacle - finally labeled for corn. Excellent post control of pigweed and common lambsquarters. Apply early - 2 to 6 leaf corn. Needs surfactant. One rate - like soybeans - 1/4 ounce per acre

Preemergence control of triazine-resistant weeds in corn

Products to consider:

Basis - 1/3 to ½ ounce per acre (add your other preemergence herbicides with it).

Bicep Magnum TR - has flumetsulam (Python) in it.

Broadstrike/Dual - may be phasing out - has flumetsulam (Python) in it.

Prowl - add to your regular preemergence herbicide program - I've found it inconsistent

Python - add to your regular preemergence herbicide program. Hornet is also available - a blend of Python + Stinger.

Postmergence control of triazine-resistant weeds in corn

Products to consider:

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Soybeans

A lot of discussion about Roundup-Ready soybeans the phytotoxicity or chlorosis that the "imitator" (Touchdown 5) can create. Both products contain the same active ingredient, N(phosphonomethyl)glycine. The difference between the two herbicides is that Roundup is the isopropylamne (IPA) salt while Touchdown is the trimethylsulfonium (TMS) salt. Both work at the same site of action and have similar uptake and translocation in plants.

Touchdown is more likely to cause a foliar response in soybeans than is Roundup. It is unlikely that this minor burning induces a response that persists long enough to influence the yield. To avoid this burn we recommend adding 1 to 2 ounces of Basagran per acre.

New names in soybeans

Backdraft - mentioned earlier. A mixture of Roundup + Scepter. Labeled primarily as a preemergence herbicide. Rates run from 1.5 to 2.0 quarts per acre.

Boundary - Dual II Magnum + metribuzin. Will replace Turbo. Preemergence - but will not control triazine-resistant broadleaf weeds.

Domain - a different ratio of flufenacet + metribuzin than is in Axiom.

Extreme - mentioned earlier. A mixture of Roundup + Pursuit. Labeled both preemergence and postemergence at 3.0 pints per acre.

FirstRate - labeled last year, both preemergence and postemergence. Only postemergence on the Delmarva at this point in time. One rate - 1/3 ounce per acre. Good on many broadleaf weeds such as cocklebur, morningglory, ragweed and velvetleaf. May be weak on pigweed and common lambsquarters.

Outlook - mentioned earlier. The more active isomer that is in Frontier.

Information Technology

I use the above term lightly to address some of your needs. As the season progresses, we all get busy. Sometimes you need to get hold of me in an urgent fashion, but can't reach me in the office. What to do? There are a number of ways to reach me;

Office: 301-405-1329 - there is a voice mail message system. I pick up messages at least three times a day when I am away from the office.

Mobile: 301-412-9858 - this is my truck phone which also has a voice mail message system.

Home: 301-490-4959 or 301-490-3754 - early morning (between 7:00 a.m. and 8:00 a.m.) is best. Evenings and weekends are OK until 10:00 p.m. As with my office and truck, there is a voice mail message system on both numbers which I check periodically when I'm on the road.

FAX: 301-490-3754 - You may need to punch 55 after dialing and before FAXing.

Sometimes you may have a weed to identify. Make a photocopy of it and FAX the image to me. It doesn't always work, but sometimes it does.

EMAIL: rr24@umail.umd.edu - During the season I may not check it as often as I want.

Yet, email is very useful if you have a digital camera. You can send me an image of the weed you want identified or injury problems you may encounter in the field.

That's it for now!

Until next time,

Ronald L. Ritter

Extension Weed Control Specialist

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