CMEG Crop Management Extension Group

Field Crop News

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

June 20, 2006    Vol. 06:09

IN THIS ISSUE:

Dates to Remember

SARE Soil Quality Workshop, Rodale Institute — July 5, 6, and 7. Contact Mary Barbercheck meb34@psu.edu for additional information.

Agronomic Weed and Plant Disease Management Research Tour — July 11. See article below for additional information.

2006 Penn State Agronomic Field Diagnostic Clinic — July 18 and 20. Visit our website at http://cropsoil.psu.edu/extension/clinic.htm for more information.

For Additional CMEG Activities, Please Visit the Calendar of Events: http://www.events.psu.edu/cgi-bin/cal/webevent.cgi?cmd=opencal&cal=cal209&

Weather Outlook — Paul Knight, PA State Climatologist

While the humidity levels will be lower on Wednesday, readings will rise well above seasonal values (into the upper 80’s and low 90’s again). A surge of humid air on Thursday will be preceded by scattered thunderstorms, some in the morning in the west. It will be a duller day and noticeably stickier. A cool front pushing southward from the Great Lakes will bring showers and thunderstorms on Friday. While it will stay humid, clouds will keep readings in the 70’s to mid—80’s. The front will stall just south of Pennsylvania during the weekend leading to cloudy skies in southern sections along with a few showers on Saturday. Most places will see some sunshine on Sunday, though a slow—moving disturbance will bring clouds back across the region later Sunday with showers following by Monday. A few spots may receive more than 3 inches of rain, but most sections will get an inch or so. The front may stay in the region until Wednesday with additional showers, but warm, humid conditions are likely to return later next week.

Corn Sidedress Nitrogen Management Tips — Doug Beegle, Soil Fertility & Nutrient Management Specialist

There are a number of ways that corn can be sidedressed. The most common is to dribble UAN solution on the soil surface between the corn rows using drop tubes or hoses over the nozzles. Dribbling reduces plant injury and also reduces volatilization losses compared to broadcast applications. Dribbling between every row is preferred, but N can be dribbled between every other row if it is precisely placed in the middle between the rows. Sprayers with 20” nozzle spacing with drop tubes can also be used but expect a little more injury because sometimes the tube will be on the row.

Another common method is to broadcast urea over the top of the corn. There is a greater potential for injury with this method, however the injury that occurs rarely hurts yield. Also, there is usually greater volatilization loss with broadcast urea.

Incorporate urea or UAN solution to minimize the loss of N by volatilization. If you are going to be cultivating, timing the N application right before the tillage will provide a major benefit. If you are in no—till, timing the application right before a soaking rain will do a good job of incorporation. Also, in no—till surface banding of UAN (dribblilng) instead of spraying achieves a significant amount of the benefit that you would get from incorporation. Losses are greatest if the urea is broadcast on a moist soil surface after a rain when evaporation is high. A urease inhibitor can also help reduce volatilization losses from surface applied urea.

Crop Residue Survey Shows Dramatic Increase In No—Till — Sjoerd Duiker, Soil Management Specialist

Over the last two weeks I completed the Centre County crop residue survey with the help of USDA—NRCS and the Centre County Conservation District. It was for sure an eye opener! We traversed some 130 miles through the County and observed whether farmers used no—till (>30% residue), mulch till (tilled, but more than 30% crop residue left to meet conservation tillage definition), reduced till (15-30% residue cover) or conventional tillage (<15% residue cover). About every ½ mile we stopped and determined tillage system at both sides of the road (wherever there was farmland). Whereas it was straightforward in the case of corn and soybeans, it was really the wrong time of the year to look at tillage systems for alfalfa and small grain establishment, so those estimates are not as good as those for the summer crops.

I was unable to determine when the last crop residue survey had been completed in Centre County. It is likely that estimates submitted to the Conservation Technology Information Center in recent years were mere adjustments of previous years. The 2004 survey indicated that no—till was used on 30% of the acres, 13% mulch till, 19% reduced tillage, and 40% conventional tillage. Estimates of 2004 showed that no—till was used on 37% of corn, 17% of soybeans, 21% of winter small grains and 20% of new forage stands.

The 2006 survey indicates that no—till use has increased dramatically compared to previous estimates. Our data show that 67% of corn and 56% of soybeans was no—tilled. Mulch till was used on 1% of corn acres and 7% of soybean acres, and reduced tillage on 8% and 10% of corn and soybeans, respectively. Conventional tillage was used on 25% of corn acres and 27% of soybean acres. No—till did not seem to be commonly used for small grain establishment: we estimated conventional tillage was used on 80% of small grain acres. Of the forages we estimated that no—till was used on between 30—50% of newly established stands.

I learned a lot more about tillage use in Centre County by doing this survey. For example, it seems almost impossible to meet conservation tillage requirements (>30% residue cover) without using no—till. I also learned that the Amish in Centre County are starting to use no—till customarily. In fact, some of the best no—till stands we saw were on Amish farms. It was a surprise for me to see so many soybean acres still planted in conventionally tilled fields. We saw beautiful no—till corn planted in corn or soybean stubble and old hayfields. On the other hand, we also saw some awful results with no—till: soybean fields overgrown with weeds such as dandelion and dock, a corn stand in incompletely killed alfalfa sod, terrible no—till stands because of lack of planter penetration, uneven corn emergence, hairpinning, and lack of slot—closure. Next week I hope to be able to share some pictures of my adventures with you.

What this survey shows me is that no—till is catching on in our Commonwealth, and previous estimates may need thorough revision. I would therefore encourage all agronomy extension educators to team up with Conservation District and USDA—NRCS personnel and complete a residue survey in your County. It is not hard and you learn a lot about tillage system use in your County. It also helps you determine how you can best assist producers be more successful in their crop production. For Centre County, we definitely need to focus on getting those no—till skills under our belt to make success the norm. It seems less necessary to convince our growers of the benefits of no—till, because most of our farmers are already using it.

POST Horseweed and Lambsquarters Control — Bill Curran, Weed Management Specialist

Horseweed/marestail continues to be a common concern in the NE. Glyphosate—resistant horseweed 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. A survey in southeastern Pennsylvania conducted during the summer of 2005, showed that a number of populations of horseweed were in fact glyphosate resistant. This summer, horseweed is even more apparent in no—till fields in PA and every indication is that this weed, resistant or not will give our farmers more trouble particularly in no—till soybeans. Purdue, Ohio, and Illinois published an excellent joint fact sheet last year 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.ces.purdue.edu/extmedia/GWC/GWC-9-W.pdf

Waiting to control horseweed POST in soybeans is not a good strategy. We suggest earlier spring application with 2,4—D and/or cloransulam (FirsteRate) in the program (watch out for ALS resistance where FirstRate is not effective) or fall or spring applied residuals (Valor, Python, Canopy EX or Canopy, etc.). If you find horseweed in emerged soybean now and you suspect glyphosate resistance, add 0.3 oz/acre FirstRate and/or increase the glyphosate rate. Most glyphosate resistant horseweed will respond favorably to higher glyphosate rates, but small increases in rate (i.e. 25%) generally do not make a difference. Double (2X) and 3X rates will increase control and glyphosate can be applied to Roundup Ready soybeans as an in crop application (cracking through flowering) at up to 3 quarts per acre (4 lb active ingredient/acre or 3 lb acid equivalent(ae)/acre). This should be used as a rescue, not as a planned approach.

Common lambsquaters Erratic common lambsquarters control with glyphosate is also on the rise. Several states including Delaware, Virgina, and Pennsylvania have reported lamsquarters control problems, particularly in soybean. In soybean, the most consistent control of common lambsquarters will result from use of PRE herbicides or a combination of PRE plus POST herbicides. Growers should avoid use of total POST herbicide programs for control of common lambsquarters in soybean, particularly where there has been a history of control failure.

Soybean herbicides with POST activity on common lambsquarters should be applied to small common lambsquarters plants that are less than about 4 weeks old. Glyphosate should be applied at a rate of 0.75 to 1.5 pounds ae per acre (1 to 2 qt/acre of a 3 lb ae/acre) when plants are less than 6 inches tall. Use a minimum of 1.1 pounds acid equivalent per acre for plants approaching 6 inches and 1.5 pounds acid equivalent per acre for plants greater than 6 inches tall. A second application of glyphosate may control plants that survive an initial application and also greatly reduce weed seed production, which may help slow the development of resistant populations. However, this approach is strictly a “rescue” treatment and is not sound for reducing selection for glyphosate—resistant weeds.

Review of In—Season Alfalfa Herbicides — Dwight Lingenfelter, Crop & Soil Sciences

Although there is nothing new for weed control in alfalfa, we wanted to provide you with a listing of some herbicide choices to consider for in-season weed control.

Butyrac 200 2E (2,4—DB) — Apply 1 to 3 qt/A when weeds are actively growing and no more than 3 inches tall. 2,4—DB is more effective on lambsquarters, pigweed, ragweed, and mustard species and weaker on common chickweed, henbit, and most perennials. It has no activity on grasses or nutsedge. Do not apply if temperatures are above 90ºF during or shortly after application. 2,4—DB is not labeled for use on mixed stands.

Gramoxone Max or Inteon (paraquat) — May be applied at 0.7 pt/A of Gramoxone Max (or 1 pt/A Inteon) plus a surfactant to established or first year stands with 2 inches or less regrowth. Apply immediately after alfalfa has been removed for hay or silage. Do not treat more than 5 days after cutting. The weeds must be actively growing at the time of application. Gramoxone will desiccate any green tissue including actively growing alfalfa. Gramoxone is effective on low to moderate infestations of annual weed species. Do not use on mixed stands.

Poast Plus 1E (sethoxydim) — Poast Plus controls annual grasses and suppresses perennial grasses in seedling and established alfalfa. Apply Poast Plus at 1.5 to 2.5 pt/A plus crop oil concentrate to actively growing grassy weeds. However, Poast Plus should be applied to small grasses. Tank mix with a broadleaf herbicide such as 2,4—DB to increase the control spectrum. Do not used on mixed stands.

Pursuit 70DG or 2AS (imazethapyr) — Pursuit may be used for weed control in seedling or established alfalfa. Apply Pursuit at 1.44 oz 70DG or 4 fl oz 2AS plus adjuvants to actively growing weeds 1 to 3 inches in height. Pursuit is effective on many annual br oadleaves and grasses including small chickweed, mustards, pigweed, smartweed, velvetleaf, foxtail, and panicum. It is weak on lambsquarters, ragweed, and crabgrass. Pursuit may be used on established alfalfa-grass mixtures.

Raptor 1AS (imazamox)— Raptor is similar to Pursuit and may be used for weed control in seedling or established alfalfa. Apply Raptor at 4 to 6 fl oz plus adjuvants to small, actively growing weeds and before alfalfa regrowth reaches 3 inches tall. Raptor generally provides somewhat better control of lambsquarters, ragweed, and panicum compared to Pursuit. Do not use on alfalfa-grass mixes.

Select 2E (clethodim) is a postemergence grass herbicide that is similar to Poast. Apply Select at 6 to 8 fl oz/A plus necessary additives. Select provides good control of many annual grasses and can suppress perennial species. Tank mix with a broadleaf herbicide such as 2,4—DB to increase the control spectrum. Do not used on mixed stands.

Glyphosate can be used over—the—top in Roundup Ready alfalfa varieties. The typical use rate is 0.75 lb ae/A which provides control of many weed species. Do not used on mixed stands.

Low pH Still a Problem — Doug Beegle, Soil Fertility & Nutrient Management Specialist

Again this year one of the more common soil fertility problems our Crop Management Extension Group has encountered around the state has been low pH. This has resulted in a number of stunted crops with no possibility for in-season correction to the problem. The symptoms on the plants in problem fields include a combination of symptoms such as: purpling, striping, pale color, stunted growth, and poor root growth. In many fields, low pH appears as a patchy problem, however, it can often impact a sizeable portion of the field.

There are two main impacts of low pH on plants. First, at pH below 5.5 root growth is severely restricted by aluminum toxicity. Plants with reduced root growth are not able to adequately take up necessary nutrients, especially immobile nutrients like P and Mg. This is why we see the combination of different symptoms. To make this worse, low pH also reduces availability of many nutrients in the soil.

Even if limestone could be applied to the growing crop, it would probably not react fast enough or deep enough to result in a major benefit to the crop. The main thing is to soil test and apply the recommended limestone as soon as possible after harvest in the fall to begin correcting the problem for next year.

The bottom line is that we need to make liming a higher priority. Almost 1/3 of the soil tests in PA have a pH less than 6.0 and over 13% are less than 5.5. Soil pH has a tremendous, although not often as dramatic, impact on many aspects of crop production. Regular liming based on soil testing to maintain the soil pH in the 6.0 to 6.5 range is critical.

A field pH test kit can be very useful for diagnosing pH related problems in the field. If a low pH is found, a regular soil test should be run to determine the amount of limestone that is required to correct the problem.

Pre-Sidedress Soil Nitrate Test (PSNT) on Sweet Corn — Doug Beegle, Soil Fertility & Nutrient Management Specialist

The PSNT has been used effectively to help improve N management on field corn for a number of years. Some farmers have asked about its application to sweet corn. Dr. Joseph Heckman at Rutgers University has done research on using the PSNT on sweet corn and found that it does a good job of assessing N status and improving N recommendations on sweet corn, especially in fields that have a history of manure application. The procedure for the PSNT on sweet corn is the same as for field corn ie. sample when the corn is about 12” tall, sample to 12” depth, dry the sample quickly and thoroughly (same day) before sending it to the lab. The interpretations developed from the Rutgers research are different than for field corn. They are using 25 ppm NO3-N for manured soils and 30 ppm NO3-N for unmanured soils as the critical levels. Above this level no sidedress N is recommended. Below this level, N is recommended based on the actual test level. The recommendations and more details on using the PSNT for sweet corn can be found in the Rutgers Coopertive Extension Factsheet by Heckman and Prostak which is available at: http://www.rce.rutgers.edu/pubs/publication.asp?pid=FS760

Early Season Corn Crop Update — Greg Roth, Grain Crop Management Specialist

Overall our corn crop is in good condition, with development at average or slightly ahead of average due to the early planting and generally above average heat units. The dry conditions during last week should not have a major impact on the yield potential of the crop. Rain in many areas this week should cause the crop to resume rapid growth. During this stage of development corn producers should pay attention to crop characteristics that can provide some important feedback.

As the crop progresses through these later vegetative growth stages, it is growing rapidly and the demand for nutrients, especially N and K is high. At the six to seven leaf stage corn in fields with inadequate N supplying capability will begin to lose leaf color and develop N deficiency symptoms on lower leaves. This symptom is the inverted yellow “V” on the lower leaves.

Fields with an inadequate K supply or a restriction on the development of roots will show K deficiency symptoms that include yellowing on leaf margins on lower leaves. No—till fields with sidewall compaction, compacted soils, fields with marginal K soil test levels and fields experiencing some root pruning due to rootworm damage may show stunted areas with these symptoms. To diagnose these issues consider soil testing good and poor areas and digging plants and washing the roots to look for some of the diagnostic symptoms of these crop problems.

According to our pest development website (http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu#), corn rootworm development is moving along rapidly and third instar larva and their damage should be present in some fields. Now is a good time to begin to assess the efficacy of corn rootworm treatments. Insect pressure overall has been greater than average and it will be interesting to see how much rootworm damage we encounter this year. Treatments can be assessed by digging some representative plants and using a node—injury scale developed by Iowa State (http://www.ent.iastate.edu/pest/rootworm/nodeinjury/nodeinjury.html) that rates roots on a 0—3 scale that assesses the number of nodes that are destroyed by the larva. The relationship between the ratings and yield is variable— under difficult conditions yields can be reduced with ratings as low as 0.25. None of the insecticides provide 100% control, so often some damage is present.

During this period of late vegetative growth, the number of kernel rows and kernels per row are set. The number of kernel rows is thought to be established by the V8 stage, while the number of kernels per row is set by the V12 to V15 stage. Stress factors such as drought, hail, or those discussed above can limit ear development and limit the yield potential of the crop.

Armyworm Hotspots — Jeff Graybill, Lancaster County Extension Educator and Dave Messersmith, Wayne County Extension Educator

Locally high populations of true armyworm have been observed recently in portions of southeastern PA. While not approaching the widespread “outbreak” we had back in 2001, growers should be on the alert for this pest as larvae develop in northern and western PA over the next few weeks.

Armyworm damage is observed most frequently in no—till fields that were sod the previous year. The first symptoms will be ragged feeding on the top leaves with wet, brown pellets in the area. The culprit usually can be found hiding well down in the whorl or at ground level under clumps of grass. Conventional—plated corn may also be damaged by caterpillars that originate in a nearby small grain or grass hay fields prior to migration.

Corn fields likely to be attacked should be checked every few days during the first 2 weeks of June. Control is recommended when 10% or more of the plants are infested. A number of insecticide sprays can be used as a rescue treatment. Consult your Agronomy Guide for products and rates or visit the Agronomy Guide on the web at: http://agguide.agronomy.psu.edu/

Register Now for the Rock Springs Agronomy Weed and Plant Disease Tour — July 11, 2006

Attend the Annual Agronomic Weed and Plant Disease Management Research Tour at Penn State— July 11, 2006 at the PSU Agronomy Research Farm, Rock Springs, PA (Meet at the Agronomy Farm, Rock Springs, Rt. 45 west of State College). A number of experiments will be showcased and available for viewing including new corn, soybean, pumpkin, and snapbean herbicides plus the latest information on herbicide resistance, and cover cropping and weed management research. Also hear an update on the latest crop disease developments including soybean rust and white mold from this year's wheat disease research. Pest Management CCA CEU's will be available.

Agenda:
8:30 — 9:00 am — Registration
9:00 am —12:00 noon — Tour
12:00 noon — 1:00 pm — Catered lunch

Registration for this event will be $15.00 and includes lunch and a tour book. Please pre-register by Friday, July 7 with Lisa Crytser by phone (814-865-2543) or email her at lac8@psu.edu for a registration form.

Contributors:University Park Faculty/Staff: Marvin Hall, Doug Beegle, Erick DeWolf, Sjoerd Duiker, Greg Roth, Bill Curran, Mary Barbercheck, Paul Knight, Dwight Lingenfelter and Ron Hoover. Extension Educators: Kevin Fry (Armstrong), Andrew Frankenfield (Montgomery), Joel Hunter (Crawford), Jeff Graybill (Lancaster), Mark Madden (Sullivan), Dave Messersmith (Wayne) and Dwane Miller (Schuylkill).

Editor:Dave Messersmith, Penn State Extension, Wayne County

Real time pest and heat unit activity: http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu#

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

Readers can subscribe electronically to this newsletter at the Field Crop News Web site.

If you have problems subscribing or wish to cancel your subscription, please contact Lisa Crytser by e-mail at lac8@psu.edu or by phone at 814-865-2543.

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