CMEG Crop Management Extension Group

Field Crop News

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

May 24, 2006    Vol. 06:05

IN THIS ISSUE:

Weather Outlook — Paul Knight

The pendulum is about to swing the other way, but there is a possible ‘fly in the ointment’ for the big warm-up on the Memorial Day weekend.

Wednesday will be mainly sunny and milder after a final frost threat in the northeast counties at daybreak. Clouds will temper the warming trend on Thursday with scattered showers mostly in the western half of the state. Humid air will be more noticeable on Thursday. Expect clouds much of the time on Friday and Saturday as dew-points reach into the 60’s.

The most likely time for thunderstorms will be Friday afternoon and evening in central and western sections and then on Saturday afternoon in the eastern counties. At this point, expect more sun than clouds from Sunday through Tuesday with rather humid conditions and daytime readings from 75 degrees in the northern mountains to near 90 degrees in parts of the southeast. Average rainfall for the next week will be 0.50-1.00” or about 70% of normal.

Cold Conditions and Crops — Erick De Wolf, Greg Roth and Dwight Lingenfelter

Corn:

The cool and cloudy weather conditions that we have experienced during the last week or so have really resulted in some of the yellowest corn I have seen in a long time.  This is usually due to limited chlorophyll synthesis and will likely clear up with a few of the warmer days forecast for the end of the week.  This extended cool period may predispose the corn for some stalk rots later in the season, so that will be something to monitor in the future.

Purpling in corn also is possible, and has shown up in some fields. This is usually associated with a restriction in root growth caused by cool soils or other stress factors.  Plants accumulate anthocyanin pigments in the leaf tissues when sugars can’t be readily translocated to the roots.  I think the lack of photosynthesis during the last week has limited this problem to some extent.

If the cool, cloudy weather wasn’t enough, we had some reports last night of frost damage to corn.  Joel Hunter in Crawford County reported temperatures as low as 24 degrees and frosted two leaf corn in his region.  The best advice for dealing with these fields would be to come back later in the week and assess the regrowth and conditions in the crown.  Look for clean white crown tissue, which would be indicative of healthy plants.  Exposure to several hours of temperatures below 28 degrees can be lethal to corn in some cases.  I expect that most of this corn will recover, but some fields may experience some stand loss due to the extended amount of stress.

Some emerged soybean fields in the cotyledon stage also were hit by frost, but initial indications are that they are not showing the injury observed on corn.  The best advice for these fields also is to return in a few days to a week and examine the seedlings for injury symptoms and the conditions of the cotyledon buds, which could be killed even though the cotyledons appear ok.  For an excellent review of the symptoms associated with these frost issues on corn and soybeans, review an article from Purdue University, “Symptoms of Low Temperature Injury to Corn and Soybean”.

Once an assessment is made on the surviving plants, then consider replanting options using our guidelines in the 2005-2006 Agronomy Guide.

Wheat:

The growth stages of wheat in Pennsylvania range from boot in the north and flowering or early grain fill in the southeast.  Wheat at these growth stages are particularly vulnerable to frost damage and the low temperatures on Monday and Tuesday may spell trouble for some wheat fields in the state.  Once wheat has reached the boot stage of development temperatures at or below 28 degrees for two hours or more, freeze injury can result.  At the heading or flowering stages of growth, temperatures at or below 30 degrees for two or more hours can result in damage.

Symptoms of frost damage at these growth stages include floret sterility, head entrapment, and leaf discoloration.  Symptoms of freeze injury will not become obvious for 3 to 5 days.  After this time we may see entrapped heads become distorted as the stem continues to elongate.  Sterile sections of the developing heads may remain green but will not fill grain normally.  These sections of the head may appear sunken relative to florets that have normal grain development.  In severe cases, the damaged head tissue may become white.  This symptom is most common on the tips of the head but lower or middle sections may also be affected.  In some cases the entire head may be damaged.  Yield loss from will be minimal if only the top florets are damaged, otherwise yield loss is proportional to the percentage of head tissue that is killed. Yield loss from distorted heads or minor leaf injury is usually minimal.

Weeds:

Weed control is less than ideal in many corn fields, even where preemergence herbicides were previously applied. Some things to keep in mind as you assess weed control and make decisions on postemergence treatments:

Although weeds may be escaping preemergence treatments, the weed population in these fields is going to be much lower than fields where no herbicides have been applied. So, the timing of postemergence application is probably less critical with regard to minimizing yield loss due to weed-crop competition. However, postemergence grass herbicides in corn are most effective when grasses are not more than 3 to 4 inches tall, and application timing should be based on the size of grasses in the field (unless grasses are absent from the weed population).

Injury from postemergence corn herbicides is more likely when the health of the corn plants is less than ideal, as in a number of corn fields where corn is currently struggling. We generally advise delaying postemergence applications until the crop resumes active growth, when it is better able to metabolize herbicides (a few days of sunshine will really benefit the crop and reduce the potential for herbicide injury).

The risk of injury from ALS-inhibiting herbicides is increased during periods of cool weather, such as we are experiencing this week. We have occasionally observed an increase in the frequency of stunting, yellowing, and internode shortening (stacking) when ALS inhibitors were applied to corn under cool conditions. We suggest avoiding postemergence applications to corn for a few days based on the following: 1) the health of the corn crop is less than ideal; 2) cool and cloudy conditions can increase the risk of herbicide injury; and 3) weed growth should be minimal under the cool weather conditions.

On a final note, corn development under this spring’s weather conditions may result in somewhat shorter plants for a given growth stage, compared to other years. In other words, a plant in the V5 stage might be only 13 inches tall this year, whereas in other years it might be 16 inches in height or taller. Staging corn properly is important to reduce the risk of injury from ALS-inhibiting herbicides (Accent, Option, Hornet, etc). Labels of products containing an ALS-inhibitor generally allow broadcast application through the V5 or V6 stage of corn development, and also specify a maximum corn height.

Renovating Grub-Ravaged Pastures with Summer Annuals — Mena Hautau and Mark Madden

Growers around the state are reporting poor growth and performance of established pastures and the talk of the farm is that white grubs are widely to blame.  Grubs are dirty white, soft-bodied insects with a brown head and six well-developed legs.  The size of the grub varies by species and age.  The species may include the Japanese beetle, Asiatic garden beetle, masked chafer, European chafer, oriental beetle, as well as any of the May or June beetles. Refer to the May 10 Field Crop News for the article “Grubs in Pastures and Hay Fields” posted by Delbert Voight.

Renovating a pasture may be necessary if sufficient damage to the existing sward is extensive. With forages in short reserve as a result of the dry conditions in 2005, a producer may want to consider a summer annual crop that will provide forage this summer.

Rotating with a summer annual may give the producer an opportunity to break the pest cycle or the ability to reestablish a more favorable pasture species the following year. Tillage will physically destroy grubs or bury them into the soil profile.

There are several summer annuals to consider such as corn, soybeans, sorghum sudangrass and millet. Follow the summer annual crop with an early fall planting of permanent pasture. Consider the opportunity to adjust soil pH and fertility when you rotate.

For more information about summer annuals, read Paul Craig’s post that follows, “Forage Supplies Are Tight” or read the publications on emergency forage, “Summer Annual Grasses for Supplemental or Emergency Forage” and “Producing Summer Annual Grasses for Summer or Emergency Forages” at http://www.forageinfo.com/pubs/Topics/Summer_Annuals/Emergency_Forages/

Forage Supplies Are Tight — Paul H. Craig

Across the southern regions of Pennsylvania, forage producers have noted a significant reduction in yields of first cutting of all forage crops. Prior to harvest, forage supplies were already short due to the drought in 2005. The potential for limited supplies of forage has increased interest in the production of small grain silages and summer annual crops.

When late season forage production is considered, the first crops that come to mind are sorghum type plants, including grain sorghum, forage sorghum and sorghum sudangrass hybrids. Previously considered an “emergency” forage crop, the introduction of highly digestible, high yielding forage sorghums and sorghum-sudangrass crosses have introduced many forage producers to a crop that is more than an emergency crop. These crops will perform well in dry conditions but have the potential to produce high quality forage under optimum growing conditions too. Late May to mid June is an ideal time to establish these forage crops for both dry and normal growing conditions.

Grain sorghums and forage sorghums are planted for a one harvest system. Sorghum sudangrass hybrids are multiple harvest crops. Select for high forage quality characteristics. Hybrids with brown midrib (BMR) genetics are preferred for highest forage quality but management is important too. Plant anytime after soil temperatures are above 60 degrees for rapid seedling development. These crops are adaptable to conventional and no till production.

For sorghum sudangrass hybrids seed at 65 to 70 pounds of seed per acre and plant at a depth of ½ to ¾ inch. Do not plant too deep! Rarely will weeds out-compete the development of sorghum sudangrass hybrids and because of multiple harvesting, weeds are rarely problems thus no herbicides are needed after establishment. Start with a clean or burned down seedbed at planting. High fertility levels are necessary for optimum yields. Phosphorous and potassium requirements are similar as for corn silage. Sorghum-sudangrass hybrids are also significant users of nitrogen. One hundred pounds of nitrogen is recommended at planting and a second application of 50 to 100 pounds of nitrogen following first cutting is recommended for high yield potential. Base this second application on moisture levels and yield potential.

Establishment up to July 4 is possible in the southern portion of PA. Many growers stagger plantings to reduce harvest risks. Harvest stands at 3 to 4 feet height. These plants grow rapidly and soon after reaching 3 feet can reach 5 feet or more. Some observers have noted 4 to 7 inches of growth per day at this time. Do not let these stands get ahead of your planned cutting height. Under optimum growing conditions, second cutting may be ready for harvest in as little as 22 - 25 days. Mow at a cutting height of 4 inches to encourage rapid regrowth. Do not harvest stands less than 2 feet in height.

Sorghum sudangrass hybrids contain high levels of moisture and will require wide windrow management to ensure rapid dry down. The shorter the time period, from mowing to ensilage, the higher the quality of the forage that is produced. This crop is an excellent choice for haylage or baleage production.

Don’t Confuse Trade Names and Application Rates — Bill Curran

This time of year is always hectic with planting, fertilizing, making hay, killing weeds, and maintaining some quality of life.  With so many crop protection chemicals on the market, it’s becoming increasing easy to make mistakes that can have lasting impacts.  The wrong product or rate can leave illegal residues, kill or injure the crop this year and next, not control the pest, and certainly waste valuable dollars.  Many products have similar names or label or container colors, yet are quite different in what they are intended for.  We recently heard about an individual that applied a glyphosate product instead of the intended dicamba (Clarity) product to a new grass forage seeding.  Needless to say that reestablishment was in order.  Define vs. Distinct, Accent vs. Ally, Classic vs. Cimarron, Option vs. Osprey, ounces vs. pints vs. quarts, and the list goes on.  So, as hard as it is this time of year, slow down, measure twice, and saw once.  A little extra attention will go a long way.

Yellow Flecks on Wheat — Erick De Wolf

There have been multiple reports of pale green or yellow flecks appearing on upper leaves of wheat this season. I have seen these symptoms in numerous fields myself and also observed them in our variety trial here at Rock Springs.  The intensity of the symptoms appears to range from tiny yellow flecks to more than 30% of the leaf tissue affected. The intensity of the flecking varies with variety and previous crop. I have incubated samples of leaves with this affliction and found no evidence of fungal or bacterial pathogens.  I also have sent a sample away to be tested for eight common viral diseases of wheat, but the results indicate none of these viruses are present. Soil tests and management records for these fields suggest that the crop is not lacking nutrients.  At this point it would appear that these symptoms are the result of a physiological disorder known as genetic fleck or chlorotic fleck.

This chlorotic fleck has been reported in several surrounding states and is often associated with periods of cool and cloudy weather followed by bright sunny days or large swings in temperature during the spring. We have certainly had both weather patterns in PA this spring. I have not been able to find any information about potential yield losses, but it seems logical that yield loss will be proportional to the severity of the flecking.  I believe losses will be minor in all but the most severe cases of this disorder.  My biggest concern on this issue is that some growers may mistake this disorder as early symptoms as powdery mildew or other leaf diseases and make a potentially unneeded fungicide application.  The bottom line...Take some time to carefully evaluate symptoms and potential causes before making a fungicide treatment to wheat.

Field Day Announcement — Using Cover Crops for Ecological Weed Management

Three diverse field days will be offered this summer focused on managing cover crops and weeds.  We will emphasize ecologically-based weed management aimed at prevention and maximizing beneficial processes within the farming system.  Programs will be offered at the Penn State Agronomy Farm near State College on June 13, 2006, Village Acres organic farm in Juniata County on June 28, and at Cedar Meadow Farm in Lancaster County on July 14.  These programs are part of the Pennsylvania Association for Sustainable Agriculture (PASA) 2006 Farm-Based Education Series and involve Penn State, PASA, and other organizations.  Pest Management CEU’s will be offered for those that are Certified Crop Consultants.  For more information, contact Heather House at PASA at 814-349-9856, ext. 7 or register online at www.pasafarming.org

Contributors: State Extension Specialists: Douglas Beegle, Erick De Wolf, William Curran, Marvin Hall, Dwight Lingenfelter, Gregory Roth, Department of Crop and Soil Sciences.  Paul Knight, Department of Meteorology.  Extension Educators: Paul Craig (Dauphin), Andrew Frankenfield (Montgomery), Donald Fretts (Fayette), Jere Wingert (Franklin), Mena Hautau (Berks), Joel Hunter (Crawford), Mark Madden, (Sullivan), David Messersmith (Wayne), Dwane Miller (Schuylkill), Thomas Murphy (Lycoming), J. Craig Williams (Tioga).

Editor:  Mena Hautau, Penn State Cooperative Extension-Berks County, CCA

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.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Penn State Extension is implied. 

This publication is available in alternative media upon request.

The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, or veteran status.  Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA  16802-5901, Tel 814-865-4700/V, 814-863-1150/TTY.