CMEG Crop Management Extension Group

Field Crop News

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

May 10, 2006    Vol. 06:03

IN THIS ISSUE:

Weather Outlook — Paul Knight

Very good news! After one more mild, dry day on Wednesday, most of the state will have showers on each day from Thursday through next Tuesday. In fact, rainfall during the six day period will average between 0.75–1.50 inches. Parts of northeast Pennsylvania should receive 2 to 4 inches and some other sections may also get as much. Temperatures will drop well below seasonal levels as sunshine will be infrequent (only 12 hours during that 6 day stretch) and a steady wind from the east will direct ocean-cooled air across Pennsylvania. The most likely periods for steady rain will be from Thursday afternoon (west) to Friday evening (northeast) and again starting Monday late afternoon and ending on Tuesday. There’s a chance that as low pressure stalls across the region that rain will continue into the middle of next week, resulting in a flood risk, particularly in eastern Pennsylvania. No return to above average temperatures are expected before May 20th at the soonest.

Weed Control and Drought — Bill Curran

Managing weeds with herbicides in a drought can be challenging.  All soil applied herbicides require rainfall for mobilization.  In general, a minimum a 0.5 inch is necessary for adequate activation, but this does depend on soil moisture conditions at application and some herbicides require greater amounts than others.  Although not the only factor, water solubility of the herbicide can make a difference.  For example, atrazine is relatively low in solubility, Dual and the other grass herbicides are in the middle, and products like Banvel are high in solubility.  The amount of rainfall necessary to move the soil applied herbicides into the weed seed germinating zone can differ based on the chemical characteristics including water solubility.  The bottom-line is that a good 0.75 to 1 inch of rainfall will mobilize all the products. 

When herbicides have been applied for ten days to 2 weeks with little or no rain following application, some weeds will germinate and emerge and not be controlled.  This is particularly a problem with grasses like the foxtails.  However, most herbicides that were applied in the last two weeks are still present and waiting for an activating rainfall.  The good news is that weed seeds also require moisture and will wait until warm temperatures and rainfall arrive before they germinate and emerge.  The next good rainfall will not only bring on the weeds, but will also help mobilize the herbicides.  The grassy weeds that have already emerged as well as bigger (1 to 2 inch) broadleaves may not be adequately controlled even after we receive rain.  Some of the newer pigment inhibiting herbicides including Balance Pro or Radius and Lumax or Lexar can provide some “reach-back” on the broadleaves and some grasses as long as they are relatively small.  You might as well wait and see what the soil applied program does to the weeds before turning to the next control option.

Mechanically incorporating the soil applied herbicide can offset the need for mobilizing rainfall.  This requires thorough incorporation using two passes with a field cultivator or finishing disk or a combination tool.  Some rainfall is still necessary after mechanical incorporation to fully mobilize the herbicide.  Less aggressive tools such as rotary hoes and tine weeders can help control emerging weed seedlings (white thread stage) by physically disrupting their progress, but they do little for activating soil applied herbicides.

Finally, if the weather continues to remain dry and you have not yet sprayed your corn, save the soil-applied program for another day or see if what you already purchased can be used early POST in corn.  You still need to apply a burndown program in no-till, but a number of soil-applied herbicides can be applied to emerged corn in combination with a POST grass herbicide such as Steadfast, Option, or Equip or with glyphosate in Roundup Ready corn or Liberty in Liberty Link corn.  An appropriate early POST application to V-2 corn when the weeds are small can be successful and is not as reliant on timely rainfall.  Check the latest herbicide label to ensure it is allowed.  Although not completely up to date, see our Field Crop News article from April, 2004 titled What Can be Done if the Corn is Up and a Pre Herbicide Wasn't Applied?.

Precut Rye Straw — Andrew Frankenfield

Rye is being mowed for straw around much of PA at this time. The challenge this year is the lack of rain to bleach the rye.  Some rye has dried enough to bale but is still green and needs a shower.  Most growers mow just prior to flowering to maximize the yield, but also want to get it off in time to double crop soybeans or sweet corn.  Unlike hay, rye needs a rain shower or two to bleach it from green to yellow or almost white in color.

Since the straw market has increased in recent years, more farmers are looking for ways to bale more straw and have it earlier in the season.  Rye does both of those things and more.  Rye is relatively easy to establish and can be planted later than wheat and yields more straw. A 1½ – 2 ton yield would be average, but it can yield over 3 tons per acre.  It is an excellent nutrient scavenger and a good cover crop to protect the soil over winter after soybeans or other low residue crops like vegetables are harvested.

Rye is mowed after heading but before the seed develops.  It is tetted once or twice while it dries and needs a couple tenths of an inch of rain to bleach, then it is raked and baled.  Most of the market in Southeastern PA is small square bales for mulch on construction sites, but it makes great bedding for livestock and horses.  Precut rye straw is longer, cleaner, and brighter than wheat straw, making it favored bedding at livestock shows and fairs.

For more information on precut rye straw see the article in Hay and Forage Grower “Nothing But The Best”.

Corn Stand Assessment — Greg Roth

In general, this has been a great year for planting corn and another corn crop is emerging in many parts of the state now.  Corn planting has progressed rapidly (USDA reports 58% planted, 17% ahead of 5 year average). The generally dry soils and soil physical conditions have been especially good for no-tillers.  Tilled fields have had some reports of crusting, and some rotary hoeing has been done to try to alleviate the problems.  Also, with the dry conditions, I anticipate we will see some problems with delayed or reduced emergence this year in tilled seedbeds.  These are often associated with shallow (less than 1.5 inch) plantings.  If plant emergence is spread out by more than 1.5 weeks, these later emerging plants can have a negative effect on yields.  A good reference on this issue can be found here:  http://web1.msue.msu.edu/msue/iac/disasterresp/Crops/nrc344.pdf

Another issue to be on the lookout for this year would be soil insect injury to seedlings.  We are receiving lots of reports of grub activity this year.  Delaware’s IPM specialist Joanne Whelen reported last year that she found good control of grubs in many situations with Poncho 250 and Cruiser seed treatments, but they did note a few failures under high pressure conditions.  On germinating corn seeds, grubs will feed on the fine roots, which interferes water and nutrient uptake. This leads to symptoms of wilting and purpling of the stem.

Assessing corn stands early in the season allows replant decisions to be made on a timely basis.  In crusted fields, one judgment call is whether to count the sickly or injured plants in your population count.  If plants haven’t emerged after a week or 10 days of the original stand, I would tend not to count them in the stand assessment for replanting.  Use the tables in our Agronomy Guide http://agguide.agronomy.psu.edu/cm/sec4/sec4toc.cfm for an assessment of the yield potential of fields with reduced stands and replanted corn.  We provide two tables, one for high yielding fields and one for lower yielding fields (<125 bu/acre) where lower populations are adequate.

Grubs in Pastures and Hay Fields — Del Voight

Grubs are continuing to affect grass hay. Here is a discussion of the management of grubs by Kathy Flanders an Alabama Entomologist.  While their mild environment is different they deal with these issue more than we do in the North.  To view the entire publication, ANR-991, with photos follow this link. http://www.aces.edu/pubs/docs/A/ANR-0991/

Four types of grubs are common in grass pastures. They are the larval stages of green June beetles, May beetles in the genus Phyllophaga, southern masked chafers (occasionally northern masked chafers), and Japanese beetles.  The green June beetle is an increasing problem in Alabama. The grubs of this beetle rarely feed on grass roots, but their extensive burrowing activities disrupt the root-soil contact. Once the soil around the roots is loosened, grazing cattle can easily uproot the plants. When green June beetle grubs are present, the pasture will seem to have thinned out.  There will be areas where the soil is pulverized, and you may see 0.5-inch-diameter tunnels that the grubs have made. The green June beetle grub is stout, it has short legs, and it crawls on its back. This distinguishes it from other white grubs which have longer legs and typically curl up into a C-shape when disturbed. Grubs typically come to the surface at night to feed on organic matter.

Green June beetles have one generation per year. The green and gold adults fly in the daytime and are a familiar sight in July and August. Eggs hatch in August and early September. Best time to spray is in September and early October. They reach 2 inches by late fall or early spring. Pastures in high-risk areas should be checked for green June beetle grubs. High-risk pastures include (1) those in which manure has been applied as fertilizer, (2) fields on sandy or light soils, and (3) fields in fruit-growing regions. This is particularly important if winter forages will be interseeded. The tunneling activities can tear up young plants.  Green June beetle grubs tend to move along a drill row, pushing out seedlings as they go. The best way to scout for green June beetles is to look for tunneling holes or for thin areas in pastures. Then, use a shovel to carefully dig out a square-foot surface area to a depth of 10 to 12 inches. Sift the soil carefully, looking for the grubs. Check at least five samples per field. Treat fescue with an insecticide (see Table if more than two to four grubs per square foot are found. Bermudagrass should be treated if four to six grubs per square foot are found. Fields where winter annuals are planted should be treated if more than one green June beetle grub per square foot is found. See Extension Circular ANR-991 for more details on green June beetle biology http://www.aces.edu/pubs/docs/A/ANR-0991/.

May beetles, chafers, and Japanese beetle grubs feed on the roots of pasture grasses. They can prune the roots so intensively that the pasture sod can be rolled back like a carpet. In some years, pastures may not recover from this severe pruning. At least 2,000 acres of pasture were lost to May beetle grubs in 1985–1986.  Smaller populations of grubs can reduce plant stand, allowing invasion by broadleaf weeds. The broadleaf weeds, in turn, make it easier for Scarab females to get down to the soil to lay eggs, causing further damage to sod. White grubs occur in mixed populations. It is rare that an infestation consists of a single species. If all species had similar life cycles, feeding impact, and response to insecticides, management decisions could be made without identifying species. However, this is not the case. Currently, there are no insecticides registered on pastures that are effective against May beetles, Japanese beetles, and southern masked chafers. Cultural practices to promote vigorous growth can help the grass sod recover. Weed control may be necessary for 1 to 2 years after damage has occurred.  Japanese beetles, southern masked chafers, and green June beetles have a single-year life cycle and their larvae are most damaging in late summer and fall. May beetles have 1- to 3- year life cycles, and their larvae are actively feeding except during the coolest months of the year.

Alfalfa Weevil — Mena Hautau

A combination of dry weather and a mild winter has produced alfalfa weevil infestations at levels that producers should evaluate if and when they need treatment. Many fields in southeast Pennsylvania have heavy feeding where the leaves are skeletonized and exhibit a “frosted appearance”.

In these cases, producers should be harvesting alfalfa now and checking plant regrowth. If the larvae are crawling back on to the stems and refeeding, an insecticide treatment is necessary. If there is no feeding, there is no reason to treat the stand.

In areas of the state where alfalfa weevil has yet to be active, take time now to scout fields and asses activity. The publication, “A Pest Management Program for Alfalfa in Pennsylvania”, can be found by searching this site http://agmap.psu.edu/Publications/ ,has scouting and economic injury threshold tables, where a decision is made based on plant height, the value of hay and the price of insecticide.

You can also view the progress of the Alfalfa Weevil development at http://www.ento.psu.edu/extension/field_crops/predictionmaps.htm

For insecticide recommendations, go to the Penn State Agronomy Guide, Forage Pest Management, Table 2.6-11.

Wheat Disease Update — Erick DeWolf

Wheat in southern counties is now moving through the boot stags of growth and will be heading during the next 7 to 10 days.  Growth stages in the central and western counties of Pennsylvania ranges from flag leaf emergence to boot stage of growth.

Dry conditions have kept powdery mildew in check in most locations this year, and levels of powdery mildew are low in most fields.  However, over the past week I have observed several fields in the central region that are showing significant amounts of powdery mildew.  Fields should be checked this week to make sure that powdery mildew is not building up to significant levels.  Research indicates that the most effective fungicide applications are applied between the flag leaf emergence and early heading stages of growth.  Fields with 2 or more pustules of mildew on the second leaf (located just below the flag leaf) are candidates for a fungicide application.  Fungicide products including Tilt, Quilt, Headline and Quadris will all provide good control of the powdery mildew.  It is worthy of note that labels for Tilt and Quilt fungicide was changed this year, allowing application of this product until full head emergence in wheat.

We are planning a field day at Rock Springs on May 30 this year to review a number of key topics in winter grain production: new wheat and barley varieties, diseases, weed control, seed certification issues and the potential for organic small grain production.  We’ll also be looking at some hard wheat, hulless barley, spelt and triticale in our tests. It’s a great opportunity to get some pictures of all these crops.   The event will start at 10 a.m. and the cost is $12.   For a complete brochure, visit our small grains website.

Evaluating the Risk of Wheat Head Scab — Erick DeWolf

Head scab of wheat has caused serious problems from Pennsylvania producers in recent years. The disease was wide spread in 2003 and 2004 when warm weather and frequent rains favored the reproduction and infection by the fungus that causes head scab (Fusarium).  In these years, yield in heavily infested fields in the state were reduced by 10 to 20% and the damage grain was often contaminated with the mycotoxin DON.  Wheat is most vulnerable to the disease beginning at flowering through the early stages of grain fill, and we will be entering these critical stages of growth here in PA during the next two to three weeks. 

Penn State is part of multi-state effort to develop disease prediction models that help producers and the agriculture industry evaluate the risk of disease.   These prediction models use temperature and humidity to predict conditions that are favorable for the development of the head scab fungus and are designed to predict the risk of a disease epidemic with a field severity greater than 10%.  The current risk map of PA is all green indicating that the risk of head scab is low.  This is because the cool dry weather has not been favorable for the development of the fungus.   If the weather becomes more favorable the map will become yellow or red indicating moderate or high risk of disease.  We suggest that you check the maps frequently over the next few weeks to monitor the risk of disease.  If the risk of disease increases as we approach flowering, a fungicide application may be warranted to help suppress disease losses.  You can look at the risk maps for PA and other states online at:  http://www.wheatscab.psu.edu/

Contributors:  State Specialists:  Doug Beegle, Erick DeWolf, Sjoerd Duiker, Greg Roth, Bill Curran, and Dwight Lingenfelter.  Extension Educators:  Gary Micsky (Mercer), Dwane Miller (Schuykill), Paul Craig (Dauphin), Kevin Fry (Armstrong), Andrew Frankenfield (Montgomery), Jere Wingert (Franklin), Don Fretts (Fayette), Mena Hautau (Berks), Joel Hunter (Crawford), Jeff Graybill (Lancaster), Dave Messersmith (Wayne), and Mark Madden (Sullivan).

Editor:  Kevin Fry

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

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