CMEG Crop Management Extension Group

Field Crop News

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

July 12, 2006    Vol. 06:11

IN THIS ISSUE:

Weather Outlook — Paul Knight

A spell of hazy, hot and humid weather is expected from Thursday afternoon until next Monday. The sultry conditions will be preceded by showers and thunderstorms on Wednesday in the west and north and early Thursday in the southeast sections. Rainfall will vary from 2–4 inches in northwest and north central sections to less than a quarter of an inch in parts of the lower Susquehanna and Delaware valleys. Severe storms with damaging winds are possible in the central sections on Wednesday afternoon. Much of the time from Thursday afternoon until midday Sunday will be rain-free, though increasingly sultry. Afternoon readings will reach the middle 90’s in the Susquehanna and lower Delaware valley during the weekend. Relief will arrive in the northwest on Monday and spread across the state on Tuesday. A period of drier, cooler weather is likely during the majority of the later half of next week.

Watch Damage to Corn Silks from Beetles (Rootworm, annual grub beetles) — Del Voight

Rescue treatment for rootworm beetle silk clipping is warranted if 5 or more beetles are found per silk mass when 75% of the plants have silked and silk clipping to ¼ inch or less is observed. Rescue treatment for Japanese beetle silk clipping may be warranted if there are 3 or more beetles per silk mass and pollination has not occurred. The important thing to check for in corn at this time is whether or not the corn has pollinated. If pollination has occurred, then silk clipping by rootworm or Japanese beetles should not affect yield.  Source: Ron Hammond Ohio State University.

…And On Soybeans — Del Voight

Defoliation by beetle pests (bean leaf beetle, annual grub beetles, Mexican bean beetle) need to approach 15% in R stages and 30% defoliation at vegetative stages before treatment is necessary.  Consult this Web site for the color defoliation guide.

Flooded Corn Update — Greg Roth, Marvin Hall, Dave Messersmith

Flooded Corn Assessment

Recovery of corn from flooding across eastern PA has been variable. Some corn that was flooded only a short time (less than 24 hours) is not doing well; however other fields have recovered nicely after several days under water. One of the factors in recovery seems to be the amount of silt deposited on the plant. The more silt, the less the corn has been able to recover.  Also hot weather during and after flooding seems to have reduced the corn’s ability to survive and recover. The rate at which fields dried out after flooding, due to soil differences and other factors, may also factor into the variability in recovery we’ve seen.

In fields where there was moving water and less silt deposited, recovery has been much better. Individual corn stalks have either fully straightened or have “goose necked” back to more or less upright. End of season yield in these fields is still uncertain, but it looks promising.

Many corn fields (both flooded and not-flooded) are showing signs of nitrogen deficiency such as overall yellowing and “firing” of lower leaves. This is no doubt due to a combination of N leaching and denitrification as a result of heavy rains and prolonged wet soils.

As harvest begins, growers will also need to be alert for debris and gullies. Flood waters left behind everything from tires to trees in fields. In fields where there was heavy erosion, gullies as deep as 4 or 5 feet have been seen.

Replanting Options

Some growers with flood-destroyed corn are looking to replace lost corn silage with another crop. Below are some replanting options for fields that were flooded.

There is a small window of opportunity in longer growing areas to re-plant corn for silage; however in the shorter growing areas the window for re-planting corn is rapidly closing. If re-planting corn, consider a full season hybrid to maximize stalk yield and harvest after several hard frosts. Refer to this Wisconsin fact sheet for a discussion on late planted corn for silage.

Summer-Annual Grasses (e.g. Sorghum, Sudangrass, Sorghum-sudan hybrids, and Millet). After July 15 these crops are really only an option for Pennsylvania’s more southern and warmer counties.  For most of the State these crops will not mature before cool fall weather and frost stops their growth.

Oats (use taller varieties). Oats should be planted as soon as possible in the more northern part of the state.  In southern counties planting should be held off until late July or early August. It should be harvested for silage in the milk to soft dough stage.  Generally, the milk stage is less desirable than the early dough stage because it is less palatable and studies indicate that animal performance may be reduced.  Moisture levels between 60 - 70% are best for ensiling small grain silage. Small grain silage below 60% moisture is difficult to pack and excessive heating and nutrient loss may occur.  In addition, making sure that the theoretical length of cut is less than 3/8 inch is important with small grains because some stems are hollow and filled with air.  Minimizing the length of the chopped material will help minimize silage heating and maintain forage quality.  In a Penn State study conducted at the Landisville (Lancaster Co.) Research Center small grains yielded more than corn or sorghum-sudangrass when all were seeded on August 5.

Yield and TDN of four crops seeded on August 5
Corn (harvest on 10/5) 1.5 ton/a and 61.2% TDN
Sorghum-sudan hybrid (harvest on 10/5) 1.6 ton/a and 61.2% TDN
Oat (harvest at soft dough) 2.1 ton/a and 75.8% TDN

Be sure to consider replant or recrop restrictions on all herbicides applied earlier in the season. Restrictions range from none to at least 26 months.  Most atrazine containing treatments have at least a 10-month restriction before planting small grains.  Forage sorghum or sorghum-sudan grass may be better alternatives for atrazine-treated corn fields.  You can find recrop restrictions in the 2006 Penn State Agronomy Guide either in hardcopy or at http://agguide.agronomy.psu.edu/.

Getting Ready for Summer Seedings of Alfalfa — Paul Craig

Now is the time to begin making plans for summer seedings of alfalfa. Many forage producers actually favor summer seedings over the “traditional” spring seedings. The most common reason for this is usually less weed and insect pressure and the opportunity to make establishment steps when soil conditions are more favorable.

Frequently referred to as a fall seeding, most successful seedings of alfalfa at this time are actually mid to late summer seedings, usually early to mid August. Seeding into small grain stubble is the most common establishment practice at this time however some late summer seedings are actually reseedings into unsuccessful spring establishments.

Ideally summer seedings should have 8 to 10 weeks of growth prior to the date of the first killing frost in your area. Seeding too late does not allow the seedling plants to develop adequate root carbohydrates for winter survival. Also later seedings can result in small root systems that may tend to increase the risk of winter injury from heaving before next spring.

Soil moisture conditions at establishment are critical. There is no sense making a seeding if adequate moisture is not available to ensure germination and development of small roots. Base your establishment decisions on existing soil moisture conditions and short term weather forecasts. Because of warmer soil temperatures with adequate soil moisture levels, seeds will germinate and develop much faster than spring seedings.

Getting ready for a summer seeding

As soon as possible after small grain harvest take soil tests to accurately determine recommendations for soil fertility corrections. Correcting soil pH levels and providing adequate levels of phosphorous and potassium are best made prior to establishment. Control of existing weeds prior to establishment is also important. If perennial weeds such as quack grass, hemp dogbane, pokeweed or burdock are present, be certain to apply adequate amount of carrier and herbicides to get optimum control.

No till establishment in summer seedings is preferred if proper seeding equipment is available due to the advantage of soil moisture levels. If tillage will be used to prepare a seedbed be certain to consider the “fluffiness” of the seedbed. A loose seedbed in summer seedings can significantly reduce germination and establishment. Generally, with tilled ground, the use of a cultipacker before and after seeding will be beneficial. Consider what affect tillage will have on existing soil moisture levels prior to seeding. Seed at recommended seeding rates and at a depth of ¼ to 3/8 inch.

Post establishment weed control challenges will need to be monitored. Summer annual weeds will not become well established. However, winter annual weeds including chickweed or purple deadnettle and many others, will germinate in September and October and can present significant problems if not controlled. In small grain stubble fields volunteer small grains can present another weed control issue. There are many options for weed control available. Treat this year, when weeds are small. Controls next spring will be less affective.

Do not harvest late summer stands this fall. By not harvesting root reserves will be maximized resulting in improved winter survival and rapid plant development next spring. Next spring; manage the stand as you would your other established stands.

Take the time now to start planning for your summer seedings. Review existing weed and soil fertility conditions. Watch soil moisture levels and weather patterns. Like any good Boy Scout — Be Prepared!

Crop Insurance and Sprouted Wheat — John Rowehl

Wheat growers that have insured acreage in which the grain has sprouted in the field should immediately contact their crop insurance agent. Certainly everyone wants to get the rest of the crop off as soon as possible. But it is best to be in contact with an adjuster on what to do before you “destroy the evidence”. If an adjuster cannot get out there promptly, they may allow for small unharvested strips to be left in the field to be checked later.

Contributors: State Specialists:  Marvin Hall, Greg Roth.  Extension Educators:  Paul Craig (Dauphin), Del Voight (Lebanon), Andrew Frankenfield (Montgomery), Mena Hautau (Berks), Joel Hunter (Crawford), Jeff Graybill (Lancaster), and Dave Messersmith (Wayne).

Editor: John Rowehl (Cumberland)

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