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6/15/2009 - 6/21/2009

Few Acres of Soybeans Still to be Planted in Southeast Iowa

By Palle Pedersen, Department of Agronomy

Southeast Iowa has again experienced heavy rainfall and after talking to several agronomists yesterday and today it seems that there are still a few acres left to be planted in this area. With the heavy rain passing through Iowa over night and with more rain in the forecast for tonight it could be another 4-5 days before we can be back in the field planting. Because of that the questions have arise on what to do when planting soybean in late June or later and what to expect.

Late planting of soybean is going to have a significant impact on our yield. The good news is that the response to planting date and the yield loss from planting in late June is less for farmers in southern Iowa compared to farmers in central and northern Iowa. A large study conducted by my predecessor, Dr. Keith Whigham, documented that yield loss from planting in mid-June was much higher for northern and central Iowa than for southern Iowa. In southern Iowa you can expect 82 percent of your yield potential by planting in mid June but only around 60 percent can be expected for farmers in central and northern Iowa. 

Changing to an earlier maturing variety is not necessary unless the planting and/or replanting date is very late. It is recommended to plant the “original” full season variety until June 20 in northern and central Iowa and early July in southern Iowa. If planting occurs after these dates it is recommend shorten the maturity group by 0.5 to 1.0. The seeding rate is the same in late April as it is in June. However, weed management should be a top priority at late planting simply because of the lack of canopy and competitiveness. It is highly recommended, if possible, not to plant soybeans now with your corn planter (30 inch rows or greater). Using a split-row planter or a drill should help you to increase light interception and biomass accumulation to maximize your yield when planting late.

Finally, if you are debating whether you need to replant, the magic number is 73,000 healthy uniform distributed plants per acre. Economically, a soybean stand of 73,000 or more healthy, uniformly spaced plants per acre in early June or later is probably worth keeping. And again, weed competition is detrimental at these low populations so be sure to control weeds when they are small.

More information on soybean planting and soybean management decisions can found at www.soybeanmanagement.info

Palle Pedersen is an assistant professor of agronomy with research and extension responsibilities in soybean production.

Hail Injury on Corn

By Roger W. Elmore and Lori Abendroth, Department of Agronomy

Hail pounded various parts of Iowa over the last two weeks. Storm systems continue to march aggressively across the state. Shredded, twisted corn lies in their paths (Figure 1). Corn across the state ranges from 6th to perhaps the 10th leaf stage. That means that corn growing points extend above the ground. Damage to the growing point compromises recovery and yield.

Cornfield

Figure 1. Corn field damaged by June 14, 2009, hail storm. Photo on June 18 near Bloomfield, Iowa. R. Elmore photo.

Hail decreases yields by reducing stands as well as destroying leaves. The severity depends on the crop’s growth stage. Corn has an advantage over soybean early in the season when storms roll through since corn’s growing point remains below ground until about the sixth-leaf stage. Young plants like this are not killed if only leaf or stem tissue is lost.

Before we go on though, remember that the staging method used by most agronomists differs from that employed by hail adjusters The sixth-leaf stage of the ISU leaf-collar system correlates to the seventh-leaf stage used by hail adjusters. From V8 and following (ISU system), the hail adjuster method is about two leaves ahead. We will use the ISU leaf-collar system in this discussion.

Here are some points to keep in mind if your field has been hailed:

1) Patience. Call your crop insurance agent, hail adjusters are trained and equipped to assess hail damage losses. Wait at least three to five days after a hail storm to obtain an accurate damage appraisal. Allow recovery time for the plants.

2) Evaluate crop growth stage. Corn growth stage at the time of the storm is critical. If the plant has less than six collared leaves, yield will rarely be affected. Expect re-growth. This is true regardless of the amount of defoliation if weather after the storm favors growth. As mentioned above though, most Iowa corn has more than six collared leaves - growing points are vulnerable.

3) Assess viable stands. Evaluate injured plants to determine the growing point’s viability. Use a sharp knife and cut lengthwise down the stem. The growing point of a healthy plant is white to cream color. Plants with a healthy growing point should survive. Make assessments of plant survival three to five days after the storm allowing plants to recover. If weather is not conducive for plant growth for a prolonged period after the storm, assessing the remaining stand may require waiting up to a week.

Some plants in near Bloomfield damaged from a June 14 storm will not recover because of a rot that developed in the stalk. The rot was visible only when plants were cut lengthwise (Figure 2). Cool damp weather following the storm discouraged rapid plant recovery allowing the organisms to invade stems destroying (the plant's) opportunity to recover.

Damaged Corn

Figure 2. Corn plant damaged by hail on June 14, 2009, with base of stem cut lengthwise. Brown discoloration above growing point will likely kill the plant's growing point. Weather following the hail storm was not conducive for vigorous plant growth and recovery. Bloomfield, Iowa, June 18, 2009. R. Elmore photo.

4) Estimate yield losses from defoliation. As just mentioned, leaf loss or defoliation will rarely affect yield before the sixth leaf stage. Plants with six leaves or greater will experience yield losses depending on the extent of the defoliation - see Table 1.

Table 1. Estimated percent yield reduction from leaf loss caused by hail damage.

Table 1

Corn can withstand a substantial loss of leaf area without major yield losses. A reduction in leaf area less than 50 percent does not reduce yield if it occurs before V13. For example, at V13 - thirteen collared leaves - a 50 percent reduction in leaf area reduces yield by only 10 percent. However, when the crop is tasseled, VT, yield is reduced by 31 percent.

5) Estimate yield losses from stand reductions. Stand loss may occur following significant hail storms. Small reductions in plant survival do not impact yields much; for example a one-third reduction in stand will only reduce yield by 1o percent if it occurs before V8. Neighboring plants compensate to some extent for the lost plant.

However, after V8, yields are reduced by the same amount that the stand is reduced. A one-third reduction in stand will reduce the yield potential by one-third. We are conducting research in conjunction with the crop insurance industry to determine if this is still valid with modern hybrids and management.

Twisted whorl plants – a.k.a. tied or buggy whipped - may result from hail injury. A study on twisted-whorl plants by Thomison and Mangen at the Ohio State University found that in fields with major hail damage exhibited 36 to 61 percent twisted whorls. One month later that number was reduced to 0 to 9 percent; most plants grew out of it. The site that had the largest yield losses experienced major stand losses.

Once plant survival is established, use Table 2 to determine yield potential of the current stand based on the original planting date and plant population. Compare this to the yield potential of a replant. Replanting corn now is difficult to justify based on normal planting date responses.

Table 2. Relative yield potential of corn by planting date and population.

Table 2
Note: Values based on preliminary Iowa research and modeling; 100% yield potential is estimated to occur with 35,000 plant population and early planting.
From: Iowa State University Extension, Corn Field Guide, CSI 001. 2009.

Overall, remember the key is to assess plant viability thoroughly once plants have had a good chance to recover. Contact your crop insurance company before destroying the crop or replanting.
For more information on replanting, see:
www.extension.iastate.edu/CropNews/2009/0514elmoreabendroth.htm
For an article on earlier season hail damage, see: http://www.agronext.iastate.edu/corn/production/management/early/hail.php
For more information other corn issues, see our ISU Extension Corn Production web site: http://www.agronext.iastate.edu/corn/

Roger Elmore is a professor of agronomy with research and extension responsibilities in corn production. Lori Abendroth is an agronomy specialist with research and extension responsibilities in corn production. Elmore can be contacted by email at relmore@iastate.edu or (515) 294-6655; Abendroth can be contacted by email at labend@iastate.edu or (515) 294-5692.

European Corn Borer Numbers Are Up in 2009

Erin Hodgson and Jon Tollefson, Department of Entomology

Like 2008, first generation European corn borer activity has increased compared to the early 2000s. Dr. Tom Sappington (USDA-ARS Corn Insects and Crop Genetics Lab, Ames) and entomologists in Nebraska have recently reported increased adult catches in black light traps and in sweep net sampling. This means that corn not protected against corn borers, including refuge corn, should be scouted now for European corn borers to determine if an insecticide needs to be applied.

Scouting 
Although all refuge fields should be scouted every year for European corn borer, mated females are often attracted to and lay eggs in the tallest cornfields first. Sample corn plants in at least 100 feet from the field edge. Look for larval feeding in the leaves, also known as “shot holes.” There is usually no reason to perform an in-depth plant survey if shot-holed leaves are not detected in the field. If larval damage is evident, pull the whorls from five plants at five locations throughout the field (10 plants at 5 locations would be even better). Whorls should be selected at random. Unwrap the whorl leaves and count the number of live larvae. Do not pull whorls only from plants with shot-holed leaves because this approach actually overestimates the European corn borer population.

If corn borer larvae are found, don't schedule a spray too early. If most of the larvae are less than one-fourth inch long, wait 3 to 5 days for predators, pathogens, rainstorms, high winds, and high temperatures to naturally reduce populations while new larvae hatch. Larvae can be controlled with insecticides, but an application must be done before they begin boring into the stalk. Be sure to spray before most larvae reach the fourth instar (eleven-sixteenths inch in length); at this stage they leave the whorl or leaf midrib and tunnel into the stalk.

If the economic threshold is not reached after sampling, but considerable small larvae are found within the whorls, resample that field in 3 to 5 days. Do not add the previous counts to the most recent field counts. Discontinue scouting when large larvae are tunneling into the stalk and small larvae are no longer found in the whorls.

Management 
To facilitate calculating the changes in the action threshold for European corn borer action threshold, an Excel spreadsheet has been created. These calculations use the expected yield and the anticipated market value of corn to determine the profit/loss margin. Please use anticipated yield estimates that are appropriate for the stand that has been planted and is established. This calculation assumes only 80 percent control by an insecticide.

To make these calculations easier, follow this link to dynamic threshold spreadsheet. By saving the Excel spreadsheet to your personal computer, it can be used repeatedly as the value of corn and cost of control change. There is an explanation with two examples to demonstrate the spreadsheet tools. If the user downloads the Excel spreadsheet and inserts their values (in Ex. 3 column) for expected yield, anticipated market value, larval density and the cost of control - a profit/loss margin will be calculated in dollars.

There are several foliar products registered in Iowa for European corn borer control in corn (Table 1). Follow label directions and pay attention application guidelines and preharvest intervals.

Table 1. Labeled foliar insecticides for European corn borer. threshold table

* Restricted use pesticide.
† Active Ingredient.
Ω Please see ICM News article on Furadan and residues for 2010 and beyond.

 

Portions of this article were first published in ICM News in 2000.

 

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at ewh@iastate.edu or phone (515) 294-2847. Jon Tollefson is a professor of entomology with responsibilities in research and extension. He can be reached at tolly@iastate.edu.

Time to Scout for Corn Rootworm Larvae

By Erin Hodgson and Jon Tollefson, Department of Entomology

Reports from neighboring states have indicated corn rootworm larval hatch for 2009. June 6 has been considered an average hatch date in Iowa, so first and second instars should be actively feeding if present. This is the time to apply a rescue treatment for corn rootworm, and scouting will help determine if action is necessary.

There have been reported failures of Bt corn in Iowa, so we recommend scouting every field every year to ensure root protection. Of course Bt fields require a refuge, and that is where larvae are more likely feeding. If an average of one or more larvae per plant is found, a rescue insecticide should be considered.

There are limited products registered in Iowa for corn rootworm larvae after corn emergence (Table 1). Follow label directions and pay attention to spray guidelines. Post-emergent insecticides applied after the end of June will not be as effective because most of the root injury will have occurred already.

Table 1. Labeled post-emergent insecticides for corn rootworm larvae.

larvae chart

* Restricted use pesticide.
Ω Please see ICM News article on Furadan and residues for 2010
  and beyond.

 

Three additional resources that may be of interest for corn rootworm management are:
The Corn Rootworm Home Page
Interactive Node-Injury Scale
Evaluation of corn rootworm hybrids

 

 

 

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at ewh@iastate.edu or phone (515) 294-2847. Jon Tollefson is a professor of entomology with responsibilities in research and extension. He can be reached at tolly@iastate.edu.

Study Results Released - Weed Control in Roundup Ready® Cropping Systems

By Micheal Owen, Department of Agronomy

Weed scientists from six universities have joined forces to examine grower weed management practices and develop programs to evaluate and improve the sustainability of weed control in Roundup Ready® cropping systems. Called the Benchmark Study, this multi-state research project is now in its fourth year.  Funding for the study has been provided by the Monsanto Company.

University weed scientists have been concerned that frequently employed herbicide programs could affect the sustainability and effectiveness of weed control in Roundup Ready cropping systems. They reasoned that weed populations may shift to species that are more tolerant to glyphosate. Also, without proper management, the potential to select for weeds resistant to glyphosate could adversely impact the utility and life cycle of the weed management system on the farm.

The Benchmark Study began in the winter of 2005-2006 with a telephone survey of approximately 1200 growers from six states. Growers planting Roundup Ready corn, soybean or cotton for a minimum of three years were included in the survey. The survey was developed by a team of university weed scientists to evaluate tillage practices, herbicide use patterns, grower perceptions of weed pressure, and problematic weeds before and after adopting Roundup Ready cropping systems. Growers were questioned about their awareness of and actions taken regarding weed resistance to glyphosate.

The results of this survey were recently published in the journal Weed Technology in a series of peer reviewed scientific papers. The university collaborators and Monsanto are releasing summary reports – herbicide, weeds, resistance, tillage and overview summaries – highlighting  information from each of the Benchmark Study scientific papers. More details are available under new articles on the ISU Extension weed science Web site.

In addition to the survey, the Benchmark Study is in year four of a field study that began in 2006.  Approximately 150 growers in six states were randomly selected from among the survey respondents to participate in on-farm trials. In each of these on-farm trials, the growers’ current herbicide program is compared to a herbicide program recommended by university weed scientists.

The researchers expect the herbicide program recommended by the university to reduce the potential risk of selecting for glyphosate resistance. They have been monitoring weed populations, weed species diversity, weed seedbank, crop yields and economic returns from both herbicide programs throughout each growing season. 

This information is currently being reviewed and evaluated, with targets to publish the first two years of the field study in late 2009.  The results of the Benchmark Study may provide valuable data comparing the sustainability of growers’ current weed management programs compared to more diversified weed management programs, while reducing the risk of selecting for weed resistance to glyphosate.

 

 

Micheal Owen is a professor of agronomy and weed science extension specialist with responsibilities in weed management and herbicide use. Owen can be reached by email at mdowen@iastate.edu or by phone at (515) 294-5936.

Degree Days - Cool Weather Continues

By Rich Pope, Department of Plant Pathology

A third straight week of cooler than average weather has slowed crop progress across Iowa. Sporadic rainfall has limited field work, and for many fields weeds are a growing concern (pun intended). There has been slow weed response to herbicides, especially with glyphosate. The answer to this lies in getting some warmer weather to stimulate growth. So patience is a virtue.

During the week of June 7-14 Iowa crops accumulated about 40 to 60 degree days fewer than the long term averages (30-year running average). That is equivalent to the crop putting in a four to five day week!

Degree day accumulations from May 1 through June 14, 2009

The degree day accumulations posted here are for the growing season that arbitrarily starts on May 1 each year, but many fields are planted in April. From April 15 through May1, base-50 degree day accumulations ranged from 107 in northwest Iowa, to 121 in central Iowa to 148 in the southeast.   All these values were close to average.

 

Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted by email at ropope@iastate.edu or by calling (515)294-5899.

June 15 Crop and Weather Report

By Doug Cooper, Extension Communications

Two words summarize the crop conversations this week – cold and weeds. Iowa State University Extension weed specialist Bob Hartzler, integrated pest management specialist Rich Pope, and soybean agronomist Palle Pedersen discuss the influence of both on Iowa crops during this week's crop and weather report.

Hartzler says the cool and wet weather is allowing weeds to get a jump on planted fields this spring. Farmers need to keep an eye on weed development to maintain maximum yields this year.

Pope tells of early reports of soybean aphids in a few fields across the state.

Despite the cool, wet weather the soybean fields are looking quite good, says Pedersen. There are a few fields with growing weed problems, but overall this has been a pretty good year.

Don't Let Potato Leafhoppers Burn Hay

By Erin Hodgson, Department of Entomology

There have been recent reports of potato leafhopper in Iowa alfalfa, and it's time to think about sampling again. Potato leafhoppers do not overwinter in Iowa, but adults migrate here every spring.

Females deposit 2-3 eggs per day in plant stems. Pale, green nymphs emerge in 7-10 days depending on the temperature; the fastest development occurs at 86 degrees F. Nymphs look similar to adults except they are smaller and are wingless. They go through five instars in about 2 weeks. Adults are lime green, one-eighth inch long, and have a broad, wedge-like head. Adults live for 4-7 weeks.

As a result of the extended egg-laying period, at least two overlapping generations occur in Iowa every year. Potato leafhoppers are very active and easily disturbed – adults jump or fly away while nymphs quickly move sideways and backwards.

plh nymph and adult

Nymph and adult potato leafhopper.
 

Damage
Potato leafhoppers have a piercing-sucking stylet mouthpart. They cause physical damage when probing to feed and also inject saliva that plugs vascular tissue. Initially, alfalfa leaf tips will turn yellow, commonly referred to as "hopperburn." Heavily infested plants will be stunted, particularly new stands and regrowth after cutting. In some cases, large leafhopper populations can significantly reduce tonnage of the current crop, as well as the following crop.
 
Scouting 
Potato leafhoppers do not typically build up to damaging levels during the first crop in Iowa. Fields should be monitored weekly after the first cutting until the end of the season. A sweep net is the most effective way to sample for nymphs and adults.

Fields should be sampled when dry and in calm conditions. Sweep vigorously through foliage, using a 180-degree motion for one sweep. For each field, stop at 4-5 locations and take 25 sweeps per location. Count the number of nymphs and adults at each location and estimate the number of potato leafhoppers per sweep for each field. Keep in mind nymphs will be near the sweep net ring and adults will be at the bottom of the net.
 
Management
Remember, healthy and vigorous stands are able to tolerate potato leafhopper (and other insects) feeding. Heat or drought-stress can make alfalfa more susceptible to insect feeding. Protecting alfalfa from potato leafhopper usually involves a three-pronged approach.

1. The use of glandular-haired, potato leafhopper-resistant alfalfa varieties can significantly reduce yield losses. Using resistant varieties does not mean fields will be hopper-free, but plants should be able to tolerate moderate populations compared to conventional varieties. Newly-planted resistant fields may not show tolerance immediately, but should express tolerance after becoming established. Consider using potato leafhopper-resistant varieties if the local area is consistently infested.

2. The cultural control tactic of cutting management can disrupt potato leafhopper populations as they develop in alfalfa. Delaying harvest will allow nymphs enough time to become adults and start reproducing. Young nymphs will be destroyed or starve before regrowth occurs. Timely cutting will force adults to move to nearby crops, but they often move back into a field after regrowth. It is important to start scouting 7-10 days after each cutting to monitor for reinfestations.

3. Insecticide applications can protect alfalfa yield from potato leafhoppers, and are economically justified with regular scouting and the use of action thresholds. The fluctuating values of hay and control costs are important considerations for making a treatment decision. Tables 1 and 2 offer a dynamic action threshold for potato leafhopper based on conventional and tolerant alfalfa. There are several products registered in Iowa for potato leafhopper control in alfalfa (Table 3). Follow label directions and pay attention to preharvest interval guidelines. 
 

Table 1. Action thresholds for potato leafhopper (# per 10 sweeps) on conventional alfalfa.

plh table 1

 


Table 2. Action thresholds for potato leafhopper  (# per 10 sweeps) on tolerant alfalfa.

phl table 2

 

 

Table 3.  Insecticides registered for potato leafhopper control in Iowa.

phl table 3

 

 

 

Erin Hodgson is an assistant professor of entomology with extension and research responsibilities. She can be contacted by email at ewh@iastate.edu or phone (515) 294-2847.

Take Time for Sprayer Cleanup

By Kristine Schaefer, Department of Entomology

Thoroughly cleaning spray equipment between different pesticide applications is an important part of responsible pesticide use.  It can be difficult to find the time when weather limits opportunities to spray, but failing to clean equipment may result in contamination and crop injury.

The risk of injury is greatest when: crops highly sensitive to the contaminating herbicide (or other pesticide) are being sprayed; the product is very active in small amounts; and residues from non-selective herbicides like glyphosate and glufosinate remain in the spraying system.

Herbicide residues are more likely to cause visual crop injury but contamination can occur with all pesticides. Spray equipment should be cleaned between different applications whether the products are herbicides, fungicides or insecticides.

 

Injury risks can linger
Crops can be injured for up to several weeks after being treated with contaminated equipment, including after several separate applications. Water alone is generally not adequate to remove all pesticides, and injury can occur when residues that adhered to sprayer surfaces are brought back into solution. Some herbicides – such as plant growth regulator (dicamba, 2, 4-D, Status, NorthStar etc.) or HPPD inhibitor (Callisto, Impact, Laudis) herbicides – may be particularly difficult to clean from a sprayer and can cause very visual symptoms on soybeans.

Several herbicides (glyphosate in particular) make very effective tank cleaners and do an excellent job of removing any pesticide residues that were not removed by rinsing, thus increasing the risk of injury from residue remaining in the spraying system.  Leaving a sprayer load standing for a few hours or overnight can also increase the risk of contamination.  For some products, very small amounts remaining in the sprayer system can result in crop injury. This is especially important to note when switching from one crop to another or from herbicide-tolerant to non-tolerant hybrids or varieties.

 

Follow good cleaning practices
To reduce the risk of crop injury or contamination from previous applications, keep these clean-up guidelines in mind:

• Don’t wait to clean. Clean sprayer as soon as possible after use. Sprayers can retain significant amounts of pesticide solution even after they are considered “empty.”  Leaving the spray solution in the sprayer for long periods of time increases the risk of contamination.  Dried pesticides are harder to remove than pesticides still in solution.

• Determine where to clean. Clean spray equipment where the rinsate can be safely disposed of and will not contaminate water supplies or other sensitive areas. The best place for rinsate disposal is usually in the field, consistent with the product’s label.

 Use the right cleaner. Cleaning agents should be selected based on the pesticide and formulation to be cleaned.  Refer to the label for specific cleaning products to use. Some product labels recommend the cleaning solution stand in the sprayer for several hours or overnight.

• Clean all equipment parts. Focus on more than just the tank. Pesticide residues on hoses, sumps, strainers, pump surfaces and other sprayer components can also cause contamination.

• Clean strainers daily. Check and clean strainers daily as these can be a source of contamination. Most sprayers have up to three different strainers. In addition, partly plugged strainers may create a pressure drop and reduce the nozzle flow rate. 

• Handle safely. When cleaning sprayer equipment, wear the same personal protective equipment (PPE) required by the pesticide label for making the application. It is also a good idea to wear a chemical-resistant apron and eye protection.

Remember that cleaning practices will vary depending on equipment and products used. Always refer to the pesticide label for specific cleaning instructions.

 

 

Kristine Schaefer is a program specialist serving on the Pesticide Management and the Environment team. Schaefer can be reached by email at schaefer@iastate.edu or by phone at (515) 294-4286.

Some Producers are Now Discovering Winter-Injured Hay Fields

By Stephen K. Barnhart, Department of Agronomy

Some producers apparently made their spring hay field winter injury assessment from afar because now they are finding that their hay fields are coming up short on stand density and hay yields.

The factor most common to these winter damaged fields is that they are three years or older in age. By the plants per square foot method, alfalfa stands of this age with less than four plants per square foot are considered to have yield limitation due to low stand density.  

The other method for assessing stand adequacy for yield, for fields of any age, is the stems per square foot method.  An average of more than 55 stems per square foot indicates that the stand is at full production potential. If stem counts average 40 to 55 stems per square feet, the stand will likely produce less than full yields. Fewer than 40 stems per square foot indicates a stand with low, noneconomic yield potential.

With both methods make stand counts in several places in each field. While making stem or plant counts, dig representative plants and evaluate the health of crowns and taproots. Severely diseased taproots are another indication that stand productivity is declining. ISU Extension bulletin Evaluating Hay and Pasture Stands for Winter Injury (PM 1362) provides more information on stand assessment.

Producers with low yield potential have several management alternatives:
- Continue to harvest the low producing stand, and plan for either a new late-summer or spring forage seeding.

- Attempt to thicken the existing stand with perennial forage grasses or legumes. New alfalfa into a thin, existing alfalfa stand is not recommended. Over seeding (best with a no-till drill) red clover or a perennial forage grass will not contribute much to this season’s yield, but should improve production from the field next year.

- Drill in a temporary forage supplement such as oats, spring wheat or barley into the existing stand. These ‘cool-season’ cereals would grow quickly, but will probably head at a short height and provide only one growth cycle. By delaying harvest, seed stems will add to yield, but will likely reduce palatability and feeding value.
Drill annual ryegrass, also called Italian ryegrass, or perennial ryegrass into the existing thin stand. Note that these are not the same as cereal rye or grain rye used as an overwintering cover or forage crop. The ryegrasses have relatively rapid seedling emergence and growth, and will add modestly to forage yield for the remainder of the season. They can have a summer dormancy limitation during hot, dry summers, and should not be considered to be long-term components in the stand due to relatively poor winter hardiness.

- Plant a supplemental or emergency warm-season summer annual grass such as Sudangrass, or one of the annual forage millets in another field.  See the 2008 ICM Newsletter article on annual or alternative forages for more details on these emergency summer annual grass choices.

- A last consideration, and it should be considered as a ‘least tested (in Iowa) choice, is planting teff or "summer lovegrass". Teff is a warm-season, annual grass of African origin that has grown reasonably well in some Midwest U.S. locations. It establishes relatively quickly, with its first harvest in about 45 to 50 days. If planted in early June, it should produce two or three cuttings through the remainder of the growing season. It has very small seeds and must be planted very shallowly (1/8 to 1/4 inch) in a very firm seedbed. Seed sources are limited.

Regardless of the short-term management option chosen, plans should be made to establish either a new late-summer or spring forage seeding.

 

 

Stephen K. Barnhart is a professor of agronomy with extension, teaching, and research responsibilities in forage production and management. Barnhart can be contacted at (515) 294-7835 or by email sbarnhar@iastate.edu.



This article was published originally on 6/22/2009 The information contained within the article may or may not be up to date depending on when you are accessing the information.


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