Field Crop News, Vol. 12:10, May 8, 2012

May 8, 2012    Vol. 12:10


Weather Outlook — Kyle Imhoff, Department of Earth and Mineral Sciences

After a very soaking rain that fell across much of the region early in the week, a much drier period will begin starting early Thursday and last in to the upcoming weekend. Some showers will occur across parts of the state during the day on Wednesday, with far southeastern Pennsylvania having the potential for some heavier showers later on in the day. Beginning on Thursday, a ridge of high pressure will build in to the area from the west, resulting in dry conditions and moderating temperatures. On Friday and in to the weekend, temperatures will remain near normal levels with clear conditions across the state. Some showers may try to enter the region later on Sunday in to the early part of next week. As discussed in the previous outlook on May 1st, alternating episodes of dry and wet weather will continue through the middle part of the month as next week looks to bring another period of unsettled weather to the state.

Thin Alfalfa Plantings: Deciding When to Give Up — Marvin Hall, Penn State Forage Specialist

I have received many phone calls and email messages over the past several weeks expressing concern about new alfalfa seedings being very thin (few plants per square foot). These communications inevitably end with this question “how thin is too thin to keep the seeding?”

I have generally said that the bare minimum number of alfalfa plants in a new seeding should be 15 per square foot. If the numbers drop below that threshold then the stand will not yield as well as it could, stand longevity may be compromised and weed competition may be a greater problem. I recently went back to alfalfa studies I’ve conducted over the past 20 years where the new stands were variable (17 locations/environments) but we kept the plantings and collected data from them.

Unfortunately, 16 alfalfa seedlings per square foot was the lowest density (average of five locations) we collected data from. The new alfalfa seedings with plant densities of 16 alfalfa plants per square foot produced less yield than the greater plant densities only for the 1st harvest in the seeding year (see Table). Subsequent yields were not different between 16 and 60 seedlings per square foot.

Yield of alfalfa with different plant densities 4 weeks after planting.
Plant density 4 weeks after planting
Plants per square foot
1st Harvest Yield Seeding year total yield 1st Harvest yield in year after seeding
(% of average)
16 0.91 0.95 0.98
19 0.93 0.96 1.03
21 1.01 1.03 1.00
25 0.98 1.00 0.94
29 1.00 1.02 1.02
35 1.04 1.02 1.00
37 1.00 1.01 1.03
50 1.07 1.04 0.97
60 1.03 1.04 1.02
Least Significant Difference at 0.05 0.04 NS NS

We also monitored the plant density from these studies for five years and found no difference in stand density after 18 months. Consequently, initially thinner stands of 16 plants per square foot had the same length of stand life as much higher stand densities.

So, if your new alfalfa plantings have 15 or more seedlings per square foot then they are worth keeping!

Maturity and Diseases on Winter Grains — Greg Roth, Grain Crop Management

Maturity of our winter barley and wheat is well ahead of normal and could have some important consequences on crop yield and management this year. Barley heading dates for Thoroughbred, a popular winter barley were April 29 at our Rock Springs trial this year, compared to May 12 last year and May 5 in 2010. Our wheat lines started heading May 7 compared to May 26 last year and May 15 in 2010. This will likely mean that our small grains, if not damaged by previous frost, could benefit from cooler temperatures during the grain fill period, and perhaps a longer grain fill period and higher yields.

Harvest could also be earlier this year leading to expanded opportunities for double cropping with soybeans. With the current price of soybeans, this could be a good opportunity for grain producers who plan accordingly.

The disease situation in wheat is critical to monitor. Powdery mildew and Stagonospora have been advancing upward in the canopy in our variety trial recently with the cool wet conditions. With the potential high yields in this year's crop, it is important to try to keep these diseases off the top two leaves. There are striking differences among varieties for mildew resistance in our trials so if you are seeing heavy mildew infestations, you may want to reevaluate varieties for next year.

Most wheat is heading and or flowering and is at or approaching the critical stage for treating for head scab or other diseases if the risk is high. The risk for head scab has been low on the FHB Risk Assessment Tool, but today high risk areas began to appear on our map, likely due to the warm and wet conditions this week. There is also some risk of a leaf rust infestation as Kentucky has reported rust in many fields. Some of those spores could have moved here during the last two weather fronts that moved through.

I would be monitoring wheat diseases and planning fungicide applications accordingly. Triazole fungicides such as Caramba and Prosaro have the most activity on Fusarium Head Blight when applied at flowering. These products also provide good control of powdery mildew, leaf blotches and rust when applied for the critical early grain fill period.

Preemergence Soil Residual Herbicides For Soybean — Bill Curran and Dwight Lingenfelter, Penn State Weed Science

We have seen a number of new soil applied soybean herbicide products come into the market place over the last few years. Most of these are new mixtures of active ingredients found in other products although a few such as Sharpen (saflufenacil) are new active ingredients. Unlike some areas of the US, most PA farmers that grow soybeans have fortunately had fairly diverse rotations that include corn, small grains, Roundup Ready and conventional crops, maybe alfalfa or other types of hay and probably some tillage helping to diversify the weed management program. Herbicide resistant weeds and in some cases no-till are driving the adoption of residual herbicides. Some northeastern farmers certainly do and would benefit from residual herbicide programs in soybean, so where do they make the most sense?

Here is our list:

  1. Long-term continuous no-till where reliance on herbicides is greater than where tillage is used is a prime candidate.
  2. Roundup Ready crops - This becomes even more important in continuous Roundup Ready soybeans and corn which often depend heavily on glyphosate for weed control. This is where horseweed/marestail is a problem in soybean and glyphosate alone will NOT work.
  3. Wide-row soybeans can benefit from a residual herbicide in combination with a single well-timed post application. This helps suppress the weeds early in the summer and the post application cleans things up.
  4. Perennial weeds – With problem perennials like Canada thistle, pokeweed, hemp dogbane, or other problem perennials, glyphosate applied to the perennial weeds at the bud to bloom stage will have the biggest bang for the buck (or better yet in the fall). Control the annual weeds with the soil- applied residual program to allow for the slightly later more optimum post application targeting the perennials.
  5. If you routinely have problems controlling annual weeds because of high severity, prolonged germination pattern, or other reasons with a single in-crop application, then a soil applied program can make sense.
  6. If you are unfortunate enough to be dealing with glyphosate resistant or tolerant weeds like horseweed (marestail), ragweed, or lambsquarters, then a soil residual program will help this effort. This can also be true for ALS-resistant weeds like shattercane, pigweed, and foxtail.
  7. Finally, a soil residual program can definitely provide some insurance and lessen the workload when weather and tight spray schedules are frequently a problem in making a well timed application.

So, as you prepare to plant that soybean crop, consider where residual programs make the most sense and choose the program for good reason(s).

Two Caterpillars to Consider: Black Cutworm and Armyworm — John Tooker, Penn State Entomology Specialist

Unlike the Midwest and Great Plains that have experienced heavy black cutworm flights this spring, Penn State’s Black Cutworm Monitoring Network has yet to formally detect a significant flight of black cutworm moths (eight moths over two nights) in any of our traps across the state. While we have not detected a significant flight, we have had the highest trap activity near Kutztown (Berks County) and Hallam (York County). Given the warm spring across the eastern US, it may be that spring flights have been protracted a bit, preventing large populations from coming north all at once.

Nevertheless, as young corn seedlings grow across the state, growers would be wise to scout their fields for cutting damage. Seed treatments and transgenic corn varieties can still be vulnerable to some damage, and it is worth reiterating that well-timed scouting and spot rescue treatments are usually the most economical strategy for managing black cutworm. For more details on black cutworm, its biology and management options see our fact sheet.

True armyworms: While Penn State does not have a statewide monitoring effort for true armyworm moths, Mary Barbercheck in the Department of Entomology has a few traps out in Centre County this Spring. These traps have captured an impressive number of moths, telling us that at least in the central part of the state true armyworm moths have arrived and their larvae are likely to be active soon. Growers should be aware of this pest and some of the factors that contribute to fields being “at risk” for damage. True armyworm typically causes problems in reduced tillage or no-till systems when corn is planted after a small-grain cover crop or when corn is adjacent to recently harvested small grains. They can be particularly problematic when the window between burning down a small-grain cover crop and corn planting is too narrow (less than two weeks).

Adult moths fly into Pennsylvania after overwintering in the soil in states to our south. Females lay their eggs on weeds and/or grasses along field margins or on small grains and move to corn when weeds or grain cover crops are killed with herbicides. Armyworm can occasionally cause problems feeding on small grains sowed for harvest, but tend to be problematic more often in corn when small grains are harvested because armyworms move to young corn plants. Armyworms tend to feed at night along the margins of corn leaves, avoiding midribs. During the day, larvae hide in leaf sheaths or in the soil or leaf litter.

Rescue treatments are usually the most efficient and economical tactic for managing true armyworm because populations are very spotty and preventative applications may not have sufficient residual activity to kill caterpillars that hatch out later. Armyworms can warrant treatment should infestations reach 25% of plants in a field. A recently revised fact sheet provides more information on armyworm.

Residual Corn Herbicides in Post Applications — Dwight Lingenfelter and Bill Curran, Penn State Weed Science

The unusual weather patterns interspersed with recent rainy and windy periods have made it difficult for timely herbicide applications. In some cases, burndown herbicides and residuals were applied a few weeks ago and are now running out of steam or the corn is already coming up and no herbicides, including a burndown, have been applied. Unless it’s Roundup Ready or Liberty Link corn, the options for broad spectrum burndown are very limited. (We do not recommend application of Gramoxone even if the corn is in spike stage, but would suggest other herbicide tank mixes or using 2-pass herbicide programs.)

There are a number of herbicides, including residual products that can be applied after planting up until corn and weeds reach a certain size or growth stage. The greatest risk of failure comes with trying to control annual grasses such as foxtail and panicum as they are emerging without including a foliar applied herbicide.

With the increasing acres of Roundup Ready (glyphosate) and Liberty Link (Liberty 280) corn, we have more flexibility in how we manage weeds after emergence. In addition, a number of “conventional corn” products are available to control emerged grasses (e.g., Accent Q, Basis Blend, Capreno, Equip, Impact/Armezon, Laudis, Option, Realm Q, Resolve, Resolve Q, Steadfast (ATZ) and Steadfast Q). Even more products are available for broadleaf weed control.

In most cases, these POST or foliar-applied herbicides can be tank-mixed with residual products to provide several weeks of control. For most products, do not apply in a liquid fertilizer carrier if corn has emerged or injury may occur. Maximum corn and weed sizes vary for early POST herbicide applications in corn depending on the product.

Herbicides such as Balance Pro, Radius, and Princep must be applied before corn emergence. Balance Flexx and Corvus contain a safener and can be applied up to early POST (V2 growth stage) to corn. Other herbicides such as Bicep II Magnum, Bullet, Dual II Magnum, etc. can be applied to corn up to 5 inches tall. Acetochlor-containing products such as Degree (Xtra), Harness (Xtra), FulTime, Keystone (LA), and SureStart can be applied to corn up to 11 inches tall. Herbicides including Atrazine, Lumax, Lexar, Guardsman Max, and Realm Q can be applied to corn up to 12 inches tall (20 inches tall for Resolve Q). And finally, Prowl H2O, Halex GT, and Warrant can be applied to 30 inch tall corn or less.

Keep in mind, when tank-mixing with other pesticides, to follow the most restrictive product label. For a listing of additional herbicides and maximum corn heights and information on maximum weeds sizes for these products please refer to Table 2-2.12 in the Penn State Agronomy Guide. Or refer to the most recent herbicide label for use guidelines and additional information— or or

Slug Populations are Ramping Up, Alfalfa Weevil Ramping Down — John Tooker, Penn State Entomology Specialist

We are starting to hear about slug infestations this spring. The warm winter likely allowed more slugs to survive the cold weather, and the recent wet weather and cool evenings have been ideal for slugs. Now, we are starting to hear of slug infestations across the state in emerging corn and soybean fields. Slugs, of course, are most often problematic in no-till systems and thrive in high moisture, high residue fields.

While growers have limited control options available for slugs, an integrated approach that deploys a suite of tactics against slugs is best. For fields with heavy residue or a history of slug infestations, growers should consider mechanical, biological, and chemical options. Even in no-till fields, some light mechanical options may be available and helpful. Some of our research in collaboration with Sjoerd Duiker here at Penn State indicates that a shallow, vertical disking of only three inches deep prior to planting can knock back slug damage by nearly 80%. This disking appeared to be useful because it reduced the amount of residue on the soil surface, perhaps decreasing housing for slugs. Similar results may be found with turbo-till units, though we have not been able to assess these vertical tillage units very well.

Natural enemies common to most agricultural fields also have a chance to contribute to slug control. Some ground beetle species and other soil dwelling creatures are voracious slug predators. Unfortunately, natural enemy populations in many crop fields never get a chance to build because of regular use of insecticides. Some growers tank-mix insecticides in the spring as an insurance policy against other potential crop pests, but it should be recognized that applications of insecticides in absence of crop damage are economically dubious and have the potential to disrupt often unrecognized natural enemy-provided control.

If slug problems are particularly bad, growers have to consider chemical options. Metaldehyde baits (e.g., the Deadline line of products) are typically the first choice, but are usually most effective when applied carefully over just the infested portion of the field rather than being broadcast field wide. As an alternative to metaldehyde baits, some growers have had success controlling slugs with nitrogen solutions, which are typically applied at night with 30% nitrogen mixed one to one with water and sprayed over the field at 20 gallons to the acre. This is a contact poison with no residual activity so it needs to contact slugs when they are active and available on plants (it is not clear how much of the nitrogen becomes available to the plant). As a last resort for fields with severe slug problems, growers in Pennsylvania have the option via a “2ee Recommendation” to use Lannate LV against slugs. I am aware of only one evaluation of Lannate for slug control and the results were not perfect, so I would encourage growers to use this as a last option primarily because of the toxicity of this carbamate insecticide.

For a full sense of slug life history and control options available, see our recently published slug fact sheet.

Alfalfa Weevil: For most of Pennsylvania alfalfa weevils should be winding down—if you still see them in the field, the larvae should be nearly mature and almost ready to pupate. According to the PA-PIPE (Pest Information Platform for Extension and Education) system (following the link at the top of the page and then click “public maps” and then “alfalfa weevil”) alfalfa weevils should be in the non-damaging pupal stage, whereas central and northern counties should be seeing later instar larvae.

Alfalfa weevil is typically a pest of the first cutting of alfalfa, and it is uncommon for economic populations to feed on the re-growth of the second cutting—so resist any temptation to treat economically meaningless populations. For details on the life cycle, economic thresholds, and management options, see our alfalfa weevil fact sheet.

PA Crop Insurance Update — May, Gene Gantz, RMA/USDA, 717–497–6398,

PA producers received $61.4 million in crop insurance indemnities that were paid to over 8,500 farms for a statewide average of $2.95 for each dollar of producer paid premium. Enrollments for 2012 crop insurance protection increased, as did the level of protection purchased, with nearly 600 more policies enrolled at the coverage levels of 70% and higher, compared to 2011.

2012 may well be the year that will reward producers for paying more attention to details. These details include placing extra emphasis on production and risk management throughout the growing season. Many producers have already made their decision to insure their corn, soybeans and other crops at levels of protection that they have determined are necessary to manage their risk exposures and as a foundation for their crop marketing plan.

The remaining ongoing responsibility will be to file prompt notice of damage of loss to your insurance agent if damage occurs. Many fruit growers have already taken this action because of late frost damage. As you do your field work, remember that many insurance policies for field crops include replanting and prevented planting coverage, as well as full growing season protection. But be sure to remember that a prompt notice of damage is required and an adjuster must be able to evaluate the damage in order for you to receive the full benefits of your policy(s). Also, be sure to file an accurate acreage report before the deadline.

If you have questions on deadlines for your area or on other issues, contact your crop insurance agent promptly.

Wishing you the best of success in 2012!

Lots of Mustard Family Weeds Bringing Color to the Landscape — Bill Curran and Dwight Lingenfelter, Penn State Weed Science

As you drive around the state this time of year, you will see lots of yellow and white flowering herbaceous plants. Many of these are considered weed species and members of the mustard family also known as the Brassicaceae or Cruciferae family. Plants in this family are numerous and often winter annuals or perhaps biennials and perennials. They generally form a basal rosette that over winters and produces a branched flowering stems in early to mid spring. The flowers are yellow or white (sometimes purple) have four petals and four sepals. The fruits are seed pods and are either a compact silicle which is usually ovate or an oblong silique that looks like a bean pod.

I discovered a nice publication from the University of Idaho published back in 2000 titled Mustards in Mustards which describes some common mustards and how to distinguish them Another useful website is from which does a nice job looking at different flower and fruit color and shape Below are some of the more common mustard species that you now see flowering around our region.

  • Birds-rape mustard (Brassica rapa) also known as field mustard and wild turnip is a winter annual or biennial. The leaves are smooth and clasp the stem. The plants often reach 3-feet in height, the flowers are yellow, and the fruits are siliques. This species is very similar in appearance to rapeseed or canola (Brassica napus)
  • Dames rocket (Hesperis matronalis) is an erect biennial or perennial that can reach 5 feet in height. It is unique from other mustards in that the flowers are pink or purple in color. It is often confused with phlox species which have opposite leaves that are not toothed and flowers with five petals rather than four. Although it is considered somewhat invasive, its attractive appearance has helped it spread and has sometimes been a component of wild flower seed mixes.
  • Field pennycress (Thlaspi arvense) is one of the most common winter annual mustards in the region. The flowers are white and the fruits are distinctly round and flat.
  • Field pepperweed (Lepidium campestre) is a winter annual forming a basal rosette with finely toothed leaves. The plant bolts producing small white or greenish flowers that develop into egg-shaped silicles. This plant is very similar to Virginia pepperweed. The fruits of Virginia pepperweed are flat and round.
  • Garlic mustard (Alliaria petiolata) is a biennial that is most common in wood lots and along field edges. It can become established in no-till and unmanaged pastures. The foliage has a “garlic” like odor when crushed. Generally considered an invasive species the first year’s growth is short statured with triangular to heart-shaped leaves. The flowering plants that you see now have conspicuous white flowers that will produce long siliques
  • Shepherd’s-purse (Capsella bursa-pastoris) is a winter annual producing a prostrate basal rosette. The flowering stems are mostly unbranched with mostly inconspicuous flowers producing a triangular to heart shaped silicle that is referred to as a “shepherd’s purse”.
  • Wild Radish (Raphanus raphanistrum) is a winter or summer annual. The stems have stiff hairs and the leaf margins are toothed. The flowers are light to pale yellow fading to white with age producing a pod-like fruit (silique).
  • Yellow Rocket (Barbarea vulgaris) a winter annual or biennial that has bright yellow flowers forming siliques. This is a weed found along roadsides, fallow fields, and sometimes in hay and pasture.

Upcoming Events

ALS-Resistant Chickweed Research Tour — May 9, 1:30 — 3:30pm at the John Hess Farm near Maytown/Marietta.

This field day will provide an overview of the latest research to control ALS-resistant chickweed in small grains. Participants can view various herbicide treatments and discuss ways to manage chickweed with Penn State specialists. There is no registration fee for this event. Credits will be available to those who attend (Pesticide credits: 2+2; CCA: 2 IPM).

The farm location is: 230 Rock Point Road, Marietta, PA 17547; for additional directions to the field site, type this information into Google Maps ( ) or Bing Maps ( ). From Mt. Joy, take 772 south to Rock Point Road. The farm is located just on the eastern edge of Maytown on Rock Point Road. For additional questions about the field day, please contact John Bray — 717–821–0814.

Soil Health Field Day — May 23, The Antler Club, 231 Sunset Ave, Lucinda, PA 16235 (Clarion County), 8:30 AM, Contact Brittany Dittemore, Headwaters RC&D Council, 814–503–8653 or

Farming for Success Field Day — Thursday June 21, Southeast Agricultural Research and Extension Center, Contact Jeff Graybill 717–394–6851,

Soil Health and Nutrient Conservation Research Tour — June 27, 2012 Samuel E. Hayes, Jr. Livestock Evaluation Center and the Agronomy Research Farm at the Russell E. Larson Agricultural Research Center. Contact Craig Altemose,, 814–355–4897

Grain Marketing Meeting — Wednesday, June 27, 5:00PM Mertztown, PA

All-you-care-to eat pig roast and sweet corn dinner. Contact John Berry 610–391–9840

Agronomic Weed and Insect Pest Research Tour July 11, 2012, Penn State Agronomy Research Farm, Contact Bill Curran,, 814–863–1014

Penn State Agronomic Field Diagnostic Clinic — July 26 and 27, 2012, Penn State Agronomy Research Farm, Rock Springs. (Additional details are forthcoming.)

Soybean Growers’ Field Day—August 23, 2012, Southeast Ag Research and Extension Center, Contact Del Voight,; 717–270–4391

Commercial Applicators’ School — September 12, 2012, Southeast Ag Research and Extension Center, Contact John Bray,; 717–270–4391

Contributors:County Educators: Jennifer Bratthauar (Franklin), Nicole Santangelo (Potter), Dwane Miller (Schuylkill) Mena Hautau (Berks), Greg Hostetter (Juniata), Joel Hunter (Crawford), John Rowehl (York), Del Voight (Lebanon). Craig Williams (Tioga), Jeff Graybill (Lancaster), Mark Madden (Sullivan), Department of Crop & Soil Science: Bill Curran, Sjoerd Duiker, Marvin Hall, Dwight Lingenfelter, Greg Roth, Department of Entomology: John Tooker. Department of Meteorology, College of Earth and Mineral Sciences: Kyle Imhoff

Editor: Mike Fournier (Bucks County)