Vol. 96:1
March 15, 1996
The information revolution continues to allow access to more and more news and information. If you are familiar with the internet and using the World Wide Web, you can retrieve information including the Field Crop News the day it is placed in the system. To access the Field Crop News as well as other Penn State College of Agricultural Sciences information on PENpages via the internet, use the following address: http://fcn.agronomy.psu.edu. Once in PENpages, click on the PENpages gopher server link to access newsletter information. Alternatively, you can access the Department of Agronomy's home page at http://cropsoil.psu.edu/ and then click on Extension program. The Field Crop News will also be available via the Department's home page. Happy surfing!
I've received some requests to provide some Internet or Web address for good corn information. A number of excellent resources are out there, so if you not already on the web and you're interested in corn production, I' d encourage you to get on. Here's a few of the good sites I've located:
http://info.aes.purdue.edu/agronomy/cornguid.htm - The Corn Growers Guidebook- a resource of corn fact sheets, resource people, and other interesting web sites related to corn production from Purdue.
http://www.ag.iastate.edu/departments/agronomy/cornpage.html - The Maize Page at Iowa State University - a good starting point for searching for corn information onproduction, genetics and more.
http://www.ag.ohio-state.edu/~ohioline/lines/farm.html#FCORN - Ohio State crop production fact sheets on corn.
gopher://shelley.ca.uky.edu/00/.agwx/usr/markets/usda/MSGR711 - A summary of grain prices on the Chicago Board of Trade
http://www.intellicast.com/weather/lga/radar.gif - An excellent radar weather map for Pennsylvania and the surrounding states.
http://info.aes.purdue.edu/agronomy/othragry.htm - A good summary of "Agronomy Links Across the Globe" from Purdue.
Also, be on the lookout for a Penn State site on corn production coming on line this spring.
Narrow row (15 or 20 inch) corn has received a lot of attention in the national press this winter, and most of the reports have been consistent with our results. The potential benefits are an earlier canopy, better weed control, improved soil erosion protection and in some cases higher yields. Several midwest universities reported the grain yield response to narrower rows over the winter and these included a 5% increase in Iowa, 3% increase in Indiana, and a 10% increase in Minnesota. These results are similar to the 4% increase we found in our narrow row grain studies in 1993 and 1994. We focused on silage in our trials in Pennsylvania in the last two years and found significant increases in 4 of 8 trials. The average response to going to a narrow row, higher population (34,000 ppa) system was a 13.7% or 3T/A increase compared to a 30 inch, 27000 ppa system. The response to increasing the population alone was about 3.6%. Our study and a number of other studies have shown that there are often considerable differences in how the narrow row response is affected by hybrids, fertility, and the growing season.
It is still unclear what combinations trigger the best response to narrow rows, but there seems to be some tendency for larger responses in shorter season areas, in environments with early season stress, and where N is not limiting. Yield responses to narrow rows are most always positive, but there are a few cases when they have been negative. There is the possibility of artificial effects being introduced into field comparisons because of equipment limitations that could be influencing the results of some studies. For example, doubling back to achieve narrow rows may cause reduced stands and increased compaction under the tractor tires that hurt the narrow row yields. This is especially true where two or four row planters are used. Likewise, harvesting 15 or 20 inch corn with a 30 inch head could increase harvest loss and reduce narrow row yields. Consider these effects if you plan to evaluate narrow rows. Also, take the time to drop the population back on the planter, otherwise you'll end up with a double population which will result in disappointing results. Our results indicate you could increase populations up to about 32-34,000 ppa in narrow rows on good soils. Above that level, we've seen some potential for increased barrenness, reduced grain yields and lower forage quality.
For those interested in learning more about narrow row corn and farmer experiences with it, a new 48 page publication entitled "Ultra narrow row corn... squeezing the most out of your crop" provides some useful tips. Contact Lessiter Publications (1-800-645-8455) for purchasing information.
Greg Roth
Research indicates that stem number rather than plant number is a more accurate determination of when to plow up an alfalfa stand. Typically, the magic number of plants that indicated that it was time to rotate out of alfalfa has been 4 - 5 plants per square foot. However, depending on fertility and weed invasion, alfalfa stands with 5 plants per square foot can yield as much as a stand with 10 or 15 plants per square foot. The correlation between plants per square foot and yield is very low since individual alfalfa plants respond to decreasing stand density by producing more stems. Increased stems per plant compensates for fewer plants and maintains the yield.
Better than the number of plants as an indication of the productivity of an alfalfa stand is the number of stems per square foot. Fields with 55 or more stem per square foot produce maximum yields. As the stem number declines to 40 stems or less per square foot yields are reduced by 25%. Researchers suggest that this is when alfalfa fields begin to loose profitability and should be rotated out of alfalfa.
Unfortunately, this technique of counting stems works well if the decision to reseed is made during the growing season. The technique does not however, work when a decision must be made early in the spring after a hard winter. A decision at this time of year to rotate out of alfalfa must be based on the 4 - 5 plants per square foot threshold.
The high costs associated with seeding forage crops makes it a rather "high stakes" farming operation. The days of spreading some seeds on the ground and hoping for nature to cooperate are past. Today, success is imperative. Forage producers must minimize risk as much as possible to ensure successful forage crop establishment. Here are some basic steps that can improve the successfulness of forage crop seedings.
Our last newsletter for 1995 included some information on new herbicides for 1996. Here is a little more detail about three of those new products.
Basis 75%WDG is labeled for postemergence use in field corn. It is a mixture of thifensulfuron, the active ingredient in Pinnacle, and rimsulfuron, a new sulfonylurea herbicide for corn. Both of these ingredients are ALS inhibitors herbicides. Basis controls 1 to 2 inch annual grasses including barnyardgrass, the foxtails, and fall panicum and 1 to 3 inch broadleaves including Pennsylvania smartweed, ladysthumb, lambsquarters, redroot pigweed, velvetleaf, and wild mustard. Apply to corn from spike through the 4-leaf stage (2 collars or 6 inches- do not apply to corn having 3 fully emerged collars) at 1/3 oz per acre (1 packet per 4 acres) and include a spray adjuvant (surfactant or crop oil) and an ammonium nitrogen fertilizer. Basis may be tank-mixed with atrazine, Banvel, Clarity, Marksman or Scorpian III to increase the spectrum of control. Basis can interact with certain soil applied insecticides, so unless IR or IMI corn is used, check a current label for precautions. Basis has a 10 month recrop restriction for pop and sweet corn and alfalfa.
As you can see from label directions, for maximum corn safety and performance, Basis must be applied to small weeds early post in corn. In PSU research, Basis performed well at the early post application timing. Although, we did not make applications beyond the 2 collar stage of corn, both research from Dupont and from other University trials shows an increased potential for crop injury to corn beyond the 3-collar stage. Although some residual control comes from the rimsulfuron component, with moderate to heavy weed pressure additional measures will be needed (residual partner or a follow-up cultivation). Basis is not a herbicide for every producer. It requires accurate weed identification and application timing during a rather narrow window of opportunity. However, for those producers able to meet these requirements, it also offers relatively affordable annual grass and broadleaf weed control in corn.
Scorpian III 0.843WDG is a new herbicide labeled for postemergence weed control in field corn. Scorpian III contains a mixture of three ingredients, flumetsulam (ALS inhibitor), clopyralid, and 2,4-D. Flumetsulam is an active ingredient in Broadstrike products and clopyralid is the active ingredient in Stinger. This three-way mixture is active on a number of broadleaf weeds including pigweed, cocklebur, jimsonweed, lambsquarters, ragweed, smartweed, and velvetleaf. In addition, the clopyralid and 2,4-D components within Scorpian III should help in the suppression of Canada thistle. When applied at 0.25 lb per acre, Scorpian III includes 0.125 lb 2,4-D (1/4 pint), 0.063 lb clopyralid (2.7 fl. oz. Stinger), and 0.023 lb flumetsulam (flumetsulam rate equivalent to that found in 0.92 pint per acre of Broadstrike+Dual). Apply to corn up to 8 inches in height when weeds are at the 2 to 4 leaf stage. Include a nonionic surfactant at 0.25% v/v (1qt/100 gal) with all Scorpian applications. As with other applications of 2,4-D postemergence on corn, crop safety declines as corn matures. Therefore pay close attention to application timing for both corn safety and weed control. In PSU research, Scorpian III performance was good on some common annual broadleaf weeds including lambsquarters, pigweed, ragweed, and velvetleaf. Scorpian III has a 10.5 month plant back restriction for alfalfa, soybeans, popcorn, and sweet corn.
Roundup Ready soybeans are available for use this season. The following are some considerations on the use of this new biotechnology.
Dwight Lingenfelter
Burcucumber is becoming a serious problem for Pennsylvania producers. It is a summer annual broadleaf weed characterized by its pentagon-shaped leaves, long vines and spiny seed clusters. Burcucumber emerges all season long starting in early May and continuing through mid August, although plants emerging after mid July often do not produce viable seed. In Pennsylvania, burcucumber is most common in the southeast but is also found in scattered patches throughout the state.
In general preemergence herbicide programs are not effective for control of burcucumber in corn or soybeans. Several post-emergence herbicides look promising for control of burcucumber in corn. Prosulfuron and primisulfuron (Beacon), available as a pre-mix called Exceed, provided good control of burcucumber in two of three of Penn State's 1995 field trials. Other products including Marksman, Buctril plus atrazine, and Beacon plus Banvel or atrazine can also provide control of emerged plants. In soybeans, research from Maryland and experience by Pennsylvania producers suggests Classic post is effective for controlling emerge plants. Regardless of herbicide, consistent residual control will continue to be a problem in some fields. The following table ranks the performance of several corn and soybean herbicides. No-tillage systems may help reduce burcucumber populations over the long run possibly due to less mid and late season seedling emergence, although effective post control must be used in combination. Also, harvesting infested fields as silage may reduce the spread of burcucumber if the seeds are not fully mature. Burcucumber spread is thought to be mostly tied to moving equipment from field to field and farm to farm, so remember basic weed management practices such as cleaning equipment before leaving infested fields and monitoring purchased feed for burcucumber seeds. Finally, attack small infestations before they become bigger problems.
| Corn | Contact/Residual | Soybeans | Contact/Residual | ||
|---|---|---|---|---|---|
| Accent | 7/N | Canopy (pre) | 7/6 | ||
| atrazine (1.5 - 2lb/A) | 8/6 | Scepter (pre) | 7/6 | ||
| Banvel (1pt/A) | 7/N | Classic | 8+/6 | ||
| Beacon | 8/6 | Cobra | 8/N | ||
| Buctril | 8/N | Blazer | 8/N | ||
| Exceed | 8+/7 | Reflex | 7/N | ||
| + 1/2 pt Banvel | add 1/0 | ||||
| + 1.5 lb atrazine | add 1/+ |
David Messersmith, Graduate Research Assistant, Dept. of Agronomy, and
Bill Curran
There are several species of insects which can feed on the root system during the first five or so weeks of corn development. A variety of symptoms can result from this feeding, including wilted plants (particularly the youngest leaf), skips in the rows, and stunting.
The first activity of seedcorn maggot is the emergence of the adults in April, and this flight activity can occur from April to about mid-June in our climate. Although there are probably two generations during this time, it is difficult to predict any high vs. low-risk planting dates based on these two generations, because they are too variable. These flies emerge and lay eggs in fields. Larvae locate the seeds using carbon dioxide emitted by the germinating seeds. They prefer seeds which have absorbed moisture. Generally, they feed only on the endosperm and germ, although they can do some feeding on the growing point of soybeans. They do not feed on roots, as do wireworm and white grub. This is important to remember, because once the corn plant is emerged and has active green tissue and is therefore not dependent on the seed for energy, the plant is past the danger point with seedcorn maggot. There are certain environmental situations associated with seedcorn maggot problems. Populations tend to be associated with legumes, particularly alfalfa. Problems are also worse when there are multiple stress factors such as cold/wet weather, deep seed depth, poor seed (low energy reserves) and herbicide injury. There are also some tillage and cropping patterns which may lead to seedcorn maggot problems. See table 2 for a brief summary of these associations.
The reason that seedcorn maggot is associated with tilled green vegetation and manure is probably the presence of decaying organic material which attracts egg-laying females. Waiting a week or two after tillage of the plant material (cover crop or weeds) to allow the vegetation to break down, or leaving the material on the surface and using a burndown herbicide, will mean that the field will be less attractive to the flies.
Wireworm, of which there are several species, are most often associated with corn fields planted into established sods, meadows, pastures, small grains. This is because the larvae spend several years underground feeding on roots of grasses, and will be present at the time of planting a corn crop. Similar to the seedcorn maggot, these larvae eat the germ and hollow the seed. Larger larvae bore into underground stem, and may feed on tender roots during summer. White grub is similar to wireworm in that it most likely attack corn planted into ground which has been perennial sod. The insect feeds on roots in the spring and perhaps into the summer.
There are no scouting techniques for seedcorn maggot. Instead, the tillage, cropping, and environmental conditions need to be assessed in order to make a judgement as to whether this insect may be a problem. Fortunately, effective and fairly inexpensive chemical control options exist to control seedcorn maggot. Seed treatment products cost about $0.80 to $1.00 per acre. They are effective if two things are kept in mind: good seed coating and the active ingredient. First, studies have shown that inadequate coating of the seeds will result in skips in the corn rows, presumably where seeds have not been coated. Put the seed into a separate container (be careful about exposure; read the label) to coat the seed well before putting it in the planter box. Table 3 shows that products containing diazinon are more effective at controlling seedcorn maggot than those containing lindane.
| Tillage/Cropping | Likelihood of Having Seedcorn Maggot Problems |
|---|---|
| Planting immediately into tilled, green vegetation | Higher |
| Presence of Manure | Higher |
| Waiting after tilling to plant | Moderate |
| Planting into green vegetation | Moderate |
| Planting into corn or soybean stubble | Lower |
| Low residue | Lower |
Wireworm can be controlled under low to moderate population densities with a seed treatment, and products containing lindane are better at controlling this insect (see table 3). Seed treatments, however, may not work for this insect under high populations. None of these seed treatments will control white grub. There are a number of granular insecticide options available (see The Agronomy Guide for more information).
How can wireworm and white grub populations be assessed prior to planting? We are lacking research in this area, but some general guidelines exist. A simple shovel is one way to look for these insects. If you find one or more white grubs or wireworms per square foot of soil, a granular treatment may be needed. Another way to look for wireworm is to use a bait trap.
This is simply a hole about 9" wide and 6" deep, with a handful each of wheat and corn seed (untreated), covered with loose soil, then finally covered with clear or black plastic, with the plastic held down with soil or rocks. Two of these traps are placed in the field about 4 weeks prior to planting. Three weeks later (1 week prior to planting), the seed is uncovered and examined for wireworm. Research in New Jersey and Missouri has suggested the following guidelines for wireworm control based on this trap. If about 1 wireworm per trap is found, a seed treatment is suggested. If no or very few wireworms are found, no treatment is needed. If much greater than 1 per trap is found, then a granular is suggested.
| Insecticides (+fungicides) | Product | Controls: |
|---|---|---|
| diazinon (+captan) | Agrox 2-Way Blue Ribbon Protector | seedcorn maggot |
| lindane (+captan) | Isotox Seed Treater-F | wireworm* |
| diazinon + lindane (+captan) | Agrox-DL Plus | seedcorn maggot, wireworm* |
| diazinon + lindane (+carboxin) | Germate Plus | seedcorn maggot, wireworm* |
Steve Spangler and Dennis Calvin
William S. Curran
Assistant Professor Weed Science
wsc2@psu.edu