CMEG Crop Management Extension Group

Field Crop News

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

April 7, 2009    Vol. 09:05

IN THIS ISSUE:

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

After a mild and much drier than average February and March, the weather pattern has shifted to a moister and rather chilly regime. In fact, the snow which has coated the northwest hills and Laurel highlands during the past day or so may return a couple more times during the next week. Abundant clouds and persistent cold winds will be the rule into Wednesday with some sun in the eastern sections later in the day. A few snow showers are possible early Thursday in the southern mountains and then a fast-moving low pressure system will spread a cold rain across the state on Friday. In the higher terrain and especially across the north, the rain should start as snow or sleet on Friday and after turning to rain, it may end as a mixture on Saturday morning. A fresh surge of cold, dry air will arrive for Easter Sunday and much of Monday with comfortably cool days and widespread freezes at night. A complex storm will approach the region later Monday and Tuesday with enough cold air in place to raise the risk of a sloppy mixture of rain, sleet and in some places snow—particularly in the mountains and northern counties. A warming trend is likely from April 16–19 before more cool air returns for the week after.

Odds still favor a cooler and wetter than average April. It may be that the warmest weather of the upcoming summer will be like a bookend, occurring in June and September with near or below normal temperatures expected in July and August. There are also indications that hurricane numbers and intensity will be down this summer compared with past years.

Planter Set-up and Operation in the Field — Sjoerd Duiker, Soil Management

To get good results, it is important to take time to set your planter up appropriately in the field, and to make adjustments according to soil conditions. You don’t want to plant in soil that is sticky and wet. Ideal is to have crumb soil conditions. The planter needs to be level with the soil surface, as well as the parallel arms on the planter units. The units cannot be cocked forward or backward. The most common remedy is to raise or lower the hitch on the tractor. More weight may also be needed on the planter in some cases. The next step is to drop the planter in the field, tie up closing wheels and seed firmers, and make a run with the planter. Count seeds in each furrow and measure the distance between them. At 30" row spacing, measure seeds in 17'6" length and multiply by 1000 to get the plant population per acre dropped by that unit. Spacing between seeds should be similar. Check how deep the seeds are placed and adjust depth gauge wheel settings until it is 1.5–2" deep. Untie the closing wheels and seed firmer and run the planter some more. The closing wheels cannot run on top of the seed and should close the seed furrow. If this is not the case, pressure may need to be increased on the closing wheels. However, the pressure should be set as light as possible to avoid compacting soil too much above the seed. Coulters should run to seed depth, preferably not deeper. Unit down pressure springs need to be adjusted according to field conditions. Fertilizer and insectide flow rates need to be checked to make sure you apply the right amount. Chains need to be oiled daily, and depth wheel arm greased twice daily. Add one tablespoon of graphite in each hopper for each 6 bushels of seed. You may need to increase the graphite application if the seeds are insecticide coating (check seed company specs).

Allelopathy, Friend or Foe — Bill Curran, Weed Science

Allelopathy refers to the harmful effects of one plant on another plant through the release of plant chemicals (allelochemicals). Allelopathic chemicals can be present in any part of the plant including leaves, stems, roots, flowers, or fruits. The chemicals can be released while the plant is living or after the plant dies as the plant parts decompose. Allelopathic inhibition is complex and can involve the interaction of different classes of chemicals (phenolic compounds, flavonoids, terpenoids, alkaloids, steroids, carbohydrates, and amino acids) with mixtures of different compounds sometimes having a greater allelopathic effect. One of the most well known examples of allelopathy is black walnut (Juglans nigra) which produces the allelochemical juglone, which affects some species greatly, while others not at all.

Although not all plants are allelopathic, many plants show some evidence of this chemical competition or protection. Much of the research in this area has focused on the allelopathic potential of weeds and crop plants. Several weeds including quackgrass, johnsongrass, and Canada thistle have been identified as species that produce allelochemicals. For crops, cereal rye (Secale cereal) has often been identified as an allelopathic species and has widely been studied as a potential suppressor of weeds. Other crop plants including oats, fescue grass, sorghum, and even corn and sunflower have been identified as allelopathic. Unfortunately, much of this research also shows that allelochemicals are generally short-lived, their concentrations can vary widely by species, cultivar, and growth stage, and they are often unpredictable in the real world. A study by Reberg-Horton et al. 2005 (Journal of Chemical Ecology 31:179-193.), examined ten different cultivars of cereal rye. He found significant differences in the amount of one common allelochemical (DIBOA) depending on cultivar. “Wheeler” rye inhibited goosegrass and pigweed root elongation 91 and 50% respectively, compared to a North Carolina “variety not stated” cultivar that inhibited goosegrass 77% and pigweed by only 8%. “Wrens Abruzzi” rye inhibited root elongation in both weed species over 90%. In the same study, concentrations of the allelochemical were higher when rye was younger (Feekes scale 5/6) compared to later stages of develop. However, with both Wheeler and the NC cultivar, the total amount of DIBOA per plant was greater later in the season simply because more rye biomass was produced.

At the same time, if a plant is known to successfully inhibit germination and growth of weeds, then it could have negative impacts on crops including corn. We often hear about the concern for allelopathy particularly with cereal rye and other small grains and this is especially a concern for small seeded crop species like alfalfa, clover, and forage grasses. However, corn growth is also sometimes reduced when planted into freshly killed cover crops such as rye. Soybeans planted into cereal grain cover crops is less of a concern. Whether allelopathy is a factor or other causes are playing a role (N immobilization, cooler soil temperatures, poor seed to soil contact, insects, etc.), several management considerations can reduce the potential for problems.

For most producers using cereal rye, wheat, or other winter cereal grain cover crops; 1.) ensure you apply adequate amounts of N prior to corn planting either through fertilizer or manure. The rapidly growing cereals will take up much of the available N and not return it to the system until it begins to decompose, plus the soil microbes require available N to breakdown the cover crop residues. So, a combination of factors can compete for soil N, potentially making it a limited resource; 2.) Kill the small grain when it is less than 15 inches tall before it reaches the boot stage (before Feekes 10); and 3.) Maybe most importantly, spray or kill the cover crop a good 10 days ahead of corn or soybean planting to give it time to “melt” down, recharge surface moisture, and help avoid certain insect problems associated with heavy crop residues. With this scenario, do not expect much if any help from the cover crop toward summer annual weed control. In order to impact germinating weed seedlings, the small grain cover must accumulate large amounts of biomass and almost reach the flowering stage (Feekes 10.5) to provide significant physical suppression of weeds from the surface mulch. Allowing the cereal to reach maturity and attain high levels of dry matter is a different objective than what is discussed here and requires additional considerations for success.

Important Stewardship Guidelines for Aminopyralid (Milestone and Forefront) Use in Pastures — Bill Curran and Dwight Lingenfelter, Weed Science

Because of the rapid success and adoption of Milestone and Forefront herbicides for managing weeds in grass pasture and hay, Dow AgroSciences is reminding farmers that these products have appropriate and also less suitable markets — they are not appropriate for all grass growers. Dow AgroSciences is actively promoting the stewardship of this chemistry to avoid potential problems by emphasizing the herbicide label directions to minimize injury to nontarget crops. Nontarget plant exposure and injury is the primary concern if the treated grass and subsequent produced manure is not managed properly. In the Northeast, two key areas of concern should be considered:

  1. Manure and Hay Management — Aminopyralid remains intact in forages in treated pasture and hay. When these forages are consumed by livestock, the herbicide passes through their digestive tracts without change and into the animal’s urine and manure. Aminopyralid passes through an animal in three days.

    Do not move animals from treated areas to fallow land if that area will be planted to a sensitive broadleaf crop without first allowing three days of grazing on an untreated pasture. Manure should be left on the pasture or if collected, it should be spread back out on pastures.

    Do not use treated plant residues including hay and straw (or manure from animals that have grazed forage or eaten hay harvested from treated areas within the previous 3 days) in compost or mulch that will be spread to areas where commercially grown mushroom or broadleaf plants may be grown.

  2. Crop Rotation — Aminopyralid is designed for use on permanent grass pastures and is not intended for use on temporary grass pasture or hay fields where the intent is to plant other crops.

    Do not rotate to any crop within one year following treatment. Do not plant broadleaf crops until an adequately sensitive field bioassay shows that the level of aminopyralid present in the soil will not adversely affect the broadleaf crop. In the Northeast, soybean, forage legumes including the clovers and alfalfa, tobacco, and vegetable crops are all a concern for carryover injury.

Early Season Insect Pests in Alfalfa, Timothy and Wheat — John Tooker, Penn State Entomology Specialist

Across Pennsylvania insect activity is starting to increase and growers need to keep an eye on their fields to ensure that economically damaging populations do not develop. Alfalfa fields are starting to see alfalfa weevil damage, timothy mites are active, and some cereal leaf beetle activity has been reported in wheat.

For the southeastern and southwestern portions of the state, alfalfa weevil is becoming active with first instar larvae causing pin hole-sized damage to leaves near the tips of plants. To get a sense of the expected developmental stage in your part of the state, see the alfalfa weevil map on the PA-PIPE system. Most of this early season feeding does not result in economic loss, but it is good to recognize the damage and be aware of which fields have greater activity. Those fields with larger populations will of course be where economically significant populations are more likely to develop.

Economic thresholds for alfalfa weevil are determined from the size of plants, the value of the hay, the cost of insecticidal treatment, and the number of larvae per 30 stems of alfalfa. To sample weevil larvae, systematically select 30 stems from across a field and shake them into a bucket. If the number of larvae exceeds the numbers in Table 1, a treatment might be warranted. Many compounds are available for controlling alfalfa weevil. See the Agronomy Guide for details.

Table 1. Threshold levels (# of larvae) for alfalfa weevil on plants 12–18 inches tall.
  Plants 12–18 inches tall
Value of hay per ton $60 91 114 137 160 183 225
$80 68 85 102 119 136 171
$100 54 68 81 95 108 137
$120 45 57 68 79 91 114
$140 39 49 59 68 77 99
$160 34 43 51 60 68 86
  $8 $10 $12 $14 $16 $20
  Cost of insecticide application per acre

Timothy growers should be on guard for timothy mite feeding. Feeding by this cool season pest causes the leaf blades to roll up tightly, but the mites are microscopic and challenging to see even with good magnification. Treatment is recommended if 25% of tillers show the leaf curling within several weeks of green-up. Chemical options are limited, but Sevin XLR has a supplemental label allowing its use against mites on timothy in PA.

Lastly, there are some reports from Delaware that cereal leaf beetle adults are active in wheat. So keep an eye on those wheat fields for this small black beetle, which has a reddish thorax or “neck.” These adults will lays eggs and the larvae from these eggs can quickly cause economic damage if they are overlooked.

Refuge Requirements for Transgenic Corn — John Tooker, Penn State Entomology Specialist

As growers plan to plant their corn fields, it is good to remind folks of the refuge requirements that accompany transgenic (Bt) corn. Whether using Bt lines that are active against rootworms and/or European corn borer (and other caterpillar pests), Insect Resistance Management strategies require that growers plant 20% of their acreage as non-Bt corn. This is a contractual obligation that growers accept when purchase the Bt corn. For rootworm traits, this 20% refuge has to be within the same field or in an adjacent field. For corn borer traits, this non-Bt refuge needs to be within a half a mile of the Bt field. For stacked traits, it is best to follow the rootworm requirements because they are more restrictive. Relying on a refuge planted on a neighboring farm is not allowed.

Seed companies check refuge compliance on a couple thousand farms each year and a county educator in southeastern PA recently learned of a compliance check in that part of the state. So be sure to plant those refuges, which are vital parts of preventing insects from developing resistance to Bt toxins and ensuring the effectiveness of this powerful transgenic technology.

Pennsylvania Women’s Agricultural Network Addresses Extension Needs of Women Farmers — K. Brasier, M. Barbercheck, N. E. Kiernan, C. Sachs. College of Agricultural Sciences, Penn State

The face of farming in American agriculture has changed, most notably through the steady increase of women farm operators. According to the 2007 Census of Agriculture, women were 30% of all farm operators. In 2007, there were 306,209 female principal operators (14% of all operations) in the US as compared to 237,819 in 2002. This constitutes an increase of almost 30 percent in five years (USDA, http://www.agcensus.usda.gov/). In 2007, women increased to nearly 14% of all principal operators in Pennsylvania. In total, there were 26,405 women farm operators in Pennsylvania, accounting for 29% of all farm operators in the commonwealth.

The increasing diversity of farm operators presents new audiences for whom Extension personnel and administration may want to develop programs to accommodate their unique educational needs and opportunities. The Pennsylvania Women’s Agricultural Network (PA-WAgN, http://wagn.cas.psu.edu/) is an organization that was founded with the purpose of creating educational opportunities for women farmers. Membership in PA-WAgN has grown from about 100 in 2004 to over 1000 in 2009. Members are women farmers, agricultural professionals, and educators committed to supporting and providing educational opportunities to women working in agriculture and ag-related businesses. PA-WAgN’s offerings target the needs of women farmers, but are available to all. These include on-farm education and hands-on workshops and on-line newsletters. Topics of recent farm-based, educational events have included business planning, farm management, direct marketing, farm equipment and safety, and health.

College of Agricultural Sciences faculty members of PA-WAgN also conduct research on the educational needs of women farmers. Some of our recent research on PA-WAgN farmer members found that:

For more information about PA-WAgN activities, and how you can participate, visit the Web site at http://wagn.cas.psu.edu/, or contact Linda Moist, lsm9@psu.edu.

Mark Your Calendar

Contributors: County Educators: Kevin Fry (Armstrong), Mena Hautau (Berks), Jonathon Rotz (Cumberland), Joel Hunter (Crawford), Paul Craig (Dauphin), Susan Alexander (Jefferson), Del Voight (Lebanon), Mark Madden (Sullivan), John Rowehl (York). Department of Crop and Soil Sciences: Greg Roth, Sjoerd Duiker, Marvin Hall, Ron Hoover, Dwight Lingenfelter, and Bill Curran. Department of Entomology: John Tooker. College of Agricultural Sciences: K. Brasier, M. Barbercheck, N. E. Kiernan, C. Sachs. Meteorology: Paul Knight.

Editor: Joel M. Hunter (Crawford County)

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