CMEG Crop Management Extension Group

Field Crop News

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

April 8, 2008    Vol. 08:05

IN THIS ISSUE:

The real time pest prediction maps are up and running, soil temperatures are rising and weevil hatch is beginning. Be sure to bookmark the website for future use. http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu%23#

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

The battle between maritime air (cool, damp, dull) and much milder weather (sunny, above seasonal readings) will continue to be centered near Pennsylvania during the next five days. After some showers move through on Wednesday, sunshine will return in most sections for about a day with more pleasant conditions in eastern sections. Ocean—cooled air will return to the eastern two—thirds of the state later Thursday and part of Friday. A complex storm will cross the region on Saturday and be followed by several days of chilly, breezy, dull weather (particularly in the mountains). This may also bring the last widespread snow showers (or mixed sprinkles and flurries) to the hilly terrain late Sunday into Monday. A brief warm—up is expected at the middle of next week, otherwise temperatures will stay near or below seasonal levels for the majority of April.

There is a growing drought in the Mid—Atlantic region that may influence southern and eastern parts of the Commonwealth later in April or more likely in May, though cooler than average conditions should persist into May. There is a possibility of a late killing frost in parts of the state during mid—May. Summer rainfall is expected to be a bit below normal, but June and August are favored to be on the wet side for the majority of the state.

Evaluating Alfalfa Stands — Marvin Hall, PSU Forage Specialist

As alfalfa begins spring growth many producers are looking at alfalfa stands questioning if they are worth keeping another year or should they be harvested early and rotated to corn this spring. Unfortunately this is not always a yes or no decision.

Established Stands: The magic number of plants that traditionally indicated when it is time to rotate out of an established alfalfa stand is 4 – 5 plants per square foot. However, depending on fertility and weed invasion, alfalfa stands with 4 – 5 plants per square foot can yield as much as a stand with many more 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 number of stems per plant compensates for fewer plants and maintains the yield.

A better indicator of the productivity than the number of plants is the number of stems per square foot. Fields with 55 or more stems per square foot produce maximum yields. As the stem number declines below 55 per square foot yields begin to decline. Once stem numbers falls below 40 per square foot alfalfa fields begin to lose profitability and should be rotated out of alfalfa.

Alfalfa plantings made last fall or this spring: Plant density in new alfalfa seedings should be a minimum of 15 plants per square foot. This greater density is needed because the plants have not developed large crowns yet and will consequently have fewer stems per (directly related to yield) plant than older plants.

Alfalfa Weevil Scouting — Marvin Hall, PSU Forage Specialist

Spring is here and many south facing slopes have accumulated more than 300 growing degree days (GDD base 48 °F) which is the threshold for alfalfa weevil to become active. Alfalfa plants have just begun to grow so a little weevil damage can have a big impact on 1st cut yield and plant health. Weevil larvae (cause the most damage) have “biting and chewing” mouth parts so initial damage is easy to identify as feeding (chunks missing) on alfalfa leaflets. If you see feeding damage and want to determine if they are approaching the “economic threshold”, collect an alfalfa stem from 30 spots in the field (total 30 stems) and place them upside down in a plastic bucket. Beat the stems, in groups of 10, against the bucket 15 times to dislodge the weevil larvae from the stems. Count the larvae and refer to economic threshold tables in “A Pest management Program for Alfalfa in Pennsylvania”.

Soil Temperature for Corn — Sjoerd Duiker, PSU Soil Management Specialist

I was checking the soil temperature under my lawn in the early morning and it varied between about 40–42 degrees here in Centre County. Now is the time to check your soil temperature as one ingredient into corn planting decisions. As a general rule, soil temperature measured at 2” depth at 7–8am should exceed 50F customarily. ZedX reports average soil temperature measured under short—mowed grass (http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu%23#). The information shows that average soil temperatures in the southeast are close to 50F. However, the average daily temperature is the sum of the daily minimum and maximum temperature divided by 2, so it will be higher than the minimum temperature. To get an estimate of the minimum soil temperature you ought to take off some 4–5 degrees from the average daily temperature. Best is to measure the soil temperature yourself, however, because soil temperature depends on 4 local—specific factors: (1) incoming radiation; (2) outgoing radiation; (3) heat conduction and (4) heat capacity. The incoming radiation is affected by cloudiness and aspect (north or south—facing slope). The outgoing radiation is affected by the albedo (reflection) of the soil surface (dark soil reflects less, light residue reflects more). Heat conduction is affected by the residue cover (acts as insulation) and moisture content of the soil (more moisture — greater conduction of heat to deeper depths). Finally, the heat capacity of the soil varies with moisture content (wet soil takes more energy to warm up than dry soil). The soil temperature at 2 inch depth varies widely during the day, and more so in bare, tilled soil than in no—till soil with residue cover. The soil temperature between morning and early afternoon can vary 20 degrees on a sunny day in conventionally tilled soils. In no—till the amplitude is usually more like 10F. On a cloudy day the swings in soil temperature are small. A few years back we measured the soil temperature during a sunny day in May in a trial. It is evident that the minimum soil temperature was not very different between tillage systems, but the maximum temperature was quite a bit higher in the conventionally tilled soil. This trial was planted into corn stalks. Strip and zone tillage helped to increase the soil temperature in the row, resulting in faster germination and early growth than in no—till, but in the end the corn yields were not affected by tillage system in our study (over a 3—yr period).

Optimizing Gramoxone and Glyphosate Burndown — Bill Curran, PSU Weed Specialist

Timothy Mite Update — Andrew Frankenfield, Montgomery County Educator and Marvin Hall, PSU Forage Specialist

Cereal rust mites (a.k.a. timothy mites) eggs have hatched and are feeding on timothy leaves across southeast Pennsylvania. These mites are active only early in the spring and are generally not a problem after first cutting. Now is the time to get out there and determine if they are in your timothy fields. Be sure to check the whole field, the edges and middle. Look for purple or wrapped leaves especially in fields with a history of timothy mite problems. Under magnification (20x) they look like white maggots laying in troughs between the leaf veins. The eggs are round and clear to white to reddish in color.

The mites feed on the surface cells of the leaf between the veins. This causes the leaf to curl, as if drought stressed. This is really obvious in April when there is plenty of soil water and little transpiration is occurring. The effect of the mite on timothy can reduce yield between a 30 and 100%. In addition, herbage has a brownish color that lowers timothy’s market value.

Treatment
Sevin XLR PLUS is the only known and registered method of controlling cereal rust mites. It should be applied at 3 pints per acre with at least 20 gallons of water or UAN (25 gpa is better). The timing of the application is typically mid to late April or 3–4 weeks after green up on fields with a history of mites and/or when 25% of the plant tillers are beginning to curl.

There have been reports of leaf burning, stunting of growth and reduced yields as a result of applying UAN, Sevin XLR PLUS and 2,4–D as a tank mixture in years past. If this application is planned it would be best to apply to the oldest stands due to the risk of injury. It is safest to spray the UAN and Sevin together and then put on the 2,4–D later as a separate application. The mixing order is important as well. If you are spraying Sevin, water and UAN use this order: add the desired amount of water to the sprayer tank, add the Sevin slowly to the tank and then add the UAN then agitate and then add 2,4–D if desired. If you are using straight UAN: put some UAN in the sprayer tank (blend aid can be added at this point) then mix the Sevin in a 5 gallon bucket with water and add to the tank then fill to half full, agitate and add 2,4–D if desired and fill the remainder of tank.

For more information on Cereal Rust Mites visit
http://www.ento.psu.edu/extension/factsheets/cerealrust.htm
PA Supplemental label http://www.ento.psu.edu/extension/SevinXLRrm.pdf
Sources: http://www.ento.psu.edu/extension/factsheets/cerealrust.htm and Del Voight

Horse Pasture Renovation and Management — Andrew Frankenfield, Montgomery County Extension

As the grass begins to green up horse owners are eager to improve their pastures to get rid of those weeds and grow more grass. Stocking rate and turnout time are the two most important factors that affect a horse pasture. When there is less than 2 acres per horse rotational grazing and a sacrifice area must be used to maintain the pasture’s productivity. In this situation a group of compatible horses can graze a paddock (area of divided pasture) for approximately 3 to 6 days, then be moved (rotated) to a fresh paddock. Limed and fertilized Kentucky bluegrass should be the main grass in this system, because it withstands close and continuous grazing better than most other grasses. When well established and properly fertilized, it produces a reasonably dense and attractive sod. There are newer varieties of pasture grasses such as meadow brome, diploid perennial ryegrass, orchardgrass and bluegrass that can tolerate shorter grazing heights, but they too benefit from a rest period.

Often pasture owners want to reseed in the spring when they realize they don’t have as much grass in their pasture as they do in their lawn. Unfortunately throwing some grass seed on bare ground in April and hoping for a nice pasture by May is unrealistic. Many times it is better to wait until August to reseed a pasture so the following steps can be completed for a total pasture renovation.

  1. Soil test to determine exactly how much lime and fertilizer are needed.
  2. Apply required lime several months before seeding. Disk or plow to mix lime evenly with the soil. If large amounts of fertilizer are to be applied, it should be disked into the soil prior to planting. Small amounts of fertilizer can be applied through the seeder at planting.
  3. Select a seed mixture that complements the pasture drainage characteristics.
  4. Destroy or suppress old pasture by plowing or using herbicides.
  5. Use the appropriate method of seeding, based on extent of tillage.
  6. Protect the seeded area until new plants are well established. When recommended mixtures are seeded without a companion crop and weeds are controlled, new seedings can become established in a single year.

Remember if the stocking rate is less than 2 acres per horse a sacrifice area and rotational grazing must be utilize to prevent overgrazing; if not, it is likely that the pasture will return to the condition it was in prior to renovation within a year or two.

Penn State has a number of good publications; here is a link to them. http://www.das.psu.edu/publications/index.cfm?queryKeywords=9&searchByKeyword=%AB+By+topic&queryString=

Land Rental Agreement Survey — Andrew Frankenfield, Montgomery County Educator

The Crop Management Extension Group at Penn State Cooperative Extension are asking for your help to benchmark land rent throughout Pennsylvania and it's counties over time. Currently the average cash rental rate in Pennsylvania according to PA Agricultural Statistics is $48 per acre for cropland and $30 per acre for pasture. From that value it is impossible to determine what the range of cash rental rates are in a specific county and with varying soil types.

This information will to be used internally by Extension and will not be publically disclosed.

Responses are anonymous.

These results will not be printed and shared with the public.

Thank you.

Please click on the link below to access the short survey http://www.surveymonkey.com/s.aspx?sm=PVCdqb4GNDX_2fc252Mc3rnQ_3d_3d

Contributors: Extension Educators: Andrew Frankenfield (Montgomery), Kevin Fry (Armstrong), Mena Hautau (Berks), Mark Madden (Sullivan), Tom Murphy (Lycoming), Dave Messersmith (Wayne), Craig Williams (Tioga), John Roehl (York), and Jeff Graybill (Lancaster). Dept. Crop & Soil Science: Marvin Hall, Sjoerd Duiker, Del Voight.

Editor:Kevin Fry, Extension Educator, Armstrong County

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