CMEG Crop Management Extension Group

Field Crop News

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

May 27, 2008    Vol. 08:12

IN THIS ISSUE:

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

A surge of rather cool, but dry air will spread across the state by Wednesday morning. In fact, readings in the northern tier will likely be near freezing at daybreak. Clear and seasonably cool conditions will be the rule for Wednesday and Thursday with virtually no chance of rain either day. By Friday, a return flow of warmer and more humid air will deliver partial cloud cover and a thunderstorm in the northwestern counties (Mercer to McKean). May should end with the first risk of strong to severe thunderstorms for the southern and eastern half of the Commonwealth. It will be sticky on Saturday and as a cold front presses into the state, showers and thunderstorms will erupt, some may be very strong later in the afternoon and early evening. Cooler, drier conditions are expected on Sunday with an active breeze. The beginning of next week (Monday—Tuesday) promises dry and milder weather with another opportunity for showers centered on Wednesday, though it may also rain some on Thursday.

The longer term outlook for June indicates that cooler than average temperatures are likely and below average rainfall — at least until mid—month. The anticipated early June short heat spell appears more likely during the third week of the month. Once again, summer temperatures are expected to average near normal — likely meaning a cool start to the season (Jun—Jul) and a very warm conclusion (Aug—Sept).

Check out the predicted Growing Degree Days (base 55) for Pennsylvania for the next two weeks at: http://climate.met.psu.edu/data/regional_gdd.php

Alfalfa Weevil Update — Paul H. Craig, Dauphin County Educator

Across the southern region of PA most, but not all, of the first cutting of alfalfa and orchardgrass stands has been harvested. In many situations forage producers took an “aggressive” forage harvesting strategy and were able to get first cut alfalfa and grasses at the late pre—bud stage or right at bud stage resulting in excellent forage quality. However reports from producers across the area are noting an increasing sign of alfalfa weevil damage to stands that were not treated with insecticides nor harvested by this time. Scouts and producers are reminded to check regrowth of second cutting for feeding injury from these weevil larvae.

In early May crop scouts across the state were reporting increasing levels of weevil larva in first cutting. At that time many producers optioned to treat their stands and excellent control was noted. Other forage producers decided to take the aggressive harvest strategy but the weather did not cooperate and harvest was delayed by a week or so and this delay resulted in the further development of this pest and some significant forage loss. Some fields that have not been harvested with high levels of the larva are showing the characteristic symptoms of a silvery cast to the field as the larva feed and leave shredded leaf tissue across the tops of the stands.

Scouts and producers are reminded to take a close look at the regrowth of harvested alfalfa stands for feeding injury to the newly developing buds on the crowns. High levels of larva can easily consume the new buds faster than they can grow. If your harvested stands are not greening up, a closer examination of the stand is in order. When the small shoot is destroyed the plant needs to regenerate new growth and these buds can be damaged also. The result is a long delay in regrowth rates and a significant reduction in plant reserve levels.

To examine for the regrowth feeding you will need to take a close look at the stubble. This cannot be done from the seat of a truck or four wheeler. You will need to almost get down on your belly. Look closely at the development of the new shoots. Where larva levels are high there will not be any new growth evident. Look on the remaining stubble for evidence of regrowth and check the crowns for new shoots forming. If lack of regrowth is evident or if you observe 2 or more larva per crown a rescue treatment will be needed.

This spring the alfalfa weevils hatched over an extended time period and because of the “cooler” weather this spring development of the pest has been slowed resulting in increased pressure later in the season. Across the northern part of the state the insect is continuing to be found. Southern exposed fields are noted for being attractive to adults to lay eggs early and should be watched closely if you have not treated and are still waiting to harvest first cutting. Shortly the larva will be forming a pupa and eventually hatching as adults. When pupa stage begins the feeding damage ends. The adults will later hatch from the cocoon and lay some eggs in the fall on alfalfa stubble or overwinter and lay additional eggs next spring to start the process over again in 2009.

Forage Weed Control Issues — Dwight Lingenfelter, PSU Weed Science

Herbicides and alfalfa replant considerations: We are receiving reports about poor alfalfa stands that need to be replanted or overseeded. However, before simply dropping the seeder into the ground, you must first consider what herbicides have been previously applied. Below are the intervals necessary before replanting alfalfa for commonly used alfalfa herbicides:

Gramoxone Inteon 2S: no restriction
Poast Plus 1E: no restriction
Pursuit 2AS/70DG: 4 months
Raptor 1AS: 3 months
Select Max 0.97EC/Select 2EC: no restriction
2,4–DB/Butyrac 200 2E: not stated on label (3–4 weeks should be sufficient)
Buctril 2E: 1 month

Herbicide options in alfalfa: For those of you who are still battling weeds in alfalfa here is another reminder about some herbicide options to consider:

2,4–DB/Butyrac 200 2EC — May be applied at 1–3 qt/A to seeding or established stands to control broadleaves. Be cautious of hot weather (>90° F) during or shortly after application.

Gramoxone Inteon 2 (paraquat) — May be applied between cuttings at 1.5 pt/A to established stands immediately after harvest. Use only 1 pt for stands less than one year old. Do not use on mixed stands.

Poast Plus 1E (sethoxydim) — Poast Plus controls annual grasses and suppresses perennial grasses in seedling and established alfalfa. Apply Poast Plus at 1.5 to 2.5 pt/A to actively growing grassy weeds. Poast Plus should be applied to small grasses and performance improves with warmer temperatures. Do not use on mixed stands.

Pursuit 70DG (imazethapyr) — Pursuit may be used for weed control in seedling (2 trifoliates or larger) or established alfalfa. Apply Pursuit at 1.08 to 2.16 oz/A plus adjuvants to actively growing weeds 1 to 3 inches in height. Pursuit performance improves with warmer temperatures. If spraying during extended cold periods, expect weeds to respond slower or the herbicide can have reduced activity. Pursuit is effective on many winter annual broadleaves including small chickweed. Pursuit may be used on established alfalfa—grass mixtures.

Raptor 1AS (imazamox) — Raptor may be used for weed control in seedling or established alfalfa. Apply Raptor at 4 to 6 fl oz/A plus adjuvants to small, actively growing weeds and to established alfalfa in the fall or in the spring. Any application should be made before significant alfalfa growth or regrowth (3 inches) to allow Raptor to reach the target weeds. Like Pursuit, Raptor performance is influenced by temperature. Therefore, try to apply the herbicide on warmer days and when weeds are actively growing. Raptor has a similar spectrum of winter annual weed control as Pursuit. Do not use on mixed stands.

Select 2EC (clethodim) — Apply Select at 6 to 8 fl oz to actively growing grasses that are less than 6 inches tall. Rates up to 16 fl oz may be used to control larger grasses, annual bluegrass or perennials such as quackgrass. Include a crop oil concentrate in the spray mixture. May be tank—mixed with Pursuit, Buctril, or 2,4–DB for broadleaf weed control. Do not use on mixed stands.

Velpar 2L (hexazinone) — Apply Velpar to established alfalfa at 2 to 6 pt/A between cuttings and before 2 inches of regrowth. Velpar is effective on annual broadleaves and grasses.

Weed control in grass forages: Every so often we get questions regarding herbicide considerations and restrictions for grass forage situations. Over the past few years the options have remained the same. See Table 2.6–8 in the Penn State Agronomy Guide for a listing of products choices and comments. http://agguide.agronomy.psu.edu/pm/sec6/table2-6-8.cfm

For most of the products that contain plant growth regulator type herbicides (2,4–D, Clarity, Crossbow, ForeFront, etc.) remember to allow the seedling forage grasses to get established (4–5 inches tall, have a good secondary root system, and show good vigor) before making a herbicide application. Cimarron Plus also has some necessary establishment periods for different grass species before herbicide application that should be observed. Also, most herbicide for use in grass forage crops will severely injure or kill legumes. Don’t use these products if loss of legume species cannot be tolerated. In many cases, weed control is very important during the grass establishment period since weeds can become very competitive.

Adjusting Soybean Seeding Rates for Lower Quality Seed — H. Grant Troop, No–Till Agronomist, Capital Region

Obtaining adequate soybean stands can be challenging in light of the fact that a lot of lower quality soybean seed has been brought to the farm this year. Germination test rates have been noted from 75% to 90%. Let’s look at seeding rates for a variety that averages 2,700 seeds per pound at three different germination test ratings. The goal is 180,000 plants per acre from 180,000 Pure Live Seed (PLS).

90% germ x 2700 seed/lb = 2430 PLS/lb
180,000 ÷ 2430 PLS/lb = 74.07 lb/acre seeding rate

85% germ x 2700 seed/lb = 2295 PLS/lb
180,000 ÷ 2295 PLS/lb = 78.43 lb/acre seeding rate

75% germ x 2700 seed/lb = 2025 PLS/lb
180,000 ÷ 2025 PLS/lb = 88.88 lb/acre seeding rate

If you expect seed loss greater than that accounted for by germination test, adjust seeding rates accordingly. For example, if you expect an additional 5% field seed loss from a combination of cold soil, planter seed damage, and insects, run the numbers for 90% germination seed at the 85% germination level (10% loss to germination + 5% field loss) for an accurate seeding rate.

% germination — % field loss x # seeds/lb = PLSS/lb
PLSS/acre ÷ PLSS/lb = lb acre seeding rate

When we factor in field loss and subtract it from germination loss we end up with the projected Pure Live Seed Survivors (PLSS) (see equation above).

Early planted soybeans have been slow to establish. Soybean stand assessments should be done as soon as the crop is fully emerged. Early assessments allow for inter—seeding of thin stands. Significant delays in possible replant decision may require the complete reestablishment of soybean field(s) with inadequate stands. Do the math ASAP.

Rye: From Silage to Straw to Grain — John Rowehl, York County Educator

How many acres of cereal rye were to have been harvested for silage this spring and then got over mature because the rain held up harvest? Or perhaps the plan was to make “long straw” out of it and the rains then may have scuttled that plan and the priority for mowers, rakes and balers is now with getting hay crops harvested. So now they may be at “Plan B”; harvest it in July for grain and straw. That is a way off at this point but it is not too early to think about marketing, harvesting and handling, cleaning and storing, depending on your past experiences with this situation.

If you plant a lot of cover crop, marketing may not be a concern. But if you won’t use rye for seed for yourself, it would be a good idea to start thinking about who you might want to sell it to, wholesale of retail. That leads to the next consideration. Can you sell it all in bulk or will you have to get it bagged up? And, depending on how good of a job the combine will do of cleaning it in the field and on whether it will be drilled or broadcast, you may need to have it run through a cleaner.

If rye is held in bulk during storage, it should be no more than 14% moisture. If it needs to be dried to get down to that moisture level, the temperature of drying air should not ever be over 110 degrees F to avoid any effect on germination.

Since rye needs to be stored over the hot weather months before use, it has the potential for infestation and damage from insects. Whether you store it in a bin, a gravity wagon, piled on a concrete floor or in bags, you should make sure that the storage has been cleaned of any old grain that may be harboring potential storage insect pests. From what I can find, rye is not listed on most of the grain protectant insecticide product labels. Malathion dust and Bt do have rye on the labels. In my experience, Indian meal moths are the most frequent pest problem for rye. It is the larval stage that does the damage. But malathion resistance is known to occur and may not be that effective on this species. Hopefully with dry grain and good sanitation, you will be able to get away without a protectant. Bt can be used as a topdress treatment in the top 4–6 inches if it is held in a bin, wagon or truck. Bagged grain poses the bigger challenge of excluding the Indian meal moth larvae. This was probably more of a problem in the short term with burlap than now with paper or plastic. Keep an eye out for the silk tunnel—like webbing of the larvae on top of bags or grain piles that is a sign of larval feeding.

Upcoming Events—use the link to Calendar of Events (below) for contact information

June 1–3 Agriculture and the Environment Workshop in Harrisburg: Achieving a Balance
June 4 Small Grains Field Day at Landisville
July 1 Cover Crop Field Day at Tim Rodgers’ Farm, Centre County
July 1 Weed Twilight Tour—Landisville
July 2 No—tilling for Success Field Day—Landisville
July 10 Rock Springs Agronomy Weed Tour
July 22 and 23 Agronomic Field Diagnostic Clinics, Rock Springs Agronomy Farm

Contributors: Extension Educators: Susan Alexander (Jefferson), Paul Craig (Dauphin), Andrew Frankenfield (Montgomery), Kevin Fry (Armstrong), Mena Hautau (Berks), Mark Madden (Sullivan), Grant Troop (Lebanon) Dept. Crop & Soil Science: Marvin Hall, Sjoerd Duiker, Dwight Lingenfelter

Editor: John Rowehl (York)

Upcoming Events

Real time pest and heat unit activity: http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu#

Calendar of Events: http://www.events.psu.edu/cgi-bin/cal/webevent.cgi?cmd=opencal&cal=cal209&

Readers can subscribe electronically to this newsletter at the Field Crop News Web site.

If you have problems subscribing or wish to cancel your subscription, please contact Lisa Crytser by e-mail at lac8@psu.edu or by phone at 814-865-2543.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Penn State Extension is implied.

This publication is available in alternative media upon request.

The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901, Tel 814-865-4700/V, 814-863-1150/TTY.