August 8, 1997 Vol. 97.10

IN THIS ISSUE:

Calendar

• NCRS Program on Soil Conservation postponed until September 23 & 24, 1997

Announcements

• NEW Book! - "Weeds of the Northeast"

Production

• Crop Rotations in 1997

Pest Management

• Manage Those Perennial Weeds This Fall
• Effect of Ensiling and Animal Feeding on Weed Seed Viability

Agent's Corner

• Fayette
• Lebanon
• York

Degree Day Accumulations

ANNOUNCEMENTS:

NEW Book! - "Weeds of the Northeast"

This new book contains about 300 weed species that are common to the Northeast region, from south to Virginia, north to Maine and southern Canada, and west to Ohio and Wisconsin. It contains weeds species from various groups including grasses, grass-like weeds, herbaceous broadleaves, and woody perennials. This guide helps to identify species based on vegetative characteristics rather than floral features. Many color photos and line drawings are included to provide additional help in identification. A description of characteristics for each species is included, as well as, other information on habitat, geographic distribution, potential toxicity problems, and similar species. This book also includes a vegetative key to the weeds, numerous identification tables, and a glossary.

"Weeds of the Northeast" by R.H. Uva, J.C. Neal, and J.M. DiTomaso, 1997, is published by Cornell University Press at a cost of $29.95 for a paperback and $60.00 for a cloth cover copy. To order, include a check or money order and send to Cornell University Press, P.O. Box 6525, Ithaca, NY 14851-6525 or call (607) 277-2211 to order.

This book is an excellent reference guide for weed identification and related practical information on weeds in the northeastern U.S. It contains some species not found in other popular texts and is formatted in an easy-to-use lay-out.

Dwight Lingenfelter

Production:

Crop Rotations in 1997

Last winter I spent some of my time at winter meetings reviewing the benefits of well thought out crop rotations that avoided long rotations of corn or alfalfa. Our experiences in the field in 1997 are reinforcing my belief in the need for a sound crop rotation plan. Here's my top ten list for rotations in 1997.

1. Rotations enhance no-till success. Stand problems and delayed emergence in 1997 no-till corn on corn were common. Corn stands were better following other crops.
2. Rotations reduce insects. This year corn rootworm beetles are high on corn following corn and corn rootworm damage is common- even on some treated fields.
3. Rotations increase drought tolerance. I've seen several examples where corn following corn was rolled due to drought while corn following sod in the adjacent field was not.
4. Crop rotations increase crop diversity. Small grains did well this year and soybeans may benefit from late rains. Having some of these crops on the farm helps out in drought years.
5. Rotations reduce weeds. Dandelions in alfalfa and perennials in no-till corn seemed especially bad this year. Rotation is a good cure for these problems.
6. Fall killed sods are good for corn. Controlling sods this spring was difficult and many needed to be resprayed. The regrowth used up valuable moisture. Those who fall killed their sods were ahead of the game.
7. A well planned rotation helps to avoid mid-summer feed shortages. Silage and hay was expensive this summer. Its risky to transfer silages in hot weather. Also, cows don't like the change in rations.
8. Short rotations reduce fertilizer use. We interviewed several farmers this year about rotations and each shared success stories how they have cut back on N and K inputs with short rotations or by including soybeans in a corn/alfalfa rotation.
9. Open winters are hard on alfalfa. Stand counts from 20 alfalfa fields that we scouted in Franklin county were unusually low this year- possibly due to the open winter we had last year and in 1995-96. Many were good candidates for rotation.
10. Double crop corn after alfalfa is great. What! Double crop corn has been real ugly this year. Well, I guess 9 out of 10 isn't bad.

Greg Roth

Pest Management:

Manage Those Perennial Weeds This Fall

Over the next several weeks, the opportunity for reducing infestations of perennial weeds such as hemp dogbane, common milkweed, wirestem muhly, Canada thistle, and quackgrass is greatest. Unfortunately, in order to take advantage of this window, the appropriate crop rotation that allows a timely herbicide application is necessary. Fall control of perennial weeds using a systemic herbicide requires coming out of a fall or spring seeded small grain such as wheat or oats or an early maturing summer annual such as snapbeans or peas, or rotating away from a pasture or hay crop. Regardless, the rotation must allow a 4 to 6 week period of weed regrowth prior to the herbicide application.

Many of our herbaceous and woody perennial weeds tend to go dormant with or shortly after the first frost. Shorter day length and cooler night-time temperatures signal plants that winter is approaching and to start the movement of sugars and carbohydrates from leaves to roots. An effective systemic herbicide such as Roundup, 2,4-D, or Banvel can translocate or move along with the sugars and carbohydrates to perennial vegetative structures such as rhizomes killing the active buds or meristems. The harsh winter environment can further stress the treated perennial plants aiding in their eventual destruction. Some follow-up tillage 2 to 3 weeks after application can also help. In general, herbicide applications should be made from early September to mid-October, depending on geographic location and weed species. Treat weeds such as wirestem muhly, horsenettle, hemp dogbane, and common milkweed by mid September if possible, while Canada thistle and quackgrass control may still be achieved in mid-October. Perennial plants should have healthy green leaves present, an indication that they are active and likely susceptible to the herbicide. If the leaf tissue is discolored, or the plants have been trampled or injured by harvesting equipment or insect feeding, or if many of the leaves have fallen, it is doubtful that a herbicide application will be effective. The following table provides some herbicide effectiveness information for some perennial broadleaf weeds.

Bill Curran

Effect of Ensiling and Animal Feeding on Weed Seed Viability

The viability of seeds that weeds produce can be affected by many on-farm practices like ensiling, animal feeding, and subsequent manure storage. The effect of ensiling on weed seeds is species dependent, however ensiling generally reduces the viability of most weed seeds. Grass species tend to be more sensitive to ensiling than broadleaf species. This can be attributed to the hardness of the seed coat since many broadleaf weeds have harder seed coats than grass weeds. Field bindweed, velvetleaf, burcucumber, and jimsonweed are all broadleaf weed species that have been shown to be capable of surviving the ensiling process. Velvetleaf can even have higher germination rates after being ensiled. Recent research at Penn State with burcucumber indicates that seed maturity can also influence the ability of a seed to survive in a silo. Burcucumber seeds that were immature at the time of ensiling were essentially killed after 2 months in a silo while mature burcucumber seeds were not affected by ensiling. The importance of silage temperature, moisture, and pH on the survival of weed seed is not known. Also, no consistent relationship has been found between length of time the seed remains in the silo and its ability to germinate. It is generally agreed that the danger of spreading certain species of weeds by means of corn silage or haylage is reduced but not eliminated by ensiling the crop.

Animal feeding and subsequent manure storage can further reduce weed seed viability. The viability of most species, especially grasses, can be dramatically reduced by feeding and manure storage. However some hard-seeded species can pass through an animal and be relatively unaffected. In one study, the viability of velvetleaf seed was not affected by passing through the digestive tract of cattle and germination was actually increased. Velvetleaf seed can also remain viable after being buried in cow manure for one month or more. With that said, dairy manure appears to only be a minor source of weed seed. In a sampling of manure from 26 New York dairy farms, Cornell researchers found a large number of weed species but relatively few viable seeds of each species. When compared to typical seedbank populations, the total amount of viable weed seeds found in the manure samples was minor. The Cornell researchers concluded that manure from New York daries was only a minor source of weed seed. However, weed seed contaminated feed and manure can be responsible for introducing new or exotic weed species into an area - especially if they have a hard seed coat.

Dave Messersmith
Union County

AGENT'S CORNER

Fayette County Wheat Variety and Planting Date Trial

On October 7, 1996 fourteen varieties of wheat were planted no-till on Burd Farms in corn stalk residue and on October 24 in a portion of the same field a later planting was made.

The purposes of the trial was to develop some yield information on recommended varieties planted in the SW area of the Pennsylvania and to cooperate with other agents in the state to develop data relative to early and late planting of wheat and the potential effects on yield.

Varieties used were Pioneer 2540, 2545, 2548, and 2568, Challenge, Clemens, Coker, Elkhart, Dynasty, Freedom (with and without Bayleton), Foster, Pennmore, Sawyer, and Wilkens.

The plot was sprayed with Roundup and Banvel in the fall and with Banvel again in the spring. Rich Burd also applied a split application of nitrogen in the spring using 300 lb. of 18-5-9 and 260 lb. of 19-19-19 equivalent three weeks form the first application.

After a relatively mild winter with little snow and a significant freeze in March that was threatening, the crop recovered nicely and the obvious visual differences between the early and late planted areas disappeared. The spring was dry which reduced the effects of diseases.

Harvesting occurred on July 18 where each plot's yield was weighed and adjusted for acreage and moisture. Yields ranged from 70 bushels per acre to 95.6 bushels per acre with a 15 bushel variance of the "check" variety. Test weights were consistent between 58 - 60 lb. per bushel.

The later planted wheat yielded 7.13 bushels less than the same "check" variety planted adjacent to it and earlier. Holes in the stand were noted in the late planted plot where the seed or seedling didn't survive and winter.

More complete detail about the yields is available from me if there is interest.

SW PA Drought

Most of the SW PA area either has or still is suffering from some drought stress. Small grain crops were good, but corn and aftermath hay crops are stressed. Isolated areas of the region have received sufficient moisture within the past two weeks to significantly help the corn and third cutting hay crops. But in other areas, bad drought stress remains as of August 6, 1997.

There are a few farmers planning to cut some corn for silage due to poor crop conditions.

Don Fretts
Fayette County

Lebanon County

Lebanon recieved a rainfal that basically saved most of the crop. More than 3.5 inches of rain fell over a 36 hour period. If it had waited another week pollination may have been severely affected. Although the rain brought some new growth it still continues to be dry. Some producers have corn 4 feet high and tasseling. In addition Japanese beetles and rootworm beetles were feeding heavily on the silks. It is still too early to determine pollination but it appears pollination will not be affected by the dry conditions at this point.

Third cutting of alfalfa was sparse and fourth cutting is getting much pressure from potato leaf hoppers. So far alfalfa seems to be growing well under these dry conditions.

Soybeans are pretty much fully podded and starting to fill the pod. We need rain soon to assist pod-fill. Also, weeds are coming back and some producers will need to apply additional herbicides to manage them or they may wait and use a Roundup preharvest application.

Pastures are greening and already some have allowed animals back into them. This is not a good idea however, it would have been better to wait until the pasture fully recovered before letting animals out.

Del Voight
Lebanon County

York County

Much needed rainfall came to our area July 22-24. Growers reported as low as 1.1 inches in the southern part of the county to as much as 3+ inches in the northern part. Extremely hot temperatures following the rain somewhat couteracted the benefit, but fortunately that was followed by a period of cool weather as a large part of the corn acreage was entering tasseling.

Still we went from a potentially disasterous crop year to one which still has the potential for a fair to good yield for corn and good for full season beans. We're not "out of the woods" yet and what rain we get from here on for grain filling periods will still be the deciding factor. Mite damage was beginning to show up on the edges or corners of some bean fields just as the aforementioned rain came. Excellent yields and test weights were reported for wheat. Double crop bean fields look like double crop bean fields that don't get any rain - short, thin and spotty.

Leafhoppers are continuing to make their presence known as shown by the yellowing of fields which are ignored or otherwise left unsprayed. Stay tuned.

John Rowehl
York County

William S. Curran
Assoc. Prof. Weed Science

1997 DEGREE DAY ACCUMULATIONS:

To track corn and insect development, compare the 1997 cumulative degree-days shown in Table 2 to the required values in Tables 3 and 4. Choose a location that is closest to your site when making comparison.

The cumulative degree day value given is for the number of degree days needed after tillage of manure or green surface vegetation before it is recommended to plant corn in a field to avoid injury from seed corn maggot.

Dennis Calvin

William S. Curran
Associate Professor Weed Science
email: wsc2@psu.edu

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