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August 10, 1998 Vol. 98.11

IN THIS ISSUE:

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 layout.

Dwight Lingenfelter
Agronomy

Production:

COUNTDOWN TO HARVEST

In many areas of Pennsylvania, corn has reached the silking stage by August 1 or shortly thereafter. Silking generally represents the midpoint of the corn plants growth cycle and indicates that approximately 60 days will be required until the grain reaches physiological maturity . Kernel development proceeds through a number of stages which have been characterized by such terms as blister, milk, roasting ear, soft dough, dent, etc. Since these descriptive terms can sometimes be difficult to interpret, alternative systems have been proposed. A staging system widely used by agronomists and crop consultants divides kernel development into six stages, designated numerically as R1, R2, through R6. This system can be used to predict potential dates of harvest for silage and grain. For example, some of our silage corn trials had just begun silking at Rock Springs on August 1- indicating they should be ready for silage harvest about a week to 10 days after full dent (or in about 50 days or September 20) and should then reach maturity about October 1.

KERNEL DEVELOPMENT IN CORN
Stage* Description Approx. Days from Silking
Silking (R1) fresh green silks, no visible blisters --
Blister (R2) visible blisters w/ abundant fluid 12
Milk (R3) mostly yellow kernels w/milky-white fluid, no solids yet (true roasting ears) 21
Soft Dough (R4) pasty or semi-solid (not edible), no visible denting 27
Dent (R5) majority of kernels dented or denting 41
Black Layer (R6) maximum kernel dry weight, kernel moisture 27-32% 64
*R-stages 1 through 6

Greg Roth, Agronomy,
Corn & Sorghum Management

WINTER GRAIN FERTILITY

As with any crop the fertility program for winter grains should be based on a regular soil testing program. Ideally, the soil levels for pH, phosphorus, and potassium should all be in the optimum range on the soil test report before planting. For wheat the pH should be between 6.0 and 7.0 and for barley it should be between 6.5 and 7.0. If the pH is low, the recommended limestone should be applied and worked into the soil as far ahead of planting as possible. If the magnesium is low, a dolomitic type lime should be used.

Both wheat and barley take up large amounts of phosphorus and potassium. If soil tests are in the low range, nutrients must be applied to build the soil up into the optimum range plus replace what is removed in the crop. For soils already in the optimum range, the recommendation only considers replacing what is removed. At high soil test levels there may be adequate nutrients in the soil to supply what the crop removes without any added phosphorous or potassium, in which case, the recommendation will be zero. For winter grains, all of the recommended phosphorus and potassium should be broadcast applied prior to planting. A small portion of this requirement can be applied through the drill. To minimize fertilizer injury, do not apply more than 30 pounds per acre of the recommended nitrogen plus potash through the drill. All of the commonly available fertilizer sources of phosphorus and potassium are acceptable for application to winter grains.

Nitrogen requirements of wheat and barley are also substantial. The actual amount of fertilizer nitrogen needed to meet this requirement will depend on the amount of nitrogen supplied by the soil. In Pennsylvania, this is largely influenced by the manure history of the field. Thus, nitrogen recommendations for small grains are mainly based on the manure history of the field as summarized in the following table:

Crop Manure
Every 1-2 yrs.		 Manure
Every 3-4 yrs.		 Manure
None recently
  ----------N recommendation (lb/acre)----------
Wheat 0-30 30-60 60-90
Barley 0 0-30 30-40

Within a given manure history category, the actual rate selected will depend on the yield potential and the nitrogen history of the field. For higher expected yields use the higher end of the recommendation range. Use the lower end of the recommendation range where the previous manure or nitrogen fertilizer rates were high or where lodging has been a problem in the past. Remember that because of the potential for lodging do not apply excess nitrogen to small grains.

Only up to 15 lb. per acre of the nitrogen should be applied in the fall at planting time. The balance of the nitrogen should be applied in the spring. If the plants did not tiller well in the fall the nitrogen should be applied by mid-March, otherwise, apply it anytime up to growth stage 5, which is the stage just before the stems start to elongate. The commonly available forms of nitrogen fertilizer are all acceptable for the winter grains.

Douglas Beegle
Agronomy, Soils

Pest Management:

INSECT ALERT

The following insects can be active during this time period. This does not mean they have been seen in the State, but it is the period of time when they can injure crops. Insects that have been reported are shown in bold type and specifics about their management are presented in individual articles. Pictures of each corn insect species, economic thresholds, and scouting guidelines can be seen on the world wide webpage, http://www.fra.cas.psu.edu/.

Corn
Corn rootworm adults and larvae
first generationEuropean Corn Borer larvae
second generation adults and eggs
single generation European corn borer larvae
fall armyworm
grasshoppers
Japanese beetle
Soybeans
potato leafhopper
green cloverworm
two-spotted spider mites
cabbage & soybean loopers 		bean leaf beetle
Mexican bean beetle
Japanese beetle
grasshoppers
stinkbugs
Alfalfa
Meadow spittlebug
pea aphid
Spotted alfalfa aphid 		potato leafhopper
alfalfa blotch leafminer
grasshoppers
clover leaf weevil
Small Grains
True armyworm grasshoppers  

Corn Rootworm Adults - Beetles continue to emerge in most areas of the state. Begin scouting fields when 10 % or more of the females abdomens are swollen and eggs can be squeezed out of the body. This indicates that the females are read to lay eggs and will stay in the field. Prior to this, newly emerged females up to 10 days old have undeveloped eggs and they tend to migrate between fields. Therefore, scouting too early can lead to an improper estimate of adult numbers in the field. Typically, mid-August is the ideal time to scout fields for beetles and make a management decision for next year.

Economic Threshold Values
Western corn rootworm, first year corn field 1.0 beetles per plant
Western corn rootworm, second year or more of corn 1.5 beetles per plant
Northern corn rootworm, first year corn field 2.0 beetles per plant
Northern corn rootworm, second year or more of corn 3.0 beetles per plant

European corn borer - First generation larvae and larvae from the single generation type of corn borer are in the last two instars and pupal stages of development. Adults are beginning to emerge in central Pennsylvania. Adult emergence should have begun about 10 days ago in southern areas of the state. Second generation moths will be flying and looking for fields to deposit their eggs during the remainder of August and into September. Fields that are in green silk during this period will attract adults and have larval infestations. Extremely late planted corn fields will have the highest corn borer populations.

Economic Thresholds Values - See the "Field Crop IPM Training and Reference Manual" for methods to calculate specific thresholds which vary based on plant growth stage, yield potential, percentage control, and market value of the crop.

Potato leafhopper - Leafhopper numbers continue to be moderate in Pennsylvania alfalfa fields this summer. A high percentage of second- cutting fields were treated. As alfalfa regrowth develops between 2 to 12 inches, watch for development of potato leafhopper infestations. See the Agronomy Guide for Insecticide Options.

Economic Threshold Values - See the Publication, "A Pest Management Program for Alfalfa in Pennsylvania", for specific thresholds.

Threshold Ranges:
For 0 to 4 inch high alfalfa - 0.2 to 1.0 leafhoppers per sweep
For 5 to 8 inch high alfalfa - 0.3 to 1.7 leafhoppers per sweep
For 9 to 12 inch high alfalfa - 0.8 to 5.0 leafhoppers per sweep

Japanese beetle - Adults continue to be actively feeding on soybean leaves and corn silks across the state. Typically this feeding causes little damage to the plant, but when numbers are high the pest can cause economic losses.

Economic Threshold Values - See the "Field Crop IPM Training and Reference Manual" for specific threshold information for corn and soybeans.

Corn - 3 or more beetles per ear and 50% or more of plants are still in green silk
Soybeans - 20% of leaf area removed during bloom and pod fill

Dennis Calvin,
Entomology


Precision Vision:

GETTING READY FOR AG PROGRESS DAYS

For those of us here at the Penn State University Park Campus, Ag Progress Days is probably as hectic as harvest on the farm. This is when it all comes together, and we strut our stuff of "academic agriculture." The APD site is looking beautiful - green and manicured. Soon the empty streets of the site will be sprouting canopies and equipment. The College of Ag Sciences theme building is featuring high-tech agriculture booths this year with a new look-colorful bannering and new display panels.

What you find as you walk through the doors will be a variety of booths all connected with a common theme-advanced concept agricultural technologies. Similar to the concept cars of Detroit, when the new ideas for the future are put on display. The difference is that most of the technologies we have on display are being used by some ag innovators today.

What you will see

David Wagner,
Ag & Bio Engineering, Precision Ag


Agents Corner:


ADAMS COUNTY

On July 30, our county received 1.5 inches of much needed rain. This well timed moisture pushed most of the corn through pollination, and relieved the moisture stress symptoms that were appearing. Pollination appears successful with good ear fill.

Third cutting alfalfa has been completed with above average tonnage. Sweeps on the re-growth are showing less than threshold numbers of leafhoppers. Some of the early harvested grass fields were mowed again this week. There are numerous soybean fields which were sprayed postemergence that are showing herbicide injury. This is due to tank residues that resulted from improper cleaning of the sprayer. It appears that just rinsing the sprayer with water is not adequate cleaning when switching from corn herbicides to post soybean herbicides.

Snap bean harvest averaged 3.5 tons per acre in our area. Corn silage harvest will soon be approaching. Now is the time to be sure your chopper maintenance is completed, and that your trenches or silos are getting cleaned out properly, and ready to be refilled.

Larry Swartz
Adams County

CENTRE/CLINTON COUNTIES

It's county fair season across the state, and August is a particularly busy time around these two counties. The Clinton County Fair runs August 8-15; Ag Progress Days is August 18-20; and the Grange Fair will be August 27 to September 3.

As for the crops, it continues to be a strange year. When it rains, it pours. The problem is, it doesn't rain often enough. The soil is really dry at the moment, and the crops are beginning to show signs of stress. Later planted corn is looking particularly rough, as the leaves are curled each day. Likewise, regrowth of alfalfa after cutting is slow. Soybeans, as usual, are holding their own.

Most of the small grains have been harvested, although some fields of oats remain. Yields have been fair, and test weights have been light to normal.

We still have the potential for some good crops, as long as we get some moisture soon.

Gary Dauberman
Centre/Clinton Counties

SCHUYLKILL COUNTY

All this beautiful sunshine is great but we have overrun our time factor of always being just two weeks away from a drought. The crops are beginning to suffer, particularly in the eastern part of the county. Yields on late planted corn will undoubtedly be reduced. Some producers are already assessing fields to decide which ones might best be harvested as silage.

Every year seems to be different than the one before and to some extent they are different. But maybe the differences don't effect the crops as much as we suspect. This is the fourth year for a county corn trial plot and the similarities between growth stages and maturity are very interesting. The plot is irrigated when needed. The following table seems to indicates the crop has the ability to adjust to the growing conditions it encounters.

Schuylkill County Corn Trial
Growth stage comparisons:
Growth Stage 1995 1996 1997 1998
Planting 22-May 17-May 12-May 16-May
Emergence 29-May 22-May 26-May 22-May
Leaves 29-June 27-June 26-June 19-June
14 leaves 24-July 20-July 24-July 11-July
Tassel 26-July 30-July 30-July 23-July
Pollination 28-July 5-August 5-August 29-July
Blister 4-August 16-August 12-August  
Dough 20-August 25-August 19-August  
Begin Dent 29-August 9-September 29-August  
Full Dent 14-September 24-September 10-September  
Maturity 30-September 4-October 10-October  
Harvest 6-November 28-October 30-October  

J. Allan Shoener
Schuylkill County

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

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