FCN Logo College of Agricultural Sciences Penn State

July 2, 1999 Vol. 99.7

IN THIS ISSUE:

Mark Your Calendar

Announcements

Production

Pest Management

Agents Corner

Degree Day Accumulations

Announcements:

1999 PENN STATE AGRONOMIC FIELD DIAGNOSTIC CLINIC: REGISTER NOW!

This year's Field Clinic is less than a month away! As in the past, the Clinic is a one-day event conducted at the Penn State Agronomy Research Farm near Rock Springs, PA. This year's Clinic will be held on Tuesday, July 27 and then repeated on Thursday, July 29, 1999. The Clinic begins at 9 a.m. and ends at 4 p.m. The topics include:

CCA and pesticide applicators license credits will be offered.

The registration cost is $40/person, which includes a delicious lunch, refreshments, and support materials. Register soon (before July 16) by returning your orange registration form (sent previously). If you did not receive a form and would like to attend please contact Lisa Crytser at (814) 865-2543. For additional information or comments about the Diagnostic Clinic contact Dwight Lingenfelter at (814) 865-2242 or by email, DXL18@PSU.EDU.

We look forward to seeing you at the Clinic.

Dwight Lingenfelter, Agronomy Weed Science

CHANGES IN EXTENSION NUTRIENT MANAGEMENT PROGRAM

On July 1 several significant changes occurred in the Pennsylvania Nutrient Management Extension program. Paul Craig has finished his tour of duty in the Nutrient Management Office at PDA and has returned to Dauphin County. In addition to his county duties Paul will also be working regionally with the Capital Region Agronomy Team as the forage specialist. Norm Conrad who worked full-time on this project for a number of years returned part-time to Union County last year and now this year he will be completely back in Union County. Thanks to Paul and Norm for their efforts in the Nutrient Management Education Program. Also on July 1, Jerry Martin will be joining the project. Jerry has extensive experience in nutrient management extension. He worked in the Pequea-Mill Creek Project and more recently as agronomy agent in Dauphin County. Jerry will be located at PDA in Harrisburg. If you have questions about the Nutrient Management Extension Education Program please don't hesitate to contact me at 814-863-1016 or Jerry at 717-783-9704.

Doug Beegle, Agronomy, Soils

Production:

DROUGHT EFFECTS ON VEGETATIVE CORN

Some areas of the state have missed many of the showers that passed through the state during June. Corn in these areas has been taking on a grayish cast, exhibits leaf rolling beginning mid-day and leaf area development has ceased or even appears to be declining. It is difficult to estimate the effects of this stress on the final yield. The textbook answer is that 4 days of visible leaf wilting or rolling could result in a 5-10% yield loss. These figures often seem to overestimate yield losses, though, since corn has a remarkable ability to recover from early season drought. In a study conducted by Dan Knievel and Eva Pell at Penn State in the early 90's, they compared corn that received no rainfall from emergence to V9 (July 7) and then was well watered to corn that was irrigated the whole season. They found in both of two years that this treatment reduced yields by 20% compared to the irrigated corn that yielded close to 200 bu/A. The yield reduction was mostly due to reduced number of kernels/plant. This study suggests that the yield potential in these drought stressed fields has been reduced but they still have significant potential to recover. In field situations, not all fields will be "well watered" the rest of the season and other stress factors are present that can increase the effects of the drought. Insect injury, soil compaction, potassium deficiency, reduced nitrogen availability, and weed competition are all factors I'm hearing from folks in the field in affected areas. Unfortunately drought stress is part of growing corn in Pennsylvania. Developing a management program that minimizes the effects of these periodic droughts is a key to survival. For example, some hybrids will tolerate this drought more than others and sharp corn producers and their advisors will note this for future reference.

Greg Roth, Agronomy
Corn and Sorghum Management

Pest Management:

INVASIVE SPECIES IN THE LIMELIGHT

Last February President Clinton signed an Executive Order which instructed the Departments of Interior, Agriculture, and Commerce to develop a national management plan for invasive species which focuses on animals and plants not "native" to the United States. Invasive noxious weeds feature prominently in the invasive species problem and they will be a significant component of any plan which address the problem.

Noxious and invasive weeds currently infest over 100 million acres in the U.S. They are a direct threat to agricultural production both in cultivated crops and on grazing lands. Invasive aquatic weeds are a prominent nuisance which interfere with productive and recreational uses of lakes and waterways. Invasive plants are also a significant problem in natural environments where they have been identified as the second most severe threat to endangered species. In response to this problem, the Departments of Agriculture, Defense, Energy, Interior, and Transportation along with over 80 public and private organizations have cooperated in development of an initiative, "Pulling Together, A National Strategy for Invasive Plant Management". The strategy outlined nine specific research objectives to address the problem of invasive plants. The objectives are as follows:

  1. Develop procedures to improve inspection at ports of entry and assess the invasive potential of accidental and deliberate imports.
  2. Develop effective protocols for detecting reporting, and monitoring new infestations of invasive plants.
  3. Develop methods to access the economic impact of invasive species so that management priorities can be established and justified.
  4. Develop methods for optimal establishment of native plantings including production of weed free seed and managing competition during establishment.
  5. Develop integrated control methods which may utilize hydrologic manipulation, prescribed burning, biological or chemical control methods.
  6. Identify and evaluate the efficacy and safety of biological control agents.
  7. Develop methods to eradicate, control, contain, and prevent infestations of invasive plants in vulnerable ecosystems.
  8. Develop methods of restoring stable ecosystems in conjunction with invasive plant control.
  9. Develop methods for certifying weed free status of pack animal feed and "native" wildflower seed mixes.

The Presidential Order and emphasis being placed on invasive species is an exciting development which could greatly increase our ability to detect and manage invasive species including weeds. However, it also raises some concern as to what we define as invasive or noxious and where we place our resources in the fight against weeds. In some peoples mind, a native plant, or one which was present before settlement by Europeans, is often good. Conversely, an introduced or non-native plant is usually bad. With the exception of corn or maize, most of our widely grown agricultural crop plants are non-native - soybean from China, wheat from the Middle East, barley from Mesopotamia or Southeast Asia, Oats from the Mediterranean and near East, and Rice from India or Indochina. Of course this is also true for most of our fruits and vegetables, forages species, and many valued landscape plants. Non-native is not always bad and native is not always good - burcucumber, pigweed, common milkweed, and hemp dogbane are native to North America and can be problematic weeds to name only a few. Some native species can become a problem just like some non-natives when placed under the pressures of human intervention. Careful selection and management are very important in deciding the appropriateness of a plant species. The issue of native vs. non-native, good vs. evil, and noxious vs. healthful is not black and white.

Over the next 12 months, these issues will be in debate at the State, region, and Federal level. States and regions are forming "invasive species councils" that will help decide the direction we take in managing invasive species including weeds. In the end, hopefully we can adopt programs that are sensible, meaningful, and may even have an impact.

Bill Curran, Agronomy, Extension Weed Science
Rob Hedberg, Director of Science Policy for Weed Science Society of America

POISONOUS PASTURE WEEDS

Calls and reports concerning livestock death due to poisonous weeds frequently increase during the next few weeks. During the hot and dry months of July and August, the condition of many pastures becomes poor and over-grazed. Cattle may be forced to graze on weeds that they normally would not, or they may eat a weed out of curiosity. Scout your pastures and remove these weeds before they cause livestock health problems. Keep in mind, there are numerous poisonous plants that could invade an area or a pasture. If you suspect a poisonous plant and are unsure of it's identity contact your local Extension agent or another knowledgeable resource. Following are descriptions of some of the more common poisonous weeds:

White Snakeroot (Eupatorium rugosum).

Perennial. Leaves and stems are the dangerous parts of the plant. Has a fibrous root system. Leaves are opposite along stem, oval, toothed margins and with long petioles. Small white flowers in compound terminal clusters are conspicuous in late summer. Found in woods, damp and shady pastures, and occasionally in thickets and clearings. Newly cleared lots may also contain this weed.

Nightshades (Solanum spp.).

Several different nightshade species are close relatives, including eastern black nightshade, bitter nightshade, jimsonweed, groundcherry and horsenettle, and have been known to be poisonous to livestock and pets when parts of the plant are consumed. Plant appearances vary between species, but most all (except jimsonweed) produce small berry-like fruits. Most of the plants in the Nightshade family are considered poisonous; however, the green leaves, stems, and seeds are especially toxic. The green fruit may be quite poisonous while the ripe fruit may be relatively nontoxic. The concentrations of the toxins are higher following dry conditions and often lower following damp, rainy periods. The toxic properties are not removed by drying and are relatively heat stable. Portions of the plant stored with forage will remain poisonous, so producers must be cautious when feeding livestock nightshade-contaminated hay. The toxicity of the green plant material varies from 0.1% to 1% of the animal's body weight.

Wild Black Cherry (Prunus serotina).

Perennial woody tree or shrub. Not necessarily a "pasture weed," but sometimes found in or along fencerows bordering pastures. Damaged or wilted leaves or branches are the dangerous parts of the tree. Leaves are alternate, simple, elliptic-pointed, leathery in texture, and finely toothed on the margins. Flowers are showy, fragrant, and white, hang in drooping clusters, and produce dark-red to black cherry fruits.

Poison Hemlock (Conium maculatum).

Biennial. It looks very similar to wild carrot or wild dill. Leaves are alternate and have a lacy appearance, while the small white flowers are arranged in compound umbles. Stems are smooth and covered with purple blotches. All parts of the plant are poisonous, however, stems are less poisonous than the rest of plant. Generally, it is not palatable to livestock but ingestion of as little as 0.25 to 0.3% of body weight of poison hemlock is lethal. It grows in moist soils of pastures, ditches, roadsides, and disturbed sites.

Spotted Waterhemlock (Cicuta maculata).

Perennial. In general, it looks like wild carrot or poison hemlock and grows primarily in wet areas including marshy meadows and pastures. It has smooth stems with purple spots and the leaves are 2-3 times pinnately compound with large well defined leaflets (i.e., not lacy like carrot or poison hemlock). Small white flowers are arranged in compound umbles. Unlike wild carrot and poison hemlock, water hemlock has a cluster of fleshy, bulbous taproots at the base. Although all parts of water hemlock are poisonous, the roots are extremely toxic. If ingested, very small amounts (e.g., walnut-size) of the root can kill livestock. Also, if the roots are crushed (e.g., by livestock hoof), the toxic chemical, cicutoxin, can mix with the standing water and then be ingested by livestock.

Common Pokeweed (Phytolacca americana).

Perennial. Pokeweed can grow as tall as 10 feet with alternate oblong leaves, smooth reddish purple stems, and deep purple berries (mature) in clusters. The roots are the most poisonous part of the plant, while the berries are the least poisonous part. Poisoning is rare in animals since the large taproot is generally difficult for animals to forage and ingest. Found in pastures, no-till fields, shady roadsides, wasteplaces, woodlots, and fencerows.stock hoof), the toxic chemical, cicutoxin, can mix with the standing water and then be ingested by livestock.

Certain weeds or plants such as pigweed, lambsquarters, and sorghum normally have feed value and can be consumed by livestock, however, during extended dry periods they can accumulate toxic amounts of nitrates.

Dwight Lingenfelter
Agronomy, Weed Science
(some parts from Purdue Pest & Crop Newsletter)



BT-CORN AND THE MONARCH BUTTERFLY

Many of you have probably seen the numerous news reports of Bt-corn pollen killing monarch butterflies. Reporters have approached some of you on this topic. This article is to help put the reports into the proper perspective. In the last "Nature" publication an article by Dr. John Losey of Cornell University was published that showed increased mortality of monarch butterfly larvae when exposed to certain concentration of Bt-corn pollen. The article also showed that sublethal levels of Bt-corn pollen could lengthen the time required for the insect to complete its life cycle. The intent of this article was to alert the general public and scientific community that Bt-corn could potentially have some unanticipated adverse effects within the agroecosystem. It was not intended to be an indictment of Bt-corn. Unfortunately, the press jumped on it because of all the other controversy surrounding Bt-corn and other genetically altered crops. Their reports were sensationalized and in most cases did not provide the proper balance.

As we all know there is no completely safe pest management tactic. Everything we do including tillage, crop removal, etc. effects the number of organisms that survive in the farm landscape. In the urban setting, road building, home building, lawn care, etc. all effect the number of organisms that survive in that ecosystem. The question is how much of an effect on any organism's numbers is reasonable. At this time, researchers have no information to judge the degree to which Bt-corn pollen will effect monarch butterfly numbers. Although, Dr. Losey's research methods were adequate, they are only relevant within the Bt-corn pollen concentrations used in the study. I have talked extensively with Dr. Losey on this topic (he was my graduate student). When John began this work, he had no idea of the concentration range that monarch butterflies are exposed to in the field. Therefore, he used a range of concentrations without any knowledge of what they should be. It is likely that the concentrations are higher than those that most monarchs will be exposed to in the field. Dr. John Obrycki of Iowa State University has done similar work and found the same results as John did in the laboratory. Dr. Obrycki, however, is currently looking at the amount of pollen collected on milkweed plants at increasing distances from a corn field. This work should begin to tell us whether the Bt-corn pollen levels are at concentrations high enough to cause monarch mortality or effects of time of development.

Although, it is unlikely that Bt-corn pollen will cause major effects on monarch butterfly numbers, it is important that we understand that the Bt-corn toxin can move beyond the boundaries of a field. There are many other lepidoptera (moth and butterfly) larvae feeding in areas near corn fields. These species may be more important as food for birds and rodents, then the monarch butterfly. As everyone knows, birds will not eat monarchs because of the glycosides sequestered during feeding on milkweed plants. The monarch's significance to man is its beauty. Because it is beautiful and known by most people, it is the national insect.

The significance of Dr. Losey's research is that it points out the need for research on Bt-corn's effect on non-target insects and its indirect effect on other organisms in the food chain. It does not mean that Bt-corn is bad. Research questions that need to be answered include: 1) what stage of development are monarch butterflies when the corn is shedding pollen, 2) how far does corn pollen move away from corn fields in concentrations high enough to cause monarch mortality and influence development, 3) what is the natural density of monarch butterflies and their relationship to corn fields, 4) what concentrations of Bt-corn pollen cause lethal and sublethal effects on monarchs, 5) if Bt-corn pollen causes mortality and changes in the length of the life cycle, how will this influence the population size of monarchs in the future and 6) what other lepidoptera (moths and butterflies) are affected by the pollen. Bt-corn is a valuable pest management tool of European corn borer. We do not want to lose it as a control option. Therefore, answering these questions is imperative to alleviate public fears about the technology.

For a more in-depth discussion of the Monarch/Bt-corn issue see the article written by Dr. Marlin Rice of Iowa State University at the website www.pme.iastate.edu/info/monarch.htm. This is an extremely well balanced and written article that can help answer many questions.



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 our webpage at: http://www.fra.cas.psu.edu/. Also, insect and insect injury images for all crops are being added to the new Agronomy Guide website. Other websites of interest include the University of Maryland's Pest Report in (http://pest.umd.edu/ipm/AgIPM/CropAndIPMReport/CropIPMReport.html). Information on insect trap data and other IPM information can be found under http://www.udel.edu/IPM/. This website contains black cutworm data from a network of 50+ pheromone traps operated by Terra Inc., Bridgeville, DE (Galen Dively). The data is for Delaware, but may provide an alert to future black cutworm injury in Pennsylvania. A website of the Maryland Department of Agriculture operated by Dick Bean has information from a network of blacklight and pheromone traps. You can access the data at ftp://ftp.mda.state.md.us/plantpro/blt/weekly/ or call 800-492-2106. Again, the information is not for Pennsylvania but can provide an alert to pending insect problems.

For information on European corn borer, fall armyworm, and corn earworm flight activity in Pennsylvania and surrounding states, you can call 1-800-PENN-IPM (only for Pennsylvania) or access the Sweet IPM webpage at http://www.ento.psu. edu/vegetable/sweetcorn/default.html.

Corn
aphids
black cutworm
corn rootworm larvae
flea beetle
grape colaspis
Japanese beetle adults
stalk borer
true armyworm		 billbug
corn rootworm adults
1st gen. European corn borer
garden symphylan
grasshoppers
sod webworm
thrips
Soybeans
bean leaf beetle
potato leaf hopper
thrips		 green cloverworm
Mexican bean beetle
spider mites
Alfalfa
clover root curculio
pea aphids
spittlebug		 grasshoppers
potato leafhopper
Small Grains
grasshoppers true armyworm

Aphids
There appears to be a minor outbreak of aphids in the southeastern area of the state. There are several species of aphids that can be found in field corn in Pennsylvania. The extended drought conditions are ideal for buildup of aphid populations. The most common aphid species is the corn leaf aphid, which tends to feed in the unemerged portion of the whorl. The English grain aphid has long, black cornicles, extending backward from the rear of the abdomen (tailpipes). Its legs and antennae are also black and the body is a general green to bluish green color. The oat bird-cherry aphid is yellowish green and characterized by a prominent reddish-orange spot at the base of the cornicles. These species can be found feeding on the underside of leaves, but usually not in large numbers. Corn leaf aphids have bluish-green bodies with long dark cornicles, antennae, and legs. Their cornicles are shorter than those of the English grain aphid.

Under most conditions, aphids do not cause economic losses in field corn. In dry years, numbers may explode because fungal pathogens are not able to attack the pest and regulate its numbers. If temperatures are warm, the generation time is shortened allowing more generations in a short period of time. With each generation, numbers increase rapidly. Another trait of most aphid species is all or most are females, which bear live young.

Infestations observed in a field have primarily been on the lower leaves of the plant. In general, the lowest leaves on corn plants do not contribute much to grain yield. In fact, as the plant nears the reproductive stages (anthesis), the lower leaves become parasitic on the plant. If aphid populations remain confined to these leaves, they are unlikely to cause economic losses. If aphid numbers continue to increase and the colonies move upward on the plant, their potential to injure the plant increases. If significant numbers of aphids are feeding on the leaves that will be near the developing ear, then the likelihood of economic injury increases greatly. Corn leaf aphids can feed on the tassel and upper stem dropping honeydew onto the silks interfering with pollination.

Economic Threshold Values

If 50% of the plants have more than 100 aphids per plant and plants are under drought stress or more of the plants have their tassels and upper leaves heavily infested, plants are under moisture stress and aphid populations are increasing.

Bean leaf beetle
This soybean pest has been observed in some areas of the state, but not at economic levels.

Economic Threshold Values

Before bloom - 30% of leaf area removed and there are 5 or more beetles per foot of row
After bloom and before pod fill - 20% of leaf area removed and there are 16 or more beetles per foot of row.

Black cutworm
Based on degree day accumulations we should be past the major period of first generation black cutworm clipping. However, some late planted corn fields may be subject to attack by offspring of late migrating females or second generation larvae that resulted from early developing first generation individuals. These fields can be injury up to the five leaf stage. In rare situations under drought stress conditions, cutworm larvae can borer into the plant below ground level and then tunnel up into the stem of larger plants. Many times this is done by the dingy cutworm, which looks similar to the black cutworm. In these cases, there is no way to effective kill these individuals.

Economic Threshold Values

seed leaf emerged - 2% of plants cut
two leaf stage - 3% of plants cut
three leaf stage - 5% of plants cut
four leaf stage - 7% of plants cut
five leaf stage - seldom of economic importance after this stage.

Corn Rootworm Adults
The beginning of adult emergence should begin within the next couple of weeks in warmer regions, in about three to four weeks in central areas and about four to five weeks in more northern, cooler areas. Northern corn rootworm adults are about ¼ to 3/8 inch long and a solid, bright green color. Western corn rootworm adults are similar in size and can be either green with three dark strips down their back or a solid black. In both cased, the underside is yellowish green.

Economic Threshold Values (number per plant):

Species 1st year corn two years or more of corn
Northern corn rootworm 2.0 beetles 3.0 beetles
Western corn rootworm 1.0 beetles 1.5 beetles

Corn Rootworm Larvae
All areas of the state have passed the corn rootworm larval hatch period. Larvae should now be in the first through third instars. A few individuals may be pupating in the warmer regions of the state. It is the second and third instars that do most of the feeding that causes plant injury. In fields with significant root feeding, stalk lodging should begin to show up by the second week of July in southern areas and by the third week of July in central areas. At this time, it is too late for any remedial action to control the pest. Stalk lodging should be used as an indicator that the field may benefit from a soil insecticide or rotated to another crop next year.

First Generation European Corn Borer
Based on degree day accumulations, the first generation ECB flight should be about 2/3 or more complete across the state for the two generation type of corn borer. In central and northern areas of the state where the single generation type of corn borer is dominate, the overwintering adults should begin to fly and laid eggs when about 828 DD have been accumulated. This type of ECB will reach peak egg deposition at about 1008 DD and continue to lay eggs until 1413 DD are accumulated. The following chart shows details on the number of degree days required for a population of ECB to reach various stages of development.

Table 1. Two Generation ECB Type (Bivoltine)
Stage of Development Expected Degrees to Each Stage from January 1
 
  Beginning Peak Termination
Overwintering      
Spring Pupation 135 315 675
Adult Emergence 310 490 850
Egg Deposition 378 558 918
 
First generation      
1st instar (egg hatch) 468 648 1008
2nd instar (time to scout) 554 734 1094
3rd instar 642 822 1182
4th instar 739 919 1279
5th instar 849 1029 1389
Pupation 1036 1216 1576
Adult emergence 1211 1391 1751
Egg Deposition (beginning 2nd gen.) 1279 1459 1819
 
Second generation      
1st instar (egg hatch) 1369 1549 1909
2nd instar 1455 1635 1995
3rd instar 1543 1723 2083
4th instar 1640 1820 2180
5th instar (overwintering stage) 1750 1930 2290


Table 2. One Generation ECB Type (Univoltine)
Stage of Development Expected Degrees to Each Stage from January 1
 
  Beginning Peak Termination
Overwintering      
Spring Pupation 585 765 1170
Adult Emergence 760 940 1345
Egg Deposition 828 1008 1413
 
First generation      
1st instar (egg hatch) 918 1098 1503
2nd instar (time to scout) 1004 1184 1589
3rd instar 1092 1272 1677
4th instar 1189 1369 1774
5th instar 1299 1479 1884

The importance of these tables is to help with timing of the pest's management. If a farmer intends to use an insecticide program, first generation scouting should begin at initiation of the second instar. If a pesticide program will be used, the material should be timed to about 50% (peak) completion of the second instar for best results. Second generation management, however, is much more complex and difficult. To implement an effective control program, scouting must occur during the egg laying period. Ideally, a control decision should be made by 50% completion of the egg laying period. Once larvae hatch they will move to protected areas of the plant and effectiveness of an insecticide treatment will decline rapidly. Once larvae bore into the plant (3rd to 4th instars), control is impossible and a waste of money. This is why, second generation management is typically not recommended. The use of Bt-corn does not require scouting and properly timing of insecticide applications, but a farmer should evaluate whether the technology effectively controlled the pest. The effectiveness of Bt-corn can be evaluated during the period when the majority of the population has entered the 4th instar. By this time tunneling will be evident on the plants, in the event that the Bt toxin was ineffective in controlling the pest. As resistance management programs are implemented for farmers using the Bt-corn technology, this assessment will become a requirement to monitor for ECB populations that are resistant.

Japanese Beetle
This pest should begin to emerge within the next week. Its first arrival is usually around the 4th of July. The beetle may be found feeding on the edges of corn and soybean fields. Typically, they are not general across a field and are very seldom at numbers high enough to cause economic losses.

Economic thresholds:
Corn - 3 or more beetles per ear and 50% or more of plants are still in green silk.

Soybeans - 20% of leaf area removed before bloom and pod fill

Potato leafhopper
Numbers are increasing across the state. As the new regrowth of the third cutting of established stands and second cutting of new seedings come on, alfalfa fields should be scouted for PLH populations and a control decision made. Scouting should begin when the regrowth reaches 2 to 4 inches. See the publication "A Pest Management Program for Alfalfa in Pennsylvania" or "Field Crop IPM Training and Reference manual" for economic thresholds and scouting procedures.

Stalk Borer
Most areas of the state have passed the critical window of stalk borer injury.

Two-spotted spider mites
The warm and extended dry weather is ideal for outbreaks of spider mites in soybeans. Therefore, it is important to watch drought stressed soybean fields closely. The injury looks like yellow stippling on the leaves. Upon observing the underside of leaves, very small orange spots that are moving and a whitish appearance will be seen. The whitish appearance is due to cast skins of mottling mites. As with aphids, mites are all females that cause produce up to 1,000 offspring per female and have a generation time of 7 to 10 days. This reproductive potential can lead to almost overnight outbreaks. In two generation 14 to 20 days), one female, if all her offspring and grandkids live can result in 1,000,000 individuals. A heavily infested field has billions of individual mites. When looking for mites, the first sign is usually a general yellowing around the field margins. This is because the mites develop first on grasses around the margins and then blow into the field. For insecticides to be effective, the material must get down into the soybean canopy. Once rains begin to fall, mite populations typically drop off very rapidly.

Economic threshold:
Treatment is usually justified when plants along field margins are showing leaf discoloration and mites are present.

Dennis Calvin, Entomology

Agents Corner:


ADAMS COUNTY

Like some other areas of the state, we could surely use some moisture. We continue to be below normal for rainfall, with most local municipalities enacting some water restrictions.

First cutting alfalfa was begun around May 15. With a county wide emphasis on forage quality, many producers began mowing when their alfalfa was just budding or at the soft bud stage. The winner of our county forage contest, for first cutting, was an alfalfa sample which tested 165 Relative Feed Value and 24.8% protein.

Second cutting tonnage was slightly less than normal as a result of the reduced moisture. Yield was below average, however, the quality was again exceptional. One producer, cutting on a 25-day interval, produced a second cutting which tested 184 RFV and 26.0% protein. Leafhoppers were just beginning to arrive at cutting time.

Soybean emergence has been spotty as a result of the dry conditions. Population counts on our test plots indicate emergence at only 2/3 of the dropped seed count.

Wheat harvest has begun and early reports are indicating 58 lb. test weights. Current market price for new wheat is approximately $2.55/bushel.

Despite the current conditions, corn is growing well, with some corn reaching the 9-10 leaf stage. The dry weather has exposed those corn fields where fertility was marginal, by allowing the corn to show nutrient deficiency symptoms.

Larry Swartz
Adams County

BERKS COUNTY

Yesterday the weather was like "Wiley Coyote". Everyone was looking up at the impending rain clouds, but a few drops would fall and then the hot sun would reemerge. What a trickster!

Berks County has such a variation in individual conditions. On shale ground, producers barely have anything for a second cutting of alfalfa. In western Berks, potato leafhopper was over economic threshold in a new seeding by last week. Yet, on the eastern side closer to the Lehigh Valley, I helped a producer take a robust second cutting off because we got some scattered showers.

Producers are working their way through barley harvest and preparing for double crop soybeans. Corn development varies, but I am starting to see induced nutrient deficiencies in corn. Last week when we pulled PSNT samples on our demonstration nitrogen plot, we found no need for additional nitrogen. With lack of rain, nutrients are staying put! I have seen few fields with canopies closed in soybeans. It seems that if we would just have a shot of rain , we would see these crops grow overnight!

We are conducting a timely demonstration of various warm season crops for graziers to consider during the summer slump. This includes sorghum sudangrass, soybeans and brassicas. We planted it back in May (planting conditions poor) and today we harvested samples for dry matter production and nutrition. Considering how dry it is, I am amazed. Any producer would be grateful for the production for either grazing or chopped feed. We will have an evening pasture walk on July 27, at 7 pm. Call for farm directions if would like to come and join us.

Mena Hautau
Berks County

CENTRE/CLINTON COUNTIES

The rain finally fell this past week, and it was a blessing for all the crops. The amount of rainfall varied across the county, but seemed to average around two inches. It wasn't a soaking rain, but it was a blessing nonetheless. Afterwards, the crops seemed to perk up overnight.

Corn ranges in height from about knee high on late-planted corn to shoulder height in many earlier planted fields. Many fields were showing signs of stress prior to the rain. Even though it isn't the Fourth of July yet, one would be hard pressed to find a field that is less than "knee-high" at this point.

Soybeans are growing slowly, but will likely take off now. Many fields appeared to have severe weed infestations early, but many have been cleaned up, especially if they were Roundup Ready varieties. Velvetleaf, thistle and burdock seem to be doing particularly well in many areas.

Barley is currently being harvested, and wheat will soon follow. The small grains are relatively short in height, but the grain heads seem to be all right. Most oat fields look rather poor. Some oat fields are beginning to turn yellow.

Timing has been everything in regards to alfalfa. Its progress has depended on the date of first cutting and its growth stage when the rains fell, as well as the date of second cutting. Some second cutting yields have been very poor, because so little rain was received between first and second cuttings. Many fields have yet to be cut for the second time this season. Potato leafhoppers have returned and populations in some fields have warranted spraying.

Gary Dauberman
Centre and Clinton Counties

FAYETTE COUNTY

During May very little rainfall fell until the rains of May 22-24, and since then there was relatively little beneficial precipitation in southwestern PA until June 28 - 29, when most areas received from .5 to 1.1 inches of rain. As a result the following applies to the agronomic crops in the area:

Corn - Field populations are variable, as is uniformity of height and health. Corn is somewhat stunted, annual and perennial broadleaf weeds have escaped many of the pre-emergence herbicide treatments. Some fields look great and some look rough. Conventional or minimum till corn has looked better than no-till corn from emergence, probably due to the relatively cool nights in May. In the past week or so though, there has been some equalization if good no-till weed control was achieved. No significant first generation corn borer has been observed.

Alfalfa - Mid May harvested alfalfa survived the dry weather quite well and some producers were able to harvest second cutting at about 28 days after first cut. First cut alfalfa harvested after June 1 has not produced significant regrowth and the recent rains should help increase tonnage for second cut. Leafhopper has not been a serious problem for all, only some spot spraying occurred.

Grass Hay - Some producers are still harvesting grass hays. Yields are down 30% on typically managed meadows, but not so on well managed farms, one orchard grass yield check produced 1.8 tons (hay equivalent) per acre. Due to the weather, heat and drought, there has been little regrowth even on meadows harvested early.

Small Grains - Barley yields were not record breaking, again due to the dry May, but the harvest weather was excellent and barley matured 7 - 10 days early. Wheat and oats are ripening together and it may be a toss up whether all the wheat will be harvested before switching to oats. Early planted (late March) oats will outdo later planted (mid-April) in grain and straw yield, primarily due to the rainfall timing mentioned above.

Soybeans - Early planted (early May) beans really got off to a slow start, but are looking pretty good now if producers were able to control weeds. Beans planted just prior to the May 22 rains, didn't fare as well, due to some soil crusting. The wildlife has mowed their share of fledgling bean plants, especially near areas of good ground cover.

Pastures - Pastures fared no better than other fields. Continuous pastures are dried up and dormant, rotational pastures with legumes are doing much better, as would be expected. If the dry weather continues, graziers will need to feed winter stocks of hay, thereby creating a potential shortage of winter roughages.

Conclusion, we need more rain, as does most of the state.

Don Fretts
Fayette County

Degree Day Accumulations:

1999 DEGREE DAY ACCUMULATIONS

To track corn and insect development, compare the 1999 cumulative degree-days shown in Table 3 to the required values in Tables 4 and 5. Choose a location that is closest to your site when making a comparison.

Table 3. Cumulative Degree Days for Corn and Insects for the Period Ending June 27, 1999
    Corn Insects
County Location 1999 30-year ave. SCM/SB AW BCW CRW ECB
    50F 50F Diff 40F 48F 50F 53F 55F
Erie Waterford 811 675 135 1739 1038 887 687 571
Crawford Meadville 850 725 125 1833 1101 946 737 615
Mercer Mercer 846 725 120 1845 1106 949 739 616
Bradford Towanda 852 725 127 1836 1094 938 728 607
Lycoming Montoursville 895 776 118 1951 1168 1006 787 658
Tioga Mansfield 806 673 133 1737 1029 878 677 561
Susquehanna Montrose 750 610 140 1629 952 805 614 505
Butler Butler 882 771 111 1942 1167 1006 788 659
Indiana Indiana 871 762 109 1934 1157 996 778 649
Lawrence Lawrence Jct 862 733 129 1841 1110 955 746 624
Blair Martinsburg 838 729 109 1882 1116 957 743 617
Centre State College 845 730 115 1869 1111 952 740 615
Columbia Bloomsburg 901 787 114 1982 1184 1021 799 667
Clearfield Curwensville 841 724 117 1850 1102 945 734 610
Dauphin Elizabethville 920 813 107 2048 1225 1057 831 695
Bedford Bedford 886 787 99 2004 1197 1030 807 674
Mifflin Belleville 891 784 107 1981 1184 1020 798 667
Northumberland Sunbury 929 818 111 2050 1230 1063 836 700
Lehigh Trexlertown 938 831 107 2096 1252 1081 852 714
Schuylkill Hegins 892 782 110 1982 1181 1017 795 664
Westmoreland Greensburg 866 761 106 1940 1160 997 779 650
Somerset Somerset 764 646 118 1744 1023 869 665 547
Washington Washington 910 811 99 2042 1231 1062 837 702
Franklin Chambersburg 945 851 94 2145 1289 1113 878 738
York York 974 880 93 2216 1333 1153 913 769
Lancaster Ephrata 928 827 101 2095 1250 1078 848 710
Berks Hamburg 948 842 106 2117 1268 1096 865 725
Corn degree-days based on a May 1 starting date. Insect degree-days based on a January 1 starting date.


Table 4. Cumulative Degree-Days Required for Insects to Reach key Periods for Scouting or Management
  Maturity rating (days)
80 90 100 110 120
50% Silking 1100 1150 1250 1300 1400
Black Layer Formation 1900 2100 2300 2500 2800


Table 5. Cumulative Degree-Days Required for Insects to Reach key Periods for Scouting or Management
  Stalk Borer Alfalfa Weevil Black Cutworm* Corn Rootworm European Corn Borer Seed Corn Maggot
Adlt Emrg 5% Hatch 1st Gen 2nd Gen
SB AW BCW CRW ECB1 ECB2  
Initiation 1400 300 91 1283 380 WCRW** 558 1550 450***
Termination 1700 500 430 2253 478 NCRW** 1228 2045  

*Degree-day accumulation should begin at first moth capture in a black light or pheromone trap.
**These values represent degree day accumulations for optimal timing of Furadan 4F post emergence applications. WCRW-Western Corn Rootworm, NCRW-Northern Corn Rootworm
***This number of degree days represents the number of degree days required from plowdown of green vegetation until it is safe to plant corn or soybeans and avoid seed corn maggot injury.

Dennis Calvin, Entomology

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

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