May 16, 1997 Vol. 97.4
IN THIS ISSUE:
Production:
With all of the early planting that went on this spring, I suspect we may see a few more calls on poor emergence than usual. Here's a few things to keep in mind when troubleshooting stand problems.
When to get concerned- it takes about 125-150 GDDs for emergence to occur. That usually happens in two weeks or less, but can be three weeks under cool conditions. My experience indicates if corn hasn't emerged for three weeks, emergence may be less than desired. I'd start careful evaluation at 2-3 weeks after planting, since an early diagnosis of a problem can lead to a more timely replant if necessary.
Things to note- Evaluate the following:
Also, note patterns that may be associated with poor stands- fertilizer injury, insects, and planter problems are often associated with field patterns. Look for differences among hybrids or seedlots in similar fields.
What to do- Note the potential yield loss of keeping the stand compared to replanting at full plant population. Consider the cost and risk of replanting in making a judgement. Also, consider an earlier hybrid if replanting is delayed significantly. Use the problem as a learning experience to change management practices in the future.
Greg W. Roth
Pest Management:
Burcucumber (Sicyos angulatus), a native to North America, is becoming a serious weed problem in agronomic crops throughout the Northeast. Originally found along stream banks and other damp, shady areas, burcucumber has invaded river bottom and upland fields. Burcucumber seed germinate from mid May through September. Because burcucumber germinates throughout the season, it is difficult to control with herbicides that lack residual activity.
Traditionally, higher rates of triazine herbicides have successfully controlled burcucumber in corn. However, atrazine at less than 2 lbs has been variable. Cyanazine (Bladex) and simazine also have activity on burcucumber. Also, with the trend toward lower rates of triazine herbicides, alternative herbicides or approaches are needed to manage problem weeds such as burcucumber. Non-triazine (i.e. Broadstrike, Prowl, etc.), preemergence corn herbicides have not effectively controlled burcucumber.
Postemergence broadleaf herbicides exhibit variable results with burcucumber. Applications of 2,4-D ester at 1/2 pint (0.25 lb ai/acre) were ineffective. Dicamba (Banvel) provided 78% control of burcucumber some research while in other work control was considerably less. Mixtures of nicosulfuron (Accent) or primisulfuron (Beacon) in combination with atrazine or Banvel are better. In some studies, high rates of chlorimuron (Classic) provided 97% control of burcucumber although season long control varied. Several new post emergence broadleaf herbicides have not been fully tested on burcucumber. Prosulfuron (Peak), a component of Exceed,was one of the best treatments for burcucumber control in Penn State field research. Other products such as Expert (new experimental) on soybeans also show promise, but data on burcucumber control is lacking.
Research at Penn State revealed that no-till in combination with postemergence herbicides generally can lead to improved burcucumber control. These studies seem to indicate that no-till encourages a more uniform burcucumber seed germination and emergence. Tillage buries some seeds at lower depths which seems to prolong the germination pattern. With a lack of residual control, these later emerging seedlings can be difficult to manage.
In corn, season-long control of burcucumber requires an effective postemergence control program that may include split application timings or tank mixing effective herbicides with Banvel or atrazine to improve control. Timing of the post application should coincide with optimum weed coverage and before crop safety is greatly reduced (3 - 6 leaf stage); corn and burcucumber less than 12 inches in length. No-till systems may reduce burcucumber infestations over a period of time, although effective post control must be used in combination.
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| Corn |
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Soybeans |
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| Accent |
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Canopy (pre) |
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| Atrazine (1.5-2lb/A) |
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Scepter (pre) |
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| Banvel (1pt/A |
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Classic |
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| Beacon |
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Cobra |
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| Buctril |
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Blazer |
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| Exceed |
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Reflex |
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| +1/2 pt Banvel |
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Synchrony STS |
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| +1.5 lb Atrazine |
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Roundup Ultra |
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A9 = 85 to 95%, 8 = 75 to 84%, 7 = 65 to 75%, 6 = 55 to 65%, N =
less than 55%.
BContact control equals control of emerged
plants; Residual control equals suppression of later plant emergence.
An article in the last issue discussed ways to reduce weed control inputs when using a preemergence herbicide program. This article will present some reduced input options to consider when applying postemergence herbicide products. Postemergence chemical load reductions are possible with: 1) application during ideal climatic conditions at susceptible weed seedling stages; 2) proper use of adjuvants; 3) control of certain weed species; and 4) use of tankmixes and/or split applications. Unfortunately, most postemergence herbicide applications are not made at the ideal time, but rather when it becomes "convenient", which can make control more difficult and crop injury more likely.
The use of postemergence herbicides allows you to determine the weed problem and verify intensity before application, so the weed control program can be adapted to the problem. Foliar applied (postemergence) herbicides are generally not affected by soil texture and do not need incorporation. However, performance is modified by temperature, soil moisture, humidity, and spray adjuvant. High temperature and humidity may allow the use of a lower rate (i.e., 25-50% less than a normal use rate). Weeds developed under droughty conditions may require a higher rate, while succulent weeds may be controlled by a lower rate.
The addition of certain adjuvants may allow the use of a lower rate of post herbicides. These rates must be determined by experience depending upon the weed specie and size, the climatic conditions, and the spray adjuvant used. Check the herbicide label for specific adjuvant recommendations, but some general guidelines are; crop oil concentrate (COC) generally makes herbicides "more active" and thus, should be used during cool/dry conditions, when weeds are not as susceptible, harder to control, larger, or on "waxy" weeds like lambsquarters. COC however can reduce the herbicide selectivity and cause potentially more crop injury under good growing conditions. Nonionic surfactants (NIS) are often used in combination with N-fertilizers such as 28-0-0 (UAN), 10-34-0 (APP), or ammonium sulfate (AMS). This combination reduces leaf surface tension and may help solubilize the leaf cuticle for better absorption of herbicide into the plant. N-fertilizers can increase velvetleaf control and provide more consistent control of annual grasses when added to grass active sulfonylurea or imidazolinone products. AMS is commonly used with Roundup to minimize the effects of hard water which can reduce its herbicidal effect. Most postemergence herbicides, such as Accent, Exceed, Pursuit, Synchrony, Fusillade, Atrazine, etc., always require the addition of an adjuvant, however, certain products such as Banvel and 2,4-D may not. Be sure and check the label for adjuvants allowed with 2,4-D, Banvel or 2,4-DB tank-mixes.
Rates for foliar applied herbicides vary with the size and specie of the weed. The use of lower rates may be possible with an early application when weeds are small (2 to 5 leaf stage; <3 inches tall). For example, PSU research shows that lambsquarters can be controlled with 0.25 -0.5 pt/A of Banvel or Buctril or 0.08-0.17 oz/A of Pinnacle when applied by the 5 leaf stage under good growing conditions. Delayed application may require a higher rate. Tank-mixing products can allow reduced rates and provide a broader control spectrum as well. For example, in corn, a 1/8 to 1/2 pint of 2,4-D or Banvel can help improve products like Accent or Exceed and reduce the cost of the total program. Also, remember that weed control costs can be reduced by using a less expensive herbicide which may have greater risks. 2,4-D costs less than Banvel, but likelihood of corn injury is greater. Reduced rate herbicide application and cultivation is also a viable way to reduce chemical load and herbicide costs. It is best to use separate operations when using this method.
Proper sprayer operation is important to get maximum performance from post herbicides. Post spray height is measured from the nozzle tip to the top of the weed; not from nozzle tip to soil. "Contact" herbicides require good spray coverage, so use the correct nozzle and spray pressure. Calibrate the sprayer to give the correct spray volume per acre.
Most post herbicides have little soil activity so late emerging weeds may not be controlled by early sprays. Lambsquarters, smartweed and ragweed emerge early, while pigweed and fall panicum can emerge late. So split applications may be needed for reduced-rate treatments on such a weed complex.
Irregular localized infestations can be spot treated with post herbicides. Post spot treating and rope or sponge wick applicators are ideal for localized treatments allowing rate reductions to be maximized.
Finally, factors other than yield reduction often play a role in weed control programs. Low populations of weeds may not cause a yield reduction, but some landlords believe that the degree of weed control indicates a farmer's management level. Moreover, such weed control may be justified to prevent the spread or establishment of new weed problems, as well as reducing harvest problems.
In summary, to reduce overall inputs in a weed control program you must know your soil, your weed problem, your herbicide, and your equipment. Fine tuning is only possible if you really know the situation. Reduced rates may require better management and more time in planting or cultivation. Decisions must be based on accurate knowledge and not just guess work.
Dwight Lingenfelter and Bill Curran
The following is an article that Dr. Mark Loux, Ohio State Weed Specialist developed. I thought it was very appropriate for our early season cropping situation.
With nighttime temperatures still dipping into the 30's and 40's, be aware that the activity of Roundup, Touchdown, and 2,4-D will be reduced. Small annual weeds may still be controlled, although very slowly. Larger annual weeds and perennial weeds can be extremely difficult to kill in cold conditions.
Weeds that were reaching the proper growth stage for good control, such as quackgrass, have been set back by the cold. For maximum burndown activity, wait until a few days of warm, sunny weather have occurred before applying herbicides. Adding ammonium sulfate to Roundup and Touchdown is especially beneficial under cold conditions. Factors that reduce Roundup and Touchdown activity, such as hard water, mixing with residual herbicides (atrazine, metribuzin, etc.), and applying in 28% N instead of water, will likely be more of a problem under cold conditions. The good news about this weather - many small annual weeds are likely to be killed by the cold.
A number of restrictions exist with corn herbicide combinations. Here is a quick summary of what's on the labels. Products not included in the following table generally do not have specific restrictive statements concerning tank-mixing. For more detail, see the most recent label.
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| Accent (post) |
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| Basis (pre or post) |
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| Basis Gold (post) |
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| Beacon (post) |
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| Broadstrike +Dual (pre) |
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| Exceed (post) |
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| Hornet (soil-applied) |
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| Hornet (post) |
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| Permit (post) |
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| Resource (post) |
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| Scorpion III (post) |
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The North Central Weed Science Society is selling one of the best books available for weed seed identification. The book, Illustrated Taxonomy Manual of Weed Seeds, contains species in 40 plant families common throughout the Midwest and Northeast. The illustrations are color photographs of seeds magnified two to six times and are accompanied by a detailed taxonomic key.
It is written by Richard Delorit, professor emeritus at the University of Wisconsin-River Falls. Anyone doing weed seed bank work, those participating in crop and weed science contests, instructors of weed science courses, personnel in certified seed laboratories, extension agents and specialists who identify weeds, and anyone else with an interest in weed seed identification should have one of these unique books.
To order the book, send $20.00 along with your request to the North Central Weed Science Society (NCWSS), 1508 W. University Avenue, Champaign, IL 61821-3133. Or order by phone by calling 217-352-4212.
Bill Curran
Corn planting has already begun in many areas of the state. As these young corn seedlings begin to germinate and grow, they will be exposed to a number of potential insect pests. This article and the following newsletter article will address the biology and symptoms of these early season insect pests. This article (Part I) addresses those insects that attack corn from the point of planting until emergence: seed corn maggot, slugs, wireworm, and white grub. Part II will address those insects that attack young plants from emergence to about the 5th leaf stage.
Seed corn maggot - This insect is an occasional problem in field corn and soybeans and is usually associated with cool, damp growing conditions and high levels of organic matter. Under these environmental conditions it can cause serious stand reductions. A consultant or county agent may be called by a farmer to determine why his/her field has spotty emergence. Spotty emergence is the symptom of many agronomic problems and is not diagnostic of seed corn maggot injury by itself. When a field has been attacked by this pest, it can be difficult to confirm unless the insect or the remains of the seed can be found. In many cases, the insect will have consumed the internal contents of the seed and left to pupate before crop injury is observed. If this is the case, the only evidence that seed corn maggot was the culprit is a clear seed coat with no internal contents remaining. If injury is observed early enough, however, small white maggots will be found feeding internally on the soft endosperm and germ tissue of the seed.
Fields with the highest risk of developing seed corn maggot infestations are: 1) fields with naturally high organic matter levels (few in Pennsylvania), 2) fields where heavy applications of manure have been applied and tilled under, and 3) fields where green plant material (hay fields, green manures and old pastures) has been recently plowed under. It has been shown, that unless green plant material and manure are plowed under, the field is not highly attractive to egg laying seed corn maggots. This same research has shown that waiting 450 GDD (using a base threshold temperature of 39°F) after manure or green vegetation is plowed under in a field will help avoid problems with seed corn maggot (See the table of degree day accumulations for stalk borer to approximate seed corn maggot degree days). This is the time required for seed corn maggot to reach the pupal stage and to avoid crop injury.
Several management options exist for seed corn maggot at planting time. Once the injury has occured, assess the damage and consider replant options if necessary.
Wireworm and White Grub - From a pest management standpoint these two insects are potential pests under the same field conditions. Injury from both pests is associated with corn planted into an old sod or hay fields. Both insects feed primarily on the roots of grasses. Some researchers, however, believe that wireworms are primarily predatory insects with some tendency to feed on plant tissue. This belief is supported by the anatomy of their head, which has the orientation of a predator and not a plant feeder and the fact that wireworm larvae seldom consume the entire seed or plant root system. Wireworm larvae may then be attracted to grassy fields because of the abundance of arthropod prey and not the presence of grasses. Injury by wireworms to seed can be distinguished from that of the seed corn maggot by the germ missing with the endosperm intact (i.e. the seed is not entirely consumed).
Wireworm injury to seedlings (less than 6 inches tall) shows up as the terminal leaves drying up in the whorl. On close inspection of the plant, a hole is chewed into the stem at the soil interface cutting off the growing point.
White grub is definitely a plant feeding insect. The immature stage is adapted to movement in the soil to search for roots. The true white grub is the most important species in Pennsylvania corn fields. This species has a one to three year life cycle and feeds on the roots of grasses, including corn. Two other species, the annual white grub and Japanese beetle, have one year life cycles and tend to be none pests of seedling corn. When true white grub populations are high in an old sod or hay field and corn is planting into the field the following year, the insect can cause significant stand reductions. Because the pest has a two to three year life cycle, injury by the pest may not show up for one or two year after rotating into corn. This is because many of the larvae are small during the first year or two of corn and do little feeding, but upon reaching more mature larval stage they consume up to 80% of their total diet causing significant injury to young plants. Wireworms have a similar two to three year life cycle.
Management of these pests can only occur at planting. There are no reliable rescue treatments available after the crop is planted. The difficulty in dealing with these pests is their low frequency of occurrence. Less than 1 in several hundred fields have economic infestations of these pests. Therefore, insurance applications of insecticides to protect against injury is not advised. We do know, however, that they are associated with corn planted into an old sod or hay field with significant sod grasses. Armed with this information, we can assess old sod and hay fields for these pest prior to planting and determine which fields require protection.
Slugs - This pest is not an insect and typically only attacks corn after emergence. However, in no-till fields it can sometime cause emergence problems. When corn is planted into soil that is a little to wet, the seed slit may not close properly or open as the soil dries out. Under these conditions, if slugs are present in the field, they will move into the slit for shelter from the sun and feed on the softened germinating seed. This can lead to a poor stand and the need to replant.
Implementing an Integrated Pest Management Program (IPM) for insects requires knowledge about: 1) insect identification, 2) insect life cycles and behavior, 3) economic thresholds, 4) sampling methodology, and 5) control tactics. Although all types of knowledge are necessary, understanding an insect's life cycle is key to good pest management. A knowledge of an insect's life cycle tells you when to scout for the pest and when to time control tactics. For any pest species there is a key life stage or stages when control should be implemented for optimal results. For example, alfalfa weevil control should be aimed at the late instar larval stages. If the timing is off and the adults are killed, then important biological control agents that develop inside the adults are killed leading to continued outbreaks in the field. If control is timed too early, then additional larvae may hatch and cause some injury to the field. Another example where degree days can be used to help time control is for the stalk borer. If treatment for this pest is not timed to its movement from grasses to corn, then insecticide applications will be ineffective. Once the pest has entered the corn seedling, it cannot be controled by an insecticide application. The pesticide must be in place before the insect moves from its grass host to corn, but not too early so that the insecticide residue has declined to ineffective levels. The timing of these events can very as much as five weeks between years or from one location in the state to another. It should be easy to see from this that applying control tactics based on calendar date is not a reliable approach to insect management.
How do we know when these important periods of time occur each year? Fortunately, development of insects is tied to temperature because insects are cold blooded (poikilotherms). Therefore, their rate of metabolism speeds up as temperatures increase leading to faster development and slows as temperature decrease.
Because we know that insect development is tied to temperature, researchers have been able to establish mathematical equations that predict the rate of development at different temperatures. These researchers have simplified predicting insect and plant development by developing an index of development called "growing degree days" or "heat units". A degree day is simply a measure or index of the amount of heat accumulated during a day to drive the metabolism or development of a cold blooded organism or plant. Researchers have developed a number of methods to calculate degree days, but the following equation is the simplest:
Daily Degree Days = (Maximum temperature + Minimum Temperature / 2) - Base threshold temperature
In order to use this equation properly, several pieces of information are needed. First, one needs to know the base threshold of development (BT). The BT is the temperature at which an organism's developmental rate goes to zero or development stops. Because each insect and plant species is adapted to different environmental conditions, the base threshold varies between species (See the degree day table for BT of each species). For instance, oats is more cool tolerant than corn. Secondly, one needs some way to estimate the maximum and minimum temperature for each day. This can be done by purchasing a max-min thermometer (about $25.00) or by purchasing the information from a reliable meteorological service. This is what we have done for 27 sites in Pennsylvania in this newsletter (Zedx, Inc., Boalsburg, PA). Zedx, Inc. uses a slightly different method of calculating degree days that is more accurate than the above equation. However, using the above equation should provide similar degree day accumulations and adequate accuracy. The advantage of having your own max-min thermometer is that the degree days calculated will be specific to your farm or site. The disadvantage is that not all max-min thermometers are properly calibrated when purchased, which can lead to errors in degree day calculations. For purposes of timing scouting activities, the degree day information provided in this newsletter letter should be adequate. Timing of control tactic implementation, however, is best done by calculating degree days at a specific location.
When calculating degree days using the above equation, there are several rules that need to be followed. These rules are as follows:
To estimate key times for insect management, degree days are accumulated over time from a specific date or event. Table 3 contains the degree day totals required for various insect management considerations. Degree days for Alfalfa Weevil (AW), Stalk Borer (SB), European Corn Borer (ECB), and Corn Rootworm (CRW) are all based on the accumulated number of degree days from January 1. Black cutworm (BCW) degree day accumulations are also from January 1 in the table, but the key number needed to begin scouting is the total from the time peak numbers of moths are collected in a pheromone trap. Currently, few individuals are running pheromone traps in the state, but this is a reliable method of estimating the beginning of seedling clipping. Although, cumulative degree days for seed corn maggot are not included in table 1, the base threshold for seed corn maggot is essentially the same as stalk borer. See the section on seed corn maggot for information on how degree days can be used to manage this pest.
To use the degree day information provided in table 1, you will need to determine which site is closest to your geographic location. Once you have determine which site best represents your farm, then follow the accumulations for those pests of concern as the newsletters arrive. For instance, suppose you are located in Centre Co. and you want to know when to expect alfalfa weevil injury on your alfalfa. Table 3 indicates that alfalfa weevil scouting should begin when 300 GDD have accumulated at your site. Next look at table 1 which indicates that as of April 26, 1997, 94 GDD have accumulated at State College, PA in Centre County. Based on this information you would conclude that it is still too early to expect significant alfalfa weevil feeding. This does not indicate, that early instar alfalfa weevil will not be present in fields. Typically, alfalfa weevil eggs hatch at about 200 GDD and late instar feeding begins at about 300 GDD. To estimate when key scouting and management activities should be initiated or terminated see the accumulated degree day requirements in table 3.
Dennis Calvin
The sustainable Agriculture Research and Education training project for agents and producers still has funds available to provide mini-grants and/or to provide consulting support for establishing on-farm demonstrations. On-farm trials involving farmers, their equipment, and facilities can provide unique opportunities for obtaining information and demonstrating university recommendations. New ideals for designing on-farm trials and evaluating their usefulness to producers and extension agents are also welcome in this project. Do you have a producer who's curious about a new product or has a particular problem that needs to be analyzed? This is the second and last year for this project so take advantage of its availability now.
Phil Rzewnicki
Blair County
By May 1, corn planting throughout lower and upper Dauphin County was increasing. Earliest plantings were around April 19, with some corn planted as snowflakes fell. Soil temperatures were in the low 50° F and the soil surface was dry. A few soybean acres have also been sown. Wheat fields have initiated jointing and no disease or insect problems have been reported. Many wheat fields have thinned stands with limited tillering and/or winter killed crowns.
Sclerotinia was observed on a fall seeded alfalfa stand. Alfalfa weevils can also be found throughout the county. Ryelage harvest has begun. Grass hayfields and pastures do not appear as productive due to limited moisture as a result of the third driest April on record at Harrisburg.
Paul Craig
Dauphin County
Lebanon producers were very busy planting corn the last two weeks. The earliest Corn was planted the week of April 7, 1997. Much of the corn was planted the week ending April 18, 1997. I have been keeping record of growing degree days from March 1, 1997, and currently we have accumulated 178 GDD (4/28) using a 50 degree base. The weather station we use is located at the Lebanon Valley College campus in Annville. This information will be useful in forecasting corn emergence from date of planting and insect development. For example, the forage corn hybrid test plot was planted on 4/18/97 and to date we have 50.5 GDD. Based on this number, the corn in the plot should be half way through emergence (emergence = 110 GDD). If anyone needs GDD information, Sarah my office assistant in Lebanon County, can relate the information to you. A simple planting date and heat accumulation will give one needed information to track growth.
It is vital that growers check seed depth and population. Producers have had many questions on properly doing this. The important measurement is that a 1.5 inch depth means that 1.5 inches of soil are covering the seed. This requires checking depth in several rows, not only one. Another point is population. Remember to increase populations in early planted fields to compensate for potential loss. I recommend 15 % for early planted corn. Again, the best way to ensure proper drop is to run the planter on a hard surface and count the seeds and measure spacing.
In Lebanon, the rye crop has reached the boot stage and some growers have it mowed and are awaiting proper dry down. Wheat and Barley is approaching Stage 6 for early seedings and stage 3 to 4 for later plantings. Soil conditions were ideal for most field activities but the surface is dry. A well timed rainfall occurred on April 28, 1997 (.8 inches). There has been ideal conditions for planting corn this spring.
Del Voight
Lebanon County
1997 DEGREE DAY ACCUMULATIONS:
To track corn and insect development, compare the 1997 cumulative degree-days shown in Table 1 to the required values in Tables 2 and 3. Choose a location that is closest to your site when making comparison.
| Table 1. Cumulative Degree Days for Corn and Insects for the Period Ending April 26, 1997 | |||||||||
| Corn | Insects | ||||||||
| County | Location | 1997 | 30-year ave. | CSB | AW | BCW | CRW | ECB | |
| 50F | 50F | Diff | 40F | 48F | 50F | 53F | 55F | ||
| Erie | Waterford | 0 | 0 | 0 | 201 | 53 | 35 | 17 | 10 |
| Crawford | Meadville | 0 | 0 | 0 | 239 | 67 | 45 | 23 | 13 |
| Mercer | Mercer | 0 | 0 | 0 | 264 | 76 | 52 | 27 | 16 |
| Bradford | Towanda | 0 | 0 | 0 | 253 | 72 | 49 | 25 | 14 |
| Lycoming | Montoursville | 0 | 0 | 0 | 310 | 95 | 65 | 35 | 21 |
| Tioga | Mansfield | 0 | 0 | 0 | 219 | 59 | 39 | 19 | 10 |
| Susquehanna | Montrose | 0 | 0 | 0 | 199 | 53 | 34 | 16 | 9 |
| Butler | Butler | 0 | 0 | 0 | 314 | 96 | 66 | 35 | 21 |
| Indiana | Indiana | 0 | 0 | 0 | 333 | 105 | 72 | 39 | 23 |
| Lawrence | Lawrence Jct | 0 | 0 | 0 | 224 | 62 | 42 | 21 | 12 |
| Blair | Martinsburg | 0 | 0 | 0 | 341 | 110 | 77 | 41 | 25 |
| Centre | State College | 0 | 0 | 0 | 306 | 94 | 64 | 33 | 20 |
| Columbia | Bloomsburg | 0 | 0 | 0 | 338 | 108 | 74 | 40 | 25 |
| Clearfield | Curwensville | 0 | 0 | 0 | 287 | 85 | 58 | 30 | 18 |
| Dauphin | Elizabethville | 0 | 0 | 0 | 385 | 129 | 91 | 50 | 32 |
| Bedford | Bedford | 0 | 0 | 0 | 400 | 136 | 97 | 53 | 34 |
| Mifflin | Belleville | 0 | 0 | 0 | 354 | 115 | 80 | 43 | 27 |
| Northumberland | Sunbury | 0 | 0 | 0 | 365 | 120 | 83 | 45 | 29 |
| Lehigh | Trexlertown | 0 | 0 | 0 | 412 | 142 | 101 | 57 | 37 |
| Schuylkill | Hegins | 0 | 0 | 0 | 360 | 118 | 82 | 45 | 28 |
| Westmoreland | Greensburg | 0 | 0 | 0 | 352 | 113 | 79 | 43 | 27 |
| Somerset | Somerset | 0 | 0 | 0 | 311 | 102 | 72 | 38 | 24 |
| Washington | Washington | 0 | 0 | 0 | 391 | 130 | 92 | 51 | 32 |
| Franklin | Chambersburg | 0 | 0 | 0 | 462 | 164 | 119 | 68 | 44 |
| York | York | 0 | 0 | 0 | 495 | 181 | 132 | 77 | 50 |
| Lancaster | Ephrata | 0 | 0 | 0 | 436 | 154 | 111 | 62 | 41 |
| Berks | Hamburg | 0 | 0 | 0 | 416 | 143 | 103 | 57 | 37 |
| Corn degree-days based on a May 1 starting date. Insect degree-days based on a January 1 starting date. | |||||||||
| Table 2. Cumulative Degree-Days Required for Corn Hybrids to reach 50% Silking and Black Layer. | |||||
| Maturity Rating (days) | |||||
| 80 | 90 | 100 | 110 | 120 | |
| 50% Silking | 1100 | 1150 | 1250 | 1300 | 1400 |
| Black Layer Formation | 1900 | 2100 | 2300 | 2500 | 2800 |
| Table 3. Initiation and Termination Dates for Scouting Activities for Key Field Crop Pest | ||||||||
| ECB1 | ECB2 | ECB(a) | CRW | BCW | SB | SCM | AW | |
| Initiation | 648 | 1350 | 1098 | 1,645 | 300 | 1,400 | 450 | 300 |
| Termination | 734 | 1459 | 1272 | 2,336 | 600 | 1,700 | NA | 500 |
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
Website Address: http://fcn.agronomy.psu.edu/