C.O.R.N. Newsletter 2008-22

Dates Covered: 
July 14, 2008 - July 22, 2008
Editor: 
Howard J. Siegrist

How to Separate Flooding Injury from Phytophthora

Authors: Anne Dorrance

More rains last week continue to hamper soybean recovery in flood prone areas. In addition the high levels of rainfall are promoting Phytophthora across the state, even in fields and regions where this is not a common disease. Let’s review the symptoms.

1. Flooding injury – this occurs when the water is ponded on the soil surface and research at OSU (VanToai) has found that it must be there for 48 hours. When you dig up the plants one of the first things that you notice is the smell. The next step is to observe the Rhizobium nodules on the roots, cut them open. If they are pink they are healthy and the plant will probably re-root and recover. If they are soft, collapse, gray, the nodules are dead and that root will not recover. Next thing is to pull on the outside epidermis of the roots. If it comes off easy – this is a good indication that the root is dead and what will be left is the white stringy interior of the root called the stele. It might be white, gray, black or even have purple streaks. The coloration is due to the many saprophytic organisms in the soil that begin to colonize these roots not pathogens.

2. Phytophthora sojae -- this also occurs when soils are saturated, and at this time of the season only the highly susceptible varieties will develop the stem rot symptoms. The plants have a yellow color and will begin to wilt. When you dig these roots, there are very few and many are rotted. The root stele is absent, tan or soft. Most importantly, there is a dark brown (chocolate) colored canker moving up the stem.

In reality, you may actually have both problems in these fields. There will be flooded out areas, ringed by plants with flooding injury with plants affected by Phytophthora scattered throughout the perimeter. The key this year is to map these areas out and begin to work on correcting the drainage issues. The second is if Phytophthora is present in a high proportion of the plants – look at the resistance package and next time select varieties with High partial resistance combined with Rps genes – preferably Rps1c, Rps1k, or a 2-gene stack combination.

Detecting and Managing Leaf Diseases of Corn

Authors: Dennis Mills, Pierce Paul

The recent warm, wet weather conditions have had some Ohio corn growers concerned about possible foliar disease problems and the need to make preventative disease management decisions. Corn is currently between late vegetative growth stages and early reproductive growth stages (VT and R1) – growth stages at which foliar diseases normally begin to appear and fungicide application decisions have to be made. While it is true that most of the common foliar diseases of corn (gray leaf spot, northern corn leaf blight and rust) develop well under our recent weather conditions (warm temperatures, high relative humidity and wetness), with the exception of a few lesions of anthracnose on the lower leaves of some hybrids, we have not yet seen any major foliar diseases of corn in our plots nor have we had reports of any such problem in the state. Generally, disease problems show up first in no-tilled fields planted with susceptible varieties, and it is in these fields that yield reduction tends to be greatest and fungicide application most profitable.

Before applying fungicides, it is important to scout fields to determine whether the disease of concern is present. Scout no-tilled fields and fields with susceptible hybrids first and use this information as a guide as to whether you are likely to have a disease problem. Gray leaf spot, northern corn leaf blight, and eye spot fungi all survive in corn residue left on the soil surface from the previous crop, and as such, these diseases are likely to show up first in no-till fields. However, the presence of residue is no guarantee that disease will develop and reach economic levels. Fungal spores buildup in crop residue over time, and if disease levels were low last year (as was the case here in Ohio), the contribution of last year’s crop residue to disease development this year will more than likely be low. However, on-farm crop residue is not the only source of spores. Spores may be blow in from other location. For common rust, spores are generally blown in from southern states. So, it is always important to scout fields before making fungicide application decisions.

GRAY LEAF SPOT ( http://ohioline.osu.edu/ac-fact/0038.html ) – Typical lesions appear tan to brown in color, rectangular in shape, and flanked by the veins of the leaf. When fully expanded, individual lesions may be 3 to 4 inches long and 1/16 to 1/8 inch wide, depending on the distance between veins; however, if several infections occur near each other on the same leaf a broader lesion will result.

NORTHERN CORN LEAF BLIGHT ( http://ohioline.osu.edu/ac-fact/0020.html ) – Lesions are typically 1 to 6 inches long, cigar-shaped, gray-green to tan in color and appear first on the lower leaves. As the disease develops, the lesions spread to all leafy structures, including the husks.

EYE SPOT ( http://ohioline.osu.edu/ac-fact/0021.html ) - Affected leaves are covered with numerous small round spots. Spots are about 1/8 inch in diameter, oval to circular, and initially they appear water soaked. The central area of the spot soon dies, leaving a tan to cream-colored center surrounded by a distinct brown to purple border.

COMMON RUST ( http://ohioline.osu.edu/ac-fact/0031.html ) - Dark, reddish-brown pustules scattered over both the upper and lower surfaces of the corn leaves. Pustules appear oval to elongate in shape and are generally small (less than 1/4 inch long).

Foliar diseases of corn cause yield reduction when severe blighting of the ear leaf and the leaves above the ear leaf occur before and during grain fill. Most foliar diseases move up the plant from the lower to the upper leaves, with the lower leaves contributing spores for infection (penetration) of the upper leaves. If fields are scouted now and disease is detected on the lower leaves, growers will still have enough time to apply fungicides to protect the upper leaves of the plants from becoming infected. Depending on the weather and the susceptibility of the hybrid, it can take between 7 and 14 days for a lesion to produce a new crop of spores. Once these spores infect a new leaf, it may take another 7 to 14 days (or longer depending on the weather) for new lesions to develop. It will then require adequate temperatures (cooler temperatures for common rust and eye spot and moderate to high temperatures for gray leaf spot and northern corn leaf blight) and high moisture for lesions to expand and disease to spread to the upper leaves.

Several fungicides are available for use on corn to control foliar diseases. However, the economics of corn production have not permitted extensive used of these products. To achieve the desired effect, fungicides should be applied at the right time. The main goal of fungicide application is to prevent disease from spreading to the ear leaf and the leaves above the ear, since these leaves contribute a significant portion (about 75%) of the carbohydrates for grain fill. Applications should begin when the first few lesions are observed on the leaves below the ear leaf. Fields should be scouted regularly to determine the appropriate time for fungicide application. Research has shown that two applications may be more effective than one at reducing the level of disease; however, more than one fungicide application is generally not economical. Yield increase is often not enough to offset the cost of two applications.

The following should be taken into consideration when making decisions regarding fungicide application:

1- Susceptibility and yield potential of the hybrid
2- The amount of disease in the field
3- The growth stage of the crop
4- Weather conditions
5- Fungicide and application cost
6- Grain price
7- Directions and restrictions on product label

Corn Pollination Underway in Many Ohio Corn Fields

Authors: Peter Thomison

During the past week, tassels began appearing in corn fields that were planted in late April and early May. However the pollination period is going to vary widely across the state this year. According to the National Agricultural Statistics Service ( http://www.nass.usda.gov/oh/ ), about a third of our corn acreage was planted on or before May 4, then due to persistent rainy conditions, another third of our corn was planted over the next three weeks, and the remaining third of our acreage was planted (or replanted) in late May and early June. The late planted corn will not be tasselling until early to mid August. The pollination period, the flowering stage in corn, is the most critical period in the development of a corn plant from the standpoint of grain yield determination. Stress conditions such as drought or hail damage have the greatest impact on yield potential during the reproductive stage. The following are some key steps in the corn pollination process.

Pollen shed usually begins two to three days prior to silk emergence and continues for five to eight days with peak shed on the third day. Under very dry conditions, silk emergence may be delayed, and such “asynchronization” of pollen shed and silking may result in poor kernel set and reduced grain yields. However, in some years under favorable growing condition, silks may actually emerge before tassels fully emerge and pollen shed starts in certain hybrids. On a typical midsummer day, peak pollen shed occurs in the morning between 9:00 and 11:00 a.m. followed by a second round of pollen shed late in the afternoon. Pollen may be shed before the tassel fully emerges (“stretches out"). Pollen shed begins in the middle of the central spike of the tassel and spreads out later over the whole tassel with the lower branches last to shed pollen.

Pollen grains are borne in anthers, each of which contains a large number of pollen grains. The anthers open and the pollen grains pour out in early to mid morning after dew has dried off the tassels. Pollen is light and is often carried considerable distances by the wind. However, most of it settles within 20 to 50 feet. For more information on the potential for pollen drift contaminating non-transgenic (GMO) corn, consult Extension Fact Sheet AGF-135, Managing "Pollen Drift" to Minimize Contamination of Non-GMO Corn; it’s available online at http://ohioline.osu.edu/agf-fact/0153.html .

Pollen shed is not a continuous process. It stops when the tassel is too wet or too dry and begins again when temperature conditions are favorable. Pollen stands little chance of being washed off the silks during a rainstorm as little to none is shed when the tassel is wet. Also, silks are covered with fine, sticky hairs, which serve to catch and anchor pollen grains.

Under favorable conditions, pollen grain remains viable for only 18 to 24 hours. However, the pollen grain starts growth of the pollen tube down the silk channel within minutes of coming in contact with a silk and the pollen tube grows the length of the silk and enters the female flower (ovule) in 12 to 28 hours.

A well-developed ear shoot should have 750 to 1,000 ovules (potential kernels) each producing a silk. The silks from near the base of the ear emerge first and those from the tip appear last. Under good conditions, all silks will emerge and be ready for pollination within 3 to 5 days and this usually provides adequate time for all silks to be pollinated before pollen shed ceases.

Pollen of a given plant rarely fertilizes all the silks of the same plant. Under field conditions 97% or more of the kernels produced by each plant may be pollinated by other plants in the field. The amount of pollen is rarely a cause of poor kernel set. Each tassel contains from 2 to 5 million pollen grains, which translates to 2,000 to 5,000 pollen grains produced for each silk of the ear shoot. Shortages of pollen are usually only a problem under conditions of extreme heat and drought. As noted above, poor kernel set is more often associated with poor timing of pollen shed with silk emergence – with silks emerging after pollen shed (poor “nick”). However, hybrids rarely seldom exhibit this problem unless they experience extreme drought stress.

Dr. Bob Nielsen, the corn extension specialist at Purdue University, has written two good articles on the flowering stages of pollen shed and silk emergence which contain excellent images of the pollination process. They’re available online at -

Nielsen, R.L. 2007. Tassel Emergence and Pollen Shed. Corny News Network, Purdue Univ. [On-Line]. Available at http://www.agry.purdue.edu/ext/corn/news/timeless/Tassels.html .
Nielsen, R.L. 2007. Silk Emergence. Corny News Network, Purdue Univ. [On-Line]. Available at http://www.agry.purdue.edu/ext/corn/news/timeless/Silks.html .

Benefits of Tissue Testing

Authors: Robert Mullen, Edwin Lentz

Tissue testing is an excellent way to evaluate your nutrient management program during the growing season. In addition tissue testing may be an excellent diagnostic tool and a method to compare different soil fertility programs. The optimum time to measure nutrient levels in a plant is when nutrient demand is high and before the crop starts removing nutrients from the leaves. For corn, this time is at initial silking and for soybeans, initial flowering – so we are fast approaching the optimum time. In addition, select the tissue that has the greatest demand for nutrients at this time, ear leaves for corn and the upper fully developed leaf for soybeans. Most labs will need 15 – 20 leaves to complete the test. Randomly select leaves from areas that are representative of the field (avoid drowned out areas or areas that are distinctly different). Send them to a reputable lab that analyzes plant samples. A list of companies that analyze plant samples for Ohio may be found at the following web address: https://agcrops.osu.edu/tools/testlabs.pdf

Contact your selected lab prior to collecting the leaves. Each lab may have slightly different instructions on mailing samples or the number of leaves that need to be collected. Lab results may be used to see if specific nutrients are within the sufficient or marginal categories, these categories may be found on page 30 of the Ohio Agronomy Guide or at the following web address:
https://agcrops.osu.edu/fertility/documents/agron_guide.pdf

Sufficiently ranges for tissue nitrogen in corn are between 2.90 – 3.50%, phosphorus – between 0.30 – 0.50%, and potassium – 1.91 – 2.50%. Environmental factors may often be the cause of levels below the sufficiently range, such as drought or excess rainfall. In some cases, leaves collected too late may have values below the sufficiency range.

If you are using tissue testing for diagnostic reasons, collect leaves from the area showing nutrient deficiency and an area not showing the symptoms as well as a soil sample from both areas. The soil test will assist in determining whether the soil has adequate nutrient levels or the proper pH for crop growth. For example, if the soil test shows adequate potash levels for crop growth, but the tissue test shows potash deficiency – adding more potash will not correct the problem. Environmental factors (drought, excess moisture, unusually low or high temperatures) have most likely limited root development so the crop is unable to remove adequate nutrients from the soil. If environmental, the deficiency symptom will most likely disappear when adequate growing conditions return.

Tissue testing when completed for several years will provide valuable information on the need for sulfur or micronutrients in a field. University research has consistently shown that micronutrients and sulfur generally do not increase crop yields on medium to fine textures soils (loams, silts and clays) with adequate organic matter and proper soil pH. However, universities cannot complete soil fertility studies on every field in the state. A tissue test would show if a certain field has a history of a micronutrient deficiency and if not, a producer could save fertilizer dollars by not adding it to starter or in foliar programs.

Late-Season POST Herbicide Applications in Soybeans

Authors: Mark Loux

This is the time of year when we get phone calls about rescuing weed control in Roundup Ready soybean fields, and we hear most often about marestail, giant ragweed, and lambsquarters. Less than adequate weed control after several herbicide applications can often be attributed to failure to use the appropriate combination of herbicides and application timings for the weed population. However, adverse weather, crop replants, and slow crop development can also negatively impact weed control programs. Weeds that survive into mid-season can also be indicative of herbicide resistance, or a developing herbicide resistance problem. Before spending additional money on a late-season POST herbicide application, it’s important to consider what the goal of the application is, and whether any effective herbicide options remain based on what has already been applied this season.

For example, a marestail plant that has survived previous application of glyphosate plus an ALS inhibitor (FirstRate or chlorimuron) is not likely to be controlled by additional herbicide applications. A late-season application that does not control marestail will also fail to suppress it enough to make harvest any easier. On the other hand, small soybeans that are infested with late-emerging marestail plants, which have not been subject to a prior herbicide treatment, may merit an additional application where the marestail is known to be still sensitive to glyphosate or ALS inhibitors. Where someone is determined to treat marestail that have survived previous application, our recommendation is typically going to be something like a full rate of FirstRate or Classic plus up to 1.5 lbs ae/A of glyphosate. The cost of this, up to $25 or more based on current glyphosate prices, has to be weighed against its possible effectiveness.

For both lambsquarters and ragweeds, it is possible that a second POST application of glyphosate will control plants that survived a previous application. However, as we have stated in previous C.O.R.N. articles, this is most likely to occur where the first application greatly suppressed the weeds (70 to 80% control at least), and the second glyphosate treatment is applied about 3 weeks of the first. Where the previous glyphosate application had little effect on the weeds, an alternative to glyphosate would be required in the second application for control of ragweeds. There are essentially no consistently effective alternatives to glyphosate for control of large lambsquarters.

Choices for ragweeds include FirstRate, Classic, Cobra/Phoenix and Flexstar, and the decision here should be based on several factors. Classic or FirstRate would generally be the most effective option where the population is known to be still sensitive to ALS inhibitors. Where ALS resistance is known or suspected, we would suggest use of Cobra or Phoenix. Use of Flexstar should generally be curtailed as we move later into the season, since it has more restrictive guidelines for crop rotation. Where the glyphosate had substantial activity on the weeds in the first application, the second application should generally contain glyphosate plus one of the alternatives mentioned here. Keep in mind the following also: 1) expectations should be lowered for late-season applications to large weeds – plant death may not occur, but harvest problems may at least be reduced; 2) maximum labeled rates of the alternative to glyphosate are likely to be needed; 3) spray adjuvants should be optimized for the alternative; and 4) spray coverage should be maximized through use of slower application speeds, higher volumes, and nozzles that provide a greater number of relatively small droplets (for example, extended range flat fans instead of ai nozzles). As stated previously, the possible merits of a late-season application to large weeds have to be weighed against the cost and risk of soybean injury.

Another scenario faced by some growers, due to late planting, is a poorly developed soybean crop that is subject to continued weed reinfestation into August, due to our rainy weather pattern. The question here is whether a late-July or August application of herbicide might be merited, to control late flushes of small weeds (similar to double-crop soybeans). Where the soybean canopy fails to develop fast enough to shade out late-emerging weeds, it’s possible that a case could be made for such an application. Keep in mind that glyphosate should be applied by the end of the R2 stage, and that rates should be kept as low as possible to minimize the soybean injury that is occasionally observed from late-summer glyphosate applications.

In contrast to broadleaf weeds, volunteer corn is easily controlled through the use of one of several POST grass herbicides. When mixed with glyphosate, the most effective options for control of volunteer glyphosate-resistant corn are Assure II, Targa, Fusion, and Select Max. In OSU research, Select Max can occasionally be slightly less effective than the others. Avoid use of other formulations of clethodim, including Select, Arrow, etc. When applied with crop oil concentrate in the absence of glyphosate, any of these herbicides will control volunteer corn. Be sure to follow label directions for rate and use of ammonium sulfate.

Weedy Wheat Stubble Fields

Authors: Mark Loux

Weeds are taking off in wheat stubble fields, and the rainy weather pattern we are experiencing can promote rapid growth and additional weed emergence. While weed management strategies for wheat stubble can vary depending upon the primary weed target, annuals vs perennials, preventing seed production by summer annual species will reduce infestations in future years. This can be accomplished through mowing and/or herbicide application, but the latter is generally most effective.

Where mowing is used, mow fields before flower initiation and repeat as often as necessary to reduce seed production. Use of mowing to prevent viable seed production by grass species is difficult, because many grass species can produce viable seeds within about one week after flowering. Mowing will not necessarily completely eliminate seed production, because low growing plants can still produce seeds. A combination of glyphosate plus 2,4-D can be effective in many wheat stubble fields. This is often applied using a glyphosate rate of 0.38 to 0.75 lb ae/A and a 2,4-D rate of 0.5 lb/A. However, the rate of 2,4-D should be increased in fields where the broadleaf weeds are known to be resistant to glyphosate or have previously been difficult to control. The addition of dicamba may improve the control of large marestail, but the benefits of its use have to be weighed against the risk of volatility and injury to nearby sensitive plants.

Soybean Defoliators

Authors: Bruce Eisley, Andy Michel, Ron Hammond

With soybeans beginning to enter their flowering stages, we need to remind growers of the various defoliators that are starting to make their presence known. These defoliators include Japanese beetle adults, first generation bean leaf beetle adults, Mexican bean beetle adults, green cloverworm larvae, and grasshoppers, and all are now being found throughout the state. In terms of defoliation, it would be unusual for any of the above mentioned insects alone to cause significant defoliation throughout a field. However, a complex of two or more might cause defoliation levels to rise above threshold levels. Remember you need to sample from numerous locations in the field to get a good idea of what is happening across the entire field. For fields with large populations of Japanese beetles, remember that these beetles will congregate; finding one Japanese beetle means you will usually find a lot of them in the same area. Thus, at least for this insect, you need to make an extra effort to sample from numerous locations in the field to get a better idea of what is happening across the entire field.

Growers are advised to initiate scouting procedures over the next few weeks to prevent defoliation from reaching the 15-20% defoliation threshold during the reproductive growth stages, R1-R5, which then rises to 20-25% during growth stage R6 late in the summer. When sampling, check numerous places within the field, avoiding the field edges which often tend to have higher levels than the rest of the field. A list of labeled insecticides for control of all these soybean defoliators is available at http://entomology.osu.edu/ag/545/soy545.pdf .

Corn Rootworm Root Sampling

Authors: Bruce Eisley, Ron Hammond, Andy Michel

With the cool and wet weather that Ohio experienced the past two months, corn rootworm larval development has proceeded more slowly than usual. Where as rootworm adults are usually seen by now, few if any have been seen yet. Numerous states in the Midwest are also reporting a delay in their appearance. While adults might become a concern because of later silk clipping, we feel that the next couple of weeks would still be a good time to check for corn rootworm larval feeding injury. Growers should check their corn fields where corn follows corn or those fields in western and northwest Ohio where corn follows soybeans to determine the possibility of corn damage to first year corn from the western corn rootworm variant. The coming weeks will be the time to root sample because the maximum larval feeding injury will be during this time and larval feeding will be ending as the larvae pupate and new adults begin to emerge. After larval feeding has ended, the roots on some hybrids will begin to regenerate and when this happens, rootworm larval injury is more difficult to detect.

We suggest the following method to check for rootworm injury:

1. Carefully dig plants, don’t pull them, from the field taking as much soil as possible with the plant.

2. Carefully remove as much soil as possible from the plant without damaging the roots and also look for any larvae that might still be in the soil or on the roots. Rootworm larvae are white, about 1/2 inch in length when full grown with a brown head and brown plate on the tail http://ohioline.osu.edu/icm-fact/images/43.html (see picture).

3. If there is still soil on the roots you can either soak the root system in a bucket to loosen this remaining soil or you can spray the root system with a hose to remove the remaining soil.

4. After the soil has been removed, check the roots for feeding injury, either roots chewed back to the stalk or tunneling in the roots.

Root systems can be rated using the 0 to 3 scale. The scale indicates the amount of damage to the root system and can be used to determine if economic injury has occurred.

Modified Node-Injury Scale.



Rating

Visible Damage to Roots

0

no visible damage to roots

0.05

slight scarring

0.08

moderate to severe scarring with no roots chewed to 1.5 inches of stalk

0.1

one root chewed to 1.5 inches of stalk

0.5

half node of roots chewed to 1.5 inches of stalk

1

one node of roots destroyed

2

two nodes of roots destroyed

3

three nodes of roots destroyed

Western Bean Cutworm

Authors: Bruce Eisley, Ron Hammond, Andy Michel

This is the third consecutive year that we are looking at a new corn insect pest that is working its way towards Ohio: the western bean cutworm (see CORN newsletter #30-2006 and #21-2007). This insect had been a sporadic dry bean and corn pest in Colorado and Nebraska, but since the early 2000’s, the insect, and its damage, has progressively moved eastward. For the past few years, numerous Midwest states (including Ohio) and Ontario have been trapping for this pest. In two years of sampling, a total of 9 moths have been caught, 3 in 2006 and 6 in 2007. This pales in comparison to what has been found in Iowa, Illinois and Indiana for the past few years.

Ohio is again participating in this trapping program, and as of the 14th of July, we have captured a total of 10 adult moths: 1 in Allen Co, 1 in Wood Co. near Bowling Green, 1 in Clark Co, 2 in Crawford Co, and 5 in Fulton Co. This is largely consistent with numbers and locations from last year except for the 5 in Fulton Co. which is higher than in previous years; this is the first record for Allen and Clark Co. These samples likely represent moths that have blown into Ohio from the west and not established populations. Traps placed in 24 other counties spread across the state have not reported any moths. Also, we have never heard of any reports of damage to corn due to western bean cutworm in Ohio.

As the summer progresses, we will continue to check these traps throughout the state and provide updates, especially if any large amounts of moths are caught—usually the first sign of infestation. As you check your fields later in the summer, please let us know of any suspected eggs or larval infestations. Eggs will appear first white, then tan, then a deep purple, and are usually laid in bunches (~50) on the upper leaf surface. Larvae most likely will be found feeding on the ears, and unlike corn earworm, which are cannibalistic, you will probably find several western bean cutworms feeding on a single ear. As we have many other moths and larvae about this time of year that may resemble western bean cutworm, proper identification is important. Good identification guides can be found online at the North Central IPM Center website ( http://www.ncipmc.org/teleconference/wbc2007/videos/ ). For more information on this insect, including images and maps, see the following website: http://www.ent.iastate.edu/trap/westernbeancutworm/ .

Trapping for Western Corn Rootworm Variant in Soybean

Authors: Bruce Eisley, Ron Hammond, Andy Michel

Many growers have expressed a desire to do their own sampling for western corn rootworm adults in soybean. Thus, we are providing this information to growers so that they sample correctly. Sampling is done by using Pherocon AM unbaited yellow sticky traps. There are two sources of Pherocon AM traps:

Great Lakes IPM
10220 Church Road
Vestaburg, MI 48891-9746
1-800-235-0285
http://www.greatlakesipm.com

Gempler’s
PO Box 44993
Madison, WI 53744-4993
1-800-382-8473
http://www.gemplers.com

Traps should be placed in the soybean fields around the 21st of July for a period of 6 weeks. Growers should attach them to fence posts slightly above the soybean canopy (6-8”), placing 6 of them at least 100 feet from the field edge and evenly distributed in the field. The traps should not to be too close to an adjacent corn field. Twist tie wires are included with the traps; however we find it more convenient to use cable zip ties. The zip ties are thinner and faster to connect the traps to the posts. The traps should be changed each week for the 6 weeks and a new trap put in its place just above the soybean canopy.

After you change the traps, count and record the number of rootworm beetles on each trap and the number of the days the traps were in the field. The number of beetles/trap/day is determined by adding the number of beetles found on the six traps and dividing that number by 6 and then dividing by the number of days the traps were in the field. Traps should be changed every 7 days if possible but if not be sure to record the exact number of days the traps were in the field.

Catches of 5 or more beetles/trap/day during any trapping week indicates a potential problem with rootworm in the field the following year. If a field reaches this threshold, the management in that field in 2009 can be to rotate to some crop other than corn, plant one of the Bt transgenic rootworm hybrids, use a soil insecticide, or apply the high rate of a seed treatment. If you think that there is a potential for severe pressure from rootworm larvae next year, we would recommend not relying on seed treatments. Research has suggested that seed treatments do not provide sufficient protection under heavy rootworm pressure.

How do you know if you should consider sampling? Based on a decade of surveys in Ohio, the distribution of the variant across the state is patchy, and large scale recommendations for sampling are difficult to make. Data seem to suggest that areas approximately west of I-71 and north of I-70 is the current distribution. However, the distribution of the FYCRW variant is not uniform across the area where threshold populations are regularly found. Whereas some fields exceeded thresholds, others did not reach more than 3 beetles/trap/day during the entire 6 week trapping period within the same county. Because of this continued concern with this insect, we urge growers not only in this area, but in all the state, to develop a sampling plan next year in their soybean fields, and to sample roots for feeding injury in their first year corn for the presence of FYWCR (see this week’s article).

Armyworm Moths

Authors: Bruce Eisley, Andy Michel, Ron Hammond

Some areas of Ohio, especially in the north, are reporting extremely large flights of armyworm moths. These adults are those that have emerged from the large population of larvae that we experienced on wheat, corn, and various other cereal grain crops this past spring. Normally this next generation of larvae will not be a problem in field crops. However, weekly scouting in your crops should detect any unusually activity.

July 2008 Weather Report Update

Authors: Jim Noel

Last week: Generally 1-2 inches of rain for most of the state with isolated 3+ mainly in west central and northeast.

This week: Mainly dry and turning hot. Hottest weather of summer the second half of the week with most places reaching 90-95. The wet soils will limit the upside on temps but most crops have not had much heat either.

The following two weeks: Not quite as hot but temperatures slightly above average with scattered storms. Most places will return to normal to above normal rainfall after this week of dry weather.

Overall: probably pretty good conditions for this time of the year and with critical crop stages except for later this week.

Farm Focus Hosts 2008 Field Day on July 29

A variety of speakers will address issues on the minds of local and regional farmers at the Farm Focus Field Day being held on Tuesday, July 29 from 8 a.m. to 3 p.m. in Van Wert, Ohio. Local agri-businesses and equipment dealers will be on hand with demonstrations of their newest products and equipment pertaining to today’s farming needs. The Farm Focus committee invites all area farmers and agri-business persons to attend the field day which is free and open to the public.

On hand will be Natural Resource Conservation Service soil specialists Frank Gibbs, Don McClure and Don Burgess discussing soil structure and compaction along with Matt Deaton of the Ohio Department of Natural Resources and Randall Reeder, agricultural engineer for OARDC and OSU Extension. These discussions will take place around several soil pits in the subsurface irrigation fields at the site.

Barry Ward, Ohio State agricultural economist will hold discussions on crop inputs pricing and grain marketing in today’s volatile market environment.

Two separate field demonstration sessions will be held with one on liquid manure applications and one on new equipment technology. Companies participating in the liquid manure application demonstrations are Bambauer Equipment; Barnyard Supply; and Putnam county farmers Jerry and Dennis Niese. Jon Rausch, OSU Extension Environmental Management Program Director, will also be on hand to moderate these demonstrations and provide additional information on things to consider when applying liquid manures. Local companies participating in the new equipment technologies demonstrations include Archbold Equipment; Heritage Farm Equipment; and Kennedy-Kuhn Inc.

The field day will be held at the Marsh Foundation Farm on Old Lincoln Highway in Van Wert. Registration will begin at 8 a.m. The last shuttle will leave by 8:30 for the field demonstrations and sessions. Those attending will be split into four groups to allow for better interaction with demonstrators and presenters. Participants will have the opportunity to attend all four sessions. The sessions will be run concurrently with groups rotating to each 50 minute session during the morning. A free lunch will be provided courtesy of the Field Day sponsors. After lunch, participants are invited to visit with the various speakers and demonstrators on a more one to one basis as well as have the opportunity to take a wagon tour of the Farm Focus research plots. A self-guided tour of the plots is also available.

This field day offers 4.0 hours of Certified Crop Advisor CEU’s, 1.0 hour in Nutrient Management, 1.0 hour in Soil & Water, 1.0 hour in Crop Management and 1.0 hour in Professional Development for those that attend the full four sessions.

The Farm Focus Field day is sponsored by the Farm Focus committee, OARDC and OSU Extension. Financial sponsors for the show and the complimentary lunch are Ag Credit, Archbold Equipment Co., Bambauer Equipment, Barnyard Supply, First Bank of Berne, Heritage Farm Equipment Store, Kenn-Feld Group, Qualisoy, Van Wert County Foundation, Wells Fargo Bank and Williamson Insurance Agency.

For more information, contact Gary Prill, Farm Focus/OSU Extension-Van Wert County at 419.238.1214 or visit the website: http://farmfocus.osu.edu/ . If rain interferes with the Tuesday, July 29 planned activities, a rain date of Thursday, July 31 has been reserved with the same schedule for the day.

Archive Issue Contributors: 

Contributors: Pierce Paul, Anne Dorrance, and Dennis Mills (Plant Pathology), Ron Hammond, Andy Michel, and Bruce Eisley (Entomology), Peter Thomison (Corn Production), Jim Noel (NOAA), Mark Loux (Horticulture & Crop Sciences), Robert Mullen (Natural Resources), and Gary Prill (Farm Focus Program Manager). Extension Educators and Associates: Harold Watters (Champaign), Jonah T. Johnson (Clark), Greg LaBarge (Fulton), Les Ober (Geauga), Gary Wilson (Hancock), Howard Siegrist (Licking), Todd Mangen (Mercer), Tim Fine (Miami) Suzanne Mills-Wasniak (Montgomery), Glen Arnold (Putnam), Mark Koenig (Sandusky), Ed Lentz (Seneca) and Roger Bender (Shelby).

About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.