C.O.R.N. Newsletter 2004-18

Dates Covered: 
June 15, 2004 - June 22, 2004
Editor: 
Greg La Barge

What is Clipping Heads in Wheat?

Authors: Bruce Eisley, Ron Hammond, Patrick Lipps

Plant Pathologists at OARDC reported head clipping in some of their wheat plots last week. The insect clipping the heads was identified as a sawfly larva (http://entomology.osu.edu/ag/sawfly.htm see picture) not an armyworm larva as we would have suspected. Sawfly larvae are from the family Hymenoptera (wasps) whereas armyworms are from the family Lepidoptera (moths or butterflies). We had several reports about sawfly larvae in grasses last year but this is the first report from wheat in Ohio. One way to separate is by the number of prolegs on the insect. For example, armyworms larvae have four prolegs (http://entomology.osu.edu/ag/cawlpro.htm see picture) whereas sawfly larvae may have 6 or 7 prolegs. While we are not sure which of the sawflies we are seeing in wheat, one species, the grass sawfly is known as a pest of wheat. Thus wheat growers that are seeing head clipping in their wheat should be aware of these sawflies.

Many of the chemicals labeled on wheat for armyworm also have grass sawflies on the label. Below is a listing of the chemicals labeled on grass sawflies on wheat and the recommended rates. One important thing to remember at this time is the days to harvest for some of these chemicals since wheat harvest in some cases may not be far off.

Chemical
Rate ounces/A
Days toHarvest
Mustang Max
3.2-4.0
14
Proaxis
3.2-3.84
30
Warrior
3.2-3.84
30

Armyworms – When Will They Begin To March

Authors: Bruce Eisley, Ron Hammond, Patrick Lipps

Armyworms are still being reported in wheat with some leaf feeding and occasional head clipping being reported. At this time, leaf feeding is probably not as important as it was several weeks ago. Our concern at this time is that the larvae will start to “march” and what they will consume on their march. Corn located next to wheat could be in harms way when the larvae begin to march. The larvae do not normally move all the way across a corn field but will feed on the first 10 to 20 rows of corn next to the wheat and thus treating the corn next to wheat should take care of the problem. In addition to corn field other grassy areas are subject to feeding including pastures, ditch banks and lawns. For control of armyworm in turf see the following resource: http://ohioline.osu.edu/l187/l187_18.html

European Corn Borer – Will They Be A Problem

Authors: Bruce Eisley, Ron Hammond

European corn borer (ECB) moths continue to fly and we are beginning to find first and second instar larvae in V6 stage corn in central Ohio. There were only about 20% of the plants showing damage but this pest will need to be watched. To scout for first-generation ECB, we suggest checking 20 continuous plants in 5 areas of the field. Check for both “windowpane” (see picture http://ohioline.osu.edu/icm-fact/images/24.html) and “shot-hole feeding” (see picture http://ohioline.osu.edu/icm-fact/images/23.html) on the new growth in the whorl. Pull two whorls out of each 20 plants checked and carefully unroll the whorls to check for live larvae. It is important to check for live larvae on the plant before treating because there are a number of conditions that can kill the young larva. For example, we have seen a lot of mortality to larva in the past when heavy rains have occurred like we experienced last week in a large portion of Ohio.

Rescue treatment for first-generation ECB may be warranted when 50% or more of the plants have feeding damage in the whorl and early instar larvae can be readily found either on the foliage or in the whorl. It may be too late for treatment if the larvae have moved from the whorl and starting boring into the stalks or leaf mid-rib. Insecticides for first-generation ECB control can be found in the table at:http://entomology.osu.edu/ag/cornpost.htm.

Potato Leafhopper (PLH) On Alfalfa

Authors: Bruce Eisley, Ron Hammond

We mentioned several weeks ago that PLH are in the state and that it was time to start checking alfalfa for this pest. Since a lot of first cutting alfalfa has been made, it is time to start sweeping alfalfa for PLH adults & nymphs on this second cutting. We have had reports that some second cutting fields have required treatment for PLH. Check newsletter http://corn.osu.edu/index.php?setissueID=39 for PLH threshold information and chemicals to use for PLH on alfalfa.

Southwestern Corn Borer Trapping

Authors: Bruce Eisley, Ron Hammond

OSU Extension Ag Agents in Adams, Brown, Butler, Clermont, Highland, Preble and Scioto Counties along with their cooperators will be checking pheromone traps this summer for adult southwestern corn borer moths in each of their counties. Plus we will be checking a pheromone trap at South Charleston in Clark County. Southwestern corn borer as the name implies began as a pest of corn in the southwestern part of the US in the early 1900’s and has been moving east since. It has recently been reported causing economic problems in some fields in Kentucky, southern Indiana and southern Illinois. The object of the pheromone trapping in Ohio will be to determine if this pest may be moving into the state and where it might found. We did some trapping last summer in a few counties in southern Ohio but did not find any moths. Each week the results from the trapping will be forwarded to us and we will include the information in the trap report data that are listed on the web at:http://entomology.osu.edu/ag/04traps.htm . We want to thank Garst Seeds for supplying traps and lures for this survey.

Watch Out For The "Rootless Corn Syndrome"

Authors: Peter Thomison

Last week I received several calls and emails concerning corn fields with plants exhibiting "rootless corn". Rootless corn (or "rootless corn syndrome") occurs when there is limited or no nodal root development. Plants exhibiting rootless corn symptoms are often leaning or appear ready to lodge. Affected corn plants may only be anchored in the soil by seminal roots or by a single nodal root. This condition is generally observed in plants from about the three leaf stage to the eight leaf stage of development. Before the problem is evident, corn plants may appear vigorous and healthy, but after a storm with strong winds, plants will fall over because there is a limited number or no nodal roots supporting them. Leaning and lodged plants (sometimes referred to as "floppy corn") may also be wilted. When affected plants are examined they are found to lack all or most nodal roots. The nodal roots often present appear stubby, blunt, and unanchored to the soil.

Rootless corn problems are usually caused by weather related conditions that coincide with development of the permanent (or nodal) root system and various environmental factors. These include shallow plantings, hot, dry surface soils, compacted soils, and loose or cloddy soil conditions. Excessive rainfall and shallow plantings may cause erosion and soil removal around the crown region that can result in rootless corn. Nodal root development is inhibited by hot, dry compacted soils. The force of strong winds can break off secondary roots and inhibit establishment of a permanent root system. The brief period of warm, dry conditions that occurred in parts of the state last week before the weekend rains may been responsible for some of the recent rootless corn problems.

The nodal roots develop above the seed and comprise the permanent root system of corn. The nodal roots, not the seminal roots (associated with the seed), are important in providing the water and the mineral nutrients that the corn plant needs for normal growth and development. If corn seed is planted 11/2 to 2 inches deep, then the nodal (or crown) roots begin develop at about 3/4 inches below the soil surface. However, if seed are planted shallower (1 inch or less), then the nodal roots may form near or at the surface where they are more exposed to fluctuations in soil moisture and temperature. Nodal root growth is very sensitive to high temperatures (w/ root growth slowing or stopping at soil temperatures exceeding 86 degree F ). When unshaded surface soil temperatures reach the mid 90's or higher on hot days, the nodal root growth of shallow planted corn may stop. Plants are forced to rely on the seed root system or limited nodal root growth until more favorable temperatures and moisture conditions allow nodal root growth to resume.

Certain types of herbicide injury (e.g. 2,4-D, Banvel) and insect feeding (e.g. corn rootworm) may also cause lodging to occur in corn plants during vegetative development. Generally they are not the major causes of the rootless corn problems. However, there may be situations where insect feeding and/or herbicides may be a contributing factor.

Poor root development may also occur in no-till fields that were planted when soils were too wet. In addition to likely compaction-induced root problems, abnormal root development may also occur because the furrow walls may have been smeared during the planting operation, preventing good seed-soil contact. If conditions turn dry, the walls of the furrow become hard and act as a barrier to root development. Roots growing in such an environment often appear flattened and under extreme conditions may result in plants' breaking and falling over during wind storms.

Can rootless corn recover? Yes, after plants lodge, adequate rainfall will promote crown root development and plants can recover, so the prognosis for plants exhibiting the rootless syndrome last week should be good given the recent rains and moderate temperatures forecast this week. Cultivation to throw soil around exposed roots may aid the corn's recovery. Of course, this is difficult to do in a no-till situation or when the soil is hard and dry. Since affected corn is likely to be vulnerable to potential lodging problems at maturity, it should be harvested as soon as grain moisture conditions permit.

Corn Seedling Root Rots

Authors: Patrick Lipps

The continuous wet condition of fields has perpetuated seedling root disease problems throughout most of Ohio. Wet conditions in mid May created saturated soils that favored seed roots and seedling blight diseases that reduced stands. The current wet weather is increasing the root disease problems and may impact the productivity of corn plants throughout the growing season.

Several different fungi have been attacking seedling roots as plants attempt to grow in wet soils. Several species of Pythium are notorious for causing seed rot and seedling blights, but when conditions remain favorable some species are capable of causing root rots on older plants. Additionally, several species of Fusarium are also attacking corn roots and decreasing the vigor of the crop.

The first root system that develops from a corn seed is the seminal root system. It's job is to get the plant established and to provide nutrition for the plant during early leaf development (up to about the fourth leaf stage). Excessive rotting of the seminal root system early in the plants life will result in death of the plant. The mesocotyl, is a below ground stem-like structure located between the seed and the crown of the plant. This structure is the pipeline through which nutrients and water are transported to the growing seedling. A healthy mesocotyl is every important to the survival of young plants until they develop several well established nodal roots from the crown. Many of the plants we have examined have severely rotted mesocotyls making it very difficult for young plants to develop nodal roots resulting in weakened plants.

The plants are in dire need of reasonable growing conditions at this time. Drier weather would certainly help. Once the nodal root system becomes established the plants will hopefully progress rapidly. However, the relatively poor root system will likely cause the plants problems later in the season especially if the weather becomes dry. Ohio's corn crop will need adequate moisture throughout the season to produce a respectable crop, otherwise drought will spell considerable problems. The shallow root system that has developed so far this season will need all the help it can get. Corn management practices for the rest of the season should be aimed at minimizing stress on the plant.

Wheat Disease Update: Harvest As Soon As Possible!

Authors: Dennis Mills, Patrick Lipps

The wheat crop is rapidly maturing in Ohio at this time and most growers are reporting head scab as being common in fields. Reports from southern Ohio indicate that somewhere between 5 and 15% of the heads in fields appear to be diseased. Since only a portion of the head is killed by the scab fungus, this would likely put disease severity in the 2 to 3% range. Generally, wheat heads will have from 15 to 21 spikelets on each head depending on the variety and the growing conditions. The scab fungus can kill the entire head, but usually kills from 1 to 10 spikelets on the head. Thus, the percentage of infected heads (number of heads with disease out of 100) is always higher than the actual severity of the disease (percentage of diseased spikelets in the field). To determine severity, each head in a random sample of heads needs to be evaluated for the percentage of infected spikelets. Instructions and photographs of heads with symptoms are available on the web to help in severity assessments http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/WheatScabVisualSeverityScale.htm

The impact of scab on yield is sometimes difficult to predict especially when the severity is relatively low. However, when severity is high the impact on yield is generally great. It is likely that yields this year will not be greatly impacted except for those fields with very high levels of disease (50% or more). A big concern is the presence of toxins in the grain. Although there can be several toxins produced, the most important is deoxynivalenol, also known as DON or vomitoxin. The presence of toxins in the grain is a major concern for the milling and baking industry. Any grain with DON levels above about 2 ppm can cause problems for milling. This is why grain with over 2 ppm is subjected to dockage. Each grain buyer sets their own standards and dockage schedule for DON in the grain but when it is too high they frequently refuse to buy the grain.

It is generally difficult to predict the amount of DON in the grain because many factors affect the development and accumulation of DON. Generally the higher the level of scab in the field, the greater the risk of having high DON levels. Also having the grain remain wet in the field for long periods of time once it is mature will increase the risk of high DON levels. To minimize the risk of high DON, wheat fields should be harvested as soon as moisture levels permit combining. The grain should then be dried to 14% as soon after harvest as possible. When combining, turn up the blower to remove as much of the shriveled grain as possible in an attempt to improve test weight. These small shriveled grains are known to contain much of the DON that will otherwise contaminate the healthy grain. Additional screening to remove light-weight grain will further improve the grain quality, but most growers do not have the capacity to do this. Store cleaned, dry grain in a well maintained bin and examine it regularly for wet spots or mold development. Address any problems quickly to prevent deterioration of the grain. Wheat producers may wish to contact grain buyers about drying high moisture wheat. Several companies are willing to accept and dry wheat at minimal cost to assure better market quality.

Foliar Fertilizers on Soybeans

Authors: Robert Mullen

Foliar fertilization on soybeans was initially researched back in the mid 1970s. Researchers in Iowa showed that foliar application of a solution containing nitrogen, phosphorus, potassium, and sulfur between R2 and R7 could increase soybean yields 7 to 8 bu/A. Subsequent work conducted by the Tennessee Valley Authority evaluated foliar fertilization on 200 fields and showed yield increases to be negligible (less than 1 bu/A), and that yield could actually be suppressed with a late application of foliar fertilizer. Research conducted in Minnesota in the late 1990s showed no increase in yield due to application of foliar fertilizer at pod fill. Recent work out of Iowa evaluated application of foliar fertilizer between V3 and V5 growth stages. Of the 48 field trials, only 7 locations showed an increase in yield due to application of foliar fertilizer and 2 locations showed a decrease in yield. The average yield increase across all 48 locations was less than a bushel per acre. No consistent reason for the response at the seven locations could be identified. Generally speaking, fields that have P and K levels short of 100% sufficiency may show a response, but this is not absolute. Poor early season availability may also lead to positive responses. Due to the lack of evidence showing consistent increases in soybean yield with foliar fertilization, it is not promoted at this time. Considering the evidence that has been collected to date, the likelihood of an application of foliar fertilizer paying for itself is small and probably not worth the risk.

Opportunities to Learn About Soybean Rust

Authors: Anne Dorrance

There has and will continue to be much focus on the impending arrival of soybean rust in the US. Data to date does not in anyway suggest that this will happen this year, and there have been no reports (June 14, 2004) that it has entered the US. We have teamed up with the Ohio Soybean Council to assist in diagnosis of “suspect” samples received by OSU’s C.Wayne Ellett Plant Diagnostic Clinic. There will be several articles in local newspapers and the ASA Newsletter this next month. The bottom line is that if you see something unusual in your fields – we want you to send it in. The American Soybean Association is sponsoring some informational meetings this summer across the US. One of the locations will be at Der Dutchman in Plain City on July 22, 2004. I will be on the program in Ohio which will also include a representative from USDA giving a Rust Overview and How to Detect Rust. Other speakers will focus on Application Technology as well as Fungicide Information. Registration Materials can found on the web at www.SoyGrowers.com/rust. Attendance for ASA Members is Free and Non-members is $30.00.

In addition to this meeting from the American Soybean Association, the North Central Regional IPM groups is hosting a teleconference on June 29th. We will have two locations in Ohio for this meeting, Room 130 Research Services Bldg. OARDC, Wooster and the Van Wert County Extension Office. For those of you who haven’t attended a teleconference before – we will have the powerpoint presentations here – but the speaker will be in Illinois or Iowa with their voice coming over a conference phone. The agenda for the Teleconference is as follows:http://corn.osu.edu/education/soybeanrust.pdf

OSU Weed Science Field Day

Authors: Mark Loux

The OSU Weed Science field day is Wednesday, July 7 at the OARDC Western Branch in South Charleston, OH. The field day starts at 9 am, and is the usual self-directed tour of our research plots. There is a registration fee of $15, which covers lunch, drinks, and the tour booklet. For planning purposes, we would appreciate a call or email letting us know that you are attending (614-292-9081 or loux.1@osu.edu). Directions to Western Branch: From I-70, take SR 41 south approximately 4 miles. The branch is on the right side of the road. After coming in the main driveway, follow the road around to the right of the large white barn and park near the pine trees.

Harvest Aids For Wheat

Authors: Mark Loux

Several herbicides are approved for application to mature wheat to prevent weeds from interfering with harvest. Ragweeds, thistle, and lambsquarters are some of the weeds most likely to be a problem at the time of harvest, especially where wheat stands were not of uniform density. Take precautions to reduce spray drift when applying harvest aids, since sensitive crops and other desirable plants are likely to be growing in adjacent areas. Some specifics on the application of harvest aids follow (consult labels for more information).

- various 2,4-D products are labeled as harvest aids at rates of 1 to 3 pints/A depending upon the product. 2,4-D can be applied with ground or aerial equipment after wheat has reached the hard dough stage. Some labels advise that crop injury can occur, and spot treatments should be used to minimize the extent of injury. Do not feed wheat straw to livestock where 2,4-D is applied as a harvest aid. Amine formulations have less potential than ester formulations to volatilize and move off-target, but spray particle drift is possible with either.

- many glyphosate products can be applied as a preharvest treatment in wheat for control of annual and perennial weeds. Application rate is 22 oz for WeatherMax and 32 oz for most other glyphosate products. Apply at least 7 days prior to harvest, and after the hard dough stage when grain moisture is 30% or less. Glyphosate can be applied with ground or aerial equipment, and some glyphosate products can be mixed with 2,4-D. Wheat grown for seed should not be treated with glyphosate preharvest.

- Weedmaster is a premix of 2,4-D amine plus dicamba that can be applied at least 7 days before harvest when wheat is in the hard dough stage, and after all green color has disappeared from the nodes of the wheat stem. This product can be mixed with glyphosate. Do not use treated wheat for seed unless a germination test is performed on the seed prior to planting.

Preparing Bins for Wheat Harvest

The following article appeared in Purdue’s Pest & Crop Newsletter 2004, Issue 13 and is authored by Dr. Linda Mason.

The 2004 what harvest will soon be here. Preparing bins for storage now goes a long way toward preventing insect infestations during the summer. Several species of insects may infest grain in storage. The principal insects that cause damage are the adult and larval stages of beetles, and the larval stage of moths. Damage by these insects includes reducing grain weight and nutritional value; causing contamination (alive or dead); odor, mold, and heat damage problems that reduce the quality of the grain.

Newly harvested wheat may become infested with insects when it comes in contact with previously infested grain in combines, truck beds, wagons, other grain-handling equipment, augers, bucket lifts, grain dumps, or grain already in the bin. Insects may also crawl or fly into grain bins from nearby accumulations of old contaminated grain, livestock feeds, bags, litter, or any other cereal products.

Insect infestations can be prevented with good management practices. Now that many grain bins are empty, the following guidelines should be used before the 2004 grain is placed in bins:

§ Brush, sweep out and/or vacuum the combine, truck beds, transport wagons, grain dumps, augers, and elevator buckets to remove insect-infested grain and debris.

§ In empty bins, thoroughly sweep or brush down walls, ceilings, ledges, rafters, braces, and handling equipment and remove debris from bins.

§ Inside cleaned bins, spray wall surfaces, ledges, braces, rafters, and floors with an approved insecticide (Reldan (chlorpyrifos-methyl), Storcide (chlorpyriphos-methyl and Cyfluthrin), Tempo (cyfluthrin), Diacon II (methoprene) or various diatomaceous earth (D.E.) products) creating a perimeter barrier. Outside, complete this barrier by treating the bases and walls up to 15 feet high, plus the soil around the bins.

§ Remove all debris from fans, exhausts, and aeration ducts (also from beneath slotted floors, when possible).

§ Remove all debris from the storage site and dispose of it properly according to area, state and/or federal guidelines (this debris usually contains insect eggs, larvae, pupae, and/or adults, ready to infest the newly harvested grain).

§ Remove all vegetation growing within ten feet of the bins (preferably the whole storage area). Then spray the cleaned area around bins with a residual herbicide to remove all undesirable weedy plants.

§ Repair and seal all damaged areas to the grain storage structure. This is not only to prevent insect migration into the bin, but also to prevent water leakage, which leads to mold growth.

§ Do not store newly harvested grain on old grain already in storage.

§ Whenever fans are not operated, they should be covered and sealed. This reduces the opportunity for insects and vertebrates to enter the bin through the aeration system.

Archive Issue Contributors: 

State Specialists: Pat Lipps & Anne Dorrance, Dennis Mills (Plant Pathology), Peter Thomison (Corn Production), Jim Beuerlein (Soybeans & Small Grain), Mark Loux (Weed Science), Jeff Stachler (Weed Science), Bruce Eisley (IPM) and Ron Hammond (Entomology); Extension Agents: Roger Bender (Shelby), Ray Wells (Ross), Barry Ward (Champaign), Steve Foster (Darke),Todd Mangen (Mercer), Greg La Barge (Fulton), Howard Siegrist (Licking), Glen Arnold (Putnam) Mark Keonig (Sandusky), Harold Watters (Miami), Dusty Sonneberg (Henry) and Steve Prochaska (Crawford).

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.