C.O.R.N. Newsletter: 2015-11
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Don’t Forget About Alfalfa and Weevils While Planting
While most are worried about getting corn and soybean in during the next few weeks, the same heat is also making alfalfa weevil larvae develop quite quickly. Â We would expect enough heat units to have been reached in much of the state to see alfalfa weevil munching away. Scouting is essential to maintain a healthy alfalfa stand. Keep in mind too that while your alfalfa may be resistant to potato leaf hopper, it is NOT resistant to alfalfa weevil. Â As a reminder, alfalfa weevil scouting is accomplished by collecting a series of three 10-stem samples randomly selected from various locations in a field. Place the stem tip down in a bucket. After 10 stems have been collected, the stems should be vigorously shaken in the bucket and the number of larvae in the bucket counted. The shaking will dislodge the late 3rd and 4th instar larvae which cause most of the foliar injury. Close inspection of the stem tips may be needed to detect the early 1st and 2nd instar larvae. The height of the alfalfa should also be recorded at this time. Economic threshold is based on the number of larvae per stem, the size of the larvae and the height of the alfalfa. The detection of one or more large larvae per stem on alfalfa that is 12 inches or less in height indicates a need for rescue treatment. Where alfalfa is between 12 and 16 inches in height, the action threshold should be increased to 2 to 4 larvae per stem depending on the vigor of alfalfa growth. When alfalfa is 16 inches in height and there are more than 4 larvae per stem, early harvest is recommended.
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Identifying Feekes Growth Stages 7 and 8
The following steps are also explained in the following video:Â https://youtu.be/PZ7Lvsux1y8
1- Dig up several clusters of tillers with root and soil from multiple locations in the field;
2- Identify and select three to four primary tillers from each cluster – usually the largest tillers with the thickest stem;
3- Strip away and remove all the leaves that are below the lowest visible node, exposing  the lower half of the stem;
4- Now look for the presence of two nodes – one should be between 1.5 and 3 inches from the base of the stem and the other should be about 4 - 6 inches above the base of the stem. These nodes are usually seen as clearly swollen areas of a distinctly different (darker) shade of green than the rest of the stem. Note: the upper node may be hidden by the leaf sheath – you may have to run your fingers up the stem to feel for it: if only one node is present, then your wheat is still at Feekes growth stage 6.Â
5- After locating the two nodes, count the number of leaves that are on or above the bottommost (lowest) node:
5.1. If there are only three leaves at or above the lowest node, then your wheat is at Feekes growth stage 7.
5.2. If there are three leaves fully emerged and the tip of the fourth leaf (the flag leaf) is beginning to emerge or less than half way out, then your wheat is at Feekes growth stage 8. Â Â
Click on the following link for information on management practices that are recommended (or not recommended) at these growth stages:Â http://ohioline.osu.edu/agf-fact/pdf/0126.pdf.
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Barley Yellow Dwarf Virus in Wheat
Some reports of what seems like fairly high incidence of barley yellow dwarf virus (BYDV) are coming in from fields in some parts of the state. Some of these fields reportedly have as much as 20% of the plants showing symptoms typical of BYDV –leaves with yellowish to reddish-purple tips. These symptoms may sometimes be confused with nutrient deficiency, and in some cases. In addition, damaged leaf tips resulting from the freezing temperatures we had a week ago may also be misdiagnosed as a virus disease. On the other hand, plants without visual symptoms may be virus infected. For instance, although characteristic of BYDV, leaf discoloration may be absent in some cases, with infected plant showing reduced growth and normal-looking leaves. Severe stunting of plant is more common when infections occur early in the fall during the seedling stage, whereas discolored leaf tips are more typical of late infections.   Â
This disease is caused by several closely related viruses which are transmitted by more than 20 different species of aphids. BYDV tends to be most severe in fields planted before the Hessian fly-free date when the aphid population is high. Once infections occur, there is very little that can be done. No fungicide will control BYDV, and insecticides applied after infection will reduce the aphid population but will not prevent the disease from developing. The residual effect of the insecticide may not last long enough to protect against subsequent buildup in the aphid population. During active feeding, a few aphids will be enough to transmit the virus from one plant to another.
Yield reduction due to BYDV is generally greater when infections occur in the fall than in the spring. However, late infections may still lead to yield reduction, since severely infected plants may produce smaller heads and kernels and fewer spikelets per head. It is difficult to estimate the level of damage caused by BYDV at this time. Since grain fill is still about a month away, there is no way of knowing whether kernels on sick plants will be smaller and how much smaller. However, you can use the number of healthy-looking tillers per foot of row as a guide. The same way that yield potential is reduced if tiller numbers fall below 25 per square foot, yield potential may also go down if the number of healthy plants per square foot falls below 25. Sick plants will yield less than healthy plants. “Pick about 10 to 15 spots in the field and count the number of healthy-looking tillers per foot of row. A stand with an average of about 15 tillers per square foot is considered minimum for an economic crop” (http://corn.osu.edu/newsletters/2015/2015-06).Â
For more on BYDV, visit the field crops disease website at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/.
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10 Tips to Get the Most out of Your Sprayer
Spraying season is just around the corner. Just take a moment to review some common sense ideas I will mention here to get the most out of those expensive pesticides you will be spraying. The following “Top Ten” list will help you improve the performance of your sprayer and keep it from failing you:Â
1) Applying chemicals with a sprayer that is not calibrated and operated accurately could cause insufficient weed, insect or disease control which can lead to reduced yields. Check the gallon per acre application rate of the sprayer. This can only be determined by a thorough calibration of the sprayer. Use clean water while calibrating to reduce the risk of contact with chemicals. Read OSU Extension Publication AEX-520 for an easy calibration method (http://ohioline.osu.edu/aex-fact/0520.html).
2) How the chemical is deposited on the target is as important as the amount applied. Â Know what kind of nozzles are on your sprayer and whether or not their patterns need to be overlapped for complete coverage. Make sure the nozzles are not partially clogged. Â Clogging will not only change the flow rate, it also changes the spray pattern. Never use a pin, knife or any other metal object to unclog nozzles.
3) In addition to clogging, other things such as nozzle tips with different fan angles on the boom, and uneven boom height are the most common causes of non-uniform spray patterns. Â They can all cause streaks of untreated areas that result in insufficient pest control and economic loss.
4) Setting the proper boom height for a given nozzle spacing is extremely important in achieving proper overlapping. Conventional flat-fan nozzles require 30 to 50% overlapping of adjacent spray patterns. Check nozzle catalogs for specific recommendations for different nozzles.
5) Know your actual travel speed, and keep it steady as possible. Increasing the speed by 20% may let you cover the field quicker, but it also cuts the application rate by 20%. Similarly, a reduction of speed by 20% causes an over application of pesticide by 20%; an unnecessary waste of pesticides and money.
6) Pay attention to spray pressure. Variations in pressure will cause changes in application rate, droplet size and spray pattern. At very low pressures, the spray angle will be noticeably narrowed, causing insufficient overlap between nozzle patterns and streaks of untreated areas. High pressure will increase the number of drift-prone droplets.
7) Don’t waste your chemical. After all, you have paid for it. Spray drift wastes more chemicals than anything else. Don’t spray when the wind speed is likely to cause drift. Don’t take the risk of getting sued by your neighbors because of the drift damage to their fields. Keep the spray pressure low if it is practical to do so, or replace conventional nozzles with low-drift nozzles. Use other drift reduction strategies: keep the boom close to the target, use drift retardant adjuvants, and spray in early morning and late afternoon when drift potential is less.
8) Carry extra nozzles, washers, other spare parts, and tools to repair simple problems quickly in the field.
9) Calibrate your sprayer periodically during spraying season to keep it at peak performance. One calibration per season is never enough. For example, when switching fields, ground conditions (tilled, firm, grassy) will affect travel speed which directly affects gallon per acre application rate.Â
10) Be safe. Read the chemical and equipment instructions and follow them. Â Wear protective clothing, rubber gloves and respirators when calibrating the sprayer, doing the actual spraying and cleaning the equipment. Be well informed about the specific recommendations for a given pesticide, and follow the laws and regulations on pesticide application. Carefully read the product label to find out the specific recommendations.
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Pollinators and Planting
Beekeepers in Ohio again suffered substantial losses of colonies over the exceptionally long and cold winter of 2014-2015. Â Here in Wooster we lost more than half of our colonies, and beekeepers around the state are reporting levels of winter kill as high as 80%. Â While the frigid temperatures played a substantial contributing role, losses were undoubtedly made worse by all of the problems facing bees today: parasites, diseases, pesticides, breeding problems, and a general lack of summer and fall forage.
Spring is the only reliably good season for bees in Ohio.  Colonies that survived the winter and new colonies brought up from the Gulf Coast or California are in the process of harvesting nectar and pollen from  spring-blooming trees and weeds  -- but little honey will be made.  This spring bounty will be eaten by the bees themselves as they multiply and grow into large productive colonies that will be able to make a honey crop off of clovers, black locust, alfalfa and soybean in the coming months.  Additionally, robust colonies are needed to pollinate the fruit trees soon and pumpkins, squash and cucumbers later in the summer.Â
This spring build-up of honey bee colonies can be directly threatened by corn planting. Â Insecticide seed treatments used on corn seed produce an insecticidal dust when they are planted. Â Depending on conditions, this insecticidal dust can settle on the flowering trees and weeds that bees are visiting. Insecticides formulated as dusts are the absolute worst for honey bees because they do not immediately kill the bees visiting flowers. Â Rather than causing immediate death, the dust is packed up with the pollen and brought back to the colony where it is can poison young bees inside the colony.
In spring of 2013 and 2014, we sampled pollen from six bee yards in Madison, Union and Clark Counties. During corn planting, all colonies were bringing back pollen containing corn seed treatment insecticides. While no spectacular bee-kills were observed in our colonies, we did observe a significant increase in the number of dead bees appearing in front of colonies during the week of corn planting in 2014.  It is possible that different planting conditions could have led to no increase in bee death, as we say in 2013, or obvious piles of dead bees as were observed in 2012.  In 2013 and 2014, corn planting in central Ohio coincided with the start of bloom for fruit trees and hawthorns – extremely attractive flowers for bees – which likely drew bees away from the riskier and somewhat less attractive dandelions, mustards and purple deadnettle growing in corn fields and on field margins. In some years, planting may happen before or after fruit tree bloom when bees are intensely interested in weeds growing in and near fields.  This may have been the case in Ohio in 2012 when planting started early and a number of bee-kill incidents were reported.
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Adjusting Corn Management Practices for a Late Start
As prospects for a timely start to spring planting diminish, growers need to reassess their planting strategies and consider adjustments. Since delayed planting reduces the yield potential of corn, the foremost attention should be given to management practices that will expedite crop establishment. The following are some suggestions and guidelines to consider in dealing with a late planting season.
Although the penalty for late planting is important, care should be taken to avoid tillage and planting operations when soil is wet. Yields may be reduced somewhat this year due to delayed planting, but effects of soil compaction can reduce yield for several years to come.
If you originally planned to apply nitrogen and herbicides pre-plant, consider alternatives so that planting is not further delayed when favorable planting conditions occur. Although application of anhydrous N is usually recommended prior to April 15 in order to minimize potential injury to emerging corn, anhydrous N may be applied as close as a week before planting (unless hot, dry weather is predicted). In late planting seasons associated with wet cool soil conditions, growers should consider side-dressing anhydrous N (or UAN liquid solutions) and applying around 30 lb/N broadcast or banded to stimulate early seedling growth. This latter approach will allow greater time for planting. Similarly, crop requirements for P and K can often be met with starter applications placed in bands two inches to the side and two inches below the seed. Application of P and K is only necessary with the starter if they are deficient in the soil, and the greatest probability of yield response from P and K starter is in a no-till situation.
Keep time expended on tillage passes and other preparatory operations to a minimum.  The above work will provide minimal benefits if it results in further planting delays. No-till offers the best option for planting on time this year. Field seedbed preparation should be limited to leveling ruts left by last year's harvest - disk or field cultivate very lightly to level. Most newer planters provide relatively good seed placement in "trashy" or crusted seedbeds. Final tillage passes just before planting can be beneficial in suppressing weeds, but may not be practical this year. In many cases, it will be more profitable to complete planting first and control weeds with post planting applied herbicides.Â
Planting into seed-beds which contain emerged weeds will make post planting weed control critical. Herbicide resistant corn including Roundup Ready and Liberty Link hybrids may offer definite advantages in these situations. Effective burn-down applications will help minimize the potential for major weed problems developing later in the season.
Don't worry about switching hybrid maturities unless planting is delayed to late May. If planting is possible before May 20-25, plant full season hybrids first to allow them to exploit the growing season more fully. Research in Ohio and other Corn Belt states generally indicates that earlier maturity hybrids lose less yield potential with late plantings than the later maturing, full season hybrids.
With no-tillage or reduced tillage, increase seeding rates 5-10% over those used with conventional tillage. Consult seed company recommendations for specific hybrid planting rates under reduced tillage. Lower yields in no-till can sometimes be related to sub- optimal plant populations at harvest.Â
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Weather Update
As we talked about a few weeks ago, we expected the pattern to turn warmer than normal again in early May and it has done so.
Overall, May will be warmer and drier than normal across Ohio. The best chances for normal rainfall appear to be across northern Ohio.Â
Planting will likely be well ahead of recent years with this weather setup.
The summer looks to see significant swings in above and below normal temperature bursts with swings of wet and dry periods. It may only average slightly warmer than normal and normal or slightly drier than normal but with significant swings in weather, expect stresses on crops at times.
The early autumn outlook runs the risk for wetter than normal weather again which has become a common theme in recent years during harvest season.
Crop Observation and Recommendation Network
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.
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Disclaimer
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.