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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2012-18

Dates Covered: 
June 18, 2012 - June 26, 2012
Harold Watters

Mid-June to July Crop Weather update

The overall trend remains in place with above normal temperatures and below normal rainfall. Rainfall has and will continue to vary widely. Rainfall in June has been under 0.50 inches in the far western counties and 1-3 inches elsewhere with the greatest totals from southwest to north central Ohio. Normal rainfall is near 2 inches. About 20% of the state saw above normal rainfall in June, 30% of the state saw normal rainfall and about 50% of the state saw below normal rainfall so far in June.

In the last 90 days, the northern part of the state and particularly the northwest part of the state is the driest and the south is the wettest.

The week of June 19-24 calls for above normal temperatures with below normal rainfall. Hot weather with high temperatures mostly in the upper 80s and 90s will occur this week through Thursday followed by a relaxation into the 80s for late week and the weekend but still above normal. Rainfall will occur with a cold front Thursday and again with another front on the weekend, most likely Saturday night into Sunday.

The week of June 25-July 1 calls for near normal temperatures with near to slightly below normal rainfall. The warm ridge of high pressure will settle southwest next week but will battle with cool air to our north. This will set up a ring of fire pattern which means a few clusters of storms may roll southeast from time to time. The high next week will be in the 60s northeast of Ohio to the 90s and 100s to the southwest. Much of the week in Ohio will be in the 70s northeast to 80s southwest, not far from normal. Rainfall will be dependent on location of the clusters of storms, whether they stay to our west or come over us. Overall most places will see rain but it will vary widely.

Weather for the week of July 2-8 calls for above normal temperatures and slightly below normal rainfall. Normals are highs mostly 80-85 and lows 60-65.

Finally, spring 2012 will go down as the warmest in Ohio out of 118 years of records. It will go down as a little drier than normal, 30th driest out of 118. Our friends in Indiana experienced the 8th driest spring in 118 years.[]=Statewidetrank&submitted=Submit[]=Statewideprank&submitted=Submit


Dry weather and postemergence herbicide activity

Continued dry weather in areas of Ohio will affect the activity of postemergence herbicides, and this can mean a reduction in weed control compared with years when soil moisture is adequate.  A couple of decades of accumulated knowledge on dry weather and postemergence herbicide applications allows us to offer the following management suggestions, although none of these are probably hard and fast rules.

1.  Apply when weeds are small.  This is probably the single most important step to maintain POST activity in dry conditions.  Large and old plants become even more difficult to control when subject to extended dry conditions.  Keep in mind also that prolonged dry conditions suppress additional weed seed germination, so the risk of many weeds emerging after an early POST treatment is reduced.

2.  Optimize adjuvants.  Labels for some POST herbicides provide suggestions for revised adjuvant rates or types under dry conditions. A general rule for adjuvant effectiveness under dry conditions is:  MSO > COC > NIS, although this does not apply to all herbicides.  Adding AMS or 28% can also improve activity. 

3.  Dry weather does not usually increase the severity of injury to the crop from herbicides, unless coupled with very hot conditions.  However, continued dry conditions after the crop has been injured can reduce its ability to recover from injury, or extend the time needed for recovery.  Soybeans are fairly small in many fields right now, and dry weather is limiting the rate of growth.  One of our concerns always is using herbicide mixtures that cause considerable injury to small soybeans in late June, because we start to run out of time for soybeans to recover to maximum yield potential.  Applying when weeds are small will minimize the need for more aggressive herbicide mixtures.

4.  Relative to point #3, do not load the spray tank with a multitude of herbicides and snake oils to try to control marestail.  If you cannot control it with glyphosate plus either Classic or FirstRate, then adding other herbicides will not help.  Walking fields to remove plants by hand, or at least cut the tops off later in the season to prevent seed production, is probably the best option at that point.

5.  Continuation of dry weather throughout the summer will reduce the rate of dissipation in soil of certain herbicides, possibly increasing the risk of carryover into next year’s crop.  We have experienced problems with Scepter carryover following dry summers.  Scepter carryover is most likely when the field remains dry from immediately after application through summer, and can be less likely where the field received some substantial rainfall soon after application.  Callisto and Flexstar are also capable of causing carryover injury, when applied fairly late and subjected to continued dry conditions.  Soil pH is still the most important factor for chlorimuron degradation, and it is largely not affected by soil moisture. 

Twospotted Spider Mites on Soybeans

With the persistence of hot and dry weather in parts of Ohio, we are beginning to get more reports of twospotted spider mites beginning to develop on soybeans from Ohio and other states in the Midwest.  Spider mites feed on the underside of the foliage with sucking mouth parts and may be very destructive when abundant. Under hot and dry field conditions, spider mites thrive on plants that are under stress. Soybean foliage infested with spider mites initially exhibits a yellowish speckled or stippled appearance. As plants become heavily infested, foliage turns yellow, then bronze, and finally the leaves drop off the plants as the effect of heavy feeding leads to dehydration and death of plant. Although mentioned last week in this C.O.R.N. newsletter, it is time to discuss treatment decisions.  The following is a rating system to use to determine the need for spraying. This scheme was developed for evaluating infested fields based on observable symptoms and conditions as follows:

1.  Mites are barely detected on underside of leaves in dry locations or on edges of fields.  Injury is barely detected.  Non-economic population; do nothing.

2.  Easily detected on underside of leaves along edges of fields or perhaps on leaves in dry areas throughout field.  Most foliage is still green but yellow stippling caused by mite feeding is becoming detectable on upper side of leaves with the underside showing mite feeding.  Still non-economic; warrants close monitoring.

3.  Many plants are infested when examined closely, with plants showing varying degrees of stippling, possibly some speckling and discoloration of some of the leaves.  These plants may be limited to field edges, but also might be found throughout field.  Field edges might be showing signs of injury.  Economic population developing; rescue treatment warranted.  Consider entire field spray if mites are common throughout field.

4.  All plants in area, whether along field edge or within field, are heavily infested. 

Plants are discolored with wilted leaves, usually obvious from a distance.  Severe injury occurring.  Economic population; rescue treatment will save field.

5. Extremely high TSSM densities, with much of the field discolored, stunted, with many plants drying down or already dead.  Economic population; rescue treatment will only be beneficial if new growth occurs following late summer rain.

In making an assessment of a spider mite infested field, it is important that one recognize the early signs of mite feeding, which is the stippling or speckled effect that initially appears on the foliage when foliage is still green.  See the following pictures for signs of early mite injury:,,  In addition, it is essential that one use a good hand lens to view relative abundance of mites in egg, nymph and adult stages. It is important to note that one field may exhibit a severe spider mite infestation while fields nearby may exhibit minimal or no spider mite activity.

Another factor that concerns us is the possibility of mite populations exploding when other materials are applied to soybeans.  Although no firm data is available, we have seen mites increase when certain herbicides are applied post emergence.  Additionally, because mites are often kept in check by various fungal pathogens, we are worried that fungicide applications might, and we would add a big might (again, little data available), interfere with the mite fungal pathogens.  Thus, unnecessary fungicide applications could also lead to enhanced mite problems.

If a decision is made to treat, there are only a few options available. 

·      The two most common materials used in the past are chlorpyrifos (Lorsban and generics) and dimethoate. 

·      Another material more recently on the market is bifenthrin which is the active ingredient in a number of different formulations.  Although we have no experience with this material in Ohio, colleagues in other states indicate that is it a good miticide. 

We would also point out that these materials do not offer much control of the eggs, and thus, any treatment this early should be followed up with continued scouting in case newly hatched mites are not controlled by residual activity and begin to build a second time.  This might require a second treatment later, especially if hot and dry weather continues.  If a second treatment is required, we would also recommend that a different  miticide be used, and growers do not make a second application of the same material.  Although some pyrethroids are labeled as offering suppression of mites, we do not recommend their use and suggest staying with one of the aforementioned materials.  See the following fact sheet for more information on twospotted spider mite on soybean:

What to Expect from Foliar Fertilizer Programs

Strong commodity prices have encouraged producers to look for ways to increase their yields even if it is only for a few bushels. Retail businesses have of wide array of available foliar fertilizers for producers to try to get those few bushels.  Before using a foliar program one should review university research summaries and ask if the concept is sound.

University research has not shown a consistent response to foliar fertilizers. There have been sites that have seen a yield response and some that have seen a yield loss. For most sites there has been no yield change (Ohio data has not shown a yield gain or loss). When a yield response has been seen, researchers were often unable to explain why it worked at one site and not others. Soybeans have been more responsive than corn. Universities generally do not recommend foliar programs since the research results have been inconsistent, unrepeatable and unpredictable.

There are limitations to a foliar program. Crop leaves are made for photosynthesis and not nutrient absorption. A foliar has to be absorbed by the leaf before it dries by entering stomata openings or passing through the cuticle – neither one an easy process. Because of this limitation, it is highly unlikely that a plant would have the ability to absorb large amounts of any given nutrient. Thus a foliar program would be impractical to correct major deficiencies for the macronutrients (N, P, K, Ca, Mg, or S). However, a savvy marketing program often adds a small amount of N or S to a foliar for visual impact (causes the leaves to look greener giving the impression one is getting a benefit from the foliar, but generally no increase in yield). If too much N has been added tissue burn may occur.

If a soil is truly not able to provide roots a micronutrient, foliar application may be viable option since the crop only needs a very small amount. This critical amount would have to enter the leaf through the same restricted pathways as mentioned above. However, available micronutrients should easily be provided to roots in fields where the soil has the optimum pH range, has adequate organic matter, has proper soil moisture, and has followed a balanced nutrient program based on soil tests.

University research is a one tool a producer has to select production practices. There are many new foliar programs and products available each year that universities’ have not evaluated. If a producer selects one of these programs, they should leave at least one strip that does not receive the foliar program for a yield check to confirm potential benefits. OSU Extension will work with any producer, consultant or retailer who would like to set up an on-farm evaluation of these programs or products. 

Producers should be suspicious of programs that recommend foliar products based on plant analysis. There have been instances where a company pulls tissue from a field for analysis and then recommends a producer to apply certain foliar products based on that analysis, regardless of crop condition or growth stage. No university research supports this type of nutrient recommendation. Plant analysis is a diagnostic tool and not a fertilizer recommendation program. Nutrient sufficiency levels were not established or correlated to make a fertilizer recommendation but to evaluate a crop at a specific stage of development. Tissue analysis is an interpretive tool, not an absolute yes or no answer tool. When properly used as a diagnostic tool, plant tissue should be collected from a normal area and the area of concern along with a soil sample for analysis from the two areas. 

Estimating Nutrient Removal of Wheat Straw

Wheat straw is in high demand across all of Ohio for a variety of reasons, including a steady to growing demand, fewer acres devoted to wheat production, or lack of planting opportunity in the fall of 2011. What is the value of the nutrients being removed when straw is baled? This is an important question to ask when deciding whether to leave the straw in the field or bale it for sale at a later time. 

A good wheat crop will yield between 1.0 and 1.2 tons of straw per acre on a dry matter basis.  Dr. Robert Mullen reported in previous newsletters that a ton of wheat straw would provide approximately 11 pounds of N, 3 pounds of P2O5 and 20 pounds of K2O. While a laboratory analysis would be most accurate and can account for weather and other factors that occurred this year, these would be legitimate numbers to use as estimation.

Most of the nutrient value is potash, some as N, and little as phosphorus.  On June 18, 2012, a northwest Ohio co-op has the following in-season prices:  Potash (0-0-60) cost $619-$645 per ton and DAP (18-46-0) was priced at $645-672 per ton.  Besides providing nutrients, straw has value as organic matter to soil, but it is difficult to determine the dollar value for it. Removal of straw does lower soil potash levels, but a soil test should be done to accurately estimate future crop availability.

Ohio markets can be helpful on determining a potential price for straw.  The Mount Hope Auction on June 13, 2012 reported wheat straw selling at $145-$165 per ton for small square bales.  The Yoder & Frey Auction in Archbold reported the June 11, 2012 results of straw bale prices of unidentified weight of $1.20 - $3.60 per bale.



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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.