C.O.R.N. Newsletter 2010-21

Dates Covered: 
July 12, 2010 - July 20, 2010
Editor: 
Harold Watters

Brown silks common in early planted corn

Kernel Development Stages in Corn

 

Stage*

Description

Avg. No. of Days/Stage

Approx. Days from Silking

Silking (R1)

Fresh green silks, no visible blisters

4

--

Pre-blister

Silks brown, not necessarily dry visible kernel pimples, contain little clear fluid

4

8

Blister (R2)

Visible blisters w/abundant fluid

4

12

Early milk

Mostly white kernels w/milky-white fluid, some yellow kernels

4

16

Milk (R3)

Mostly yellow kernels w/milky-white fluid, no solids yet (Roasting Ear” stage)

4

20

Late Milk- Early Dough

Solids beginning to form, kernel pasty texture (barely edible)

4

24

Soft Dough (R4)

Pasty or semi-solid (not edible), no visible denting

5

28

Late Dough- Early Dent

Few kernels beginning to dent, especially near butt of ear

5

33

Dent (R5)

Majority of kernels dented or denting

8

38

Late Dent

Essentially all kernels dented, milk line may just be visible

17

52

Black Layer (R6)

Maximum kernel dry weight, kernel moisture 27-32%

10

62

 

*R-stages 1 through 6; specific number of days associated with each stage may vary from season to season, from location to location, and from hybrid to hybrid.

Keep in mind that the values for average number of days per stage and approximate days from silking in the table above are based on timely corn planting (e.g. early May). When corn is planted later, it generally requires fewer heat units to achieve R6, physiological maturity or “black layer”, and this may affect the number of days per stage and days from silking.

For more on grainfill check out the following article that Dr. Bob Nielsen which excellent pictures and diagrams. 

Nielsen, R.L. 2008. Grain Fill Stages in Corn. Corny News Network, Purdue Univ. [online] http://www.kingcorn.org/news/timeless/GrainFill.html. [URL accessed 7/12/10].

Mid-July Insect UpdateJapanese beetle on corn silks

Mid-July Insect Update

As we come to mid-July and the reproductive stages of corn and soybean, we are reaching the susceptible growth stages of field crops in terms of insect injury and crop damage.   Although we are not receiving reports of large densities of insects on either crop except for catches of western bean cutworm adults (see the article on western bean cutworm in this newsletter), we would remind growers that they should be scouting their fields for potential problems.  We are seeing Japanese beetles, adult bean leaf beetles and Mexican bean beetles, and other defoliators on soybeans.   Remember that defoliation should not go over 15-20% during the earlier soybean reproductive stages.  Although a few soybean aphids are being found, their numbers are very low.

Corn growers should be aware that European corn borer, while generally at low densities, can still occur in higher than desired numbers.  This is also a good time to check for corn rootworm root injury.   Growers should be aware that because of excessive soil moisture in some areas, root development has been poor in some locations in Ohio.  Thus, when examining roots, make sure that rootworm feeding is actually seen and that you are just not observing small roots.  Also, remember that slight rootworm injury on smaller roots might be more extensive than anticipated. 

In addition, adults of both Japanese beetles and corn rootworms are starting to feed on silks, which should be monitored by growers.  As with abnormal root development, the excessive moisture has caused many fields to have uneven plant growth, both in size and stage of development, and we are seeing areas of fields that are silking while other areas are not.  Thus, prior to treating for silk clipping, make sure the entire field is scouted.  Alfalfa growers should also be reminded to continue scouting for potato leafhopper following a cutting as regrowth occurs. 

Growers can go to our Agronomic Crops Insect web site at http://entomology.osu.edu/ag for more information on all these insect pests including their biology, thresholds, and insecticide recommendations.

 

Update on Western Bean Cutworm Flight

Western bean cutworm counts increased slightly from last week.  A total of 443 adult moths were collected from July 6 to July 12, bringing our total for the year up to 920.  Still, no egg masses or larvae have been found in Ohio.  On scouting trips past week, we noticed a lot of variability in corn development ranging from ankle high to full tassel.  Thus, a lot of corn is still at risk for WBC infestation, considering we have not reached peak flight.  Growers are still urged to inspect their fields for any eggs or larvae.  

Recently, our colleagues at Purdue University developed some short videos for western bean cutworm scouting and egg hatch (see http://extension.entm.purdue.edu/pestcrop/2010/issue15/index.html).  These videos should be helpful when scouting your fields.  

July Weather OutlookLatest 90 day departure

July Weather Outlook

Not much change from a few months ago. 

Above normal temperatures and near normal rainfall are forecast to continue for the rest of July.

As discussed in May, the trends and guidance supports near normal rainfall for the growing season after pre-growing season indicated some minor drought risk mainly in the northeast, but that quickly went away. We discussed in May that even though near normal is forecast for rainfall this growing season that the risk was to the wet side in the southwest and drier side in the northeast.

Overall, it has been wet in the western and southwest part of the state with average to slightly below average rainfall in the northeast this growing season: http://www.erh.noaa.gov/ohrfc/HAS/images/latest90daydepart.jpeg

With plenty of soil moisture alone, this will continue to support rainfall chances with not much longer than a week between rains seen anytime soon.

The 2010 Wheat Season: A look back as we move forward

The 2010 wheat harvest is coming to an end, and as we plan for the 2010-2011 season, let us take a quick look back and learn from this past crop. We had everything this year – head scab and vomitoxin, Stagonospora leaf and glume blotch, powdery mildew, leaf rust, head smut, cereal leaf beetle, plus a very hot late-spring-early-summer. The big problem this year was head scab and vomitoxin, with incidence ranging from 3 to 60% and vomitoxin from less than 1 to 18 ppm. Both Stagonospora and powdery mildew were also very severe, with a severity score of 7 out of 10 this year. Diseases combined with a short grain fill period resulted in low to moderate yield and grain quality, with average yield ranging from 40 to 90 bu/acre and test weight from 45 to 60 lb/bu.

THE POSITIVES: The good news is rarely did we see all of the disease problems in the same fields.  As is usually the case, some fields still escaped most of these problems. This is largely because those fields were either planted with resistant varieties, were planted after soybean, treated with a fungicide at the right time, flowered before or after the rains, or various combinations of the above. Even in areas where the scab levels were high, some of the fields with the lowest levels of vomitoxin, highest yields and test weights were those that received a fungicide application at flowering. However, vomitoxin levels were still higher than 3 ppm in some of the treated fields. Similarly, fields treated for Stagonospora also had better grain yield and quality than fields left untreated. Combining variety resistance with fungicides added a few more bushels to yield and pounds to test weight. Another positive from this season was the fact that the scab forecasting system did a good job of alerting us about the risk of scab. We did have more scab in 2010 than we had in 2009 and the risk tool clearly indicated that was going to be the case. 

THE NEXT CROP: As we plan for the 2010-2011 crop, here are a few things to consider from a disease standpoint. We will almost always get some powdery mildew; if it is wet and humid during the early and middle portions of the season, we will certainly see Stagonospora and Septoria leaf blotch; if it is wet and humid during flowering we will more than likely see head scab. The scab forecasting system will help us to detect this risk early, and generally when there is a high risk for scab, Stagonosora glume blotch tends to be high also. Foliar diseases can be managed effectively with resistance or with a well timed fungicide application if the variety is susceptible, with a percent control as high as 90%. Resistance must be combined with a fungicide application at flowering to achieve the best results in terms of scab and vomitoxin control. Since it is almost impossible to find a variety that is resistant to scab, Stagonospora, powdery mildew, and rust, and still yield well, we would suggest that priority be given to scab resistance, if you cannot find a variety that is resistant to multiple diseases, and be prepared to use a fungicide to manage other diseases, it the weather conditions become favorable. In fact planting resistant varieties with different flowering dates (maturity) will almost certainly reduce the chance of your entire field being affected by a disease, even if the weather becomes favorable.   

WHAT DID WE LEARN FROM 2010?: Disease management needs to be one of the top things on our list if we are going to have a great wheat crop. In any given season, if the weather conditions are favorable, diseases can take a bite out of both yield and quality of even our highest-yielding varieties. In 2010, the more aggressive managers had the better wheat. Some folks were just lucky, but in general, those who had resistant varieties planted and applied a fungicide at the right time, saw better yields, test weights, and had lower levels of vomitoxin. Let us start by choosing resistant varieties, especially to head scab, as we plan for our next wheat crop.

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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.