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http://www.ag.ohio-state.edu/~corn/ |
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August 4 to August 10, 2001
C.O.R.N. 2001-25
In This Issue:
A) Grain Fill In Corn
B) Two Spotted Spider Mites
C) Soybean Aphid
D) Bean Leaf Beetle
E) Second Brood European Corn Borer
F) 2001 Ohio Wheat Performance Test Results Soon
According to a recent USDA-Ohio Crop Weather Service report most of the state's corn crop is well into grain fill. By the end of July, 15% of Ohio's corn crop was in the dough stage. This is one day behind last year and four days ahead of the five year average.
Following pollination, grain fill (kernel development) is the last critical period for grain yield. Kernel development proceeds through a number of stages which have been characterized by such terms as blister, milk, roasting ear, soft dough, dent, etc. Since these descriptive terms can sometimes be difficult to interpret, alternative systems have been proposed. A staging system widely used by agronomists and crop consultants divides kernel development into six reproductive stages, designated numerically as R1, R2, through R6
The table below lists kernel developmental stages in sequence and provides a brief description of each phase
| Grain Fill Stages in Corn | |||
| Stage | Description | Avg. No. of Days/Stage |
Approx. Days from Silking |
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| Silking (R1)* |
fresh green silks, no visible blisters | 4 | NA |
| 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 (R4) |
solids beginning to form, kernel pasty texture (barely edible) | 4 | 24 |
| Soft Dough |
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 lines may just be visible |
17 | 52 |
| Black Layer (R6) |
maximum kernel dry weight, kernel moisture 27-32% | 10 | 62 |
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| *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. | |||
Grain fill may be affected by drought, high temperature, nutrient deficiency, disease or insect injury, shading, hail damage, overpopulation, and other stress factors. These factors may cause complete abortion of kernels toward the ear tip ("tip dieback"). Abortion occurs because nutrient flow cannot adequately supply all kernels after pollination. Such kernel abortion is most likely to occur during the first two weeks after pollination (during the blister stage). These same stress factors may also reduce kernel size and weight. Premature plant death resulting from diseases (e.g. stalk rots) or frost cuts off starch accumulation and results in small, light-weight kernels (low test weight).
Dr. Bob Nielsen, Purdue University corn extension agronomist, has an excellent set of color pictures illustrating the different kernel development stages on-line:
(http://www.agry.purdue.edu/ext/corn/news/articles.01/Grainfill-0717.html )
Fields in Ohio, especially in the more northern counties, continue to have large populations of the soybean aphid. We have been getting numerous calls about the need for treatment. We continue to recommend treatment only when significant numbers (>1000+) of aphids are observed on many plants from numerous locations within a field. See the C.O.R.N. newsletter from July 28 - Aug 3 for information related to aphid management. Observations over the past 2 weeks suggest that "hot spots", where a few plants are covered with aphids, are not increasing in size or area. There are also indications that aphid numbers might be going down, which is also being seen and suggested in other states. Researchers with experience from last year feel that we are past the major peak. Therefore, care should be taken when determining the need for treatment. However, there are fields that perhaps need treatment. Thus, growers should continue to monitor their fields, and take action if they feel it is warranted.
First generation bean leaf beetles are now active throughout Ohio. Beetles in the first generation are primarily leaf feeders, and the second generation are pod feeders. Research conducted at Iowa State University suggests a good correlation between populations of first and second generations. Thus, present bean leaf beetle activity may be a good indicator for later pod injury. Growers should check their fields for leaf feeding (generally on the upper leaves). A sweep net should be used to check the number of beetles per 10 sweeps. A count of 20-30 beetles per 10 sweeps suggests the potential for a large second generation. Although all fields should be checked in the coming weeks for pod feeding, those fields with large populations are most at risk. Identifying them now will assist in preventing losses from pod injury later this month. The C.O.R.N. newsletter in the coming weeks will have more information on preventing pod damage.
It is time to start checking for second brood European corn borer. Moths of second brood European corn borer were detected in light traps and pheromone traps last week. Second brood corn borers normally prefer late-planted corn. Early detection of second brood egg-laying is difficult. Scouting for egg masses should be concentrated on the leaves above and below the ear. A fact sheet with information about European corn borer can be found on the WEB at:
http://entomology.osu.edu/ipm/factsheets/0015.htm
Readers can subscribe electronically to this newsletter by sending an e-mail message to: corn-out-on@postoffice.ag.ohio-state.edu. A successful subscription message will receive by an automatic reply from the listserv. Contact your local Ohio State University Extension Office or e-mail labarge.1@osu.edu if you have problems subscribing.
Past versions of C.O.R.N. can be found on the World Wide Web at: http:/www.ag.ohio-state.edu/~corn/archive/
C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.
Contributors to C.O.R.N. this week include: Specialists: Pat Lipps, Ann Dorrance, and Dennis Mills (PlantEditor: Ed Lentz Web Editor: Tom Rosati
Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement 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.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.
TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868
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