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Ohio State University Extension


C.O.R.N. Newsletter 2010-33

Dates Covered: 
October 5, 2010 - October 12, 2010
Curtis Young

Corn Storage Molds

There have been reports of field dried corn producing molds in storage. Corn is dryer than average and much dryer than last year coming out of the field, however, concerns are that 15% corn put into the bin is producing storage molds. Diligent monitoring of stored grain, as always, can help producers avoid problems that too often go entirely unnoticed. Remember, even in years such as this when there is little or no ear rot problems in the fields, mold may still develop in storage if storage temperature and moisture are inadequate. Several things to keep in mind for those stored bushels. First, remember that stored grain will vary considerably in moisture and there can be considerable variance among individual kernels. It doesn't take many wet kernels to cause problems. Check the condition of the grain now and again every few weeks. Turn on the fan. When the fan is running, open one of the bin lids and smell the air exiting for signs of odor. Probe the surface to see if crusting has occurred.


• Harvest at the correct moisture and adjust harvest equipment to minimize damage to kernels. Mold and mycotoxins tend to be higher in (machine or insect) damaged kernels.

• Dry and store harvested grain to below 15% moisture to minimize further mold development and toxin contamination in storage.

• Store dried grain at cool temperatures (36 to 44°F) in clean, dry bins. Moderate to high temperatures are favorable for fungal growth and toxin production.

• Periodically check grain for mold, insects, and temperature.

• If mold is found, send a grain sample for mold identification and analysis to determine if toxins are present and at what level.

• Clean bins and storage units between grain lots to reduce cross-contamination.

For more information on harvesting, handling and storing moldy grain visit the website: prepared Dr. Richard Stroshine at Purdue University.

Reminders About Weed Life Cycle And The Timing Of Fall Herbicide Treatments

The optimum timing of fall herbicide treatments can vary based on life cycle, and we can roughly lump the various life cycles into one of two categories: 

1) must be treated before frost, which pertains to all warm-season perennials, including johnsongrass, pokeweed, milkweeds and hemp dogbane, and horsenettle.  The first frost will cause these weeds to shut down, if they have not already matured and senesced.  Herbicides are no longer effective after this occurs.

2) can be treated after frost, and in some cases even after a hard freeze.  Winter annuals, biennials, and cool-season perennials fit into this category, and they are often most effectively controlled when herbicides are applied between mid-October and mid-November.

Winter annuals, including chickweed, purple deadnettle, mustards, and cressleaf groundsel among others, emerge in late summer into fall.  They survive frost and are still sensitive to herbicides even after cold weather in December, based on our research.  Herbicide activity in these weeds slows down in cold weather, but the effective treatments still eventually kill emerged weeds.  It’s not necessary to wait until frost to apply herbicides, except that:  1) treatment too early in fall can miss the plants that are still emerging; and 2) for treatments that include herbicides with residual activity (metribuzin, simazine, Canopy, etc), the soil temperatures in early fall are still warm enough for herbicide degradation to occur.  This reduces the amount of herbicide present in spring, potentially allowing weeds to emerge earlier in spring than intended.  It’s not necessary to use glyphosate for control of winter annuals, unless winter annual grasses are present.  They can be controlled with combinations of 2,4-D and either glyphosate, metribuzin, Canopy, Basis, or simazine (see also C.O.R.N. articles from the last several weeds).

Biennials, such as poison hemlock and wild carrot, are most effectively controlled in the fall at the end of their first year of growth, when they exist as a low-growing rosette.  We do not have experience trying to control these with herbicides in winter under very cold conditions, but they are dormant then and should probably be treated in the mid-October to mid-November application window.  Fall treatments for biennial weeds will generally be most effective when they include glyphosate and 2,4-D.

Cool-season perennials include dandelion, Canada thistle, and quackgrass.  Herbicides can be more active in these weeds after a frost, which triggers the plant to increase movement of carbohydrates into the roots or rhizomes.  Systemic herbicides move to these same areas with the translocating carbohydrate.  The other key to effective control is to make sure the weeds have recovered fully from harvest, late summer mowing or earlier droughty conditions, and are fairly sizable.  Canada thistle should be 8 to 12 inches tall for best results, and dandelion should have a healthy rosette with a number of fully expanded leaves.  Delaying herbicide application until late October or November can allow more time for the needed recovery.  While winter annuals can be treated into early winter, the colder conditions will reduce herbicide activity in cool-season perennials.  Cool-season perennials will generally be most effectively controlled with combinations of glyphosate and either 2,4-D or dicamba, although combinations of 2,4-D with Basis or Canopy are among the most effective treatments on dandelion .  Glyphosate is most effective on Canada thistle when applied without other herbicides, and is really more effective than 2,4-D or dicamba on dandelion in the fall.  However, combinations of glyphosate and 2,4-D will be more effective for control of the many populations of glyphosate-resistant marestail.

Private Pesticide Applicators To See Changes on Ohio License

This fall, Ohio private pesticide applicators will receive a new license showing a change in categories. A pesticide license is required for farmers who use restricted-use pesticides in their farming operation.

“The Ohio Department of Agriculture (ODA) has simplified the categories for private applicators,” says Joanne Kick-Raack, State Program Director of the Pesticide Education Program for the Ohio State University Extension, Columbus, Ohio. “The change will mean fewer exams for new applicators and many current license holders will have fewer categories for recertification.”

The simplification undertaken by ODA has reduced the number of licensing categories from 13 to only seven. This consolidation reflects the changing needs of Ohio farming operations. Several smaller-use categories have been combined for applicators. For example, growers who raise produce will now only need one category for fruit and vegetable crops. The new categories for a private license are:

Category 1: Grain and Cereal Crops

Category 2: Forage Crops & Livestock

Category 3: Fruit & Vegetable Crops

Category 4: Nursery & Forestry Crops

Category 5: Greenhouse Crops

Category 6: Fumigation

Category 7: Specialty Uses

Some applicators will have fewer categories on their license, but will still be able to purchase and use the same pesticide products. The specialty categories of seed treatment, non-cropland, aquatics, tobacco and wood preservation were consolidated into the first six categories. This means an applicator would be able to purchase materials for these applications with at least one category on their license. For example, an applicator with Category 1 (Grain and Cereal Crops) on their license will still be able to purchase products for grain crops but also be able to buy products to treat seed and manage stored grain, non-crop areas and ponds on their farm. Tobacco and wood preservation also were consolidated.

Category 7 represents specialty uses. This category is only for applicators that do not have the first six categories on their license. An example would be someone who only does wood preservation on lumber and does not need any other crop categories.  Their license would reflect this by only having Category 7.  If an applicator has any other category on their license, they do not need Category 7.

Kick-Raack says the Core category, which covers safety and stewardship for pesticide use, remains unchanged and is required for all applicators. If applicators have questions, they can contact their local OSU Agriculture Extension Educator.  More detailed information about the new categories is also available at the Pesticide Safety Education Program website: or the ODA website at:


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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.