Has weather hurt corn pollination?

0

With the stretched out planting season this year, corn is in many stages of development, thus in varying stages of pollination.

So how has the weather the past couple of months impacted crop development, particularly as it applies to pollination success?

For a change, we have not had to worry about weather conditions being too hot and too dry.

The problem this year …

Across Ohio there are many corn fields that have been subject to excessive rainfall this year. In some areas rainfall accumulations from May 15 to July 18-19 (and there’s been more since then) range from 14.0 to 19.1inches in the southwest/west central/central regions of the state.

In some of these rainfall events we have seen more than 4 inches falling in less than 24 hours. That is a lot of water for our crop to handle especially when corn may be in a critical growth and reproduction stage such as pollination. In Clinton County, official rain data in one area collected 11.2 inches and in another location collected 13.5 inches during that time frame.

I am sure we have isolated areas that received much more and maybe some isolated areas that received less.

Because of all the crazy weather and stresses put on our corn crop throughout Ohio, Peter Thomison, Ohio State University agronomist, notes there are reports of short, waist high corn tasseling, as well as uneven development and flowering within fields.

These are not uncommon in parts of the state where heavy rains contributed to extended periods of saturated soil conditions and ponding. Now there are questions as to whether such uneven development will impact pollination and thereby affect yield.

There are two techniques commonly used to assess the success or failure of pollination, according to Thomison. One involves simply waiting until the developing ovules (kernels) appear as watery blisters (The R2 or the “blister” stage of kernel development).

This usually occurs about 1 1/2 weeks after fertilization of the ovules. However, there is a more rapid means to determine pollination success, the ear shake technique.

Each potential kernel on the ear has a silk attached to it. Once a pollen grain “lands” on an individual silk, it quickly germinates and produces a pollen tube that grows the length of the silk to fertilize the ovule in 12 to 28 hours.

Within 1 to 3 days after a silk is pollinated and fertilization of the ovule is successful, the silk will detach from the developing kernel. Unfertilized ovules will still have attached silks.

Silks turn brown and dry up after the fertilization process occurs. Thomison suggests by carefully unwrapping the husk leaves from an ear and then gently shaking the ear, the silks from the fertilized ovules will readily drop off. Keep in mind that silks can remain receptive to pollen up to 10 days after emergence.

The proportion of fertilized ovules (future kernels) on an ear can be deduced by the proportion of silks dropping off the ear. Sampling several ears at random throughout a field will provide an indication of the progress of pollination.

Unusually long silks that are still “fresh” are a symptom that pollination has not been successful.

Unpollinated silks continue to elongate for about 10 days after they emerge from the ear husks before they finally deteriorate rapidly. During this period, silks become less receptive to pollen germination as they age and the rate of kernel set success decreases.

Whether you are an optimist or a pessimist about your crop, I encourage you to get in your fields and evaluate pollination success. While out there in those fields, I also encourage you to scout your corn for other issues. If you recall last week’s column I mentioned scouting for corn rust.

On Monday of this past week, we may have found southern rust in the area. Samples have been sent to verify what type of rust it actually is. While in a few fields this week, the rust does not seem to be widespread at this time (less than 50% of plants examined). It is actually somewhat difficult to find but it is out there.

If it is only common rust that we found remember common rust is rarely ever an economic concern in Ohio.

If southern rust is present at high enough levels, the disease can act like a parasite and divert nutrients for fungal growth that would normally be used by the plant.

This process can lead to yield loss during grain fill when plant resources are needed to contribute to the developing ear.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for 29 years, currently serving Clinton County and the Miami Valley EERA.

http://www.wnewsj.com/wp-content/uploads/sites/22/2017/07/web1_Tony-Nye-1.jpg

Tony Nye

OSU Extension

No posts to display