The crop that grabs my attention this time of year is wheat, which recently revealed the green grain that will be changing to amber waves of grain in about a month.
The wheat crop will produce no more leaves or tillers by the time the grain heads have emerged from the stems. The leaves will have to provide all the photosynthetic energy the plant and grain needs until harvest.
One leaf on the wheat stem provides most of the energy for the developing grain. It is the last leaf to emerge and the first leaf below the grain head.
Agronomists and farmers call it the “flag leaf,” since it is the highest leaf and resembles a flag on a staff.
Grain yields will be significantly reduced if pests or nature damage this leaf early in the grain-fill period. To prevent these losses, a farmer may use fungicides to protect the flag leaf against foliar diseases such as septoria and powdery mildew.
Farmers will also scout fields to ensure that insects are not damaging the flag leaf and use an insecticide if the insect population is above an established threshold. The most common insect problems are armyworms and cereal leaf beetles.
This past weekend, many of the wheat fields were flowering.
Most people wouldn’t know wheat is flowering since it does not have petals. The term for flowering is “anthesis,” defined as when the anthers are visible along the wheat head. Anthers are the plant part responsible for pollen production.
The first anthers to appear will be in the center of the wheat head, progressing to the ends. Anthers are bright yellow at early emergence, and full of pollen, and white after pollen has been dispersed.
Pollination generally is completed in three to five days. During flowering, the wheat head is susceptible to infection from a serious disease called Fusarium head scab.
This can be disastrous for a wheatfield. Infected kernels may produce a toxin that is harmful to humans and hogs. It is a vomitoxin, so you can assume why we do not want it in our food supply.
Head scab was not a problem prior to about 1990. Then, farmers adopted conservation practices of leaving corn stalks and residues on the soil surface.
This same Fusarium fungus also infects corn stalks. Infected stalks on the surface then become the source of Fusarium head scab in wheat.
As a result of conservation practices, there are plenty of decaying corn stalks infected with Fusarium on the soil surface to provide spores for susceptible wheat.
However, the amount of spores is dependent on spring temperatures and spores will not infect wheat heads except during extended periods of rain and high humidity during flowering.
Resistant wheat varieties are the best control against Fusarium head scab. However, these varieties generally yield significantly less than non-resistant varieties.
The potential for head scab occurs each year, but actual infection only occurs during extended wet conditions at flowering. Even then, only part of the field or part of the wheat head may be infected, which can allow harvest and blending with good grain.
In recent years, fungicides have become available. However, they are expensive, have to be sprayed at flowering to be effective, and still only provide about 50 percent control.
Consider the logistics of applying a fungicide if it rains the whole week during flowering.
Plant pathologists and other scientists from land grant universities, including Ohio State University Extension, have worked together to develop a computer program that predicts the risk of head scab. Farmers and consultants use this program to determine the need of a fungicide.
Extension agriculture educators, including those in northwestern Ohio, collected data for many years to develop this program, which has shown low risk for head scab across the state of Ohio. The program may be found at http://www.wheatscab.psu.edu/.
The wheat crop looks good in our area. There have been few pest problems.
It is shorter than normal, so straw may be in short supply again this year. If nature cooperates, a respectable crop should be harvested in about 30 to 40 days.
Lentz is extension educator for agriculture and natural resources for The Ohio State University Extension Service in Hancock County. He can be reached at 419-422-3851 or via email at firstname.lastname@example.org.
Lentz can be heard with Vaun Wickerham on weekdays at 6:35 a.m. on WFIN, at 5:43 a.m. on WKXA-FM, and at 5:28 a.m. at 106.3 The Fox.
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