The drought monitor report as of Tuesday, March 28 indicates exceptional drought creeping further east and along the southern counties. Definitely not a good situation. The six to ten-day outlook (April 4 to 8) indicates a 33 to 50% of leaning to below normal temperatures and 33 to 40% of leaning to above normal precipitation.
The eight to 14-day outlook (April 6 to 12) indicates a 33 to 40% chance of leaning to below normal temperatures and a continued 33 to 40% chance of above normal precipitation. In theory, the long-term average indicates we should be starting to move into our “wet” period.
Last week, we discussed the Integrated Pest Management (IPM) concept of weed control. The principle is to use a variety of weed control methods, up to and including herbicides, in a safe environmentally sound manner.
The current reality in today’s agriculture is while we will use a variety of methods, it is very likely we will have to use herbicides. Today, how do herbicides work and why that matters. As a side note, yes, it is possible to grow “organic” field crops without the use of synthetic chemicals but that presents a set of challenges. Of particular concern in organic production is typically an increased need for tillage for weed control and with erosion concerns and the need to conserve soil water, it’s a problem.
Mode of Action (MoA) is simply how the herbicide injure/kills the plant. There are many modes of action and they grouped together by similar MoAs so you understand how it works. We aren’t going into detail as there are many groups. Suffice it to say that in some way they affect plant cells or their ability to develop and reproduce in some way.
They may affect photosynthesis or cell replication or energy transfer or membrane stability and the list goes on. Some examples include ALS Inhibitors, Root Growth Inhibitors, Growth Regulators, Photosynthesis Inhibitors, Pigment Synthesis Inhibitors, Aromatic Amino Acid Synthesis Inhibitors, and Shoot Growth Inhibitors for example.
These are broad categories and the are groups within them with over twenty in all. Some are “selective” and some nonselective meaning they only affect certain types of plants such as only grasses or broadleaves or pretty much effect all types of flowering plants. Some are residual, typically soil applied, while others are not.
Some only effect the tissue they contact while others are systemic and will travel throughout the plant to where they will be effective.
So why does this matter? Most of you are probably aware of the increasing resistance to certain herbicides like glyphosate and atrazine from producers relying and over using them year after year. Since plants are genetically diverse, we kill off the susceptible plants while favoring the reproduction of those partially or totally able to metabolize the active ingredient and we shift the population fairly quickly to be resistant to the active ingredient.
By using several modes of action, either varying them from year to year, within the crop year, or tank mixing several modes of action, we can prevent/alleviate this problem. It costs more money but is cheaper than dealing with resistant weeds.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207, or martinv@bartonccc.edu.
