These days, integrated weed management practices are essential in order to manage resistance to herbicides and reduce their impact on the environment. If they are to remain good allies, we must use them less, but better.
The use of herbicides may well be widespread, but it is far from the only way to control weeds. According to crop expert advisor and agronomist Kamel Hamidouche, cultivation methods, physical and mechanical weed removal, monitoring and cover crops are effective and sustainable alternatives that help reduce the use of herbicides. That being said, optimizing the potential of herbicides and limiting their impact on the environment requires a solid appreciation of how they work and their proper use.
Overview of groups 9 and 10.
Herbicides are categorized into different groups depending on how they work. Over time, plants develop resistance to the products’ molecules. Hence, it is best to alternate with other active substances from different herbicide groups.
Group 9
Active substance: glyphosate, also known by the commercial name, Round Up.
This herbicide is found in commercial preparations as different forms of salt (trimethylsulfonium salt, isopropylamine salt, etc.). It inhibits the EPSP synthase enzyme, which is involved in the synthesis of tyrosine, phenylalanine and tryptophan (aromatic amino acids). In other words, the role of glyphosate is to block the enzyme that makes certain amino acids. In practice, that means it prevents the plant from growing and results in premature senescence. This herbicide must be applied to the leaves once the weeds have emerged. It is a non-selective product that controls several different weeds at the same time. “Most of the herbicides on the market are glyphosate”, points out Kamel Hamidouche. You find it in products like Round Up, Polaris Max, Credit Xtreme, Factor 540, etc.
Group 10
Active substance: glufosinate, also known by the commercial name Liberty Link.
Glufosinate is a non-selective contact herbicide. It causes a drop in glutamine and high levels of ammonia in the tissues, which stops photosynthesis, as a result of which, the plant dies. It is an alternative to the highly popular glyphosate, which is also used to eliminate several weeds at once. Glufosinate is found in products like Ignite, Interline, Liberty Link, etc.
Best practices
The following basic principles will help avoid product waste and achieve precise and effective application:
Rule #1: contact
The product must be in sufficiently close contact with the plant once it is sprayed. If it is very windy, the product will disperse. If it is raining, the product will wash off. “In those two cases, the product will not work properly,” indicated Kamel Hamidouche.
Rule #2: timing
The herbicide must have time to seep into the plant. It must be able to reach the cells fast enough before it deactivates. It is important to follow the instructions on the product label to the letter.
Rule #3: concentration
The amount of herbicide must be sufficient to accumulate on the target site and reach toxic levels. Given that doses differ among manufacturers, it is best to refer to the product label.
Rule #4: safety
Regardless of the type of herbicide you are applying to your crops, you should always:
- store your products safely;
- rinse/clean the sprayer and rinse the containers before and after every application;
- do regular maintenance on the sprayer and its settings;
- wear protective equipment;
- follow the manufacturer’s instructions on the time between application and harvesting and returning to the field;
- pay special attention to artesian wells and shoreline buffer strips when spraying; and
- follow the instructions on the product label.
Contact your expert advisor to find out how to control weeds in your fields.