The Dos and Don'ts of Safe and Effective Herbicide Application: Part 2

Disclaimer: This series is informational only and does not act as a substitute for the Indiana Pesticide Applicators Certification. For more information on obtaining an Indiana Pesticide Applicator License please see the Office of the Indiana State Chemist. 
Click Here to Read Part 1
Click Here to Read Part 3
Click Here to Read Part 4

Effective herbicide and pesticide management is crucial for effective invasive species control, maintaining healthy crops, minimizing environmental impact, and ensuring sustainable agricultural practices. This article explores the different types of control methods, the concept of Integrated Pest Management (IPM), pesticide resistance, and considerations for herbicide selection.

What is a pest?
A pest is any organism harmful to humans or human concerns. Pesticides are chemicals used to control pests and can be broken down into herbicides, insecticides, and fungicides which control plants, insects, and fungi respectively. For these blogs, the term herbicide and pesticide can be used interchangeably, but we will use herbicide as often as possible.

Methods of Control

Biological Control
   Biological control involves using natural predators, parasites, or pathogens to manage pest populations. This method leverages the natural ecosystem to keep pest levels in check without relying on synthetic chemicals. The advantages of this approach include environmental sustainability and minimal environmental impact. Biological control is not always an effective solution, however. If no pests are known or not enough research has been done to test their ecological impact biological control may not be possible. Consult with your local SWCD or extension office to learn if biological control might be right for you.
 
Mechanical Control
   Mechanical control methods physically remove or block pests. Techniques include tilling the soil, hand-pulling weeds, using traps, and installing barriers like nets or fences. Another example of mechanical control would be pulling Garlic Mustard (Alliaria petiolata)  seedlings in the early Spring. Mechanical control is often labor-intensive but can be highly effective for small-scale operations or specific pest problems. 
 
 
Cultural Control
   Cultural control involves modifying practices to reduce invasive plant establishment, reproduction, and survival. Techniques include crop rotation, repeated mowing, mulching, adjusting planting times, and selecting pest-resistant crop varieties. These practices create unfavorable conditions for pests, thereby reducing their impact without chemical intervention.
 
Chemical Control
   Chemical control involves the application of herbicides and pesticides to manage pest populations. This method is often used when immediate and effective control is needed. While chemical control can be highly effective, it requires careful management to avoid issues such as herbicide resistance development, non-target species impact, and environmental contamination. Methods of chemical control include cut-stump herbicide application, foliar herbicide application, basal barking, and hack-and-squirt treatments.

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Integrated Pest Management (IPM)
Integrated Pest Management (IPM) is a comprehensive approach that combines multiple control methods to manage pest populations in an economically and ecologically sound manner. IPM principles include:
 

• Monitoring and Identification: Regularly inspect areas for presence of pests or invasive species and correctly identify species to ensure appropriate control measures.
• Threshold Levels: Establish action thresholds to determine when pest populations require intervention. This helps avoid unnecessary chemical applications.
• Prevention: Implement cultural practices that prevent pest problems.
• Control: Use a combination of biological, mechanical, cultural, and chemical controls. Chemical control is used as a last resort and in a targeted manner to minimize environmental impact. Use the lowest-impact option that is still effective at achieving your goals. This could mean applying herbicide with a brush or sponge rather than a backpack sprayer if you are controlling a small number of individuals in a sensitive area.

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Herbicide Resistance

What is it?
Herbicide resistance occurs when pest populations develop the ability to survive exposure to a herbicide that was previously effective against them. This resistance arises due to genetic variation and selective pressure from repeated herbicide use, leading to the survival and reproduction of resistant individuals.
 
How to Avoid Herbicide Resistance

• Rotate Herbicides: Use different classes of herbicides with different modes of action to reduce the selection pressure on pests. Herbicides with different modes of action attack different parts of the plant system, some herbicides may inhibit amino acid production while others are root or plant growth inhibitors. Click here to learn more.
• Integrated Approaches: Incorporate non-chemical control methods, such as biological and cultural controls, to reduce reliance on chemical herbicides. Cultural control is often the easiest alternate method of control/prevention for homeowners and biological control should not be attempted without professional aid.
• Appropriate Dosage: Apply herbicides at recommended rates to ensure effective control and minimize the survival of partially resistant individuals. You can find recommended dosages within the chemical label found either on the bottle or online. If the recommended dose is not listed or ineffective consult your local SWCD or extension agents. If herbicide application is only partially successful, re-treat as needed to prevent spreading of resistant individuals.
• Regular Monitoring: Continuously monitor pest populations for signs of resistance and adjust management strategies accordingly. Signs of herbicide resistance include reduced effectiveness in control, partial control, or living plants next to dead plants which were both sprayed.

Herbicide Selection
When selecting herbicides there are a variety of factors that should be considered:
 
 What Are You Managing?
Identify the specific weeds or pests you need to control. Different herbicides target different species, so accurate identification ensures effective management. Two major types of herbicides are broad-spectrum herbicides and selective herbicides. Broad-spectrum herbicides (Round Up) will kill most plants as long as the herbicide concentration is correct. Selective herbicides target a specific group of plants such as grasses or plants classified as broad-leaves. Using selective herbicides where possible helps us minimize unwanted effects.
 
 
Environmental Concerns
Consider the environmental impact of the herbicide. Choose products with low toxicity to non-target organisms, minimal soil and water contamination potential, and rapid degradation in the environment.
 
Personal Need/Comfortability with Application
Assess your comfort level and ability to apply the herbicide safely and effectively. Consider factors such as the complexity of application, required protective equipment, and potential health risks.
 
 
Effective herbicide and herbicide management involves a combination of control methods, adherence to IPM principles, and careful consideration of resistance and environmental impact. By integrating biological, mechanical, cultural, and chemical controls, landowners can manage pests sustainably and responsibly. Selecting appropriate herbicides and understanding the risks associated with herbicide use are essential for maintaining and protecting the environment. For further information or assistance, contact Hamilton County SWCD.
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