Pyrethrin insecticides explained: Safe use and garden pest control tips

With so many pests that can damage plants and crops, pyrethrin insecticides are crucial for garden pest management.Synthetic pesticides have traditionally been used to control these insects; however, they can be toxic to the environment, harmful to beneficial insects, and pose risks to human health. An eco-friendly alternative is pyrethrin (derived from chrysanthemums), a natural insecticide.

Pyrethrin attacks the nervous system of insects, eventually causing paralysis and death. It works on aphids, beetles, and caterpillars. Compared to synthetic pesticides, pyrethrin causes relatively little harm to mammals, birds and beneficial insects when properly applied in the home or small-scale garden making pyrethrin an ideal pesticide choice for organic gardening.

Pyrethrin: A Natural Insecticide

Pyrethrin is a botanical insecticide made from the flowers of two types of chrysanthemum plants:

• Chrysanthemum cinerariifolium
• Chrysanthemum coccineum

It is composed of a mixture of six insecticidal compounds:

• Pyrethrins I and II
• Cinerins I and II
• Their related esters

Together, these compounds are toxic to invertebrates (pyrethrin is a somewhat broad-range insecticide), and pyrethrum is registered for such pests as:

• Aphids
• Beetles
• Caterpillars

Mode of Action

Pyrethrin acts on the insect nervous system to kill insects. Pyrethrin's active compounds interact with sodium channels on insect nerves. Under normal conditions, sodium ions move in and out of nerve cells in a regulated fashion, transmitting electrical signals that direct movement and behavior.

Pyrethrin extends this process by forcing sodium channels to remain open longer, so that even more sodium ions pass through the cells. This disturbance with the normal electrical activity of the nervous system of the insect causes hyperexcitation and that results in a paralyzing effect on the insect. In this way, the affected insect will not be able to move, feed or do the other basic physiological processes that result in its death.

Pyrethrin acts quickly, and insects die within hours of contact. Pyrethrin acts fast, making it useful against pests that have a high reproductive rate and can do substantial foliar damage in no time.

Natural vs. Synthetic Forms

Pyrethrin comes in two varieties that are used for pest control. While both are used for pest control, they vary in composition, environmental impact, and safety. 

Benefits of Using Pyrethrin in the Garden

Pyrethrin offers a safe, effective, and eco-friendly solution for managing garden pests.

• Effectiveness Against a Wide Range of Pests: Pyrethrin works on a wide variety of garden pests such as aphids, beetles and caterpillars. It is fast-acting, and kills and paralyzes pests on contact. This quick action means less harm is done to the plant.
• Low Toxicity to Mammals and Birds: Pyrethrin is a safe, natural way to rid the garden of invasive insects. If used properly, it is of little threat to humans, pets and domestic animals. This makes it perfect for the eco-friendly gardener.
• Eco-Friendly and Biodegradable: Pyrethrin is a natural substance that degrades quickly in sunlight, so any product made with it likely will not be an environmental nuisance. It does not remain in the soil or water, so it is a very environmentally friendly option. It's exciting to maintain a good ecosystem in the garden forest.
• Quick Breakdown and Minimal Residual Impact: Pyrethrin leaves no long-lasting residue on treated plants, making it suitable for gardens growing food crops. Its rapid breakdown ensures minimal chemical presence, promoting a cleaner, safer gardening environment.
• Safe for Beneficial Insects: Pyrethrin can also be used without any risk of harming beneficial insects such as bees and ladybugs. Gardeners can use it when such insects are less actively feeding to protect beneficial species while controlling pests.
• Low Risk of Resistance Development: Pyrethrin is less likely to cause resistance than synthetic chemicals in pests. Because of its natural makeup and fast decomposition, it is more difficult for pests to build up resistance over time, which means that it will not lose its efficacy in the long run.

Top Pyrethrin Products for Organic Pest Control

Here are three top pyrethrin-based products that stand out in the market for their reliability and effectiveness in pest management:

1. Monterey Take Down Garden Spray (6/CS)

Monterey Take Down Garden Spray is a liquid concentrate containing pyrethrin paired with canola oil.

• Target Pests: Aphids, beetles, caterpillars, and other common garden pests.
• Safety: Safe for edible crops, allowing you to apply it up to the day of harvest.
• Eco-Friendly: Biodegradable, ensuring minimal environmental impact.
• Application: Can be used during both dormant and growing seasons.

2. Bonide 8oz Liquid Pyrethrin Concentrate

Another great way to control pests in the garden is Bonide 8oz Liquid Pyrethrin Concentrate.

• Target Pests: Aphids, leafhoppers, cabbage loopers, flea beetles, and more.
• Harvest Safety: Can be used up to the day of harvest without leaving harmful residues.
• Quick Action: Kills pests quickly upon contact.
• Ideal For: Vegetables, fruits, and ornamentals, providing a versatile solution for gardeners.

3. BASF Pyrethrum TR 2oz (12/Cs)

In a commercial or greenhouse setting, the BASF Pyrethrum TR 2oz total release fogger is an effective resource for pest management. This fogger contains pyrethrins and piperonyl butoxide, a compound that increases the insecticidal activity of this toxin.

• Target Pests: Aphids, gnats, mites, whiteflies, and other greenhouse pests.
• Coverage: Treats up to 3,000 square feet per can.
• Application: Ideal for greenhouses, nurseries, and garden centers. No mixing or cleanup is required.
• Effectiveness: Quick and thorough coverage for large spaces.

How to Use Pyrethrin Safely for Organic Pest Control

Safe use of pyrethrin in the garden is needed to keep it effective and yet minimize its impact on the environment, including beneficial insects and humans. Some do’s and don't for the safe and responsible use of pyrethrin in organic pest control are given below:

1. Choose the Right Product

• Pyrethrin is available, but make sure to look for it under labels such as "organic" or "natural." These products usually have chrysanthemum-derived pyrethrin, which is safe for organic farming environments.
• At Growcycle, pyrethrin is available in different forms as sprays, concentrates and dust. In garden applications, organic pyrethrin sprays and concentrates are the most common for use, and should be applied as a spray that has low exposure to non-target plants and wildlife.

2. Read and Follow Label Instructions

• Abide by the manufacturer-specific dosing and suggested application regions. Yet overusing can be damaging to the garden, increase toxicity risks and waste the product. 
• Most pyrethrin products need to be reapplied after a few days, especially if it has rained or the area has been watered. Following the recommended frequency ensures these treatments are as effective as possible and have minimal adverse effects on the environment.

3. Apply at the Right Time

• Only apply pyrethrin when beneficial insects (bees, ladybugs) are inactive. The first thing is that you should normally do it early in the morning or late evening because most, but not all pollinators are resting during that time.
• Always use pyrethrin on mild, calm days to avoid it drifting and killing other beneficial insects instead of the pests the user wants to target.
• Pyrethrin is most effective in cool temperatures (60-85°F), or between 15 and 29◦C. Do not apply in very hot weather as it may evaporate too quickly and also reduce its effectiveness.

4. Use Targeted Application

• Rather than spraying the entire garden, use pyrethrin as a spot treatment for areas with visible pest infestations. This focused approach reduces the risk of harming beneficial insects and reduces the overall environmental impact.
• Apply pyrethrin directly to the pests you want to control. Use a handheld sprayer or a fine nozzle to target the affected areas, such as the undersides of leaves or the stems where pests typically reside.

5. Wear Protective Gear

• Biopesticides such as pyrethrin have low human toxicity, but the skin should not come into contact with them unless wearing gloves and a long-sleeved shirt; the user should also cover the eyes to apply the pesticides. You should also wear a mask to protect their lungs if they are using concentrated varieties.
• Wash hands and any exposed skin with soap and water after pyrethrin application. This is to ensure that users do not have any pesticide residue.

6. Monitor Weather Conditions

• Use pyrethrin only if rain is not in the forecast, as rain can cause the pesticide to rinse off before it has time to work. Do not irrigate until the plants are dry.
• Because pyrethrin is destroyed quickly by sunlight, it must be applied early in the morning or after dark for it to hold up long enough to kill pests.

7. Avoid Overuse

While Pyrethrin will kill a wide array of pests, excessive use invites trouble for the rest of the garden ecosystem (e.g., its non-target insects) and runs the risk of losing effectiveness over time. Save pyrethrin for if you have tried other, less toxic options without success.

Targeted Pests and Pyrethrin Role

Pyrethrin is a broad-spectrum insecticide that works on most common garden pests.

1. Aphids

Aphids are small sap-sucking insects that, when feeding on plant fluids, can cause serious damage. They are also vectors of plant viruses, which cause stunted growth, curled leaves and poor flowering.

• Pyrethrin's Role: Pyrethrin is a contact killer and will provide some residual protection so that any aphids not sprayed directly with the poison will die if they start feeding on that plant.

2. Caterpillars

Caterpillars are notorious for eating just about all the foliage and fruits of plants causing extensive yield loss in various crops, most notably cabbage, tomatoes and pepper crops.

• Pyrethrin's Role: Pyrethrin will act fast to paralyze the caterpillars and stop them from feeding within minutes, preventing further damage.

3. Whiteflies

Whiteflies are minute bugs that feed on the sap of plants and fly. They weaken plants by feeding on their sap, causing leaves to yellow and distort. The honeydew they leave behind promotes mold growth, which can lead to more serious plant diseases.

• Pyrethrin's Role: Pyrethrin interrupts the whitefly feeding process and immediately kills them upon contact, stopping additional damage.

4. Leafhoppers

These pests are known for the plant diseases they spread, such as phytoplasmas which cause leaves to wilt and turn yellow. They also harm plants by depriving them of essential sap.

• Pyrethrin's Role: Pyrethrin eliminates the leafhopper presence from the garden, reducing plant disease transmission and decreasing harm to the vegetation.

5. Beetles

These beetles feed on leaves and stems as they consume leaf tissue and can eventually defoliate and stress plants. They do the most damage to vegetables and ornamental plants.

• Pyrethrin's Role: Pyrethrin is a contact killer, and when sprayed on beetles, it will kill them as they appear.

6. Mealybugs

Mealybugs are sap-feeding insects that secrete a grey-white powdery wax layer forming a sort of white and fluffy cocoon. It leads to the yellowing of leaves, wilting, and contributes to the growth of sooty mold.

• Pyrethrin's Role: Pyrethrin affects the mealybugs because it interferes with their feeding, so they become out of control to be able to eat and they will eventually die.

7. Fleas and Ticks

Even though fleas and ticks are vertebrate pests, they can affect many ornamental plants because they carry diseases.

• Pyrethrin's Role: Promotes a safe, natural means of controlling fleas and ticks on pets or in gardens so they do not spread to plants or to people.

Pyrethrin Effectiveness in Different Conditions

The efficacy of pyrethrin can be affected by many things in the environment. Learn how these factors affect the action of pyrethrin to ensure the best results.

Temperature

Pyrethrin works best when applied at temperatures from 60°F and 85°F (15°C to 29°C). At these temperatures, pyrethrin can break down fast and work effectively on bugs.

• Pyrethrin may break down too quickly when applied in high heat (above 90°F or 32°C) because evaporation is rapid.
• Pyrethrin may be another option, but it will take longer to break down in cooler temperatures and its absorption efficiency toward pests could lessen.

Humidity

Pyrethrin works best when applied in moderate humidity (40-60% relative humidity). The product has a longer life on the plant, which means more time to work on pests before it breaks down.

• Too high humidity can cause pyrethrin not to work well.
• Pyrethrin breaks down quicker in high humidity but will last longer in low humidity, thus being effective for a longer period.

Sunlight

Pyrethrin is very susceptible to UV light. Pyrethrin has low persistence since it is easily degraded by direct sunlight. So, pyrethrin is best applied very early in the morning or late in the evening, with low sunlight present.

Rain

Pyrethrin's water solubility means that it is quickly diluted by rain, washing it off the surface and reducing its efficacy. To prevent this, apply the pyrethrin on dry days providing enough time for it to be absorbed and start working on pests before the rain hits.

Summary

Pyrethrin insecticides are a natural method of pest control for gardens. This natural repellent pyrethrin is extracted from chrysanthemums grown in various areas around the globe. It has been used safely for centuries to ward off insects that feed on crops such as aphids, beetles or caterpillars. Pyrethrin is just as useful when applied to ornamental plants or those grown for food, largely because it keeps gardens healthy and free from pests.

Growcycle is providing some pyrethrin products that are great for organic gardening and pest control. By making these products available, gardeners can choose just the right solution to keep their plants safe in an environmentally friendly way.

Disclaimer: This material is for informational purposes only and should not be relied on for legal, medical, financial, or any other form of professional advice.