Organic Pesticides


Organics are no longer a compromise. I feel I can finally put those words into print after a decade in the organic green industry. When I entered the field, I realized there was a gap between science and the organic products available at the time. Organics were essentially a choice between the better of bad options to fight major pests, weeds, and disease. In some cases, inflated promises that resulted in under-delivery could mean the loss of clients or plants. It was common to hear “organics don’t work,” and rightfully so.

But that has changed. Now, it’s possible in some cases to deliver organic lawns that are close to the aesthetic delivered by synthetic or traditional products—but with lower environmental impacts and more reasonable (sometimes even lower overall) costs.

(Photo: Getty Images)


No organics have come further along in the last few years than organic weed and pest control. When I started in the industry, I had to tell people there were three holy grails of organics: selective weed control; pre-emergent weed control; and grub control. Now pre-emergent weed control remains the only organic holy grail, and even in that area steady progress is being made.

From experience, observation, anecdotal feedback, as well as some university studies; selective and non-selective organic weed killers are getting much closer, in terms of efficacy, to their synthetic counterparts such as 2,4-D and glyphosate, respectively. These have advanced recently. Currently, granular gluten and oils (such as soy or gluten) are the best of mediocre options available for pre-emergent weed killers. There is improved efficacy with these approaches—but more from refining application timing and rates based on soil temperatures, not calendar timing. There have not been improvements in technology with these products, such as is the case with other types of weed killer.

Many applicators have been highly successful using hybrid programs, which rely on synthetic pre-emergent weed killers in just the first season, to break the weed cycle. After that, improved soil and health (such as deeper roots and thicker turf) can out-compete many weeds. We often tell our full-program users “don‘t let the perfect be the enemy of the good.” Most organic clients are lost in the first year based solely on crabgrass outbreaks. Using a synthetic one-time application is a better option than going back to a 100% synthetic program.

Selective Weed Control

The best organic weed control starts with healthy soil practices to promote thicker turf with deeper roots that is in better shape to compete with weeds. Also extremely important, and often overlooked, are simple cultural practices that greatly reduce weed pressure. The two most important are higher mowing (3″ high or taller) and infrequent, deep irrigation. When break-through occurs despite these changes, or when taking on a new property with many weeds, then more direct weed control intervention may be necessary.

Not very efficacious even just a few years ago, selective weed-killing options without glyphosate are now fast acting and almost as effective as their synthetic counterparts. With recent lawsuits, the demand for other weed control options has grown exponentially—not just by homeowners, but by distributors, applicators, and insurance companies. Prices of organics continue to lower and have become more competitive. These products contain ingredients such as fatty acids (soaps), d-limonene (organic solvents naturally extracted from citrus), or other organic material and are often OMRI-listed.

The same improvements in product efficacy are also now true with selective weed control agents. In the past, there were no non-synthetic options available that were comparable to 2,4-D based synthetics in terms of efficacy. But today, advances are being seen with iron-based products. These products contain a chelated form of iron, which makes them more water soluble and stable and allows for better uptake by weeds. Without chelation, these products would have only a fraction of the efficacy, but they are not certified organic due to the chelating agent, EDTA. (Chelating agents are metal binding agents, which aggregates the iron. Unbound iron doesn’t truly control weeds.)

However, EDTA is deemed safe enough by the FDA to use in many foods, cosmetics, and supplements found in your refrigerator or medicine cabinet. It’s even approved for use in human medicine. The efficacy improvements with chelated iron products, as well as recent price reductions, have made these products a practical spot-treatment option for lawns transitioning to greener practices.

Grub Control

Grub control is the most exciting area of advancement in organics with the arrival of products containing the novel and unique microbe Bacillus thuringiensis galleria (Btg). Traditional organic solutions such as Milky Spore or beneficial nematodes have drawbacks under even best-case scenarios. Namely, 1.) a lack of broad-spectrum control for the species of white grubs (European Chafer and Asiatic Beetle) that in many areas of the northeastern U.S. are now more prevalent than Japanese Beetle grubs and 2.) the need to get products down at the early, first instar stage of grub growth in August—long before any visible damage can be seen. In other words, use only preventatively.

Btg-containing products, though, are now changing the game. Btg has been tested in head-to-head university studies with products containing active ingredients such as imidacloprid, thiamethoxam, and clothianidin (neonicotinoids); trichlorfon (an organophospate); and chlorantraniliprole. In all cases, the Btg has performed at least the same in terms of total grub control—and sometimes better—than these agents. These studies come from well-respected research universities such as UMASS, Cornell, NC State, Ohio State University, and The University of Nebraska.

Btg also has no effect or toxicity when tested on beneficial insects such as bees, beneficial nematodes, and parasitic wasps—many of which also prey on grubs. In fact, the activity of Btg is so specific for white grubs that it doesn’t affect beneficial lady beetle species that also prey on aphids and other pests. Thus, the benefits are two fold: Btg attacks grubs—but also keeps predatory systems intact.

Another advantage of Btg products is flexibility. Btg can be applied as both a preventative and a curative; whereas most chemistries need to be applied preventatively. (Trichlorfon is curative, but not an ideal preventative due to its short half-life.) Since only about 20% of lawns will actually have an infestation in the threshold requiring treatment, a curative/preventative product allows for assessment and elimination of unnecessary treatments on the other 80%.

When do you treat for grubs with Btg products? As a preventive, treatments can start in late July through mid-August when new beetle eggs hatch and begin to eat turf roots. For curative treatment, October is when grub damage will become apparent with dead or yellow spots that can be easily pulled out by hand. Keep in mind that while Btg products will stop further damage, it will not reverse existing damage from earlier in the season. Re-seeding may be necessary.

In addition to fall grub damage, secondary damage from animals and birds can be significant. These insectivores dig and tunnel through lawns to eat grubs. Although such damage can indicate an infestation, it’s not a definite sign treatment is necessary. Many animals also eat worms or other larvae present in healthy organic lawns. Therefore, grub scouting is the best assessment. Pull up the turf by cutting 1’ slices with a knife or hand shovel and pulling up or rolling back the turf. Five or more grubs in this one square foot area means treatment should be considered. Anything less than five grubs per square foot will generally not necessitate a treatment as healthy turf roots can sustain and survive this normal level of grub presence.

Smart Approaches

It’s a good time to be a turf professional looking into organics. The products now available are way ahead of where they were even just a few years ago. It’s possible to have a lawn that looks almost as good as a synthetic treated one. You can maintain cost effective organic lawns that are thick, green and healthy with a long-term approach including soil testing, cultural practices, and biological supplementations.

Keep in mind that even organics shouldn’t be used unless necessary. Some organics can be just as harmful to the environment as synthetics, so a judicious approach is always best. A smart organic approach doesn’t mean simply substituting an organic product for a synthetic. It’s a whole-system approach that minimizes inputs—even organic inputs—through building healthy soil in a strategic and targeted manner.

Organic PesticidesMagazzi, MS, is the President and Co-founder of Green Earth Ag & Turf®, a company that provides eco-friendly products and consulting services to land care professionals. He has been involved in the research and development of microbial-based products for use in turf care for many years. Magazzi has a Master’s degree in genetics (with a microbiology focus) from the University of Connecticut-Storrs. His research has been published in scientific journals such as The New England Journal of Medicine.

A previous version of this article initially appeared in the Ecological Landscape Alliance (ELA) Newsletter. Founded in 1992 and with over 1,200 members today, the ELA promotes sustainable approaches to landscape design, construction, and management. For more information, visit

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  1. The big weed killer has been under attack for a while now.I only use it in my gravel driveway.It works great but as you know it is also a big health problem.I am glad companies are trying to fix these application problems from the users.Being certified stops alot of wrong uses and application of products.

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