Integrated Pest Management: Why IPM?

Oct 10, 2021

Gretchen Heimlich-Villalta, UCCE Master Gardener and PhD student at UC Riverside ?


What Is IPM?

If you've never heard of IPM, you're not alone. I get this question from folks ranging from new gardeners to graduate students in plant pathology. But suppose you're looking for the best way to deal with the weeds muddling around in your garden, or the aphids having a party on your Lantana. You could let loose an entire bottle of Roundup®, or cut the Lantana to the ground, and just be done with the whole thing. But if you want to deal with the problem rationally and responsibly, you're going to want to know about IPM—a.k.a. integrated pest management. Let's start with a definition. There is a lot to this definition, so I'd like to unpack it a bit.??

“Integrated pest management (IPM) is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organisms. Pest control tools are selected and applied in a manner that minimizes risks to human health, to beneficial and nontarget organisms, and to the environment.”1 Mary Louise Flint, IPM in Practice: Principles and Methods of Integrated Pest Management ?

An Ecosystem-Based Strategy It's easy to skim over the ecosystem component of IPM; after all, it's a broad concept, and perhaps a bit abstract. But it's really important, so let's try to make it as simple as possible. Every ecosystem (the forest, the ocean, your garden, even your soil) is made up of individual members that do a couple things:

1. They get their energy from/feed on something(s) else.

2. They give their energy to/are fed on by something(s) else. ?

Together, the members of an ecosystem have roles that keep that system in balance and contribute to its overall function; they also provide services to humans. In your garden, this can include oxygen production, air and water purification, water capture and cycling, food production, climate regulation...I could go on and on, but I think you get the picture. Only a small portion of an ecosystem's inhabitants are pests of plants or humans. As gardeners, we are custodians of our garden ecosystems. It's a big responsibility—and an awesome opportunity!

Long-Term Prevention through a Combination of Techniques

What does long-term pest prevention look like? Suppose your favorite avocado tree is getting a bit too much water. Your new gardener has been diligently raking up the leaves under it every week, leaving the soil tidy and quite exposed. A home soil test kit would tell you the soil pH is also a little high, and it's gotten low in nitrogen. As a result, your tree is looking stressed; the roots are craving oxygen, and root rot (Phytophthora cinnamomi) zoospores are swimming through that excess water to take advantage of your vulnerable tree. Text BoxA picture containing tree, outdoor, sky, plant Description automatically generatedAs you start to see wilting and dieback, you consider your options. The canopy looks wilted and dry, so you consider giving it more water. Maybe you recognize the symptoms of root rot, and know more water is the last thing your sad avocado needs. A short-term solution might be to fumigate the soil. That could kill the Phytophthora, but would also kill off a lot of the soil microbes, including Phytophthora's competitors, making it likely that in the long-term the root rot will return with a vengeance. You could hire a tree care company to do a trunk injection of phosphonate2. You could do this today, and this would provide some short-term control as well, but if you're not dealing with the other contributing factors, there's a good chance the root rot will return. What would a long-term solution look like? Embracing your new IPM knowhow, you look at the big picture. You look up the UC IPM Avocado Pest Management Guidelines2 and learn that Phytophthora cinnamomi thrives in overly wet conditions. You cut back your irrigation, and start sticking your fingers in the soil once a week to make sure you're getting the water right. You apply gypsum, and an acidifying nitrogen fertilizer like ammonium sulfate at the recommended rate you find on the UC IPM website3 to suppress the Phytophthora and bring down the soil pH. You read about how important mulch and leaf litter are for avocados, and tell your gardener to stop raking up the leaves. You even give your tree the gift of 4–6 inches of mulch. This will discourage Phytophthora and encourage growth of beneficial soil microbes, and will also help lower the pH and improve any salinity issues you may have. Finally, you decide to hold off on the phosphonate trunk injection until May, when the application will be most effective2. And if your tree is looking better by then, you may not inject it at all.


In agriculture, farmers who practice IPM will pay close attention to details like pest numbers, natural enemies, and weather and field conditions. The home gardener will start by inspecting their plants regularly for damage and getting to know their common pests. Identifying plant pests can be a daunting task, but it's worth the effort. It's crucial to identify what's stressing your plant before attempting to treat the problem in order to avoid affecting non-target organisms. And by recognizing pests early, it may be possible to, say, knock back aphid populations with a shot of water from a hose instead of spraying insecticide once the population has gotten out of control.

So, Why IPM?

Using a combination of treatments is usually more effective than any single treatment for controlling pests. By optimizing cultural practices and using biological and mechanical controls, we can reduce or eliminate the need for chemicals. Integrated pest management allows us to reduce the damage of plant pests, and at the same time reduce the damage of pest treatments to our garden ecosystems, humans, and the environment. As thoughtful custodians of our landscape ecosystems, we can optimize plant health—and at the same time protect non-target organisms ranging from bacteria and fungi to birds, bees, and people. And this is a beautiful thing. For specific help with IPM in your own garden and landscape, contact a UCCE San Bernardino County Master Gardener volunteer at


Author info: Gretchen Heimlich-Villalta is an ISA™ certified arborist who has been a San Bernardino County Master Gardener since 2014. She received her AS in Integrated Pest Management from Mt. San Antonio College, where she has helped teach IPM since 2020. She received BA degrees in Creative Writing and Photography, and is currently working on her Ph.D. in Plant Pathology at the University of California, Riverside, where she is researching citrus root and soil health; she also helps manage the Strub Avenue Community Garden in Whittier. Sources: 1. Flint, M. L. IPM in Practice, 2nd Edition: Principles and Methods of Integrated Pest Management. (University of California Agriculture and Natural Resources, 2012). 2. Eskalen, A. & Faber, B. A. Phytophthora Root Rot. UC IPM (2016). 3. Managing Pests in Gardens: Fruit: Cultural Tips: Fertilizing avocados—UC IPM.