How well do you know the insect world of your garden? Can you tell the good bugs from the bad bugs? Did you know there are prey and predator insects? This week’s guest, Jessica Walliser, used to be a bug hater. As a horticulturist, she was trained that bugs were the enemy, and she spent many of her professional years with pesticides ready to defend the plants of her clients’ at all costs.
Times have changed. Jessica now finds herself more enthralled by the world of the insect than by the plants of the garden. She divides her professional career between horticultural advice and educating other gardeners on the fascinating activities of beneficial bugs and their pest prey. She’s written books and has been host of a gardening radio show for 14 years (which is also made available in podcast format).
Jessica Walliser keeps busy writing, hosting her gardening radio show and watching the insects at work and war in her own garden. (photo: Jessica Walliser)
Jessica’s anti-bug mindset first began to change many years ago when she employed a USDA-certified organic gardener to help her in her landscaping business. This member of her team introduced Jessica to organic options for pest control and to the unintended consequences of pesticide use.
Little by little, Jessica began to make changes in her gardening methods, but it was a David Attenborough documentary on insects that really turned her around in 2005. She realized that there was a world of activity going on in the garden that she was missing because she wasn’t paying enough attention. She began to see the lives of bugs as a valuable part of her garden ecosystem – they were no longer the enemy, they were the stars of the show.
Today, Jessica considers herself an amateur entomologist, and her years of insect research and observation offer so many useful details that I had to convert this podcast episode into a two-part series.
Beneficial Insects – The Predator/Prey Cycle
In the bug world as in the animal world, there are predators and prey. Prey insects tend to be those we consider garden pests – like aphids, Japanese beetles, mealy bugs, and white flies. Predator insects are those we consider beneficials. The most commonly-known predator beneficial is the lady beetle a.k.a. the ladybug.
Yet, there are thousands more species of beneficials crawling, buzzing and feeding all around us. Jessica shares her picks for the top 5 beneficial insects to encourage in your garden in Part 2 of this series, so don’t miss that. We’ll cover how to identify them, how to draw them in and how to know when they are at work.
Beneficial insects fall into two categories – pollinators and predators or parasitoids. If you checked out an earlier podcast series with Suzanne Wainright-Evans, you might remember the parasitic wasp is a common North American beneficial insect. They are referred to as parasitic, but the truth is that they and all other predatory beneficial insects are actually parasitoid – not parasitic. What’s the difference?
A parasitic insect feeds on its host, but the host rarely dies as a result. Think about ticks, tapeworms, and fleas – these parasitic insects rarely cause death. A parasitoid insect feeds on its host – and the result is always death. In other words, beneficial predator insects are out there – day and night – killing your garden pests for you. As long as you don’t get in their way.
There is a predator/prey cycle at work, and when you understand this natural process, it can make you a better gardener.
Syrphid flies are a common and valuable beneficial insect in the garden. (photo: Jessica Walliser)
Jessica uses the example of field mice in the Arctic to explain the cycle. When food sources for field mice are plentiful, their populations rise. Field mice are the prey of the Arctic fox, and as there are more field mice to eat, the population of the Arctic fox rises too. This doesn’t happen simultaneously. There must first be lots of field mice in order to support the increase in Arctic fox to feed on them.
Ultimately, the field mice and Arctic fox populations will balance each other out, and consequently, both populations will begin to normalize – until another good year of food sources for field mice rolls around. Then, the cycle begins again.
The same cycles are happening in your garden. As aphid populations rise, and we start really noticing their presence and damage; predator beneficial populations – like ladybugs – will begin to rise as well to feed on the bounty of aphids.
Unfortunately when most gardeners see lots of aphids, we feel the need to take action – we spray, squish or remove. We insert ourselves into the situation just as things are about to get really interesting. Since the beneficial predators are just starting to take notice and arrive to eat the aphids, they too are killed or deterred by our pest management efforts.
If we as gardeners are willing to have a little more patience – to step back and let the cycle do it’s natural thing, we would enjoy healthier gardens. Allow those beneficial insects time to find their prey and bring them under control. Unless you are dealing with an invasive pest – like the Emerald ash borers or Asian longhorn beetle (which don’t have natural predators) – pest damage rarely kills a plant.
It would be better if we took action to encourage the natural cycle rather than take steps to eradicate the pest themselves. There are simple proactive measures to design the pests out of the garden to begin with. When we select plants for their ecological value, we can do more than just encourage beneficial pollinators – we can encourage the broader insect ecosystem. More on how to do that in Part Two of this series, so stay tuned!
Subtle Garden Signals
Have you ever wondered how the beneficial insects, like lady beetles, find the aphids in the first place? When the aphid populations boom, how do the predators know there is a feast available? It turns out, some of the plants of your garden send out an S.O.S.
Studies have found that there are complex cues which take place between plant and insect. One such study found that cabbage plants under attack by a large cabbage worm population release herbivore-induced plant volatiles (HIPVs), which is an odor specifically designed to attract the exact species of parasitic wasp most likely to lay eggs in cabbage worms. When the cabbages were under attack by a different pest, they sent out a slightly different HIPV which attracted a different parasitic wasp for that pest.
Many gardeners are unaware of how differently lady beetles appear in their various life stages. Seen here are four lady beetles in varying stages preying on a large population of aphids. (photo: Jessica Walliser)
There are other subtle cues at work to draw predator to prey – from visual indicators to chemicals released by the prey themselves.
The point is that, although we think our plants need us to intervene, they are often in the process of protecting themselves. If we set the stage correctly and let everyone and everything do what they are designed to do, there can be a natural balance. There may be a little collateral damage to your plants, but as the cycle develops and the beneficial populations begin to gain ground, there will be less damage to deal with.
Jessica notes that it’s the ornamental garden areas which are the most tolerant of and the best candidates for taking a wait-and-see pest management approach. Vegetable gardens are not a normal ecosystem. Since we tend to plant each type of vegetable in groupings or rows, we are already prohibiting some of the natural beneficial insect activity. So, our vegetable gardens may need some pest management steps, but as we better understand predator cycles, we are better able to avoid getting in their way.
When we work so hard to pamper our plants – investing time and money in their health and productivity – it can really be a challenge to wait and let nature take its own course. I know I’m not happy when I see foliage disappearing or my prize crops reduced or damaged. In fact, I try to spend time every day in my garden proactively looking for early pest warning signs.
As an organic gardener, I don’t use pesticides. My favorite method of control is hand removal. I do use other organic controls – such as BT, horticultural oils, water sprays, etc.
Yet after listening to what Jessica shares in Part Two of this series, I’m rethinking how I utilize even those organic measures. Oftentimes, the beneficial insects have already done their work, and my organic methods might be unintentionally reducing beneficial insect population at the GardenFarm™.
We all just need to remain curious and learn what to look for, then we can evolve in our own gardening journey.
If you spend a little more time observing the life in action in your garden, you may be surprised by what you find. This colorful visitor is a six-spotted green tiger beetle – a fast-moving and aggressive garden predator. (photo: Jessica Walliser)
So, don’t miss Part Two to learn some of those key signs to watch for, find out Jessica’s Top 5 favorite beneficial insects, and learn some easy – and less commonly known – steps you can take to promote the predator/prey cycle (and the beneficial populations) in your own little garden space on this planet.
You don’t need to revolutionize the methods you use in your garden. This is a process, and we are all taking it just one step at a time, one season at a time. If you take a few minutes to be still and watch for the beings that will visit the plants of your garden, you too may become fascinated by what you find.
If you haven’t already listened to my conversation with Jessica, you can scroll to the top of this page and press the Play icon in the green bar under the title. We had a fun talk, and her enthusiasm for this subject is certainly contagious. So, I hope you’ll check it out.
Links & Resources
Episode 049: When Good Bugs Eat Bad Bugs: The Business of Beneficial Insects
Episode 068: Top Predatory Beneficial Insects and How to Attract Them
GGW Episode 801 – A Year in the Life of the Garden Farm; Part I
Attracting Beneficial Bugs to Your Garden – book by Jessica Walliser
Milorganite® – Our podcast episode sponsor and Brand Partner of joegardener.com
0 Responses to “067-Predatory Beneficial Insects: Feared Foes of Garden Pests, Pt. 1”
After listening to the podcast on beneficial insects I decided to stop squishing the aphids off my flowers, instead waiting and watching. But then I looked at the pictures in the show notes and wandered out to the veggie patch. There they were, two Syrphid flies, aphid predators! I don’t spray my vegetables, I just pick and squish. Perhaps I don’t even even need to do that, just get out of their way. Thanks, Joe. Can’t wait for part two next week.
Wow! I read episode 68 as well. Joe, have you incorporated more of the natural predator techniques and less of the other organic pest management tools, as you suggested, in the last two years? IF so, how is that working for you? I am curious how quickly one would see positive results – one season, one year, two years?
Hi, Liz. I have not proactively incorporated more of the natural predators in my garden, and yet I haven’t applied any biological pest controls either. My pest control methods this year were only exclusion barriers using tulle mostly, and hand picking. Beyond that, my hope was that by avoiding any bio controls at all, predatory insects had free reign and total safety to come in and feast on whatever they could find.
All in all, it wasn’t a bad year for pests, except maybe bean beetles. But I planted a LOT of beans this year and they showed up later in the season. I was ok with that.
I didn’t notice many predatory insects but that certainly doesn’t mean they weren’t there. They are very stealthy sometimes. But the lack of bad insects in my garden I will take as a good sign that they were there.