The most effective method to control houseplant pests

I think it's safe to say that most of us cringe at having pests, like globulous aphids or cottony mealybugs, sapping the life from our once healthy houseplants. If we're lucky enough to catch the outbreak early, we may try to crush them between our fingertips—(gross to some but sadistically satisfying to others). Or we may attempt to buy a natural plant-based spray, like neem oil, to try and ward them off. This can be somewhat effective, however, it's hard to manage an outbreak if its gone unnoticed for too long, and sadly, many of us just end up tossing out the whole plant. 

Fighting insects with insects (or arthropods, in the case of mites) is by far one of the MOST effective strategies I've come across in the home. I'd venture to say that most of us don't like the sound of releasing MORE insects indoors. "What if they jump in my bed?" one friend asked with a grimace on his face. "I released over 50,000 natural predators in my home two days ago and do you see or feel any bugs on your skin?" I asked with a sly grin tugging the corners of my mouth. He thought I was kidding. I wasn't. 

I don't know where most of us have developed our innate (or learned) disgust for insects. (Butterflies seem to be the only ones that are given a free pass in most peoples' books). Unfortunately, however, because of our dislike for our fellow six-legged (or eight-legged) creatures, we measurably reduce our methods to effectively control and/or eliminate buggy pests on plants in our home. 

[B]ecause of our dislike for our fellow six-legged (or eight-legged) creatures, we measurably reduce our methods to effectively control and/or eliminate buggy pests on plants in our home.

In my work room, I have my old bug net hanging on the wall, and a signed copy of For the Love of Insects by my late mentor Tom Eisner. They serve as reminders that there's a whole other world out there that's beneath our feet or above our heads that has been operating effectively far before our time here on the planet. It's part of the reason why I turned to arthropods when I started noticing an outbreak of thrips and mealybugs in my home. Gardeners and greenhouse keepers release beneficial insects—so why not do so in the home?

I checked in with my friend Justin, from Olivette Farm, to get a second opinion. Not surprisingly, he backed up my belief in beneficial insects in the home, so the first ones I brought in were 2,000 green lacewing (Chrysoperla carnea) larvae, aptly known as "aphid lions". I had been cultivating potatoes indoors, which were growing like gangbusters, but also effectively attracted aphids, whiteflies and mealybugs. Lacewings, particularly their larvae, are known to be voracious predators. Plus they are generalists. They'll feed on aphids, thrips, spider mites, mealybugs, immature whiteflies, and pretty much any other plant-sucking, soft-bodied insects, so they were a good first choice.

As soon as I got my shipment in, I released the larvae onto the potatoes and surrounding plants, and they almost immediately went to work. For those who've never watched an insect attack their prey, it's quite mesmerizing. And if you have a macro lens and a steady hand–or better yet—a tripod, then you can actually capture some of that action close-up. 

Typically, if you're releasing insects indoors, you'll often want to do it in two stages. In the case of green lacewings, they are in their larval stage for 2-3 weeks, and will then emerge as adults. Since the larval stage is the most active, consuming around 400-600 pestiferous insects during its entire stage, you'll likely want to release more larvae two weeks later so that you're certain another pest outbreak is not around the corner. If you have adult lacewings flying around your house, they'll often flock to the windows, mate, and lay more lacewing eggs on a plant if they were able to get adequate pollen and nectar in their diet, which is primarily what adults eat. If it's the summer months, you can also let them outdoors because green lacewings are native to the United States. 

I'll be writing more specifically about individual beneficial insect release in the coming weeks, but I want to quickly go over a guide to some beneficial insects that you may like consider releasing indoors.

Your guide to beneficial insects

Every beneficial insect's behavior and release tactics will vary, which I'll go into more in-depth in subsequent posts, but in the meantime, let's get acquainted with some of the coolest (and friendliest) pest-eating insects around.

Green lacewing (Chrysoperla carnea) eggs are often laid on top of delicate, sticky stalks on the underside of leaves to prevent any predatory insects, like ants, from eating or dislodging them. If you order eggs from an insectary online, they will come without stalks.

Green lacewing (Chrysoperla carnea) eggs are often laid on top of delicate, sticky stalks on the underside of leaves to prevent any predatory insects, like ants, from eating or dislodging them. If you order eggs from an insectary online, they will come without stalks.

A close-up on green lacewing (Chrysoperla carnea) larvae. Photo by: Katja Schulz

A close-up on green lacewing (Chrysoperla carnea) larvae. Photo by: Katja Schulz

Also know as "aphid lions" or often described as "little alligators", lacewing larvae are a formidable predator to aphids. 

Also know as "aphid lions" or often described as "little alligators", lacewing larvae are a formidable predator to aphids. 

The green lacewing (Chrysoperla carnea) adult is both delicate and beautiful. Adults typically will feed on nectar and pollen, but will also feast on adult aphids, though are not as voracious as their larvae. 

The green lacewing (Chrysoperla carnea) adult is both delicate and beautiful. Adults typically will feed on nectar and pollen, but will also feast on adult aphids, though are not as voracious as their larvae. 

Green lacewing (Chrysoperla carnea)
Like most larvae, lacewings don't develop wings until they're adults, so they pretty much stay put where you place them, with each individual voraciously consuming around 200 insects/week. I generally put about 10 lacewing larvae per plant, because as you'll soon see, they are fairly active and mobile.

Some folks may get skeeved out when the larvae become adults within 2-3 weeks time, but I think the adults are some of the most beautiful insects out there. The have delicate, see-through wings that are reminiscent to lace, but are unfortunately not strong fliers so you may notice them clumsily skipping across the air.

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ladybug-larvae-adult.jpg

Ladbird beetles (Coccinellidae)
Both the larvae and the adults of the ladybird beetle or ladybug are effective at controlling garden pests. Like green lacewings, ladybug larvae are generalists, and will eat soft-bodied insects like aphids, scales, mealybugs, mites and more. Larvae will quickly consume 50 to 60 aphids per day and a ladybug over its lifetime can consume around 5,000 pesky insects, making them some of the most effective predators. You can often buy the adults at your garden center, but most folks don't like releasing the adults indoors because they have a tendency to flock towards the window light and can leave yellow stains on white curtains and odorous trails if scared or disturbed. 

I personally haven't released ladybugs in my home, but a good practice for release is to lightly mist your plant with water and release the adults on an infected plant during the evening hours. If the ladybugs flock to the window, you can take a small business card and gently shoo them onto the card and place them again next to the infected areas. 

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Mealybug destroyer (Cryptolaemus montrouzieri)
Like its name would imply, the Mealybug destroyer, also known as a "Crypt", is one of the most effective predators against mealybugs (Pseudococcidae), a soft-bodied, cottony-like scale. Mealybug destroyers are beetles, like Ladybugs, and are in fact, in the same family Coccinellidae. They aren't native to the United States, but they were brought here from Australia as far back as the 1890s to control citrus mealybug (Planococcus citri) in California.  They look similar to ladybugs, except that the adult Crypts have a black body and orange head. They are sold as adults in beneficial insect control. I'm guessing it's either because they're more resilient when shipping, or perhaps because mealybug destroyer larvae look almost exactly like the mealybugs they prey on, (which is the ultimate form of mimicry), but can be confusing to those who apply the insects on houseplants.

I noticed that mealybug destroyers, like their ladybug cousins, will flock to the windows every morning, so I'll often just spend 20 minutes in the morning, corralling them on little business cards and placing them near a mealybug. Once they are in the immediate vicinity of their prey, they will eat and eat and eat and rarely stop.   

Minute pirate bugs (Orius insidiosus) have become one of my favorite pest controllers. They are quite tiny, so it's easy to confuse them with a fruit fly, if you see them from afar. 

Minute pirate bugs (Orius insidiosus) have become one of my favorite pest controllers. They are quite tiny, so it's easy to confuse them with a fruit fly, if you see them from afar. 

Minute pirate bug (Orius insidiosus
The #1 plant pest that I had in my house for some time was one of the most uncommon—thrips, which are incredibly tiny and thin slithery-looking creatures that slowly suck plant juices until they [your plants] begin to exhibit a mottled silvery appearance. I was seeking a formidable opponent to combat thrips and I came across Orius spp.the minute pirate bug. They immediately reminded me of the Assassin bugs (Reduviidae) that I raised as a kid (and wrote extensively about in my college application), which likely had led me to study entomology. Not surprisingly, their morphology is the same, and I came to find out that they're in the same Infraorder of Cimicomorpha, which is characterized by beak-like protuberances that are used to feed an animals. (Bed bugs, as you may have guessed, are also in the same Infraorder). 

I have read some reports of minute pirate bugs "biting" humans, but it's probably because they're simply exploring. If their food source is plentiful, then they'll stick to the plant you essentially put them on, and will fly to the next plant that has a food source. I do wonder if Orius is slightly territorial only because I noticed that there would always only be one adult insect per plant, even though I'd originally put on 3 or 4. I didn't find anything in the literature about this, but it's just something observed. I released minute pirate bugs in conjunction with Amblydromalus limonicus, which I'll introduce below. 

Though essentially naked to the human eye, Amblydromalus limonicus and related mites can be highly effective predators to thrips.  

Though essentially naked to the human eye, Amblydromalus limonicus and related mites can be highly effective predators to thrips.  

Predatory mites (Amblydromalus limonicus, Neoseiulus cucumeris, Amblyseius swirskii and others)
Oftentimes you may want to do multiple strategies to nip an infestation in the bud, so to speak, and that's exactly what I did for the thrips that were on my plants. I purchased both minute pirate bugs together with a thrips predator called Neoseiulus cucumeris, which is a microscopic mite. There are various other mites, such as Amblydromalus limonicus and Amblyseius swirskii, which are also intensely effective, and you just have to choose one. The mites, which usually are housed in a husk mixture, are spread across the plants, and will begin feeding on both the egg and larval stage of thrips. 


Beneficial insects are definitely not "cheap"—particularly if you're comparing what you'd spend on say—a home remedy or an insecticidal spray—but they are highly, highly effective. Since I have so many plants in my home—and in close proximity to one another—I'd rather not risk anything and invest in what works. I've had plants, like my African blue basil, bounce back from a bad thrip infestation, which I was so pleased to see, especially since it's a hard plant to come by in local garden centers. Plus, I've actually had such great fun and learnings by doing some beneficial insect releases in the home, which I can now pass on to you. And this may sound a little corny, but I love thinking of them as an extension of my little army of "pets"—working to keep my plants healthy while I'm out to work and even sleeping.

If you have any further questions about beneficial insect release in the home, feel free to ask here or on Instagram @homesteadbrooklyn