Sometimes it’s the tiniest garden pests that cause the biggest problems. As responsible gardeners, we want to manage these pest issues while having as little negative impact as possible on the good bugs that visit the land that we steward. To share expert advice on responsible, effective pest control, my returning guest this week is Suzanne Wainwright-Evans of Buglady Consulting.
Suzanne holds degrees in entomology and environmental horticulture from the University of Florida and works with greenhouses, nurseries and gardens across the United States and internationally. She is a horticultural and entomological consultant to commercial growers that are raising everything from poinsettias to lettuce to medical cannabis. She also works with botanical gardens and theme parks that are struggling with insect, mite or snail problems. She now has three decades of experience focused on biological control and using pesticides properly.
Suzanne’s approach is to use good bugs to manage bad bugs, and she says many commercial growers are adopting the practice too. She also knows that more and more homeowners want natural ways to control pests — ways that are safe for their family and pets as well as the environment. She supports the Protect Our Pollinators movement but points out that it’s not just the bees that need our support. “I love flies, and flies are huge pollinators even though nobody gives them the ‘attaboy!’” she says.
If you want even more information on combating pests, you can download my new free resource, 10 Common & Destructive Garden Pests: Prevention & Control. This guide is a great reference to have on hand for managing pests effectively and efficiently with the least impact on pollinators and other beneficial insects.
How the Buglady Helps Clients
When a grower, garden or park calls Suzanne, it’s having a pest problem. The client may not be seeing results with the control methods it’s tried, or it may be restricted from using traditional, chemical pesticides.
Suzanne’s first step is to identify what the problem is. Once she knows what the problem is, she can suggest changes to cultural practices, how they grow, and the workflow.
If those changes don’t tamp down the problem, the next step is to introduce “good bugs that eat bad bugs. Those good bugs can be purchased to be released where their services are needed. “Just like there are chicken and cow farms, there are actual insectary farms here in the United States, in Europe and Canada,” Suzanne says.
In controlled environments, the insectary farms rear beneficial insects that are already present in the local environment, so invasiveness issues do not become a concern.
“Unfortunately, we don’t have good bugs that control every pest, so sometimes we do have to come in with a pesticide spray,” Suzanne says.
She finds a pesticide spray that is targeted — rather than broad-spectrum — with minimal impact on native beneficial insects. Her ultimate goal is to leave the planet a better place than when she got here through reduction in pesticide use.
Controlling Spider Mites
Suzanne wanted to study and photograph spider mites, so she experimented with how to encourage the pest to proliferate on her houseplants. She found that Calatheas and mini roses under grow lights with lots of fertilizer did the trick. Those plants and conditions resulted in crispy webbing — the sign of an advanced spider mite infestation.
“Spider mites” is the name of a whole family of mites. The two-spotted spider mite is the one we hear about most often, but there are others that are cause for concern.
All it takes is one female for a spider mite infestation to begin. The female does not require a male to have babies, Suzanne says, so bringing one plant into the house with one mite will do it. A spider mite can also ride in on the wind from the landscape, she adds.
Spider mite eggs are tiny and perfectly round and they look like tennis balls. The lone female will lay only male eggs to start. Once those hatch, the lone female can breed with her offspring, and it’s off to the races, Suzanne says.
Spider mites sit on the leaf surface and puncture plant cells to feed on the chlorophyll. Their diet is why spider mites appear greenish under a microscope. Their damage creates white splotches on leaves.
Systemic pesticides don’t work on spider mites because systemics are concentrated in vascular tissues, and that’s not what the mites are feeding on, Suzanne says. What’s needed to control spider mites is a spray-on contact pesticide.
Today, commercial growers and home growers are moving toward using predatory mites to control spider mites. The most common predatory mite is called Phytoseiulus persimilis, a tropical species that is aggressive, bright red, and virtually blind. It uses its front legs to detect chemical cues from two-spotted spider mites and then eats the eggs, immatures and adults by sucking their fluids out.
Phytoseiulus persimilis are farmed in California and some growers use them by the billions to manage spider mites. When applied to a growing environment, they will breed if there is enough food to go around, Suzanne says, but generally what happens is they eat up all the two-spotted spider mites and then starve to death. They also freeze to death over the winter.
A predatory mite native to the Pacific Northwest is Neoseiulus fallacis. If applied to a garden, Neoseiulus fallacis will overwinter and still be there the following spring.
Suzanne adds that a knockdown spray of water is a good place to start when your plants have a big population of spider mites. Horticultural oil is the best at killing the adults as well as the eggs, she adds. Never spray in the middle of the day, and spray only a fine mist — don’t drench plants. A pump-sprayer with an angled wand is what the job calls for. Suzanne recommends Monterey horticultural oil, specifically.
Aphids are becoming more of an issue for commercial growers because retailers are less tolerant of systemic pesticides, according to Suzanne.
Aphids are like mites in that the females do not require males to reproduce. Almost every aphid a gardener sees will be a female. Instead of laying eggs, the females give birth to clones of themselves. Spraying a pesticide will knock down the population, but the few surviving aphids with an innate resistance to the pesticide will now give birth to clones with that same resistance.
“Resistance can develop really quickly in populations of insects that don’t mate, because when you mate, you get genetic diversity,” Suzanne says. “When you don’t mate, you’re basically getting clones.”
The emerging cannabis trade has regulation over plant movement but no regulation over pest movement, so the industry is contributing to spreading aphid species around, Suzanne says.
Fortunately, there are tons of beneficial insects that eat aphids. Ladybugs — also called “lady beetles” because they are not true bugs — are what most gardeners think of when they think of insects that prey on aphids, but Suzanne says there are many other beneficial insects that target aphids more efficiently.
Commercial growing operations use parasitoid wasps rather than ladybugs. These wasps lay their eggs inside aphids, and the eggs hatch then eat the aphids from the inside out. The parasitoids are specialists, so Suzanne will identify the specific aphid species that’s causing a problem in order to match with the correct wasp species.
Suzanne notes that home growers do not need to buy parasitoid wasps because the wasps will arrive on their own as long as gardeners are not using sprays that repel them, such as pyrethroids. The wasps do not sting, so gardeners do not have to worry about that.
Suzanne attracts beneficial parasitoid wasps by planting Alyssum. The adult wasps are attracted to the pollen and nectar of the flowers. Alyssum also attracts Orius, the minute pirate bug, which feeds on aphids, thrips and spider mites as well as pollen.
Green lacewings are another predatory insect for controlling aphids as well as spider mites and whiteflies. The adults are nocturnal and a beautiful green with copper eyes, Suzanne says. It’s the insect that she recommends people buy instead of ladybugs, which are wild-harvested rather than farmed sustainably.
Commercially produced lacewings are free of the diseases and parasites that wild-harvested ladybugs will introduce to your garden. The lacewings are delivered as eggs on cards that can be ripped into strips and hung on plants.
Insecticidal soap does a good job of controlling aphids when beneficial insects don’t. It desiccates the aphids, killing them. However, Suzanne says to inspect the garden with magnification for eggs of beneficial insects before applying insecticidal soap. If you see what looks like little grains of rice among aphids, those are syrphid fly eggs that will hatch in a few days and completely control the aphid problem.
Soaps and oils are non-selective, Suzanne notes, and they don’t know the difference between an aphid and a ladybug larva. The upside, though, is that they are not persistent, will not accumulate, and will not contaminate groundwater.
Controlling Squash Vine Borers
The squash vine borer is a moth that attacks zucchini and other squash. The moth lays its eggs on stems, and those eggs hatch into white larvae that bore into the stem and work their way through the inside of the plants, hollowing them out and killing them.
Suzanne says most people don’t know that there are pheromone traps that work on squash vine borers. The traps attract the male moths, which is important because the last thing a gardener wants is to attract egg-laying females to the garden.
If you find eggs on the stems you can remove them or apply insecticidal soap. But how do you know to check for eggs? That’s where the traps come in. Check the traps for adults, and when you see the adult males, you’ll know the egg-laying females are nearby.
Commercial growers use traps but also track “growing degree days” to know when to expect certain pests. Suzanne explains that growing degree days are about the accumulation of heat. Due to climate change, old calendars of when pests are expected are not always accurate.
Another way is to track what’s blooming. Do Japanese beetles show up when a certain plant blooms? Track the plant’s blooms next year, and you’ll know when Japanese beetles are arriving.
For squash vine borers, another method of control is beneficial nematodes. The nematodes can be injected into stems where borers made their holes, and those nematodes will go after the larvae.
Because squash vine borer larvae are caterpillars, they are susceptible to Bacillus thuringiensis, a biological control that’s often just called Bt. Suzanne says that Bt resistance is arising, particularly in corn pests because Bt has been genetically engineered into commercially grown corn.
Home gardeners can buy Bacillus thuringiensis kurstaki, also known as Btk, for controlling caterpillars. Commercial growers have that option as well as access to Bacillus thuringiensis aizawai.
Another bioinsecticide is Spear-T, a synthesized spider, sea urchin and scorpion venom that can be mixed with Btk to overcome Btk-resistance.
Controlling Japanese Beetles
For Japanese beetle control, there is another Bt. This one is Bacillus thuringiensis galleriae, or Btg. BeetleJUS!® is a Btg product that is reportedly effective against both the adult and grub forms of Japanese, Asiatic, June and Oriental beetles. Then there is grubHALT!® for lawn grub control, found to be effective against Japanese beetles, European chafers, green June beetles, Northern masked chafers, Southern masked beetles and Oriental beetles.
Suzanne says Btg is slow acting but it’s good because it will not harm pollinators.
Japanese beetles do not survive extreme drought or flooding, and they are not found in the South where it’s warmer, Suzanne points out.
Controlling Snails & Slugs
Did you know fireflies eat snails and slugs? Fireflies, also known as lightning bugs, are a type of beetle. When lawns are chemically treated with grub killers, beneficial lightning bug larvae are killed as well, and that means slugs and snails will have fewer natural predators.
Toads are another predator of slugs and snails, so refrain from using pesticides or fertilizers that harm amphibians.
Iron phosphate is a snail and slug bait that is a safe, organic option. It is free of metaldehyde, which is toxic to pets and wildlife. Sluggo is one of the popular brand names.
Beer traps also work, though Suzanne says no one really really wants to deal with a pool of slugs and hot beer. Another option is to go out at night, find slugs and other nocturnal pests, and pick them off.
For brown garden slugs, there is a beneficial nematode that is readily available in the United Kingdom. The company that produces the nematode is seeking permits to make it commercially available in the United States, but this is a challenge because the nematode is only naturally found in a few places here. Introducing a nematode that proves to be invasive could have a detrimental consequence to native ecology, so regulators need to be careful and thorough before approving anything.
Controlling Flea Beetles
Flea beetles do damage to plants both in the larval stage and the adult stage. In the past, growers would use systemic pesticides like neonicotinoids. The adult beetles would eat leaves of treated plants and then die. Now, since those systemic compounds are prohibited in many places, growers must use other methods, such as contact spray products that unfortunately kill everything they come in contact with.
Flea beetles may be in the soil already waiting for something to be planted, or they can fly in. They can be knocked back with insecticidal soaps, but you need to stay on top of it.
The red-headed flea beetle is an emerging pest problem that is marching its way up the Eastern Seaboard and affecting ornamentals, and there are many more species, each with its own preferred targets. On eggplants, for instance, you’ll see very tiny black flea beetles.
Natural pyrethrin pesticides can be used on flea beetles, but Suzanne says she doesn’t use pyrethrins herself because she doesn’t want to kill beneficial insects.
The Future of Biological Controls
Suzanne says an Israeli company named BioBee is introducing a new slow-release nematode product to commercial growers that has a lot of potential for home growers and seed starters. The nematodes come in a jar full of pearls that look like tapioca balls. Add a pearl to soil and the nematodes will come out and proliferate over time. They can control fungus gnats — which eat roots in the larval stage and spread damping-off disease in the adult stage — and thrips.
Suzanne is always watching for new and emerging entomopathogens, the fungal controls for insect pests. Fungus products grow on insects and kill them, and the insects show no signs of developing resistance.
Because the fungus does not kill mites, entomopathogens can be applied in concert with predatory mites. However, these products, despite being on the market for decades, are not available yet in small retail packaging for home gardeners.
I hope you enjoyed my conversation with Suzanne Wainwright-Evans on common garden pests. If you haven’t listened yet, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
What are your top garden pests? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Tomato expert Craig LeHoullier joins me in leading this course on how to grow healthier, productive tomato plants and how to overcome tomato-growing challenges.
Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, Milorganite, Soil3, Exmark, Greenhouse Megastore, High Mowing Organic Seeds, Territorial Seed Company, Wild Alaskan Seafood Box and TerraThrive. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.