It’s going to be another difficult year for plant pests. It’s always a bit of a guess, and largely has to do with localized weather, but generally, those pests that develop chemical resistance are stronger every year. So, whenever you’re reading this – it’s going to be a bad pest year.
But, before you head out to the garden store to buy your frozen bucket of ladybugs, consider some alternatives. If you’re unsure why you should look for an alternative, you need to read this: Never Buy LadyBugs.
In short, they are a waste of money and the trade of ladybugs has a negative impact on the environment – which is likely the exact opposite reason you wanted to buy them in the first place. Fortunately, if you have bought them in the past and not had an aphid problem then that means you can do nothing and not have an aphid problem. However, to be on the safe side, consider the following alternatives:
Alternative 1: Aphidoletes aphidimyza (Aphidoletes)
Why it’s good: This predatory midge is your top aphid control. It doesn’t matter if you’re problem is inside or outside and it doesn’t matter what species or size of aphid you have (with one or two exceptions); or what your budget is. Aphidoletes are native to the northern hemisphere; and in most climates will return again in the Spring after surviving the winter in underground cocoons.
Where can I get it?: Unless you would by ladybugs from a ladybug-specific supplier, chances are the person selling them are somewhat knowledgable of other biological pest control agents. But, don’t just ask them. They’ll talk you back into ladybugs (they have a much higher profit margin selling you those.) Demand Aphidoletes and they will find them for you. You can even ask at the garden store. And while most employees will have no idea about bio-control, You’ll likely find someone interested in bringing them in for you. If you buy online, then simply type in the name and choose the closest, trustworthy supplier.
You can find a distributor here to buy them from the top producer.
Why is it better? First, Aphidoletes are lab-reared. So they are not collected from the wild and will not transfer parasites, disease or viruses. Second, it is pest-specific. While they will eat whitefly scale, mealy-bugs and some other soft-bodied sucking insects, they are healthiest and will multiply on a diet of aphids. They also don’t occur in nature at the same density you can achieve by buying them. Therefore they quickly overwhelm aphids, and in their quick, 2-week, lifecycle, you can suddenly have 20x the original number taking out (and searching for) any other available aphids.
When the aphids are gone, Aphidoletes will leave. But by “leave”, I mean, “to your neighbours yard.” And they’ll come back again when aphids return to your yard. This is much more reliable than purchased ladybugs who will thaw, eat enough to build up energy and then migrate back to where they were collected from (Colorado, or California usually.) If you see ladybugs a few weeks after release store-bought ones, it is massively more likely that those are different bugs.
A typical outside application is to apply an amount of Aphidoletes that matches the area you want protected and only after aphids are discovered. This ensures food for them and may get that 20 x growth in a couple weeks. So one fruit tree with an aphid infestation requires only the smallest available package and your tree and then your yard will benefit without needing more.
Indoors, (or outdoors when crop protection is considered more valuable) then a small amount of Aphidoletes on a regular basis (every 2-3 weeks) allows them to search, find individual aphids and keep your crop clean for longer.
In my garden: I released Aphidoletes in 2018 early in the spring when a red aphid appeared on young brassicas and the native Aphidius species hadn’t arrived yet. The aphid was likely a red phase of Green Peach Aphid. I released 250 Aphidoletes (about $20) and found them in that aphid colony within the week. As I write this it is late winter in 2020. For the past few years I have not seen Aphidoletes unless an aphid population is relatively big, and then the small orange Aphidoletes larva show up en masse. I don’t plan on applying them again – Most outdoor applications in organic situations are effective for 5 years. However, I’ll always be watching for them. I will usually find them in more protected areas than exposed hot and dry leaves.
Alternative 2: Scouting and action
Don’t roll your eyes. This isn’t always a “given” for some people. Check your plants regularly, and if you’re outside, don’t panic when you see an aphid. Look also for predators. If you see a native ladybug, a small maggot, a bronzed, swollen, parasitized aphid, or tiny little wasps near the colony, it’s probably best to do nothing. If predators are already there, you have a little breeding ground for predators.
But sometimes action is required – that precious rose, or an indoor crop, an absence of predators (especially if a chemical, soap, detergent or “natural pesticide” has been used previously) or if you have an economic threshold that requires action. When action is required, immediately order Aphidoletes. But while waiting for those, walk around and squish aphids. Or take the hose and blast them off the plant. These seem like minimal actions, but they do a fantastic job of recovering plant health and defence while slowing the rapid growth of aphids. Aphids almost need to feed continually in order to multiply at their speedy rate. Interrupting this at all is usually enough to have a natural predator take over.
Special Note: Most plants have natural chemical reactions that help dissuade pests. Typically, pest populations explode so quickly it overwhelms the plant. But, if you give the plant a chance to catch up, it will sometimes develop its own chemical response quick enough to reduce the rate of pest growth on its own.
The blast of water is particularly effective for these reasons:
- Unless you blast too weak a plant, water has no negative affect on most plants. (Don’t do this to seedlings or cacti.)
- It washes the honeydew (aphid excrement) from the leaves reducing the chance of infection for your plant.
- Aphids are constantly feeding. The blast can snap-off their mouth piece. They will survive – they’ll even climb back up – but they won’t be able to feed and they’ll still be food for predators and parasitoids.
- It’s free (other than the cost of water.)
- It won’t kill predators (although it certainly interferes with their predation.)
- It seldom washes off eggs. Aphids nearly never have eggs – they reproduce by cloning themselves) but predators lay eggs near aphids, and those may survive the water and then feed on any aphids that return or were missed.
- You’re also washing spores from the leaves (Plants like rain – despite what people say), so consider it giving your plant a bath, which they love. (Don’t do it every day, though).
In my garden: I never squish an aphid. I have a lot of tolerance. Most of it comes from having to raise colonies of aphids to feed predators. It is so much more difficult to keep an aphid colony free of predators than it is to raise predators. So, I know, if I tried to raise aphids in my garden I would fail. The more aphids, the more food for predators (and the stronger the attraction.)
Alternative 3: Eupeodes americanus (American Hoverfly)
This is the newest aphid predator on the market. Like Aphidoletes, the American Hoverfly is lab reared and native to North America, so it has no negative impact in nature. It may be the best alternative to ladybugs for people who just want to see large, beautiful beneficial insects in their yard.
These hoverflies are predatory in their larva stage only. As an adult they buzz around and visit flowers, feeding on pollen, nectar and being regarded as one of the primary native pollinators (second to native bumblebees, but first in the spread of biomass and flower genetic diversity – thanks to the distances they can travel.) A recent study found that flowers low in nectar are pollinated exponentially more often by Hoverflies than bee species.) If you have pollination needs and aphid control needs, this is the bug for you.
What makes them most notable, is that their larva are vermiform (worm-like). So instead of walking, they crawl. Aphids have evolved to detect tiny insect foot steps on leaves (or to detect the chemical reaction that occurs within the leaf) and they will be alerted to predators like Ladybugs and Aphidius wasps. However, the vermiform larva of hoverflies (and aphidoletes) illicit no defence from aphids – they just sit there and get eaten. And in lab tests, the American Hoverfly larva is the single greatest commercial predator of aphids, consuming between 1700 and 2200 aphids in just their one week larval stage. That is staggeringly more than a ladybug larva. They have also been tested, and found successful in all live stages in a temperature range of 12C to 30C.
These are currently difficult to find for sale. They are reared here, in Canada, and unavailable in the US (even though they are native to the US.). But one of your Canadian Biological Pest Control Companies can get them for you.
In my garden: I have never released American Hoverflies. All of my veggie/fruit beds have companion flowers and many of those are shallow flowers like sunflowers and umbellifers. Flies love them and I see all kinds of native hoverflies show up in my yard. If I ever don’t see them, I’ll release some American Hoverflies, otherwise, the yard is fine. Although, sometimes at garden events I let kids release them just because they are easy to see and fun to watch.
Alternative 4: Micromus variegatus (Brown Lacewing)
This is the best alternative if you were considering buying ladybugs for generalist predation. Brown Lacewings are raised on aphids – their preferred food, but upon release they will lay their eggs near aphids (the larva are aphid destroyers) and the adults will feed on all sorts of plant pests – scale, mealybugs, adult whitefly and other flying insects – I could go on, but anything we throw at it it will eat.
Special Note: Green Lacewings are available to buy. They are great aphid predators as well, but the adults are not predators. Brown Lacewing are “pound for pound” more effective predators.
The best part about the Brown Lacewing is that it was discovered getting into a cool pepper house during winter months. It was quickly assessed (and found successful) as an aphid predator at cool temperatures – when most other predators have slowed, or stopped feeding. So you can apply lacewing in the Winter or cool Spring and Fall months and know that they’ll be kicking around in late spring when pests have arrived.
They are hard to find once released as they use their small size, camouflage colouring and stationary behaviour as a platform to surprise attack other insects. If you can find one, watch it a while. There are few things as satisfying as seeing it shoot-out and take down a flying insect. (I also watched one cleaning itself for 20 minutes before I gave up and left. So if you see it cleaning its feet and antennae, come back later.)
In my garden: I release these every spring. In particular I release them in my hops. The hop aphid is small and the same shade of green as the hops and because the hops grow a foot each day, and I train them vertically, I can’t scout like I’d like to. When I release the Lacewing on my hop, I will see one or two remain, but I know most will take cover in other areas and find aphids at night. Either way, it’s a benefit to my yard.
Alternative 5: Aphidius species.
I typically just allow these to arrive naturally and let their populations build. There are many Aphidius (and other parasitic wasps) but some are specific to a specific aphid. And all of them are subject to their own hyperparasites which usually arrive en masse in late spring.
The ones you can buy (Colemani and Ervi) are generalist (enough) to take on most common aphids, but they will compete with one another and should be used for different aphids. (Colemani for big aphid species, and Urvi for smaller.)
A few problems with buying them commercially have developed. First, they have been commercialized on the same aphid, which has made them roughly the same size which has prevented them from being able to take out some of the bigger aphids they were designed for. Also, there is a world-wide spread of a gut bacteria in aphids that somehow prevents parasitism by aphidius. So, currently, buying aphidius is loosing its allure.
But, they are cheep and they might help. And if they are successful, they can multiply quickly and stay in a crop for some time.
In my yard: Most parasitoids are specific to one species of aphid. I don’t have the patience to identify each aphid species and try to find a commercial aphidius that might control it. Instead, I just trust nature: When the cabbage aphid shows, so does an Aphidius. When the bird-cherry-oat-aphid shows, so does a different Aphidius. It’s the same with a grain aphid I get on rye and a black aphid that likes a variety of things. In my organic yard, there are tons of native Aphidius species.
Now you’re asking “Where do I get these?” Here’s the catch. Ladybugs are cheap because they are hibernating when they are shovelled-up, thrown in a bag or bucket and kept refrigerated all the way to your garden centre. Therefore, a garden centre can maintain a stock. You can’t maintain a stock of efficient beneficial insects because while they survive refrigeration, it severely limits them or triggers other habits. In the case of ladybugs, they have no option to feed and then fly back to their annual hibernation location. Even Aphidoletes, if refrigerated, will survive but they will no longer use the same seaching behaviours. Instead they will be desperate and all lay eggs in the same place – making their large scale release, useless.
So, do a bit of research and find a reputable retailer of beneficial insects from a reputable producer. You should have to order it and pick it up a few days later. If they say they have some in the fridge, run and try somewhere else.
And remember, just because something eats aphids that doesn’t make it a useful biological control agent. For example, you can buy praying mantises which will eat a bunch of things, but there will only ever be a few of them at most – a population too small to help with an infestation. Instead, something like Aphidoletes will lay hundreds of eggs, each. And each of those larva will eat 20 or more aphids and kill up to a couple hundred more. And that larva period only lasts a week. Then, boom, you have thousands more adults repeating the cycle. This is what augmentative bio-control (buying and applying beneficial insects and mites) is all about – it actually works.
Good luck. If you have aphid problems, send me a message. You can also find me on twitter @DDaveyspencer
Or check out what’s growing in my farm this year: Full Circle Farm Garden Journal