Hoverflies: Beneficial Insect for Aphid Control
In this article, Master Naturalist Sarah Jay explains the life cycle of hoverflies and how to usher them into the garden space. Included is a list of plants you can incorporate to be a great host for these pollinator and pest control powerhouses.
Attracting beneficial insects to the garden is a great way to lessen the energy you must put into maintenance. Syrphid flies, or hoverflies as they’re commonly called, are some of your best allies in that regard. Across species, they specialize in aphid control, consuming other pests, and pollinating!
While many of your crops will already bring in hoverflies, you can also take steps to reinforce their arrival. By using cultural pest control and interplanting methods, you can give them a place to stay and hang out.
The Syrphidae family is vast, and chances are you have more than one species working for you in the garden. When you understand hoverflies’ habits, food sources, and preferences, you can easily attract them to your growing space.
What Are Syrphid Flies?
The family Syrphidae contains 6200 species of hoverflies. 900 of those live in North America. Many of these hoverflies are important agricultural pest controllers, and all are also incredibly important pollinators. Keeping them around, therefore, has multiple benefits.
All hoverflies or flower flies as they are commonly known, have a characteristic look, with striped bodies that range from ⅛ inch to almost an inch long. At first glance, they may look like bees, but you can distinguish them from bees via their large fly-like eyes and their single set of wings (bees have two sets).
Some of these flies are sleek and slender. Others are large and fuzzy. Many are black or brown and yellow. Some have light stripes accompanied by metallic blue or green. One species, Eristalis tenax, is called a drone fly because it looks like a male drone bee. This kind of mimicry has benefits, with one being less predation risk.
Eggs and Larvae
The eggs of all members are ovular, white to cream-colored, and less than one millimeter long. Larvae of hoverflies look like maggots and vary in color depending on the species.
Expect variations of pink, brown, green, or white. Those species that consume aphids have sets of legs, and others have none.
There are two ways to distinguish larvae of the Sphyrid fly family from unrelated caterpillars. First, look for roughly 12 body segments. Another way is to locate two breathing tubes that touch on their backs. These develop toward the end of the last larval stage.
Life Cycle of Hoverflies
How does the life cycle of a hoverfly proceed? It begins with eggs that are laid near food sources. Larvae hatch from the eggs and progress through 3 instars before pupating and finally reaching full maturity. Before the pupation stage, larvae tend to move into an inactive state, garnering energy in preparation for their final transformation.
Damp, humid conditions are important for maturation as larvae develop through the instars. If the area where eggs are laid tends to be dry, larvae will move toward an area with higher humidity. At times, larvae may live deep in leaf litter – an ideal place for them to grow up!
The length of each instar is variable from species to species. Some flies have several generations a year, and some have longer life cycles than others. The entire cycle can range from three weeks to nine weeks in total.
Primary Food Sources
The larvae of these flies are diverse in their feeding habits. Some are insectivorous, eating aphids, thrips, mealybugs, ants, caterpillars, and more. Others are detritivores, eating decaying plant matter. Adult hoverflies primarily feed on the pollen and nectar of various plants. We’ll touch on which of these you can include in your garden.
Some species live in shallow, stagnant water pools, carrying out mostly aquatic lives. Some live a semi-parasitic lifestyle and build habitats within termite or ant nests. There are even some that live in bumblebee nests. The few species that do feed on plant juices and sap are sometimes considered garden pests.
A Few Common Hoverflies
The types of hoverflies you’re probably most interested in are those that eat pests. Here is a list of a few species of insectivorous hoverflies and a little description of each.
- Eupeodes americanus (the American Hoverfly): common across North America; shiny green to black with three pairings of black and white or yellow and white stripes; roughly 9-12 millimeters long
- Eupeodes volucris (the Bird Hoverfly): most common predator of aphids in orchards on the West Coast, but prominent in all of N. America; ¼ inch to ½ inch long with a fuzzy body that has prominent white or yellow stripes on the abdomen
- Eristalis tenax (the Drone Fly): common across the world, except Antarctica; looks like a male drone bee, with a stocky body and marbled black eyes; colors vary from orange to dark brown, and they reach 15 millimeters long
- Allograpta obliqua (the oblique streaktail): found across North America; larvae eat aphids; these have intricate banding on their abdomen and thorax in bright yellow and black and are roughly 6-7 millimeters long
Bringing Hoverflies To Your Garden
Now that you know more about the hoverfly, its life cycle, and its preferred foods, let’s discuss bringing these flying friends to the garden. Many of the practices involved in growing a thriving garden align with your methods for attracting them.
Interplant Hoverfly-Friendly Companions
Several of your favorite companion plants invite in syrphid flies. We’ll discuss the particulars of this in the next section. But putting companions between your favorite plants that are typically prone to aphid feeding is one great way to invite them in.
Another important aspect of interplanting is to provide the diversity in your garden that hoverflies love. That means planting multiple varieties of plants that Syrphidae love and planting them densely. You don’t want exposed soil in the garden anyway!
Leave Wild Areas
Many annual and perennial weeds are food for hoverflies, and leaving areas of the yard to the wild is one way to ensure they’re around. Of course, this isn’t always possible in every space, but it’s a viable option for those who do have larger gardens.
Planting your garden near those with plants hoverflies love will bring them closer to your crops. Wild chicory, brassicas, and more will move them toward your space.
Limit the Use of Insecticides
Just as they can for pollinators, insecticides will make your garden inhospitable for hoverflies. Instead of using them as your first line of defense, focus on cultural methods of control that integrate your pest management tools. Critter cages, good garden hygiene, and hand removal are just a few ways to focus your pest control methods toward the cultural range.
If you must use insecticides and herbicides (and sometimes they are needed in the garden), ensure you’re applying them according to the label and best practices. Avoid spraying or dusting plants in peak pollinator activity, which generally occurs after the sun rises and continues through to the evening.
Granular insecticides and herbicides are safer for gardeners who want to attract beneficial insects in general. These are less likely to cling to hoverfly bodies and cause problems for them down the line.
5 Plants That Attract Syrphidae
We’ve outlined the methods to bring hoverflies to the garden. Now, let’s discuss the plants they love to feed on. Many of these plants are perfect in a veggie garden, but they’re also adaptable to ornamental and cottage gardens!
Carrot Family Plants
Species of plants in the carrot family are beneficial in or near your garden. Not only do these attract hoverflies that pollinate and defend your plants, but they also attract other beneficial insects and pollinators. Some host butterflies and moths, and many are edible and lovely additions to the garden.
Plants like Queen Anne’s Lace, dill, fennel, water hemlock, cumin, and cilantro will all attract species of hoverflies. Many are perfect partners for various foods. So, pick your favorites and pop them in your garden!
Mustard Family Plants
Like the carrot family, the small flowers of brassicas attract hoverflies. Wild brassicas and cultivated ones both count. If you’re growing radishes for their pods, you can expect many attendant flies when the plant flowers. They’ll ensure your flowers are substantially pollinated and protected, too!
Let some radishes flower close to the season’s end, or let wild mustard cultivate an area of your yard. You can even grow alyssum, candytuft, and cultivars of shepherd’s purse to bring them to your garden.
Not only are dahlias worth the effort for their resulting blooms, but they also bring Syrphidae. Those in areas with warmer fall and winter weather are primed for more flies! But it’s important to stick to the single-flowered varieties, as double-flowered types may have too many petals for hoverflies to access the pollen.
So plant gardens with dahlia tubers interspersed throughout, or plant one full of dahlias! Either of these will bring in everyone’s favorite flies.
When looking for companions with long blooming periods, calendula is one ally you shouldn’t pass up. This perennial’s orange and yellow flowers in warmer regions bring in lots of pollinators – hoverflies included.
Like marigolds, another great option for your hoverfly garden, calendula repels tomato hornworms. Perennial plantings deter nematodes as well. The flowers make a lovely tea or natural dye. There aren’t many downsides when it comes to calendula.
Maybe you don’t know what to plant, and you’d rather condition your soil instead of trying to produce crops. Buckwheat is a prominent cover crop that’s better than other crops at making phosphorus more readily available in the soil. Keep your garden free of weeds, and grow some buckwheat to give hoverflies the signal this is a great place to live.
You can interplant buckwheat throughout the garden if you already have plants growing. Cold winter weather will kill them off, but the result is a mulch you can lay on top of the soil to prevent erosion and protect plant roots.
Having hoverflies in your garden ensures you’ve got protection against pests and higher rates of pollination. Both of these funnel into higher yields and better production overall. While you may already have them in your yard, adding plants they love keeps them there.
Additionally, many of the plants that attract syrphids also attract other beneficial insects. So why not add a few plants for hoverflies this coming growing season?