Beneficial Insects for Gardens, Farms and Greenhouses

Biological Pest Control with Insects

As more insect pests become resistant to pesticides and previously relied upon pollinators become scarce, native bees, wasps, and other beneficial insects can do the work for us. Attracting beneficial insects to your farm or garden will make your plants more productive, reduce the need to treat pests, beautify the space, and help protect the ecosystem.   

Identifying Beneficial Insects

There are three main types of beneficial insects that can help keep your farm or garden thriving. Pollinators, predators, and parasitic insects are fundamental beneficial insects for maintaining a healthy garden ecosystem. 

Interestingly many of the greatest friends to the farmer will fall into more than one of these categories depending on the life cycle stage they are in. For example, flower flies (family Syrphidae) are important pollinators as adults, but their larvae's value as insect predators cannot be overstated. The larvae of syrphid flies subsist on a steady diet of other insects like aphids.

1. Pollinators: This group includes bees, butterflies, adult flies, moths, and hummingbirds. We depend on these to pollinate all flowering crops.
2. Predators: Eliminate pests from the garden by eating them. Ladybugs, wasps, praying mantises, and green lacewing larvae are some of the most prominent members of this category.
3. Parasitics: Parasitic insects also prey upon other insects. They lay eggs on or in "bad bugs." When the insect eggs hatch, the larvae feed on the host insects, usually causing their demise. Parasitic wasps and several families of flies fall into this category. The wasp larvae and fly larvae eat aphids from the inside out. 

Spiders are helpful predators in the garden.

Although technically arachnids and not insects, spiders deserve mention here. Spiders are fantastic predators on the farm for pest insects. Common garden spiders are excellent at gobbling up pest insects, either by catching them in webs or, in the case of jumping spiders, attacking insect pests on foliage and ground-dwelling prey. 

Attracting Beneficial Insects

The best way to attract beneficial insects to your farm or garden is to provide them with what they need for every stage of their life. These needs include food, water, places to lay their eggs, and habitat, especially for overwintering. 

Food Sources for Beneficial Insects

Early blooming flowers are a great way to set yourself up for success when it comes to attracting beneficials to the garden. Many, like ladybugs, come out of hibernation hungry and looking for a place to lay that all-important first generation of Spring babies. Providing early and ongoing nectar and pollen sources will attract good bugs to your site and keep them there, even when insect prey is scarce. 

Water Sources for Beneficial Bugs

Providing an easy-to-access water source for pollinators and other beneficials in the garden is a great way to attract and keep good bugs around. Some native bees and flies have a minimal daily foraging range. Providing a water source for every half-acre to an acre of cropland will be a boon to all the insects you are looking to draw in.  

Build a Bee Waterer 

A simple bee waterer can be built by placing rocks or marbles in a shallow dish filled with water. Bees can easily fall into even shallow water and drown. The rocks give the insects a place to land while drinking. It also keeps the dish from turning into a birdbath. 

Other easy methods to provide bees water are filling a hummingbird feeder with clean water, placing rocks in an automatic pet water bowl, or purchasing a bee waterer from a beekeeping supply store.  

Habitat for Pollinators and Predatory Insects 

There are three distinct types of habitat that beneficials need to complete their life cycle successfully. Nesting sites, overwintering sites, and forage are all vital. Taking a little time to ensure you provide them all will help keep them on your farm and in your garden. Often this can be as simple as leaving some Fall cleanup tasks undone. Or you can get a little more proactive and put in intentional nesting blocks or stem bundles. 

The books listed at the end of this article have many excellent how-to guides and ideas for providing species-specific nesting sites. Most research on this topic has been focused on bees, but providing these habitat types seems to dramatically increase the numbers of other species, including butterflies and parasitic wasps, parasitic wasp larvae, and flies. 

Egg Laying and Nesting Habitat

About 70% of the native bees in North America are ground nesters. Their various burrows are often mistaken for ant hills. The simplest way to provide nesting sites for ground-dwelling bees is to leave some areas of bare ground unplanted and unmulched. Ideally, this ground should be slightly sloped above any areas that flood in the Winter. East and South facing areas are best as they help the bees and their larvae warm up in the mornings. 

The remaining 30% of native bees are tunnel nesters. Naturally, these valuable pollinators depend on abandoned tunnels left in tree stumps and snags to raise their brood. A few others will chew out the pithy centers of stems. These habitats can be created by drilling holes in wooden blocks and branches or bunching groups of stems. 

Bumblebees are one of the few social native bees. They nest in small cavities like those formed by rodents under grasses or in used birdhouses.  

Overwintering and Pupation habitat

Conveniently most beneficial insects will overwinter and pupate in a similar habitat to their egg-laying preferences. Others need leaf litter, small branches, and dried stems to make it through winter conditions and emerge as adults come Spring. 

Intentionally benign neglect breeds pollinators

Possibly the best news in creating and preserving habitat for native pollinators is that it can be as simple as neglecting to do a few Fall garden "tasks." 

• Choose to leave some areas of bare ground without mulch. 
• Leave dried stems and brambles in place over the Winter. 
• Let piles of leaves sit and break down naturally through the Winter.
• Let grasses and flowering weeds remain untilled in buffer zones and fallow land.
• Leave snags (that don't endanger structures) and stumps in place. 

Provide Forage for Native Insects

Consider planting hedges, buffer zones, or interspersed garden rows with native wildflowers and shrubs. Even a small patch of wildflowers that continues to bloom with different species throughout the seasons will draw in all types of native bees and pollinators. Flowering shrubs and berry bushes have the added benefit of providing overwintering sites, nesting material, and places for butterflies to hang their chrysalis.  

Good Bugs Love Little Flowers

Parasitic wasps and hoverflies are attracted to tiny blossoms. The wasps in particular that you are trying to attract are often so tiny that you won't really notice them. Their minuscule size means that smaller blooms are more accessible for them to feed on and are subject to less competition for food from larger bees and wasps. 

If you have ever watched the number of tiny flitting creatures that are attracted to bolting cilantro or carrot flowers, you have seen some of these lovely little workhorses of the garden. Many native wildflowers naturally have the smaller compound blossoms that these insects prefer.

Plants you NEED to make space for in the garden to attract beneficial insects for pest control. 

Many of the truly effective predatory bugs that will help you control plant pests rely on nectar and pollen for at least part of their diet. Some, like parasitic wasps, rely on flowers for their entire diet in adult form. Flowers with compound blossoms like yarrow and dill are especially important for attracting these incredible tiny farmer's friends. 

For many of these plants, just leaving a few of your garden vegetables to bloom and go to seed through the seasons and overwinter will create the habitat you are looking for. Cold hardy brassicas like broccoli and kale are excellent early sources of nectar and pollen if allowed to overwinter and flower in early Spring. We also frequently find ladybug eggs on the underside of our broccoli leaves. White and yellow flowers seem especially good at attracting early friends to the garden. 

Pictured:  Lady bug and larvae

Some of our favorite multi-functional plants for attracting, feeding, and housing beneficials in the garden are:

Alyssum - early small flowers in white and purple, ground cover habitat in mild climates

Broccoli - yellow or white flowers, old hollow flower stems make excellent habitat, 

Cilantro/Coriander - withstands mild early frost, bolts quickly in the heat, tiny white compound flowers.

Dill - compound yellow blossoms, great hollow stems

Fennel - compound yellow blossoms, great hollow stems, can be planted in late fall to flower early in the Spring.

Sunflower - a highly productive source of pollen and nectar. Look for the branching types for continual food sources through the warmer months. 

Yarrow - long-lasting compound flowers attract many native insect species.

Zinnia - bright flowers attract pollinators and predators alike; also a favorite of hummingbirds, tall stems provide habitat for web spiders.

Provide Native Wildflowers to Increase Pollinators on your Property

Planting even small patches of native flowering plants amongst your crops or around the edges of your farm as buffer zones can significantly impact native pollinator populations. Remembering that these pollinators are often fantastic predators in their larval stage means that planting for pollination is also planting to increase beneficial insects of all kinds.

Native wildflowers often do double duty, providing not just nourishment for the insects you are trying to attract but also nesting habitat and overwintering spaces. Given a choice, most butterfly and moth species will lay their eggs on native plants. This means the possibly pesky caterpillars will do their damage to your buffer plants while the adult butterflies will feed on and pollinate all of the nearby flowers.  

Bees native to North America can easily do the job of pollination without the need for nonnative honey bees as long as there is enough available habitat. As an example, 250 blue orchard bees can effectively pollinate an entire acre of apples, a task that would require tens of thousands of honey bees. Unlike honey bee colonies which are often moved around by humans, causing a host of ecological issues, native bee populations can be self-sustaining. 

A list of valuable native wildflowers for North American farms.

Aster (Symphyotrichum spp.)

Beardtongue (Penstemon spp.)

Beebalm (Mondara spp.)

Blanketflower (Gaillardia spp.)

Eryngo (Eryngium spp.)

Figwort (Scrophularia spp.)

Hyssop (Agastache spp.)

Goldenrod (Solidago spp.)

Gumweed (Grindelia spp.)

Lobelia (Lobelia cardinalis and L. siphilitica)

Lupine (Lupinus spp.)

Milkweed (Asclepias spp.) Plant the species suitable to your region to avoid confusing Monarchs.

Purple coneflower (Echinacea purpurea) is the most widely available, but other spp. are good to plant.

Scorpionweed (Phacelia tanacetifolia, P. californica and P. grandiflora)

Selfheal (Prunella vulgaris) low growing and sturdy will tolerate vehicle traffic

Spiderflower (Cleome spp.)

Spiderwort (Tradescantia spp.)

Sunflower (Helianthus spp.) Avoid "pollenless" and ornamental varieties.

Waterleaf (Hydrophyllum spp.)

Wild buckwheat (Eriogonum spp.) 

Wild geranium (Geranium spp.) Plant the species suitable to your region for best results.

For this list, we have focused on generalist wildflowers that will grow nationwide in the US, throughout southern Canada, and northern Mexico. For more location-specific flowers, be sure to check out some of the resources listed at the end of this article. In many cases, particular species (spp.) of each genus of flower will be better adapted to different regions. Some of the flowers can become pesky weeds in crop rows if not contained, do your research if you are worried about contamination. 

If you are ready to add a significant number of flowers to your growing space, we have also put together a great resource on Growing Edible Flowers. Many of the flowers we discuss in our resource guide are also excellent for attracting all types of beneficial insects. Like bee balm and hyssop, some are also wildflowers native to the US. Find the complete spreadsheet of edible flowers available for download here.

Native trees and shrubs for beneficial insect habitat

Including native trees and shrubs in buffer zone plantings or landscape planning will provide long-term benefits to the overall ecosystem on your farm or home garden. Because trees and shrubs are more location-dependent than wildflowers, we have only listed a few of the prettiest and most useful here. For more information, look into Attracting Native Pollinators: The Xerces Society Guide Protecting North America's Bees and Butterflies.

• Almond
• Blueberries
• Black Locust
• Cherry
• False Indigo
• Golden Currant
• Meadowsweet/Steeplebush
• Peach
• Plum
• Redbud
• Wild lilac
• Willow

Buying Insects to Eliminate Pests

Ideally, you will be able to attract beneficial bugs you want to see more of to your garden with the suggestions in this article. But maybe you are looking to install beneficial insects in your greenhouse to treat a particularly bad spider mite infestation. If that is the case, you can purchase insects to help treat your problem naturally. Be sure and check the regulations where you live, as some locations do not allow the release of certain types of insects. Many garden supply stores will sell ladybugs and green lacewings. For the more specialized predators, you can look up our friends over at Arbico. They sell a variety of species for pest control.

Pictured:  Lady Bug 

Beneficial Insects in the Greenhouse

Insect netting is typically used to keep bugs out of your greenhouse and off of your valuable plants. However, it can also be used to keep insects in, particularly if you will incur the expense of purchasing ladybugs or lacewings to deal with an infestation of pests in the greenhouse. You want them to stay put while dealing with your problem for you and ideally reproduce to provide ongoing control of pest insects as their new larvae feed on pests. If you will be using insect netting to keep predators inside your greenhouse, make sure you provide habitat for breeding, water, and flowers with pollen and nectar to feed the adults. 

Learn more about insect netting, check out Insect Netting for Pest Protection.

WHAT BUGS ARE BENEFICIAL IN THE GREENHOUSE?

Garden insect predators can be divided into two groups: generalists and specialists. A specialist bug will prey on just a few different kinds of insect pests, while a generalist will eat a broader spectrum of prey, including other beneficial insects. When choosing a generalist insect species, it's important to keep an eye on their population size, so they don't begin eating your other beneficial garden insects as well.

Top 10 BENEFICIAL INSECTS FOR GREENHOUSES

• Assassin Bugs: This class of predatory insect is highly efficient at hunting and killing pests insects of all kinds, from leafhoppers to boll weevils. Common assassin bugs include the wheel bug and the cone-nosed bug (or kissing bug). Just be careful when handling — these guys can bite!
• Damsel Bugs: Nymphs and adults alike will feed on soft bodied insect pests such as caterpillars, leafhoppers, thrips, aphids, and more.
• Ground Beetles: These iridescent black or brown beetles take care of ground-bound insect pests like root maggots, slugs, and cutworms, especially in their larval stage.
• Hover Flies: Technically called Syrphid Flies, these yellow and black garden insects hunt down aphids as maggots and pollinate flowers as adults.
• Lacewings: As larvae, these delicate insect specialists can devour dozens of aphids at a time. In adulthood, they tend to stick to pollen and nectar.
• Ladybugs: One of the most common beneficial insects, are voracious eaters of aphids, thrips, mites, and more! The lady beetle or ladybug is the best bug you could ask for in your garden. Their larvae feed aggressively on aphids!
• Minute Pirate Bugs: Small but mighty, these barely visible garden insects will help keep aphids, mites, and thrips at bay on garden plants.
• Praying Mantises: These recognizable insects are most effective at pest control in their nymph stage when they'll eat just about any bug in sight. They remain generalists throughout their lives, so make sure they aren't gobbling up all your lady beetles while hunting for caterpillars!
• Rove Beetles: A predatory beetle that eats soil-dwelling pests like thrips and fungus gnats.
• Spined Soldier Bugs: A type of predatory stink bug that eats caterpillars, grubs, and Colorado potato beetles, and Mexican bean beetles. It's a generalist, so make sure not to have too many.

Pictured:  Rove Beetle

HOW ARE BUGS BENEFICIAL?

The importance of beneficial insect species cannot be overstated. These helpful garden insects clear out pests and minimize damage to crops. It's a natural method of biological control to take care of your crops and get rid of pesky insects without harming pollinators or the garden plants themselves. In using beneficial insects, you can control the numbers of aphids, whiteflies, mealy bugs, leaf miners, and many other common kinds of greenhouse pests to ensure that your plants grow strong and undisturbed.

Keeping Beneficial Bugs on Your Farm

Don't spray insecticides, pesticides, or herbicides unless absolutely necessary, and even then, only in very targeted areas. These sprays do not discriminate between the bugs you want to keep around and the pest insects you are trying to rid yourself of. 

Provide forage and protected spaces in your garden and around your farm. When you do need to cultivate areas of habitat, try to only till, burn, or mow around 30% at a time. Schedule these activities in the late summer and fall when most ground-dwelling insects are not reproducing.

Resources

We could not have written this article about beneficial insects without the fabulous research done by many others, particularly the fantastic information available from the Xerces Society. You can check out our entire book list through our affiliate link with Bookshop.org showing all of the books we used to inform this writing. If this is a subject that you want to learn more about, these are some of the books we love. 

Attracting Native Pollinators: The Xerces Society Guide Protecting North America's Bees and Butterflies

Farming with Native Beneficial Insects: Ecological Pest Control Solutions

Vegetables Love Flowers: Companion Planting for Beauty and Bounty

Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening