Using Ladybugs in the Garden and Greenhouse

Pest management in a greenhouse

The primary purpose of using ladybugs is as a beneficial insect that provides pest control by eating the “bad bugs.” They are particularly useful in combating aphids, which is a major tormentor of year-round greenhouses, which stay warm and humid (great breeding conditions for aphids).

A common alternative to ladybugs (technically called “ladybird beetles” but we’ll stick to simple ladybugs) are lacewings, which can actually eat more aphids than ladybugs. 

Learn more about how to deal with pests in our blog: “6 Common greenhouse pests and how to manage them” 

For now, here’s a run through on how to use ladybugs in a garden or greenhouse.

There are two ways to get ladybugs:

  1. Attract them naturally

You can invite ladybugs to your garden by using pollinating flowers, like alyssum, fennel marigolds and others. Ladybugs will eat both insects and pollen, so planting your garden with their food will naturally attract them.

If you have a greenhouse and you’re growing in the warmer months, this also means inviting the ladybugs into your greenhouse by keeping screens off and using flowers. Yes, this does allow the bad bugs to come in as well, but in our experience the bad bugs are likely getting in one way or another, unless you’re running a completely sanitary commercial greenhouse (see previous blog on pest prevention in the greenhouse). Instead, we try to create a balanced healthy ecosystem that has both bad and good bugs. Insects are part of the natural environment and they don’t always mean “disaster.” They just need to be properly controlled.

ladybug in the greenhouse

We always recommend naturally attracting ladybugs regardless of whether you have a pest infestation or not. They provide a great preventative defense when they are around, and eliminates the possibility of purchasing ladybugs of non-native varieties. It’s important to understand that natural populations have limits — if you have a major outbreak of aphids or other insects, you probably won’t be able to attract enough ladybugs to counter this entirely. However, they still provide great supplemental and long-term defense.

  1. Purchase ladybugs

Keep in Mind: Declining ladybug populations

You may have noticed that finding the beetles at your local garden center or online has become more challenging, if not impossible. 

Where have the ladybugs gone?

There has been a shortage over the past year as the beetle population continues to decline.  The majority of Ladybugs that are sold are wild harvested in California and the Pacific Northwest, while a few are being raised successfully in insectaries. The recent wildfires in California have destroyed large areas of Ladybug habitat, impacting the population. That, on top of increased demand from farmers and consumers, has ultimately led to a Ladybug shortage.  

Additional word of caution! 

If purchasing ladybugs, the ladybugs shipped to you are probably “wild harvested” — trapped in other environments and then bred. There is some reporting that they, therefore, carry parasites that are only native to the ladybugs of that region, and once they fly away, they can transfer these parasites to the native ladybugs. We haven’t heard many other reports on this, however, for caution, we recommend using a local insectary (insect breeder) and always asking about the source of the ladybugs.

What can I use instead of ladybugs to control aphids?  

There are a variety of other biological beneficials available that are more sustainable and efficient. Green Lacewings are a great alternative, as they can eat aphids 20 times faster and they are easy to transport (1,000 eggs are about the size of a pea). The typical release rate is 1,000 per 500 square foot. Lacewings are supplied either as eggs, larvae, or adults. 

We recommend purchasing lacewings as eggs and letting them hatch before releasing them into your greenhouse. Hatching the lacewings is easy, and involves spreading the eggs out in a container mixed with vermiculite. Lacewing eggs typically will hatch within 3-5 days at room temperature. Once hatched, simply sprinkle them amongst your crop. You can expect the larvae to feed for 2-3 weeks before they mature and form cocoons, then emerge as flying adults ready to mate and lay more eggs. Lacewings are much more effective at populating the greenhouse than ladybugs. For best results keep the temperature inside your greenhouse somewhere between 67 -90 F.  You can purchase lacewings at your local garden centers or online.

Tips to keep in mind when using ladybugs

Know what they look like! Before reaching maturity, young ladybugs look very different, kind of like tiny alligators (right). Make sure you keep them around.

young ladybug in the greenhouse

Make sure you discontinue use of all insecticides before letting them loose in your garden. Insecticides, even natural ones, kill indiscriminately, both the good and bad bugs.

If using outdoors, release ladybugs in the evening, increasing the likelihood that they will stick around the garden, not fly off looking for other food.

Also in the outdoor garden, some people use netting to trap them around infested plants for some time.

If you are able to find ladybugs to purchase for your greenhouse pest management.

Ladybugs usually come in large quantities, 500 and greater. The Integrated Pest Management Department at Pennsylvania State University recommends applying 1-4 ladybugs per sq. yard every 2-4 weeks for commercial greenhouses. However, it’s hard to over apply if you have a major pest infestation. If you do not use them all at once you can refrigerate the rest of them, so they remain dormant, and release them in stages. This is also why having pollinating flowers is helpful: they can feed off these when the pest population starts to diminish.

If using ladybugs in your greenhouse, you want to keep your greenhouse closed (screened in) to ensure the ladybugs do not fly away.

Contact us to learn more

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