Using Ladybugs in the Garden and Greenhouse

By Haley Bridgnell
Pest management in a greenhouse

Using Ladybugs in the Garden and Greenhouse

Using Ladybugs in the Garden and Greenhouse

First, releasing a swarm of 2,000 ladybugs — ready to defend your garden — can be a fun activity, and a great way to get kids into the garden.

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 combatting 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. We’ll go into a comparison in our next blog. For now, here’s a run through a how to use ladybugs in a garden or greenhouse.

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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 pollens, 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 your 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.

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 you do not need to purchase any ladybugs which may introduce any 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.

2. Purchase ladybugs

If you do have a pest infestation, in which a ‘bad bug’ — aphids, white flies, gnats or other — start prolifically breeding, you can purchase larger quantities of ladybugs as an emergency measure. In the summer, ladybugs are usually available at garden stores. In the winter, they can be purchased online or in specialty garden stores. Nature’s Control has a list of carriers by state.

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. Here is an interview with a ladybug specialist commenting on the issue. 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.

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. (You can see we went above and beyond by using 2,000 in our 80 sq. ft. greenhouse.) 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.

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.

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.

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