Top Ten Beneficial Insects for Commercial Greenhouse Production

If you have plants, you’re going to have bugs. It’s a fact of life for any grower.

What to do about those bugs is not always simple or straightforward–a truly integrated pest management program focuses on prevention, monitoring, and control. In this article, we’re going to focus simply on control through the use of our favorite beneficial insects.

Before we get to our TOP 10 list of BENEFICIAL INSECTS for combatting greenhouse pests, let us give you…

Four Words of Caution about Beneficial Insects

1) Though predator bugs are great at control, they will not correct infestations. Beneficial insects need to be used before a large outbreak occurs because they are good at controlling low numbers and keeping plants clean. We have not found them to be effective against large infestations.

2) Beneficial insects need to be applied on a rotation. This could be every week or two, all depending on the recommended release rate, your current insect population, your crop, and the time of year. It is not a set-it-and-forget-it kind of program.

3) When the days are short, many insects will enter diapause. (Diapause is a sort of suspended animation where the reproduction cycle temporarily ceases or slows way down). Winter production often requires supplemental lighting for predator bugs to remain active.

4) In our experience, there is no treatment- whether chemical or biological- that will guarantee 100% clean plants all season long. Any grower is likely to have outbreaks at some point that require a more aggressive approach. If you do need to spray, be sure to spray something that is friendly to beneficials. That way new predators can be released quickly to help keep numbers low and break the pests’ lifecycle.

And now, the moment you’ve been waiting for…

Our Top Ten List of Beneficial Insects

10. Amblyseius swirskii & Amblyseius cucumeris

Amblyseius swirskii (A. swirskii), sometimes called swirskii mites, are generalists that eat soft-bodied anthropods like whitefly and thrips in the nymph stage. Amblyseius cucumeris serve a similar purpose. While these will eat the young pests, they are best when used in combination with other predators that will attack the adult stage. They generally eat ten larvae or twenty whitefly eggs a day.

For best results, give A. swirskii a temperature of 80° F with 70% humidity, but know that they only remain active above 60° F. They have no winter diapause.

9. Stratiolaelaps scimitus

Stratiolaelaps scimitus (S. scimitus) is a soil-dwelling mite that feeds on the nymph stages of other bugs. We use them mainly for fungus gnat prevention, but they can also eat thrip pupae. Because they are only active at the soil level, they are best used in combination with other aggressive predators. They eat one to five prey per day.

S. scimitus like 60-80° F temperatures and 40-60% humidity, and they are unaffected by changes in daylight. They don’t like dry soil, so they’re not as effective on dry crops like succulents and cacti.

8. Trichogramma brassicae

Trichogramma brassicae (T. brassicae) is a wasp that has done well in preliminary testing for caterpillar control (ornamental production) and corn earworm control (hemp production). While this is our first season getting a good jump on having these predators out early, we feel very confident that this will be our go-to beneficial insect. Female wasps lay eggs inside the host egg, and over fifty wasps can emerge from one egg. They can be used both indoors or in crop productions.

Ideally T. brassicae prefer temperatures between 80-90° F and will not survive below 40° F. They like a 60% relative humidity and have more longevity at 14 hours.

7. Encarsia formosa / Eretmocerus eremicus (Mix)

Encarsia formosa and Eretmocerus eremicus are our top pick for whitefly control. These small parasitic wasps lay eggs during the second and third instar stages of whitefly development. Each female can parasitize 150 developing whiteflies.

For best performance, keep temperatures between 70-95° F and a lower humidity of 60% or less. They’re non-diapausing, even through short winter days.

6. Dalotia coriaria

Dalotia coriaria (D. coriaria) also called Rove Beetles, are soil dwellers. These beneficial insects have been our most effective treatment of fungus gnat larvae. They also feed on root aphids, shore fly eggs, pupating thrips, and other soft-bodied arthropods that may be growing in the soil. Although a generalist predator, they primarily feed on eggs and larvae at the substrate level, consuming 150 fungus gnats per day.

D. coriaria are most effective with temperatures ranging from 60-90° F and 50-80% humidity. They are non-diapausing and continue hunting year-round with no supplemental lighting necessary as long as the temperature stays above 60° F.

5. Steinernema feltiae

Steinernema feltiae (S. feltiae) are microscopic roundworms which live in the soil and feed on larvae and pupae. S. feltiae are used largely for shoreflies, but these beneficial nematodes will eat anything in the soil (fungus gnats, thrips, root aphids, caterpillars, etc.). They represent a good base preventative, but they need to be paired with other predators to have a fully-rounded integrative pest management program. They locate pests, enter through a body opening, and inject bacteria into the pest’s bloodstream (without being dangerous to humans or animals).

S. feltiae, like most nematodes, thrive in a soil temperature of 60-70° F. While they thrive in moist soil, be careful not to soak the growing media after application or you might wash the nematodes right out of the pot.

4. Orius insidiosus

Orius insidiosus (O. insidiosus) are true generalists and feed on all life stages of thrips, aphids, whitefly, scale, and both two-spotted and russet mites. They are good on both ornamentals and hemp and have been our best biological control for thrips. They kill more than forty thrips a day, but will hunt many other pests based on what food is available.

O. insidiosus are very susceptible to diapause and you must do one of two things: either keep your temperatures above 72° F in the winter, or stay above 50° F with supplemental lighting. They are most effective when the humidity is over 60% with 14 hours of light.

3. Aphidius colemani / Aphidius ervi (Mix)

Aphidius colemani (A. colemani) and Aphidius ervi (A. ervi) combine to be our top beneficial hunters for aphids. These parasitic wasps work better as a pair because of their differences in size. The A. ervi are larger and tend to feed on larger aphids, while the A. colemani go after the smaller prey. Both attack the hemp/cannabis aphid (phorodon cannabis) as well. They are called parasitic because they inject their eggs into the aphids, which then grow into larvae, thus killing the aphids from the inside out.

A. colemani and A. ervi prefer moderate temperatures (around 70° F) and a humidity of 60-70%, but one of their advantages is that they continue to hunt even during short days and can therefore be used in year-round production without supplemental lighting.

2. Neoseiulus californicus

Neoseiulus californicus (N. californicus) is somewhat of a generalist, but prefers to eat mites. We’ve found it especially effective in hemp crops to deal with two-spotted spider mites, russet mites, broad mites, and thrips. For those who are growing vegetables, they will even eat pollen once the prey population no longer meets their needs, thus fulfilling a dual purpose.

N. californicus are a little more tolerable of lower temperatures–anywhere from 50-90° F keeps them active–but still require 16 hours of daylight. Although they thrive in higher humidity, they can tolerate down to 40%. They only eat around five mites per day, so they survive longer in low population densities (for long-term control).

1. Phytoseiulus persimilis

Phytoseiulus persimilis (P. persimilis) wins the award for our favorite predator. It attacks two-spotted spider mites at all life stages and feeds on young thrips as well. These guys are so ferocious that they will turn cannibalistic when the pest population drops too low.

P. persimilis eat five to twenty eggs or mites a day and reproduce faster than the mite population can. They perform best in warmer environments (82° F or above) and at least 70% humidity with 16 hours of daylight. When used outdoors, they will migrate once the mite population drops too low.

What’s YOUR Favorite Beneficial Insect?

Have you seen good success with any of these bugs? Have a favorite that didn’t make it to our list? Comment on Facebook and let us know! Other growers can benefit from your knowledge, too!

_{Caterpillar photo used by permission, Egor Kamelev, pexels.com
All other photos ©Rachel Donahue, North Carolina Farms, 2020}