Beginner's Guide to Beneficial Insects

The predator/prey and parasite/host balances that exist in nature between countless species of fauna is an aspect of indoor pest control that can be difficult to attain. Anyone who has attempted the indoor growing of food or plant crops is well aware that the artificial environments we seek to create for optimal plant growth are often equally conducive to numerous pest species, infestations of which, if left untreated, can devastate or annihilate the anticipated bounty.

We can tip the balance in our favor with the release of beneficial insects into our growing areas and into our container media. A wide range of insects, both visible to the human eye and microscopic, are available for purchase. The added advantage to using beneficial insects for pest control is that they can supplement or replace the use of insecticides, both synthetic and those approved for organic growing.

Beneficial insects come in numerous forms. The intended target pest species will dictate whether you release adults, eggs or larval stages of predatory or parasitic insects. Insects controlled include common nuisances such as whitefly, fungus gnats, thrips and aphids.

Predatory Beneficial Insects

Ladybugs

The most commonly released and recognizable beneficial insect to both novice and advanced grower alike is the ladybug (Hippodamia convergens). Ladybugs are generalists and consume aphids, whiteflies, mites, weevils, adelgids and other beetle larvae. They prefer and will seek out aphids to prey upon. An adult ladybug will consume as many as 60 aphids per day, and up to 5,000 over the course of its lifetime. Ladybugs often come in plastic pint containers containing 1,500 insects. Larger packages are available with as many as 50,000 insects.

To get the most out of your ladybug release, water plants and foliage first. Ladybugs usually come with food in their containers but not water and are likely to seek out a drink as soon as they are released, so a drop of water near their desired destination will help keep them there to do their work. Ladybugs do not typically fly after dark, so releasing your package at or after sundown is desirable.

It is good practice to routinely release a limited amount into your growing areas. An infestation or outbreak of a particular pest species may necessitate the release of many thousands of ladybugs, but otherwise do not release more than a few per square foot of growing area, or overpopulation may drive them to leave in search of other food or worse, starve to death.

Delphastus catalinae

Delphastus catalinae is a relative of the common ladybug, but is much smaller. These tiny, brown-black, round beetles are about the size of a pencil tip. Unlike ladybugs, they cannot sustain a population in the absence of prey. Females need to consume between 100 and 150 whitefly eggs daily to achieve and maintain their own egg-laying abilities. Both male and female Delphastus will consume whiteflies in all stages, including adults and nymphs. They kill their prey by biting a hole into the body of the adult or immature whitefly and extracting its contents, leaving a hollow, shell-like corpse.

Each D.catalinae can consume up to 10,000 whiteflies over the course of its life. They can be used in conjunction with a beneficial parasite, as they will not consume parasitized whitefly. Best results using these beetles are yielded when more than 10 are released at each whitefly hot spot.

Praying Mantis

Another commonly used predator for pest species is the praying mantis (Stagmomantis genus, found in the Americas). Praying mantids are sold commercially in their egg cases. These cases should be hung near plants with pest problems. The emerging mantids will be ready to consume a variety of small pest species. As they mature, they will graduate to consuming moths, houseflies and mosquitoes. Upon hatching, the praying mantids should be separated, as they can be cannibalistic when they are young.

Contrary to popular belief, there is no federal law against killing or moving praying mantids. They are not an endangered species. If you are lucky enough to find the egg case of a praying mantis in the wild, scoop it up and put it in your growing area.

Green Lacewings

Like the praying mantis, which might be found in your outdoor garden, green lacewings (Chrysoperla rufilabris) are a common outdoor predator that can be incorporated into your indoor insect control routine. They consume a wide range of pest species, but are partial to aphids and mealybugs. They will eat whiteflies and scale insects in the absence of their preferred prey.

Adults lay their eggs anywhere near a potential food source. It is the larvae of the lacewing that has the most impact on pest control. Chrysoperla are most often sold as eggs or larvae because of their youthful appetites. Larvae should be released upon receipt, as they will become cannibalistic in the absence of prey. If obtained as eggs, keep them off the ground or anywhere they might be vulnerable to predators—ants will eat the eggs. Green lacewings have been known to bite humans, but this is rare and their bites are not toxic.

Orius insidiosus

Orius insidiosus, or insidious flower bugs, are so-named due to their extreme aggressiveness towards thrips. They predate other pest species and are a particularly useful pest control option, as they will burrow into closed flower buds in search of their food if they cannot find it on the leaves, or if they have already exhausted the easy pickings.

Insidious flower bugs are only useful during summer months due to their need for daylight and warmth. Artificial lighting can be used as well as supplemental heat to extend their usefulness if needed. They are usually sold in units of 500 and are most effectively applied directly over infested plants. Like the green lacewing, O. insidiosus can bite humans, but it is a rare occurrence.

Hypoaspis miles

Hypoaspis miles are a species of predatory soil mites that can be released directly into the media of container-grown plants, or directly onto the floor surrounding them. They can be applied into the cracks of concrete floors, or into the joints of brick or stone floors and are a good choice to control insects for mushroom production. Their primary diet is thrip larvae and pupae, but they also help to control fungus gnats by consuming their eggs and larvae as well. Water the area prior to releasing, and then again a few hours later. They are usually available in quantities of 25,000 each.

Atheta coriaria

Atheta coriaria, more commonly known as rove beetles, are another soil-dwelling predator like the Hypoaspis. These tiny, often naturally occurring beetles thrive in moist, dark areas where they can feed on the larvae and pupae of fungus gnats, shore flies and thrips. Rove beetles will fly in search of new food supplies once they have exhausted their original location, so they are useful for broad coverage. They are usually sold in units of 100 and can be incorporated into soil media, on floors, in soil or in gravel.

Nematodes

Nematodes are microscopic worms that often have a bad reputation. There are numerous species of destructive nematodes, but there are beneficial species as well. Steinernema feltiae are a species of nematode that, when incorporated into soil media, can control fungus gnats, thrips and more than 200 other species of flying and crawling insects. They achieve this by preying on their insect victims while in the larval stage.

They seek out these pest insects when they are still developing in the soil to feed on them. An adult nematode can produce up to 200,000 offspring over the course of its several-month-long life. When ready to reproduce, they will spear their prey, and deposit their eggs within. The young nematodes when hatched will feed on the host species from within and then emerge ready to find their own prey.

Packages of nematodes are sold with tens of millions of active units (AU) in each. They may come embedded on granules or vermiculite flakes, which are easily incorporated into soil media. They may also be packaged and shipped on a moistened sponge that is mixed with irrigation water, or in a powder, which can be used as a soil drench. Nematodes can be stored for months in refrigeration prior to their use.

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Parasitoids

Aphidoletes aphidimyza

Carnivorous aliens that emerge from the bellies of their human hosts in science fiction movies are based on fact—this occurs in the insect world between host aphids and their parasitic killer, Aphidoletes aphidimyza. The Aphidoletes are usually obtained as pupae and are placed in an open container near plants with high levels of aphids.

Once the Aphidoletes have pupated, they will seek out aphids and bore into them to feed. Each can kill up to 65 aphids per day and will kill more aphids than they are able to consume. The Aphidoletes leave what are called aphid mummies attached to the leaf of the plant where they found them. These mummies are the hollowed-out corpses of aphids and also serve as the cocoon where the adult Aphidoletes will lay its eggs.

Encarsia formosa

Encarsia formosa is a species of small, parasitic wasps who love nothing more than to lay their eggs within the larvae of whitefly. The whitefly larva is found on the undersides of leaves, and once they have been injected with the Encarsia formosa's eggs, the affected larvae appear like small dark scales, from which the adult wasp will emerge. Encarsia are most often sold as pupae, which are glued to a perforated card that is placed in a plant infested with adult whitefly. Application of the Encarsia cards, or other carriers, should be done on a weekly basis for up to 10 weeks, even if no whiteflies are visible.

Lures

A separate, but effective biological method of pest control, specifically for thrips, is to use lures baited with a sexual aggression pheromone produced by male thrips. These are generally used in conjunction with a blue, sticky trap card. Thrips are attracted to the color blue. A small vessel containing the pheromone is placed at the bottom of the card and then the card is hung near an infested plant.

The pheromone triggers the mating response in both male and female thrips, luring them away from feeding on your plants. These cards and lures should be used before severe infestations. They should be a part of routine pest control. Beneficial insects should be used in conjunction with the lures to control severe outbreaks of thrips.

Precautions

Beneficial predators and pests are most effectively employed as part of a routine maintenance program. Waiting until the emergence or infestation of pests species in the indoor growing area is too late to be effective. Beneficial insects do not work as quickly as chemical insecticides, but can be just as effective, if not more so, when given ample time to do their work.

All beneficial insects are susceptible to many of the same insecticides (organic or not) as the pest species that they are used to control. In many cases, they are more sensitive to the use of pesticides, as they have not developed some of the same resistance to chemical pesticides that their pest counterparts have evolved. Do not release any beneficial insects, before, during or after the use of insecticides. The use of beneficial insects is an either/or proposition.