Use Good Bugs to Control Bad Bugs: Predatory insects / by Ganpati Jagdale

Before starting to write about this topic, I would like to make it clear that taxonomically all bugs are insects but all the insects are not bugs. As far as I know, both in the USA and Canada, almost all people except entomologists call each and every insect as a bug.  Even extension entomologists when they are giving extension seminars to farmers/growers about insect pests of different crops, they often refer them as bad bugs for the understanding of growers. "True" bugs are mainly belong to two insect orders including Hemiptera and Homoptera. All natural enemies of insect pests are considered as good bugs because they can kill and feed on insect pests that cause tremendous yield losses to many economically important crops. Since many of these natural enemies are commercially produced and used in the integrated pest management program (IPM), they are called as biological control agents. These biological control agents can be parasitic or predatory insects.  In addition to these predators and parasites (good bugs), there are some microorganisms such as bacteria, fungi, protozoa and viruses that can cause diseases and kill insect pests.  These microorganisms are termed as insect pathogens and also considered as biological control agents. Nematodes belonging to two families, Steinernematidae and Heterorhabditidae are also considered as insect parasites or pathogens and used as biological agents in controlling many soil dwelling insect pests of many economically important crops (in this blog, please read several posts that are devoted to insect- parasitic nematodes). Furthermore, mites are closely related to spiders but not considered as insects. Some species of mites are predatory in nature but others are serious pests of many plant species.

Predators: Although, there are many kinds of vertebrate predators including birds, amphibians, reptiles, fish and mammals that feed on insects, in this blog I am going to focus on the predatory insects that are generally used in biological control programs. These insects are called predators because they feed and complete their entire life cycle by remaining outside of their prey host as opposed to parasites that complete at least part of their life cycle inside their hosts.  Predators are generally larger than their prey, they kill and feed on both immature and adult stages of many different kinds of hosts.

Following are the examples of insect predators that can be used as biological control agents against many kinds of insect pests.

Aphid midge (Aphidoletes aphidimyza): This predatory midge fly often found in many vegetable crops (potatoes, cabbage and cauliflower), fruit orchards (apple, blueberries and peaches) and many ornamental plants throughout North America. The larval stages of this midge fly are mainly predators of aphids. This midge fly is commercially available and widely used as biocontrol agents in the greenhouses against over 60 species of aphids infesting both vegetable and ornamental plants.

Bigeyed bug (Geocoris spp.): There are four most common species of bigeyed bug (G. punctipes, G. pallens, G. bullatus and G. uliginosus) found in almost all cropping systems in North America.  Bigeyed bugs generally feed on many small insects including aphids, mites and whiteflies, eggs and nymphs of many plant bugs. They can also feed on eggs and small larval stages of cotton ballworms, pink ballworms and tobacco budworms. Since this bug is very susceptible to broad spectrum pesticides, care should be taken to avoid killing of this important biocontrol agent.  This predator is commercially available from insectories in the USA.

Brown lacewings (Hemerobius stigma): These lacewings found throughout North American forests and are mainly predators of aphids and many other soft-bodied small insects including balsam woolly adelgis (Adelges piceae), pine bark adelgid (Pineus strobi) and Cooley's spruce gall adelgid (Adelges cooleyi). These lacewings are not commercially available.

Deraeocoris bug (Deraeocoris nebulosus): This is a very important predator of many insect and mite pests different agricultural, horticultural and landscape plants in the Canada and USA. This is a true predatory bug, which is generally found in many fruit orchards including apple, peach and pecan.  They also found in cotton fields and many landscape settings.  These bugs are natural enemies of many small insects including aphids, lace bugs, psyllids, scales and whiteflies. They also feed on mites. These bugs are not commercially available.

Dragon and damselflies: Adult dragon and damsel flies generally feed on small flying small adult insects including midge flies, mayflies, mosquitoes, ants and termites in the air where as dragon/damsel fly nymphs feed on mosquito larvae in the water.

Green lacewing (Chrysoperla carnea, C. rufilabris): Lacewings adults are not predatory in nature but mainly feed on nectar, honeydew and pollens.  However, larvae of lacewings are predatory in nature and feed on insect pests of many crops including apples, asparagus, cotton, corn, cole crops, eggplants, leafy vegetables, potatoes, tomatoes, peppers and strawberries. Lacewing larvae generally prey on aphids, leafhopper eggs, eggs of butterflies and moths, mealybugs, mites, thrips, small larvae of beetles and moths. Both species of lacewings are commercially available and sold in all stages (eggs, larvae and adults).

Ladybird beetles (Hippodamia parenthesis and Harmonia axyridis): These beetles are also recognized as lady beetles or ladybugs and more than 450 of this beetles have been reported from North America. Both larval and adult stages of this predator found on many agricultural and ornamental plants and they primarily feed on aphids. In addition, they can feed on small insects, mites, scales, thrips and eggs of many moths and beetles. they can eat nectar or pollen if insect hosts are not around. These predators are now commercially available to use against many crop pests, especially aphids.

Lebia beetles (Lebia grandis): These beetles are natural enemies of Colorado potato beetle, Leptinotarsa decemlineata. Adults of the predatory insect can feed on all immature stages of colorado potato beetle. Larval stages of Labia beetles are generally parasitic in nature and therefore, they are considered as ectoparasites of larval and pupal stages of colorado potato beetles. These predators are not commercially produced.

Pirate bugs (Orius spp.): Both adults and nymphs of these predatory insects have a sharp, needle-like beak that they use to suck body content of their prey. These insects found in many crops including alfalfa, corn, cotton, pea, peanuts, and strawberries. These are predators of aphids, mites, thrips, small larval stages of many insects, eggs of many different kinds of insects. These insect predators are commercially available in the USA and most often suscessfully used as biocontrol agents in controlling greenhouse pests.

Rove beetles (Aleochara bilineata): These beetles naturally found in many vegetable crops including onions, different cole crops, turnip, radish and sweet corn.  Rove beetle adults are predatory in nature but their larval stages are parasitic in nature. Rove beetles generally feed on egg, larval and pupal stages of onion and cabbage maggots. These insects are not commercially available.

Soldier beetles (Chauliognathus marginatus and C. pennsylvanicus): These beetles are also called leatherwing beetle because of texture of their wings. Larvae of this insect mainly feed on grasshopper eggs, both adult and nymphal stages of aphids, soft bodied larvae of many insects (cutworms, gypsy moths) whereas adults mainly feed on adult aphids and other soft bodied insects. These predators also feed on snails and slugs. These insects are not pest any plant species but they can eat nector or pollen if insect hosts are not around.

Spined soldier bug (Podisus maculiventris): This is a "true bug" that also named as a stink bug because it emits a strong stinky odour when disturbed. Like Pirate bugs, this bug also uses its sharp beak to suck the body content of its prey. This predator feeds on immature stages of many insect pests including beet armyworm, cabbage loopers, cabbageworm, colorado potato beetle, corn earworm, diamond backmoth, Eropean corn borer, fall armyworms, flea beetles, Mexican bean beetle and velvetbean caterpillars. These insect predators are commercially available.