Natural Enemies

Horticultural Allies

Natural Enemies

• Organisms that – – kill– decrease the reproductive potential– or otherwise reduce the numbers – of another organism

• Can limit pest damage

Natural Enemies

• Reduce pest populations through– predation – parasitism– herbivory – competition– antibiosis

Predation

• Predators – – attack, kill and feed on several or many

other individuals

• Specialized predators – – feed on a single species or a few closely

related species

• Generalized predators – – feed on a variety of similar organisms

Predators

• Coleoptera – beetles• Hemiptera – true bugs• Diptera – flies• Neuroptera – lacewings • Hymenoptera – wasps• Arachnida – spiders• Vertebrates – birds, reptiles, coyotes,

etc.

Predators

• Predatory mites – family Phytoseiidae– controls pest mites and other insects

• Mites, collembola, flatworms, protozoa and some nematodes control pest nematodes

• Giant amoebae, various soilborne animals are pathogens to fungi and bacteria

Predators

• Birds, bats and fish prey on various insects and other pests

• Raptors, cats and coyotes prey on various pest birds, rodents and other vertebrates

Parasitism

• Parasites – – feed in or on a larger host– prolonged and specialized relationships

with hosts– typically parasitize only one host individual

in their lifetime

Parasites

• Disease producing bacteria, fungi, protozoa, viruses and some nematodes

• May attack invertebrates (insects and nematodes), weeds, pathogens and vertebrates

Parasites

• May weaken hosts without killing it

• Those that significantly weaken or kill the host are important natural enemies in biological control

Parasites

• Pathogens – – parasitic microorganisms – impair normal activities of host tissue or

cells– includes: bacteria, fungi, protozoa and

viruses

• Important controls of insects, nematodes, mites, weeds, and other pathogens

Parasites

• Parasitoid – – insect that parasitizes and kills other

invertebrates – parasitic in immature stage– kills hosts as they enter maturity– adults are free-living– adults about same size as hosts

• Can include – Hymenoptera and Diptera

Parasite vs. Parasitoid

• Parasites derives food from host organisms without killing the host

• Parasitoids end up killing the host before the parasite matures

Internal vs. External Parasites

• Endoparasite – internal– develops inside of the host

Internal vs. External Parasites

• Ectoparasite – external – develops while attached to the outside of

the host

Herbivory

• Herbivores – – animals that feed on plants– important natural enemies of weeds– specialized herbivores selectively feed on

one or several closely related weed species– some limit production by feeding on

flowers or seed

Competition

• Competition – – two or more organisms strive for the same

limited resources – i.e. food, water, shelter or light

• Can limit some weeds• Limited use as a biological control

Antibiosis

• Antibiosis – – substances secreted by organisms

inhibiting vital activities of other organisms

• May be useful in controlling some plant pathogens

• Few current applications

Common Natural Enemies

• Nematode-trapping fungi

Common Natural Enemies

• Predatory nematodes• Not particularly useful

in disturbed soils

Common Natural Enemies

• Decollate snails control . . . – European brown garden snails– citrus thrips – feeds on pupae in soil– can feed on seedlings

Common Natural Enemies

• Predatory mites– occurs in several families– tend to pear-shaped, longer-legged and

shinier than pest mites– more active than plant-feeding mites– feeds on plant-feeding mites, insect eggs,

immatures – crawler stages of scale, thrips and whitefly nymphs

– translucent, bright white, red, yellow, green

Common Natural Enemies

Common Natural Enemies

• Parasitoid wasps control . . . – various Homopterans including: aphids,

whitefly, scale, psyllids, mealybugs, and a host of other pests . . .

– as well as various Lepidopterans

Common Natural Enemies

• Lacewings (Order Neuroptera)– larvae are predaceous– not adults from all species are– feeds on aphids, whiteflies, mealybugs,

caterpillars, mites, psyllids, insect eggs, and other insects

Common Natural Enemies

• Green Lacewing (Chrysopidae)

Common Natural Enemies

• Brown Lacewing (Hemerobiidae)

Common Natural Enemies

• Lady Beetles (Coccinellidae)– over 500 species in America– most are predaceous as larvae and adults– many are prey-specific including various

insects and mites

Common Natural Enemies

Common Natural Enemies

Common Natural Enemies

Common Natural Enemies

• Assassin bugs (Reduviidae) – over 160 species in North America– all are predaceous– some attack mammals– Feeds on a range of insect pests

Common Natural Enemies

• Damsel bugs (Nabidae)– predaceous on mites, aphids, caterpillars,

leafhoppers, etc.– resembles small Reduviidae – long front appendages

Common Natural Enemies

• Syrphid flies (Syrphidae)– AKA hover flies, flower flies– larvae are predaceous – adults often resemble honey bees– feeds on aphids and other soft-bodied

insects

Common Natural Enemies

• Mantids (Mantidae)– praying mantids

or praying mantises

– predaceous – elongated thorax– long, grasping

forelegs – opportunistic and

cannibalistic