Biocontrol on Farm and at Home

RECOGNIZING NATURAL ENEMIES

Proper identification of pests, and distinguishing pests from natural enemies, is essential for effective biological control. Carefully observe the mites and insects on your plants to help discern their activity. For example, some people may mistake syrphid fly larvae for caterpillars. However, syrphid fly larvae are found feeding on aphids and not chewing on the plant itself. If you find mites on your plants, observe them with a good hand lens. Predaceous mites appear more active than plant-feeding species. In comparison with pest mites, predaceous mites are often larger and do not occur in large groups.

Consult publications listed in the References to learn more about the specific pests and their natural enemies in your gardens and landscapes. Take unfamiliar organisms you find to your local University of California (UC) Cooperative Extension office, UC Master Gardener Program, or agricultural commissioner office in your county for aid in identification.

CONSERVATION: PROTECT NATURAL ENEMIES

Preserve existing natural enemies by choosing cultural, mechanical, or selective chemical controls that do not harm beneficial species. Remember, only about 1% of all insects and mites are harmful. Most pests are attacked by multiple species of natural enemies (Table 1), and their conservation is the primary way to successfully use biological control. Judicious (e.g., selective, timing) pesticide use, ant control, and habitat manipulation are key conservation strategies.

Ant Control and Honeydew Producers

The Argentine ant and certain other ant species are considered pests primarily because they feed on honeydew produced by insects that suck phloem sap, such as aphids, mealybugs, soft scales, psyllids, and whiteflies. Ants protect honeydew producers from predators and parasites that might otherwise control them. Ants sometimes move these honeydew-producing insects from plant to plant (called “farming”). Where natural enemies are present, if ants are controlled, populations of many pests will gradually (over several generations of pests) be reduced as natural enemies become more abundant. Control methods include cultivating soil around ant nests, encircling trunks with ant barriers of sticky material, and applying insecticide baits near plants. See Pest Notes: Ants for more information.

Mark Hoddle at UC Riverside is working on a gel formulation to attract ants selectively for their control: http://biocontrol.ucr.edu/hoddle/.

Habitat Manipulation

Plant a variety of species that flower at different times to provide natural enemies with nectar, pollen, and shelter throughout the growing season. The adult stage of many insects with predaceous larvae (such as green lacewings and syrphid flies) and many adult parasites feed only on pollen and nectar. Even if pests are abundant for the predaceous and parasitic stages, many beneficials will do poorly unless flowering and nectar-producing plants are available to supplement their diet. To retain predators and parasites, grow diverse plant species well adapted to the local conditions and that tolerate low populations of plant-feeding insects and mites so that some food is always available.

Other cultural controls that can help natural enemies include reducing dust and properly fertilizing and irrigating. Dust can interfere with natural enemies and may cause outbreaks of pests such as spider mites. Reduce dust by planting ground covers and windbreaks and hosing off small plants that become excessively covered with dust.  Avoid excess fertilization and irrigation, which can cause phloem-feeding pests, such as aphids, to reproduce more rapidly than natural enemies can provide control.

REFERENCES

Dreistadt, S.H., M.L. Flint, and J.K. Clark. 2004. Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide. 2^nd ed. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 3359.

Flint, M.L. and S.H. Dreistadt. 1998. Natural Enemies Handbook: The Illustrated Guide to Biological Pest Control. Oakland: Univ. Calif. Div. Agric. Nat. Res. Publ. 3386.

Rust, M.K. and D.-H. Choe. 2012. Pest Notes: Ants. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7411.

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NATURAL ENEMIES

PESTS

Lacewings

Lady beetles

Parasitic flies

Parasitic wasps

Predatory mites

Other Groups and Examples

aphids

X

X

X

entomopathogenic fungi, soldier beetles, syrphid fly larvae

carpenterworm, clearwing moth larvae

X

entomopathogenic nematodes

caterpillars (e.g., California oakworm)

X

X

X

Bacillus thuringiensis, birds, entomopathogenic fungi and viruses, predaceous bugs and wasps,Trichogramma spp. (egg parasitic wasps), spiders

cottony cushion scale

X

X

Cryptochaetum iceryae (parasitic fly), vedalia beetle

elm leaf beetle

X

X

Erynniopsis antennata (parasitic fly),Oomyzus (=Tetrastichus) spp. (parasitic wasps)

eucalyptus longhorned borers

X

Avetianella longoi (egg parasitic wasp)

eucalyptus redgum lerp psyllid

X

Psyllaephagus bliteus (parasitic wasp)

giant whitefly

X

X

X

Encarsia hispida, Encarsia noyesi, Entedononecremnus krauteri, andIdioporus affinis (parasitic wasp), syrphid fly larvae

glassy-winged sharpshooter

X

X

assassin bugs, Gonatocerus spp. (egg parasitic wasps), spiders

lace bugs

X

X

X

assassin bugs and pirate bugs, spiders

mealybugs

X

X

X

mealybug destroyer lady beetle

mosquitoes

Bacillus thuringiensis spp. israelensis, mosquito-eating fish

psyllids

X

X

X

pirate bugs

scales

X

X

X

X

Aphytis, Coccophagus, Encarsia, andMetaphycus spp. parasitic wasps

slugs, snails

X

Rumina decollata (predatory snail), predaceous ground beetles, birds, snakes, toads, and other vertebrates

spider mites

X

X

X

bigeyed bugs and minute pirate bugs,Feltiella spp. (predatory cecidomyiid fly larvae), sixspotted thrips, Stethorus picipes (spider mite destroyer lady beetle), predatory mites

thrips

X

X

X

minute pirate bugs, predatory thrips

weevils, root or soil-dwelling

X

Steinernema carpocapsae andHeterorhabditis bacteriophora(entomopathogenic nematodes)

whiteflies

X

X

X

bigeyed bugs and minute pirate bugs,Cales, Encarsia, and Eretmocerus spp. parasitic wasps, spiders