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Biological Control and Natural Enemies Integrated Management for Home Gardeners and Landscape Professionals

Biological control is the beneficial are sometimes drastically reduced ticides, but applying these products action of predators, parasites, patho- by naturally occurring , is not considered to be biological gens, and competitors in controlling usually under conditions such as pro- control. pests and their damage. Biocontrol longed high humidity or dense pest provided by these living organ- populations. In addition to naturally Parasites isms (collectively called “natural occurring disease outbreaks, some A parasite is an organism that lives enemies”) is especially important for beneficial pathogens are commer- and feeds in or on a larger . reducing the numbers of pest cially available as biological or - parasites (more precisely and (Table 1). Natural enemies bial . These include called ) are smaller than also control certain rangeland and thuringiensis or Bt, entomopathogenic their host and develop inside, or wildland , such as Klamath , and granulosis . attach to the outside, of the host’s (St. Johnswort). patho- Additionally, some body. Often only the immature stage gens, nematodes, and also by-products such as avermectins and of the parasite feeds on the host, and have many natural enemies, but this spinosyns are used in certain insec- it kills only one host individual dur- biological control is often harder to recognize, less-well understood, or more difficult to manage. Conserva- tion, augmentation, and classical biological control (also called impor- tation) are tactics for harnessing the effects of natural enemies.

TYPES OF NATURAL ENEMIES Predators, parasites, and pathogens are the primary groups used in A. B. biological control of insects. Most parasites and pathogens, and many predators, are highly specialized and attack only one or several closely related pest . Learn how to recognize natural enemies by con- sulting resources such as the Natural Enemies Handbook and the Natural Enemies Gallery online at http:// www.ipm.ucdavis.edu. D. Adult C. Pathogens Pathogens are Figure 1. In many cases, only the immature stage of a parasite feeds on the host, as including certain , fungi, illustrated here with a species that attacks . A. An adult parasite lays an egg nematodes, protozoa, and viruses inside a live . B. The egg hatches into a parasite larva that grows as it feeds that can infect and kill the host. on the aphid’s insides. C. After killing the aphid, the parasite pupates. D. The Populations of some aphids, caterpil- chews a hole and emerges from the dead aphid, then off to find and parasitize lars, mites, and other invertebrates other aphids.

EST OTES Publication 74140 PUniversity of N and Natural Resources October 2007 October 2007 Biological Control and Natural Enemies

Table 1. Some pests and their common natural enemies.

Natural Enemies

Pests Other groups and examples Lacewings Lady Parasitic flies Parasitic Predatory mites

entomopathogenic fungi

aphids • • • syrphid larvae carpenterworm,

• entomopathogenic nematodes clearwing larvae (e.g., California pathogenic fungi and viruses oakworm) predaceous wasps spp.(egg parasitic wasps) • • • Cryptochaetum iceryae (parasitic fly)

cottony cushion scale • • vedalia Erynniopsis antennata (parasitic fly)

elm leaf beetle • • Oomyzus (=Tetrastichus) spp. (parasitic wasps) Avetianella longoi (egg parasitic wasp)

eucalyptus longhorned borers • Syngaster lepidus (larval parasitic wasp)

eucalyptus redgum lerp psyllid • • Psyllaephagus bliteus (parasitic wasp) Entedononecremnus krauteri, Encarsiella noyesii, and

giant • • • • Idioporus affinis (parasitic wasp)

glassy-winged sharpshooter • Gonatocerus spp. (egg parasitic wasps) pirate bugs lace bugs • • • spiders

• • • • destroyer lady beetle

mosquitoes Bacillus thuringiensis ssp. israelensis

psyllids • • • pirate bugs

scales • • • • Aphytis spp. (armored scale parasites) Rumina decollata (predatory snail) slugs, snails predaceous ground beetles • vertebrates

sixspotted mites

• • • Stethorus picipes (spider destroyer lady beetle)

thrips • • predatory thrips Steinernema carpocapsae and , root or -dwelling Heterorhabditis bacteriophora (entomopathogenic nematodes)

Encarsia formosa ( whitefly parasite) pirate bugs • • •

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ing its development (Figure 1). How- spp., Neoseiulus spp., and the western groups. ever, adult females of certain para- predatory mite (Galendromus occiden- sites (such as many wasps that attack talis). CONSERVATION: scales and whiteflies) feed on their PROTECT YOUR hosts, providing an easily overlooked Recognizing Natural Enemies. NATURAL ENEMIES but important source of biological Proper identification of pests, and Preserve naturally occurring benefi- control in addition to the host mortal- distinguishing pests from their cial organisms whenever possible. ity caused by . natural enemies, are essential to Most pests are attacked by several effectively using biological control. different types and species of natural Most parasitic insects are either flies For example, some people may mis- enemies, and their conservation is the (Diptera) or wasps (). take aphid- syrphid fly larvae primary way to successfully use bio- Parasitic Hymenoptera occur in over for caterpillars. The adult syrphid, logical control in gardens and land- three dozen families. For example, commonly also called a fly or scapes (Figure 2). control, Aphidiinae (a subfamily of Braco- hover fly, is sometimes mistaken for manipulation, and selective nidae) attack aphids. Trichogram- a . Consult publications use are key conservation strategies. matidae parasitize insect . Aph- such as the UC Statewide Integrated elinidae, , , and Pest Management Program Pest Notes Pesticide Management are other groups of series listed in Suggested Reading Broad-spectrum pesticides often kill tiny size to medium-sized wasps that to learn more about the specific a higher proportion of predators and parasitize pests but do not sting peo- pests and their natural enemies in parasites than of the pest species ple. The most common parasitic flies your gardens and landscapes. Take they are applied to control. In addi- are . Adult tachinids often unfamiliar organisms you find to tion to immediately killing natural resemble house flies. Their larvae are your Cooperative Extension office or enemies that are present (contact tox- icity), many pesticides are persistent maggots that feed inside the host. county agriculture commissioner for materials that leave residues that kill an expert identification. Carefully natural enemies that migrate in after Predators observe the creatures on your spraying (residual toxicity). Residues Insects are important food for many to help discern their activity. For often are toxic to natural enemies , birds, , and example, to distinguish plant-feed- long after pests are no longer affected. reptiles. Many beetles, true bugs ing mites from predaceous mites, Even if beneficials survive an applica- ( or Heteroptera), flies, observe them on your plants with a tion, low levels of pesticide residues and lacewings are predators of vari- good hand lens. Predaceous species can interfere with natural enemies’ ous pest mites and insects (Table 2). appear more active than plant-feed- reproduction and their ability to Most spiders feed entirely on insects. ing species. In comparison with pest locate and kill pests. Predatory mites that prey primarily mites, predaceous mites are often Amblyseius on spider mites include larger and do not occur in large Biological control’s importance often becomes apparent when broad-spec- Table 2. Some important predaceous insects. trum, persistent pesticides cause Common name Examples secondary pest outbreaks or pest resurgence. A secondary outbreak aphid flies Chamaemyia spp., Leucopis spp. of a different species occurs when assassin bugs pesticides applied against a target pest kill natural enemies of other spe- brown lacewings Hemerobius spp. cies, causing the formerly innocuous green lacewings spp., spp. species to become pests (Figure 3). An example is the dramatic increase ground beetles Calosoma spp., Calathus spp. in populations that lady beetles convergent lady beetle, mealybug destroyer, sometimes results after applying a multicolored Asian lady beetle carbamate (e.g., carbaryl or Sevin) or organophosphate (malathion) to con- minute pirate bugs spp., Anthocoris spp. trol caterpillars or other pests. predaceous midges (aphid midges) Aphidoletes aphidimyza Eliminate or reduce the use of broad- predaceous thrips black hunter thrips, sixspotted thrips spectrum, persistent pesticides soldier beetles Cantharis spp. whenever possible. Carbamates, organophosphates, and pyrethroids syrphid flies (flower flies, hover flies) Metasyrphus spp., Scaeva spp. are especially toxic to natural enemies (Table 3). When pesticides

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are used, apply them in a selective manner. Treat only heavily infested spots instead of entire plants. Choose that are more specific in the types of invertebrates they kill, such as Bacillus thuringiensis (Bt) that kills only caterpillars that eat treated foliage. Rely on insecticides with little or no persistence, includ- ing , horticultural or narrow-range oil, and pyrethrins.

A less-persistent pesticide can result in longer control of the pest in situ- ations where biological control is important because the softer pes- ticide will not keep killing natural enemies. One soft pesticide spray plus natural enemies can be effective for longer than the application of one hard spray.

Ant Control and Figure 2. Most pests are attacked by a complex of natural enemies. Shown here is a Producers lace bug surrounded by its common predators. Conserving these beneficial species are beneficial as consumers is the primary way to successfully use biological control in gardens and landscapes. of weed , predators of many Each pest life stage can be killed by various other species of parasites, pathogens, insect pests, soil builders, and nutri- and predators not illustrated here. ent cyclers. Ants may attack people and or are direct pests of crops, feeding on nuts or fruit (See Pest Table 3. Relative toxicity to natural enemies of certain groups. Notes: Red Imported Fire Ants). The and certain other spe- cies are pests primarily because they feed on honeydew produced by Insecticide Toxicity Homopteran insects such as aphids, mealybugs, soft scales, and whiteflies. Bacillus thuringiensis (Bt) No contact—No residual Ants protect honeydew producers from predators and parasites that botanicals (e.g., azadirachtin, Moderate to high contact—No residual to might otherwise control them. Ants pyrethrins), oils, soaps, spinosad short residual sometimes move these honeydew- producing insects from plant to plant. chloronicotinyls (imidacloprid, Bayer Low to high1 Where natural enemies are present, Advanced Tree & Shrub or Merit) if ants are controlled, populations of carbamates (carbaryl or Sevin), High contact—Long residual many pests will gradually (over sev- organophosphates (malathion), eral generations of pests) be reduced pyrethroids (permethrin) as natural enemies become more abundant. Control methods include Direct contact toxicity is killing within several hours from spraying the beneficial or its cultivating soil around ant , habitat. encircling trunks with ant barriers, Residual toxicity is killing or sublethal effects (such as reduced reproduction or and applying insecticide baits near impaired ability to locate and kill pests) due to residues that persist. plants. See Pest Notes: Ants for more information. 1 Toxicity and persistence are highly variable, depending partly on the application method (foliar spray vs. soil drench) and the life stage and species of the natural enemy. Habitat Manipulation Manage gardens and landscapes by using cultural and mechanical methods that enhance natural enemy effectiveness. Grow diverse plant

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species and tolerate low populations ever, lady beetles purchased through native habitat, study and collect the of plant-feeding insects and mites so retail outlets are unlikely to be suf- natural enemies that kill the pest that some food is always available to ficient in numbers and quality to pro- there, and then ship promising natu- retain predators and parasites. Plant vide control. ral enemies back for testing and pos- a variety of sequentially flowering sible release. Many insects and some species to provide natural enemies Successful augmentation generally weeds that were widespread pests with , , and shelter requires advanced planning, bio- in California are now partially or throughout the growing season. The logical expertise, careful monitoring, completely controlled by introduced adult stage of many insects with pre- optimal release timing, patience, and natural enemies, except where these daceous larvae (such as green lace- situations where certain levels of natural enemies are disrupted, such wings and syrphid flies) and many pests and damage can be tolerated. as by pesticide applications or honey- adult parasites feed only on pollen Desperate problems where pests or dew-seeking ants. and nectar. Even if pests are abun- damage are already abundant are not dant for the predaceous and parasitic good opportunities for augmentation. Natural enemy importation by law stages, many beneficials will do must be done only by qualified sci- poorly unless flowering and nectar- CLASSICAL BIOLOGICAL entists with government permits. producing plants are available to CONTROL OR Natural enemies are held and studied adult natural enemies. Reduce dust, IMPORTATION in an approved quarantine facility to for example, by planting ground Classical biological control, also prevent their escape until research covers and windbreaks. Dust can called importation, is primarily used confirms that the natural enemy will interfere with natural enemies and against exotic pests that have inad- have minimal negative impact in the may cause outbreaks of pests such as vertently been introduced from else- new country of release. Because clas- spider mites. Avoid excess fertiliza- where. Many organisms that are not sical biological control can provide tion and , which can cause pests in their native habitat become long-term benefits over a large area phloem-feeding pests such as aphids unusually abundant after colonizing and is funded through taxes, pub- to reproduce more rapidly than natu- new locations without their natural lic support is critical for continued ral enemies can provide control. controls. Researchers go to the pest’s success. Consult Natural Enemies AUGMENTATION When resident natural enemies are insufficient, their populations can Pest A: aphids sometimes be increased (augmented) Pest B: spider mites through the purchase and release of commercially available beneficial Natural enemies: species. However, there has been green lacewing larvae relatively little research on releas- predatory mites ing natural enemies in gardens and landscapes. Releases are unlikely to provide satisfactory in most situations. Some marketed nat- ural enemies are not effective. Pray- ing mantids, often sold as egg cases, make fascinating pets. But mantids are cannibalistic and feed indiscrimi- nately on pest and beneficial species. Releasing mantids does not control pests. A pesticide applied to control pest A Released from the control exerted by also kills natural enemies that are natural enemies, pest B builds up to Only a few natural enemies can be controlling pest B. economically damaging levels. effectively augmented in gardens and landscapes. These include entomoph- agous nematodes, predatory mites, Figure 3. Killing natural enemies often results in secondary outbreaks of insects and mites. For example, spider mites are often present on plants at low densities but and perhaps a few other species. For become excessively abundant and cause damage when pesticides applied against example, convergent lady beetles other species kill the natural enemies of the spider mites. Here a pesticide applied to () purchased in kill aphids (Pest A) not only killed aphids but also killed predaceous green lacewing bulk through mail order and released larvae and predatory mites, leading to a secondary outbreak of spider mites (Pest B). in very large numbers at intervals Insecticides applied during hot weather appear to have the greatest effect on mites, can temporarily control aphids; how- sometimes causing dramatic mite outbreaks within a few days after spraying.

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Handbook and Pests of Landscape Trees control. Natural enemies that do not WORLD WIDE WEB SITES and Shrubs to learn about situations arrive or become abundant until after Biological Control: A Guide to Natu- where imported natural enemies are pests are very abundant may not pre- ral Enemies in . Cor- important and conserve them when- vent serious damage to plants. Con- nell University. www.nysaes.cornell ever possible. versely, a parasite or predator with .edu/ent/biocontrol multiple annual generations, that can Is Biological Control “Safe”? attack a broad range of life stages of Biological Control Information Cen- One of the great benefits of biologi- the pest and can feed and reproduce ter North Carolina State Univ. http:// cal control is its relative safety for when pest populations are low or cipm.ncsu.edu/ent/biocontrol health and the environ- moderate, will likely be a more effec- ment. Most negative impacts from tive natural enemy. Biological Control News, Midwest exotic species have been caused by University of Wisconsin-Madison, undesirable organisms contaminat- Dept. of . www.entomol- ing imported goods, by travelers SUGGESTED READING ogy.wisc.edu/mbcn/mbcn.html carrying in pest-infested fruit, by 1Natural Enemies Handbook: The Illus- introduced ornamentals that escape trated Guide to . Center for Biological Control, www. cultivation and become weeds, and 1998. M. L. Flint and S. H. Dreistadt. cnr.berkeley.edu/biocon by poorly conceived importations Univ. Calif. Div. Agric. Nat. Res. Publ. of predatory vertebrates like mon- 3386. Oakland. UC Statewide IPM Program Natural gooses. These ill-advised or illegal Enemies Gallery, an online photo- importations are not part of biologi- 1Pest Notes: Ants. Feb. 2007. M. K. graphic reference, www.ipm cal control. To avoid these problems, and J. H. Klotz. Oakland. Univ. Calif. .ucdavis.edu/PMG/NE/index.html v biological control researchers follow Agric. Nat. Res. Publ. 7411. Also avail- regulations and work with relatively able online, http://www.ipm.ucdavis. host-specific insects. edu/PMG/menu.invertebrate.html 1 University of California Agriculture and Natural Resource publications may be ordered online or Help preserve our environment and 1Pest Notes: Red Imported . via telephone. avoid introducing exotic new pests. Sept. 2007. L. Greenberg, J. H. Klotz, • Toll free order line: (800) 994-8849 and J. N. Kabashima. Oakland. Univ. • Voice: (510) 642-2431 • Fax: (510) 643-5470 Do not bring uncertified fruit, plants, Calif. Agric. Nat. Res. Publ. 7487. Also • http://anrcatalog.ucdavis.edu or soil into California. Take unfamil- available online, http://www.ipm iar pests to your county agricultural .ucdavis.edu/PMG/menu.invertebrate commissioner or Cooperative Exten- .html sion office for identification. 1Pest Notes: Spiders. In press. R. S. Vet- WHAT MAKES ter. Oakland. Univ. Calif. Agric. Nat. AN EFFECTIVE Res. Publ. 7442. Also available online, NATURAL ENEMY? http://www.ipm.ucdavis.edu/PMG/ Although many prey on menu.invertebrate.html pest insects or mites, not all can be relied upon to reduce a pest popula- 1Pest Notes: Spider Mites. Dec. 2000. B. tion enough to protect plants. The Ohlendorf and M. L. Flint, eds. Oak- most effective natural enemies are land. Univ. Calif. Agric. Nat. Res. Publ. often relatively host specific, feeding 7405. Also available online, http:// on a single pest species or a group www.ipm.ucdavis.edu/PMG/menu. of similar pests such as aphids or invertebrate.html scales. Good examples include preda- tory mites, most parasitic wasps, and 1Pests of Landscape Trees and Shrubs. syrphid flies. Very general predators 2004. S. H. Dreistadt, M. L. Flint, and such as praying mantids are often J. K. Clark. Univ. Calif. Agric. Nat. likely to kill as many beneficials as Res. Publ. 3359. Oakland. pests and thus rarely provide effec- tive control.

Synchronization of the life cycle and environmental requirements of the pest and natural enemy also deter- mine the effectiveness of biological

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For more information contact the University of California Cooperative Extension in your county. See your telephone directory for addresses and phone numbers.

AUTHOR: S. H. Dreistadt, UC Statewide IPM Program, Davis TECHNICAL EDITOR: M. L. Flint COORDINATION & PRODUCTION: P. N. Galin ILLUSTRATIONS: Fig. 1: D. Kidd. Fig. 2: assassin bug: Zimmerman, E. C. 1948. Insects of . Volume 3: Heterop- tera. Honolulu: University of Hawaii Press; lacewing larva and pirate bug: by Celeste Green in Smith, R. F., and K. S. Hagen. 1956. Enemies of spotted aphid. Calif. Agric. 10(4):8–10; lady beetle: Simanton, F. L. 1916. Hyperaspis binotata, a predatory enemy of the terrapin scale. J. Agric. Res. 6:197–204; spider: Costello, M. J., M. A. Mayse, K. M. Daane, W. A. O’Keefe, and C. B. Sisk. 1995. Spiders in San Joaquin Valley Vineyards. Oakland. Univ. Calif. Div. Agric. Nat. Res. Leaflet 21530; predatory mite: Denmark, H. A., and E. Schicha. 1983. Revision of the Phytoseiulus Evans (Acarina: ). Internat. J. Acarol. 9:27–35;. Fig. 3: V. Winemiller. WARNING ON THE USE OF CHEMICALS Produced by UC Statewide IPM Program, Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations University of California, Davis, CA 95616 given on the container label. Store all chemicals in the original labeled containers in a locked cabinet or shed, away from food or feeds, and out of the reach of children, unauthorized persons, pets, and . This Pest Note is available on the Pesticides applied in your home and landscape can move and contaminate creeks, rivers, and oceans. World Wide Web (www.ipm.ucdavis.edu) Confine chemicals to the property being treated. Avoid drift onto neighboring properties, especially gardens containing fruits or vegetables ready to be picked. Do not place containers containing pesticide in the trash or pour pesticides down sink or toilet. Either use the pesticide according to the label or take unwanted pesticides to a Household Hazardous Waste Collection site. Contact your county agricultural commissioner for additional information on safe container disposal and for the location of the Household Hazardous Waste Collection site nearest you. Dispose of empty containers by following label directions. Never reuse or burn the containers or dispose of them in such a manner that they may contaminate water supplies or natural waterways. This publication has been anonymously peer reviewed for technical accuracy by University of The University of California prohibits discrimination or harassment of any person on the basis of race, California scientists and other qualified profession- color, national origin, religion, , gender identity, pregnancy (including childbirth, and medical condi- als. This review process was managed by the ANR tions related to pregnancy or childbirth), physical or mental disability, medical condition (cancer-related Associate Editor for Urban Pest Management. or genetic characteristics), ancestry, marital status, age, sexual orientation, citizenship, or status as a To simplify information, trade names of products covered veteran (covered veterans are special disabled veterans, recently separated veterans, have been used. No endorsement of named products era veterans, or any other veterans who served on active duty during a or in a campaign or expedi- is intended, nor is criticism implied of similar products tion for which a campaign badge has been authorized) in any of its programs or activities. University that are not mentioned. policy is intended to be consistent with the provisions of applicable State and Federal laws. Inquiries This material is partially based upon work supported regarding the University’s nondiscrimination policies may be directed to the Affirmative Action/Staff Per- by the Extension Service, U.S. Department of sonnel Services Equal Opportunity Director, University of California, Agriculture and Natural Resources, Agriculture, under special project Section 3(d), 1111 Franklin Street, 6th Floor, Oakland, CA 94607, (510) 987-0096 Integrated Pest Management.

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