Using Biological Control in the Home Vegetable Garden

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Using Biological Control in the Home Vegetable
Garden

• Susan Mahr
• University of Wisconsin - Madison

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Program Overview

• What is biological control?
• Natural enemies
• Implementing biocontrol
• Some common beneficials and their use in
  biocontrol in vegetable gardens

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Biological Control

• Purposeful manipulation of natural enemies to
  reduce pest numbers
• Biological control builds on what nature provides
  us
• NATURAL CONTROL is all the combined effects of
  the natural environment that help control pest
  populations includes weather

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Natural Enemies

• Beneficial insects or other organisms that
  destroy harmful insects
• Predators eat other insects
• Parasitoids develop in other insects
• Pathogens cause diseases in insects

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Predators

• Eat other insects
• Usually larger than their prey
• Consume many prey
• Feed as adults and/or immatures

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Predators

• Generally fairly mobile
• Most have fairly broad host range
• May be large, conspicuous

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Parasitoids

• Smaller than their host
• Only the larval stage is parasitic
• Immatures develop in/on other insects
• A single host for development

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Parasitoids General Life Cycle
Tachinid fly
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Parasitoids

• Adults free-living, usually winged and mobile
• Tend to be host-specific
• Often small, inconspicuous

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Pathogens

• Disease-causing organisms
• Bacteria
• Fungi
• Viruses
• Microsporidia
• Must be eaten
• Some kill quickly, some kill slowly, others just
  debilitating

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Nematodes

• Roundworms
• Several species commercially available
• Need to know host

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Implementing Biocontrol

• Simply learning to recognize natural enemies and
  their actions is the most important step in
  accomplishing biological control
• Implementing biocontrol in the home garden
• Conservation
• Augmentation

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Implementing Biocontrol

• Importation
• www.entomology.wisc.edu/mbcn/fea103.html
• Augmentation
• www.entomology.wisc.edu/mbcn/fea104.html
• Conservation
• www.entomology.wisc.edu/mbcn/fea201.html

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Biocontrol Conservation

• Keep what you have!
• Avoid / reduce broad-spectrum and preventative
  pesticides
• Increase garden diversity to provide alternate
  food and shelter

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Reducing Pesticide Impacts

• Most insecticides are more toxic to natural
  enemies than to pests
• More selective materials include insecticidal
  soaps and microbial insecticides
• Many botanical insecticides such as pyrethrum
  are directly toxic to natural enemies, but are
  very short-lived
• Use spot treatments if possible
• Consider cultural controls also

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Adult Nectar Resources

• Various species
• Annuals, biennials and perennials
• Small nectaries for small insects!

Alfalfa Medicago sativa
Yellow rocket Barbarea vulgaris
Queen Annes Lace Daucus carota
Butterflyweed Asclepias
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Adult Nectar Resources
Yarrow (Achillea millefolium)
Cilantro (Coriandrum sativum)
Sweet Alyssum (Lobularia maritima)
Dill (Anethum graveolens)
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Biocontrol Augmentation

• Sometimes natural enemies dont occur in large
  enough numbers at the right time to be effective
• Add natural enemies in a timely fashion when
  needed
• Many types of general and specialized natural
  enemies are commercially available
• Need to know pest and plant to choose best
  species for control
• No recipes for success

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Releasing Natural Enemies

• Inundation
• Inoculation
• Sources
• Suppliers of Beneficial Organisms in North
  America
• www.cdpr.ca.gov/docs/ipminov/bensuppl.htm

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Using Pathogens

• Marketed as microbial insecticides
• BT (Bacillus thuringiensis)
• Different types of Bt for caterpillars,
  fungus gnats and a few beetles
• Beauveria bassiana
• Nematodes

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The Cast of CharactersSome common biocontrol
agents
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Lady BeetlesFamily Coccinellidae

• Many species
• Eat soft-bodied insects, especially aphids
• Larvae often unrecognized

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Lady Beetles for Biocontrol

• Convergent lady beetle most often sold
• Adults can fly away
• Some specialist species

Spider mite destroyer
Mealybug destroyer
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Green LacewingsFamily Chrysopidae

• Adults have membranous wings
• Eggs laid on stalks
• Larvae have sickle-shaped mouthparts
• All larvae, some adults predators
• Feed on aphids, other soft-bodied insects
• Adults require honeydew or nectar

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Green Lacewings for Biocontrol

• Sold as eggs hatch to voracious larvae
• Better choice than lady beetles for release
  against aphids, soft-bodied insects

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Minute Pirate BugsFamily Anthocoridae

• 1-2 mm
• Black and white
• Feed on mites, insects eggs and small insects
• Orius species

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Minute Pirate Bugs for Biocontrol

• Several species commercially available
• Used against
• Aphids
• European corn borer and
  corn earworm on corn
• Potato aphids and potato
  leafhopper nymphs
• Codling moth eggs
• Whiteflies
• Spider mites

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Stink BugsFamily Pentatomidae

• Medium sized
• Green, brown, black
• Produce foul odor when bothered
• Not all predators some important pests
• Feed on caterpillars, beetle larvae and adults
  (e.g. Colorado potato beetle, Mexican bean
  beetle), others

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Stink Bugs for Biocontrol

• Perillus bioculatus (twospotted stink bug)
• Podisus maculiventris (spined soldier bug)

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Flower or Hover FliesFamily Syphidae

• Adults look like bees
• Larvae look like miniature slugs
• Larvae eat soft-bodied insects, especially aphids

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Syrphid Flies for Biocontrol

• Not sold commercially
• Many species
• Important in natural control
• Related fly, aphid midge, sold for use in
  greenhouses

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Ground BeetlesFamily Carabidae

• 40,000 species worldwide
• Usually dark colored, nocturnal
• Adults feed on caterpillars, grubs, maggots,
  earthworms
• Larvae also predaceous

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Ground Beetles for Biocontrol

• Not commercially available
• Many species, small to large
• Various habitats and prey
• Important in natural control

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Predatory Mites

• Many species in Phytoseiidae
• Feed on two-spotted spider mite and other
  phytophagus mites

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Predatory Mites for Biocontrol

• Many species commercially available for different
  conditions
• Phytoseiulus persimilis
• P. macropilis
• Galendromus occidentalis
• Mesoseiulus longipes
• Neoseiulus (Amblysius)
  californicus
• Used in greenhouses, fruit, other crops
• (minute pirate bugs can also be used against
  spider mites)

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Predatory Hymenoptera

• Large wasps in Sphecidae (muddaubers) and
  Vespidae (paper wasps, yellowjackets)
• Ants
• Feed on caterpillars, various insects

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Other Predators

• Other bugs (assassin, big-eyed, damsel)
• Rove beetles
• Spiders
• Fireflies

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Tachinid FliesFamily Tachinidae

• 1,300 species in North America
• All species parasitic
• Resemble bristly houseflies
• Most attack caterpillars and beetles
• Voria ruralis parasitizes
  cabbage looper

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Wasps for Biocontrol

• Several families
• Many species
• Most species specific
• Many commercially available

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Wasps for Aphids

• Several species of Braconidae, especially
  Aphidiinae
• Aphidius spp.
• Aphelinus spp.
• Diaeretiella rapae
• Lysiphlebus testaceipes
• Produce a mummy

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Wasps for Caterpillars

• Numerous species, but only some commercially
  available
• Some attack eggs, others caterpillars, other
  pupae

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Trichogramma WaspsFamily Trichogrammatidae

• Egg parasitoids
• Very small
• Widely used for biological control several
  species commercially available
• Attack eggs of moths and butterflies,
  beetles, flies, wasps, true bugs

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Imported Cabbageworm

• Cotesia glomerata and C. rubecula (Braconidae)
• Parasitize larvae
• Pteromalus puparum (Pteromalidae)
• Attacks pupae

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Cabbage Looper

• Copidosoma floridanum (Encrytidae)
• Attacks eggs, but
  emerges from
  last-instar larva
• Cotesia marginiventris (Braconidae)
• Prefer 1st instar larvae
• Voria ruralis (Tachinidae)
• stings larvae

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Diamondback Moth

• Diadegma insulare (Ichneumonidae)
• Attacks later instars
• Emerges from host pupa
• Diadromus subtilicornis (Ichneumonidae)
• Pupal parasitoid
• Microplitis plutellae (Braconidae) and Cotesia
  plutellae (Braconidae)
• Parasitize early instars

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Tomato Hornworm

• Cotesia (Apanteles) congregata (Braconidae)
• Cocoons protrude from caterpillars body
• Adult wasps come out of end of cocoons

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Wasps for Other Pests

• Numerous species
• Attack various stages of the pest
• Only some commercially available

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Root Maggots

• Trybliographa rapae (Cynipidae)
  for cabbage maggot
• Aleochara bilineata
  (Staphylinidae)
• Larvae parasitoids of pupae
• Adults predators of eggs, maggots
• Predators
• Ground beetles Agonoderus lecontei, A. comma,
  Bembidion quadrimaculatum, Microlestes sp., etc.
• Other rove beetles, e.g. Atheta coriaria

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Mexican Bean Beetle

• Pediobius foveolatus (Eulophidae)
• Parasitizes 2-4 instars
• Creates a mummy
• Doesnt overwinter
• best for inoculation

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Scales, Mealybugs, Whiteflies

• Aphelinid wasps (Family Aphelinidae)
• Tiny
• Many also host-feed as
  adults

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Many, many others
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Biocontrol of rabbits, voles, mice
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For More Information

• Natural Enemies of Vegetable Insect Pests
  (Cornell Univ.)
• Natural Enemies in Your Garden A Homeowners
  Guide to Biological Control (MSU)
• Biological control of insect pests of cabbage and
  other crucifers. NCR Pub 471 (UW)
• Biological Control of Insects and Mites An
  Introduction to Beneficial Natural Enemies and
  Their Use in Pest Management. UWEX Pub A3842
• Alternatives in insect management. NCR Pub 401
  (Univ. Illinois)

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For More Information

• Midwest Biological Control News (UW)
• www.entomology.wisc.edu/mbcn/mbcn.html
• Using IPM and Biological Control in the Home
  Garden
• www.entomology.wisc.edu/mbcn/fea204.htmlaphid
• Biological Control A Guide to Natural Enemies in
  North America (Cornell Univ.)
• www.nysaes.cornell.edu/ent/biocontrol/
• Biological Control Information Center (NCSU)
• cipm.ncsu.edu/ent/biocontrol/