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Beneficial arthropods: Natural enemies and pollinators

Paula Shrewsbury, Ph.D.Department of Entomology

University of Marylandpshrewsbury@umd.edu

Landscape IPM Short Course January 2020

Insects provide critical ecosystem services

• Critical links in food webs and food chains

• Nutrient recycling, decomposition

• Pollination services

• Biological control

Insects provide critical ecosystem services

• Critical links in food webs and food chains

• Nutrient recycling, decomposition

• Pollination services

• Biological control

Insects provide critical ecosystem services

• Critical links in food webs and food chains

• Nutrient recycling, decomposition

• Pollination services

• Biological control

Habitat modification

Biological Control

• The use of predators, parasitoids, and pathogens to suppress pest populations below damaging levels

• Natural enemies

• Occur naturally, some commercially available

Syllabus – starting on pg. 159

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Specialist• an organism that feeds on only

one type (species, family) of prey or host

Ex. Wasp parasitoid that only attacks EAB eggs (Oobius agrili)

Generalist

• an organism that feeds on more than one type of prey or host

Omnivore• an organism that feeds on

both animal (insect prey) and plants (nectar and pollen, seeds)

Pathogens(Entomopathogenic)

• Microorganisms such as bacteria, viruses, fungi, and nematodes that cause disease in insects

• Occur in nature; commercially produced for pest managment

Pathogens• Enter insects through the

exoskeleton, body orifices, or by ingestion of food

• Multiplies within host insect and resulting disease kills host

• Spread when host’s body disintegrates or through feces

Pathogens

• Microorganisms such as bacteria, viruses, fungi, and nematodes that cause disease in insects

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Bacillus thuringiensis (B.t.)• Soil bacterium, common in nature• Over 30 subspecies and varieties• Produces a protein crystal• Crystal toxicity is insect specific• Produced and used commercially for many

years (formulated biological control)

Bacillus thuringiensis (B.t.)

• Most effective on young larvae• Mode of action

–Ingested by larvae

• Feeding inhibition in 1 hour• Death in 2 – 5 days

B.t. Varieties and Pests Controlled

• B.t. kurstaki or morrisoni– Caterpillar larvae

• B.t. israeliensis– Mosquito, black flies, fungus gnat larvae

• B.t. San Diego– Leaf beetle larvae

• B.t. galleriae– Scarab beetle grubs, adults; weevils; flat headed

beetles (beetleGONE; grubGONE; borerGONE)

Pathogens

• microorganisms such as bacteria, viruses, fungi, and nematodes that cause disease

Viruses

• In nature, greatest impact when caterpillars and sawflies are at very high populations

• Commercially not practical

Pathogens

• microorganisms such as bacteria, viruses, fungi, and nematodes that cause disease

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Entomopathogenic Fungi

Metarhizium anisopliaeBeauvaria bassiana

Commercial Products

• Best results seen in greenhouses against aphids, spider mites, and thrips

• Also used for white grubs, locusts, mosquitoes, others

Fungi Mode of Action• spores adhere to insects body

• spores germinate

• spore tube penetrates insect (enzymes)

• fungi enters circulatory system

• reproduces inside insect

• toxins produced and kills insect

• fungal hyphae emerge from insect

• infective spores are released

Image by N. Breisch and W. Fang, UMD

Wild type and genetically modified fungal strains

Pathogens

• microorganisms such as bacteria, viruses, fungi, andnematodes that cause disease

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EntomopathogenicNematodes

Steinernema species

Heterorhabditis species

Nematode and Bacteria

• Mutualistic association– Nematodes require bacteria as food to

grow and multiply

– Bacteria require nematodes to locate insect hosts in which they grow and multiply

• Steinernema spp. / Xenorhabdus sp.

• Heterorhabditis spp. / Photorhabdus sp.

Entomopathogenic nematode life cycle

Commercially Available Nematodes

NematodeS. carpocasae

S. glaseri

S. riobravis

S. scapterisci

S. feltiae

H. bacteriophora

H. megidis

Insect (major markets)Caterpillars (turf, mint, retail)

White grubs (turf)

Mole crickets (turf), Citrus weevils (citrus)

Mole crickets (turf)

Fungus gnats (ornamentals, mushrooms)

White grubs (turf), root weevils (ornamentals, citrus, berries)

Genera: Steinernema and Heterorhabditis

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Images from: NYS Ag. Exp. Station

Signs of attack by pathogen natural enemies

www.umassgreeninfo.org

Scale images from: www.walterreeves.com

Do insects defend themselves against pathogens?

• Behaviorally – grooming

• Chemically – stink bugs, bed bugs

Parasitoid• generally a small insect that

slowly kills and consumes a larger insect called the host

• develop in or on its host

Common Parasitoid Groups

• Hymenoptera - Wasps

• Diptera - Flies

Wounding of scale by parasitic wasp

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Host feeding on scale by parasitic wasp

Endoparasitoid

• a parasitoid that develops and feeds inside its host

Ectoparasitoid

• a parasitoid that develops outside of its host while feeding through the host’s cuticle

Aphid mummies

Estimating Parasitism Rate

• Small, mobile, hard to “see”• Hosts exhibit characteristic symptoms• Changes in host color, size, shape

–Ex. Swelling of aphids into “mummies”, melanization of soft-scales and whiteflies, circular exit holes

• Use symptoms to estimate level of parasitism

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Hymenoptera

Parasitic wasp

Exit holes in scale covers- sign

www.hydro-gardens.com

M.J.Raupp

Tachinid Fly

Diptera: Tachinidae

Ectoparasitoid

• a parasitoid that develops outside of its host while feeding through the host’s cuticle

www.entomology.cornell.edu

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www.uky.edu

Predator• generally a large, active insect

that quickly kills and consumes many smaller, insects called prey

• require many prey to complete development

Common Predator Groups• Coleoptera:

– Coccinellidae - lady beetles– Carabidae – ground beetles– Staphalynidae – rove beetles

• Neuroptera: – Chrysopidae - lacewings

• Diptera: – Syrphidae – flower or hover flies

• Hemiptera: – Reduviidae – assassin bugs

• Acari: – Phytoseiidae - predatory mites

• Araneae:– Thomisidae, Salticidae, others - spiders

Lady Beetle

Video by M.J. Raupp, UMD

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Citrus mealybug

(pest)

Mealybug destroyer

(ladybeetle, predator)

Hyperaspis Lady Beetle

adult and larva

Spider Mite Destroyer

Coccinelidae

Predatory Mites (Acari: Phytoseiidae)

Green Lacewing Neuroptera: Chrysopidae

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Debris carrying lacewing

Flower or Hover Fly

Diptera: Syrphidae

M.J. Raupp

M.J. Raupp

Video by M.J. Raupp, UMD

cropwatch.unl.edu

Hemiptera: Heteroptera: Anthocoridae

Minute Pirate Bug

Assassin bugsHemiptera: Heteroptera

Reduviidae

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Hemiptera: Heteroptera: Nabidae

Damsel Bug

Soldier beetleColeoptera: Cantharidae

www.pbase.com/dougsmit/

Coleoptera: Staphylinidae Rove Beetle

Coleoptera: Carabidae

Ground Beetle

Photo Credit: Jeff Hahn

Araneae: Anyphaenidae

Araneae: Salticidae

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FloridaNature.org

Araneae: ThomisidaeP. Shrewsbury

Black and Yellow Garden Spider

Egg sac

Black and Yellow Garden Spider vs Brown Marmorated Stink Bug

Video by M.J. Raupp, UMD

www.geocities.com

www.geocities.com

Praying Mantis

Mantodea: Mantidae

bugs.bio.usyd.edu.au/

Insects provide critical ecosystem services

• Critical links in food webs and food chains

• Nutrient recycling, decomposition

• Pollination services

• Biological control

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Insects provide critical ecosystem services

• Critical links in food webs and food chains

• Nutrient recycling, decomposition

• Pollination services

• Biological control

Many natural enemies need alternative food sources = nectar and pollen = pollination

Images by M.J. Raupp, UMD

Many natural enemies are pollinators

Many pollinators are natural enemies

R. Waterworth, UMDM. J. Raupp, UMD

Beetles

Who are the pollinators?

Flies

Butterflies and Moths

Video by M.J. Raupp, UMD

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Wasps are important pollinators too

http://www.honeybeehaven.org/content/bees-101

Sarah Greenleaf photos

(Photo by Kathy Keatley Garvey)

Honey bees

Bumble bees

Ground nesting bees

Plasterer beesDigger beesMiner bees

Ground nesting bees - Sweat or halictidbees

B.Castro, TAMU

www.westerngardeners.com

Hole nesting bees –Leaf cutter bees

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Many natural enemies are pollinators

Many pollinators are natural enemies

• Practices to conserve natural enemies and pollinators should be similar

R. Waterworth, UMD

M. J. Raupp, UMD

Need to give natural enemies and pollinators a helping hand!

Biological Control Approaches

Classical / Importation

Augmentation

Formulation

Conservation

Goal of Biological Control

• to reduce pest densities to non-damaging levels – not to eradicate pests

Classical / Importation

• the importation and establishment of new species of natural enemies from the original home of introduced pests to control those pests

• USDA APHIS, State Dept. of Agriculture, University scientists

Researchers determine:

•Successful establishment of natural enemies (NE)

•Numbers of NE needed for establishment

•Site conditions required for establishing NE populations

•Interactions among exotic and native NEs

•NE dispersal rates

•Impacts on EAB populations and ash survival or recovery

•Effects on non-target species

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Formulation

• pathogens or entomopathogenic nematodes may be formulated into a product that is applied in a method

similar to conventional pesticides

B.t. Varieties and Pests Controlled

• B.t. kurstaki or morrisoni– Caterpillar larvae

• B.t. israeliensis– Mosquito, black flies, fungus gnat larvae

• B.t. San Diego– Leaf beetle larvae

• B.t. galleriae– Scarab beetle grubs, adults; weevils; flat headed

beetles (beetleGONE; grubGONE; borerGONE)

Commercially Available Nematodes

NematodeS. carpocasae

S. glaseri

S. riobravis

S. scapterisci

S. feltiae

H. bacteriophora

H. megidis

Insect (major markets)Caterpillars (turf, mint, retail)

White grubs (turf)

Mole crickets (turf), Citrus weevils (citrus)

Mole crickets (turf)

Fungus gnats (ornamentals, mushrooms)

White grubs (turf), root weevils (ornamentals, citrus, berries)

Genera: Steinernema and Heterorhabditis

Black vine weevil

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Control H. bacteriophora

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Effect of H. bacteriophora on

BVW Infesting Bergeniaa

Augmentation

• when existing natural enemy populations are low or absent at a site, additional predators or parasitoids may be purchased from a commercial insectary and released

BC sources: Syllabus on pg. 178

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P.M. Shrewsbury, UMD

Green lacewing larva feeding on azalea lace bug nymph

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60a

b

Effects of Lacewings, Beauvaria, and Acephate on ALB

cc c

6 days post-release -

2 of 150 glw recovered

P.M. Shrewsbury and D.C. Smith-Fiola. 2000

Challenging in outdoor environments

Add food and habitat to retain augmented natural enemies

Conservation Biological Control and Conserving Beneficials

The deliberate attempt to maintain beneficial organisms (natural enemies, pollinators) in the nursery or landscape habitat

1. Enhancement of the habitat to promote beneficial survival and reproduction, and to attract and retain beneficials

2. Avoidance of activities that are harmful to or disrupt beneficials