Targets and Agents for Biological Control

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Targets and Agents for Biological Control
Read Chapter 2 in your text, see Clausen
1978 Targets of biological control programs
Invertebrates (P 41-42) 300 species of
invertebrates 2 species of Gastropoda (snails)
8 species of Arachnida 1 sp. of Ixodidae
(ticks) 6 spp. of Tetranychidae (spider
mites) 1 sp. of Aranaea (spiders, the black
widow) 290 species of Insecta
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Targets of Biological Control Insecta (Pages
41-42)
Insecta 290 species in 65 families in 8
orders Orthoptera 5 families, 10 species
most are Acrididae Dermaptera Forficula
auricularia L. Hemiptera 3 families, 6
species Homoptera 11 families, 95 species 72
species of scales and 12 species of
aphids Coleoptera 6 families, 37 species 14
spp. Curculionidae, 9 spp. Chrysomelidae, 8
spp. Scarabaeidae Lepidoptera 23 families, 60
species Noctuidae, Tortricidae, Pyralidae,
Gelechiidae, etc. Diptera 11 families, 50
species plant pests, e. g. Tephritidae, animal
pests, e. g. Calliphoridae, vectors of disease,
e. g. Culicidae Hymenoptera 5 families, 8
species ag. pests, e. g. Cephidae, forest pests
e. g. Diprionidae
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Targets of Biological Control Weeds (Page 42)
Weeds 42 species in 16 families Asteraceae 15
species (Centaurea, Cirsium, etc.) Cactaceae 10
species (Opuntia) Rosaceae 3 species
(Rubus) Fabaceae 2 species 12 families with
1 species each
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Targets of Biological Control
Why do we see these patterns of distribution of
targets for biological control? Several factors
influence the taxonomic distribution of the
targets of biological control programs.
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Targets of Biological Control
Factors influencing the taxonomic distribution of
the targets of biological control
programs. Biological factors Size of the
taxon More species, more potential
pests/targets Biology of the taxon What
they do, what they do it to, where they do
it? Amenability to biological control Are
pest populations stable enough to sustain
natural enemies at effective levels? Are
there manipulable natural enemies? (This
links to the next category.)
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Targets of Biological Control
Factors influencing the taxonomic distribution of
the targets of biological control
programs. Human factors Who is working?
What is their expertise? This
influences what pests will be targeted
and which agents can/will be useful. History
People tend to work on pests in groups that
have shown susceptibility to biological
control.
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Agents of Biological Control (Pages 43-)
There is a great deal of published information on
biological control agents. Read Chapters 2
through 6 in your text. It would also be good to
see Bellows and Fisher 1999, chapters 15 -
18 Burgess and Hussey 1976, Chapters 3 8 Debach
and Rosen 1991, Chapter 2Huffaker and Messenger
1976, Chapters 5 - 7
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Agents of Biological Control
Factors influencing the taxonomic distribution of
the agents of biological control programs. (They
will look familiar.) Biological factors Size
of the taxon Biology of the taxon Amenability
for use in biological control Are they
manipulable? Human factors Who is working?
What is their expertise? History Tend
to use taxa that have been successful But, we
have learned from experience (sometimes
painful, as you will see) and have a few
generalizations to offer
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Agents of Biological Control (Page 43)
Six characteristics of an ideal biological
control agent Host specificity wont waste
time or hit non-target species High searching
capacity can efficiently locate prey High
reproductive potential allows rapid numerical
response Long-lived adult increases searching,
allows egg distribution, compensates for minor
asynchronies in phenology Multivoltinism allows
rapid numerical response Threshold temperature
near that of prey helps synchronize predator
and prey
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Agents for Biological Control of Invertebrates
Gastropoda Agents have been Coleoptera
(Carabidae, Staphylinidae), Diptera
(Sciomyzidae) and predaceous snails Arachnida
Aranaea Spiders Theridiidae
(black widow) Agents have been egg parasitic
wasps (Scelionidae Baeus sp.)
Acarina Mites and Ticks These have been the
main arachnid targets of biological control
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Agents for Biological Control of Invertebrates
Arachnida Acarina Ixodidae Few,
agents were parasitic wasps (Encyrtidae)
Tetranychidae Many, agents have been predaceous
mites, (Phytoseidae), Thysanoptera,
Hemiptera (Anthocoridae), Coleoptera
(Coccinellidae Stethorus)
Coccinellidae Stethorus species adult
Phytoseiidae Galendromus occidentalis consuming
a spider mite
Phlaeothripidae Haplothrips species
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Agents for Biological Control of Invertebrates
Arachnida Acarina Phytoseiidae (Pages 45-46)
Phytoseiidae include species several genera that
are important spider mite predators. The
feeding specificity of these species varies
- Obligate spider mite predators, e. g.
Metaseiulus spp. - Predators that can also
feed on other mites, especially the
Tydeidae (common scavengers/pollinivores), e. g.
Phytoseiulus and Typhlodromus spp.
- Polyphages that are largely pollinivorous, e.
g. Amblyseius. Consider the advantages of each
group.
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Agents for Biological Control of Invertebrates
(Page 46)
Insecta Agents have included insects,
mites, spiders, nematodes, fish, birds,
mammals, bacteria, viruses, fungi, protozoa The
diversity of agents correlates with the large
number of insect species that have been targeted
for biological control. Most agents have been
insects, but we will examine other taxa as well,
some were educational, even if not successful.
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Agents for Biological Control of Insects
Vertebrates Mammals - Mice and shrews can be
important predators of soil- dwelling
insects, e. g. pupae of introduced Diprionidae.
Not popular as agents to introduce
Too general in their feeding habits -
Bats are predators of nocturnal flying insects.
Bat houses have been used to increase bat
populations for mosquito control.
Too general in their feeding habits
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Agents for Biological Control of Insects
Vertebrates Birds (Recall the early
introduction of the mynah) - Martins are
aerial insectivores. Martin houses have been
used to increase mosquito predator numbers.
- Chickadees, etc., forage on trees
for insects to feed their young. Nest
boxes can increase local bird numbers.
Too general in their feeding habits
Purple martin and a martin house
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Agents for Biological Control of Insects
Vertebrates Reptiles Anolis lizards Introduce
d to Jamaica to control Mediterranean fruit
flies They generally ate more sedentary insects,
e. g. lady bugs. (The latter point led people to
introduce the greater kiskadee, a large,
omnivorous flycatcher, that led to other
problems.)
Anoles are largely arboreal insectivores. They
are often sold in pet shops as chameleons.
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Agents for Biological Control of Insects
Vertebrates Amphibians Bufo marinus, the cane
toad, was introduced into numerous tropical
areas to eat scarab pests of sugarcane. It grows
very large, it eats many desirable insects and
other animals. B. marinus secretes toxins from
dermal glands, dogs are often poisoned if they
attack a cane toad. Importation of B. marinus
is now banned in many areas, e. g. California
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Agents for Biological Control of Insects
Vertebrates Fish Fish have been introduced to
control weeds and insects, mostly mosquitoes.
The standard problem has been escape into
natural waters, e. g. the grass carp in
Florida. Gambusia affinis, the mosquito fish,
has been quite successful. It has controlled
mosquitoes in rice paddies and other bodies of
water. However, it too has entered natural water
systems and caused problems due to competition
with native fish, e. g. in California.
The mosquito fish is live-bearer and a member of
the guppy family, Poeciliidae.
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Agents for Biological Control of Insects
Invertebrates Arachnida Aranaea Spiders (Page
47) - Important in natural control,
common predators, e. g. 156 species in
19 families in a cotton field. -
Little used in biological control Rarely is
one species the dominant predator of a pest
Most species develop and reproduce slowly
(adapted for starvation tolerance). Hunting
spiders tend to be more important than web
spinners Can be more selective Attack
ambulatory immature insects, not just flying
adults
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Agents for Biological Control of Insects
Invertebrates Arachnida Aranaea Spiders
(Page 47) Some families of note (see
handout for additional examples) Lycosidae- wolf
spiders, active hunters Thomisidae- lynx
spiders, active hunters Salticidae- jumping
spiders, active hunters An exception to the
rule In the Philippines, a salticid spider is
the key predator of the brown planthopper, a
major pest of rice. The spider can skate
between rice plants, forages in the 10 cm above
the water line (where the pest occurs) and has a
10 day generation time.
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Agents for Biological Control of Insects
Invertebrates Arachnida Acarina
Mites Several families of mites include
predators of agricultural pests, but the major
group is the family Phytoseiidae which attacks
spider mites. Mite predators of insects are
uncommon and generally not important in
biological control, but recall the predator of
the grape phylloxera that was shipped to France
in 1873.
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Agents for Biological Control of Insects
Invertebrates Insecta (Pages 48-) The insects
include approximately 400,000 species of
predators and 100,000 species of parasitoids.
Most of these attack other insects, thus
entomophagous insects are important in natural
control of insect pests. Many insect taxa have
proven to be manipulable, thus they are also
important in biological control. The enormity
and diversity of the entomophagous
insects precludes any detailed discussion,
however the followinginformation summarizes some
points and more detail is given in the handout.
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Agents for Biological Control of Insects
Invertebrates Insecta Predators (Pages
48-53) 250,000 predaceous species are known in
20 orders of insects (all except Protura,
Embioptera, Isoptera, Zoraptera, Phthiraptera,
Homoptera and Siphonaptera) Predators occur in
about 200 families of insects. Most are
important in natural control. About 50 families
have been significant in biological
control. About 15 families have been used
extensively. See the handout from Huffaker and
Messenger 1976
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Agents for Biological Control of Insects
Invertebrates Insecta Parasitoids (Pages 54-59)
(ca 100,000 species, 85,000 Hymenoptera) Parasi
tic species are known in 7 holometabolous insect
orders (Neuroptera, Coleoptera, Strepsiptera,
Trichoptera, Lepidoptera, Diptera and
Hymenoptera) Parasitoids occur in about 86
insect families (60 Hymenoptera) Most are
important in natural control. About 25 families
significant in biological control (19
Hymenops) About 11 families have been used
extensively (9 Hyms)
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Agents for Biological Control of Insects
Invertebrates Nematodes (Pages 60-63) Numerous
nematode species have been used in BCMost
species have been in the families Mermithidae,
Neoaplectanidae or Steinernematidae Nematodes
are usually most effect in water or moist soil
Moisture for survival of the active forms
Water for movement See the notes, more
information later in semester
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Agents for Biological Control of Insects
Pathogens (Pages 64-68) Pathogens that infect
insects occur among Bacteria, Fungi, Protozoa
and Viruses All taxa include many species
important in natural control All taxa include
some species important in biological control See
the handout, more information later in semester
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Agents for Biological Control of Insects
Pathogens (Page 64) Advantages- Most of the
pathogens are highly host specific,
protectingnon-target species, including
man Disadvantages- Pathogens are usually
relatively slow to kill the pestMany pathogens
are susceptible environmental stresses,e. g.
desiccation and/or UV radiation Most pathogens
require specific environmental conditions to be
effective, usually warm and moist
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Agents for Biological Control of Insects
Pathogens Bacteria (Page 66) Most bacteria
important in biological control are spore
formers,giving us a convenient life stage for
storage and application Most can be cultured in
vitro Must enter the host via a body opening or
wound Kill by secreting toxins or by direct
impact of infection Additionally, several of the
most important agents, e. g. Bacillus
thuringiensis, are crystaliferous. Spore
includes a proteinaceous crystal that is involved
in the infection cycle and can be isolated for
use as an insecticide.
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Agents for Biological Control of Insects
Pathogens Fungi (Pages 66 68) 400 species
known to infect insects Fungi important in
biological control fall into two main
groups Hyphomycetes, e. g. Beauveria bassiana,
Metarrhizium anisopliae, and Verticillium
lecanii Entomophthorales, e. g. Entomophthora,
Neozygites, Pandora,and Conidiobolus spp.
Verticillium lecanii
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Agents for Biological Control of Insects
Pathogens Fungi (Pages 66 68) Hyphomycetes
Beauveria bassiana, etc. Easier to culture and
store Less host specific More widely
used Entomophthorales Entomophthora spp.,
etc. Often difficult to culture, some
impossible Storage can be difficult, limited
periods only More host specific Less widely
used
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Agents for Biological Control of Insects
Pathogens Fungi (Pages 66 68) Fungi are the
only pathogens that can actively penetrate the
insect cuticle, thus making them appealing as
agents and the only agents effective against
sucking insects.Penetration involves the
appressorium, enzymes and mechanical
pressure.Fungi spread through hosts body as
yeast-like cells, then begin to form hyphae, may
alter host behaviorHost dies and hyphae emerge
to sporulate
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Agents for Biological Control of Insects
Pathogens Protozoa(Pages 66
68) neogregarine ex. caterpillar Insect
pathogens occur in several groups, e. g.
flagellates,ciliates, amebae, coccidia,
neogregarines and microsporidiaHost specificity
is usually high, all are safe for
humansProtozoa must be ingested to infect the
hostMust be cultured in vivo (expensive)Often
are debilitating, not fatal without additional
stressesExamples Glugea pyraustae, Nosema
locustae
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Agents for Biological Control of Insects
Pathogens Viruses (Page 67) 1300 viruses are
known to infect insects Insect pathogens occur
in 16 families, but focus has been
onBaculoviridae and Tetraviridae, because none
infect vertebratesBaculoviridae are DNA
viruses include nuclear polyhedrosis and
granulosis viruses Tetraviridae are RNA
viruses include nudaurelia viruses
Virus particles in insect cells
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Agents for Biological Control of Insects
Pathogens Viruses (Page 67) Host specificity
is usually high, all are safe for
humansOccluded viruses tolerant of
environment Must be cultured in vivo
(expensive) Must be ingested or enter via wound
to infect the hostVirus enters cell and
subverts the cells synthetic pathways to
produce more viruses, ultimately killing the
cell.Cell ruptures, releasing virus particles
to infect other cells,until host dies
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Agents for Biological Control of Weeds (Page 69)
Insects are the dominant group of agents for weed
control 140 species from several orders,
mainly Homoptera, Coleoptera, Lepidoptera,
Diptera and Hymenoptera Mites a few species have
been important, but their significance is
increasing Pathogens, especially fungi have been
moderately important, 33 species were used by
the 1980sNematodes a few species have been
used Fish a few species used for aquatic weeds,
Tilapia best