BI207-insects as pests

how many insects are pests

1 million described but 5-10 million estimated, fewer than 1%

what is a pest

insects only become best when interact with human welfare, aesthetics or profits(physical, medical, economic)

no ecological significance per se

“any living organism, whether animal, plant or fungus which is invasive or troublesome to plants or animals, human or human concerns, livestock or human structure”

or any organism humans dont like

can be beneficial, domesticated or acceptable

insects as pests

high numbers— nuisance

pests of crops and stored products

insects of medical and vetinary importance

herbivores— eat our crops

cause allergic reaction eg capitlpillars have spines

transmit disease— mosquitoes

wheat—21.5% loss globally to pests each year

major pests

• tobacco whitefly

• cotton bollworm

• red flour beetle

• cotton aphid

• green peach aphid

why do insects become pests?

accidental introduction to areas outside native range—e.g. asian hornet now found in europe (predator to honey bees ☹ )

host switching— move from native plants to introduced one e.g. potato beetle— switched from vegetable to potato and now found all over europe (ireland free)

simplified monocultural ecosystems— dense aggregations of food resources= proliferation of certain generalist and specialist pests, less natural enemies

other farming and cultivation practices— continuous cultivation without fallow= build up of pests, prolonged insecticide use= less natural enemies, insecticide resistance

damage caused by pests of crops and plant products

• direct damage through consumption

• tramsission of plant disease

• aestheic damage

direct damage through consumption

diamond black moth

• cosmopolitan pest of cabbage and other crucifers

• larvae feed on leaves, redcuing yield and/or making plants unsealable

• can sometimes destroy virtually the whole plant

wireworms

• feed on roots

• damage potatoes, grass and cereals in ireland

colorado potato beetle

• adults and larvae feed voraciously on potato leaves, defoliating the crop

• a quarantine pest in ireland

beetles as pests of stored food

• mealworms in grain

• soya weevil

• few predators as they eat stored away food

transmission of plant disease

aphids and leafhoppers transmit plant viruses when they feed— kind alike mosquitoes

in ireland, yield reductions by viruses transmitted by aphids in winter barley can get up to 40%— barley yellow dwarf virus (BYDV)

aesthetic damage

can have serious growth economic consequences for growers e.g. apple and carrot maggot

pests of non food products and crops

pests of timber such as termites and woodworms

pests of living trees such as pine weevil; major pest on replanted clear felled conifer forests— seedlings routinely treated with insecticide— most major pests in europe

cotton pests such as bollworm— targets non food crop in world, biggest user of chemical pesticides, now more than 40% of cotton worldwide genetically engineered resistance

clothes/carpet moths—sheep keratin they like

profound appreciation of boll weevil, alabama

alabama— destroyed all cotton crops

started growing penauts and coffee— made loads more money— they are greatful

insects can cause damage to humans and animasl

stings or irritation

parasitic isects

vectors of pathogenic microorganisms

stinggs or irritations

wasp and bees venom

blister beetles

oak and pine processionary caterpillar has hollow toxin fitted hairs that cause skin irritation (urtication)

usually transient— dont last too long

allergic reaction: excessive immunological reaction following repeated exposure

anaphylactic shock— previously exposed allergy sensitive people; can be fatal

parasitic insects e.g. lice

lice (body, head, pubic)

• suck blood

• cause itching

• wound sbecome infected

• may also vector diesease e.g. typhus

fleas (human, cat, dog)

• vector of bacteria that caused plague

myiasis— parastitic dipterans: botflies, blowflies, screw worms

• larvae tunnel into hosts tissue casuing irritating elsion

• bacterial infection can occur'; left untreatsd can cause toxaemia or specticaemia

• can cause millions of dollars of damage to livestock

• endemic in south america— now spreading back into america

maggot therapy— clean wounds

insects as vectors of disease

• transmit disease

• tropical and subtropical regions— transmit causative agents of many human diseases e.g. malaria, sleeping sickness, dengue, yellow fever, river blindness and elephantiasis

• disease causing agents: bacteria, protists, viruses and nematodes

two broad types

mechanical vectors

• infectious agent carried passively by vector (legs or mouthparts) but does not multiply in it

biological vectors

• parasite or pathogen develops and/or multiplies in vector

• disease transmission requires vector

• association between disease agent and vector is often quite specific

• to control the disease, target the vector

disease cylces

single cycle disease of humans— malaria

multihost cycle disease

• chagas disease (Trypanosoma cruzi)— man y reservoirs hosts— nighttime poop on face— south americ abut moving north

• west nile virus (WNV)— birds as reservoirs hosts

• plague (bacterium)— rats as reservoir

single cycle diseases of domestic animals

• nagana: cattle sleepign sickness (trypanosoma)

• blue tongue disease(virus)

malaria

five species of plsmodium cause malaria— all female mosquitoes of genus Anopheles

• mosquitoes devleop in water— target breeding sites

disease transmission by vector depends on

• vector distribution

• vector abundance

• survivorship of vector

• anthropophily of vector

• feeding rate of vector

• vector comeptence

vector distributions

• anopheles mosquitoes occur worldwide except in cold temeprate areas

• ~400 species of anopheles

• >30 species can transmit malaria; many other species do not

vector borne diseases today

global warming increasing range of subtropical diseases

• rapid unplanned urbanisation

• changing land use patterns

• increased international travel and trade brings humans into more frequent contact with vectors

• climate and other environmental change fuel their spread worldwide

targeting vectors

• knowledge of lifecycles/ecology/behaviour

• surveillance/monitoring

• modelling

• control measures