Lecture 17 - biocontrol

biocontrol

controlling pests with natural enemies such as predators, parasitoids, and pathogens (integrates entomology & ecology)

it is important to understand...

both entomology & ecology, relationships between species, population cycles

success story of biocontrol

use of vedalia beetles to control cottony cushion scale which were pests of citrus trees

biocontrol success results in…

more introductions of natural enemies

for regulation of biocontrol….

implemented intense research and quarantine procedures before and after importation: exploration, quarantine, release evaluation

biocontrol can become a failure when…

unintended non-target consequences, impact native species, enemy populations don’t establish, populations establish but do not control pests

introduced program to stop failures

APHIS

what percent of successes

20%

what percent of partial success

35%

how many percent of failed or no change

45%

cane toad and cane beetle

failure. toads lived on ground, beetles flew so access was not there. these toads become an infestation themselves

diffuse knapweed and gall flies

gall flies had no effect on the weed, and weed population persisted

asian lady beetles and tree climbing aphids

other species of lady beetles diminished

7 ideal characteristics

Narrow host range, climatic adaptability, synchrony with host, high reproductive potential, efficient search ability, short handling time, survival at low host density

narrow host range

attracted to small range of food source, good if they only attack pests, bad if they eat many things (are polyphageous)

climatic adaptability

survive extremes of temp & humidity

synchrony with host

must be around and active at the correct time of host life cycle.

high reproductive potential

large number of offspring

efficient search ability

locate their host or prey, even in challenging locations

short handling time

consume prey rapidly and/or lay eggs quickly

survival at low host(prey) density

if a natural enemy is too efficient, it may eliminate its own food supply and starve to death

3 key types of biocontrol

importation, conservation, augmentation

importation

identify & import natural enemies of non-native pests, “classical” biocontrol

Conservation

optimize survival or effectiveness of natural enemies, provide shelter & food sources

augmentation

least sustainable, natural enemies reared and released, increase population size in critical locations

biocontrol agents

predators, parasitoids, pathogens

predators

freeliving species, consume large number of prey species (lady beetles, dragonflies, lacewings, mantids, assassin bugs)

parasitoids

kill their hosts, have a free-living period, most are hymenoptera

pathogens

bacteria, virus that can cause disease

Bt bacteria

destroys gut-lining of insects