Pest management - Ecological Applications: Toward a Sustainable World - page 142

You might imagine that the general aim of pest controllers would be to eradicate
the population concerned. However, this is rarely attempted and even more rarely
achieved. It can actually be very diffi cult to eradicate a pest. This might sound para-
doxical when in the last chapter we bemoaned the fact that people are so good at
driving endangered species extinct. But, as already noted, the species most vulner-
able to extinction tend to be those with life-history traits that are linked to low
reproductive rates ( K -selected: Section 3.4). The majority of pests, on the other hand,
possess the opposite traits and have very high reproductive rates ( r -selected: Box
3.1). Moreover, the success of pests is often related to our provision of abundant and
high quality food - pests of rice love it for the same reason we do! Finally, exotic
pests often arrive in their adopted countries without many of their natural enemies.
Fast reproduction, abundant food, few enemies - a recipe for success if ever there
was one.
So eradication may not be feasible, or at least would cost so much in time, effort
and money that it is usually not attempted. But there is a general exception, and this
concerns invaders that have only just appeared on the scene. The arrival of an exotic
species with a high likelihood of becoming a signifi cant pest should be a matter for
urgent action, because this is the stage at which eradication is both feasible and easy
to justify economically (Simberloff, 2003).
Such campaigns sometimes rely on fundamental knowledge of population ecology.
An example is the eradication of the South African polychaete worm Te re bra sa b ell a
heterouncinata , a parasite of abalone and other gastropods that became established
near an abalone aquaculture facility in California (Culver & Kuris, 2000). Its popu-
lation biology was understood suffi ciently to know that the parasitic worm was
specifi c to gastropods, that two species in the snail genus Teg ul a were its principal
hosts in the area and that large snails were most susceptible to the parasite. Volun-
teers removed 1.6 million of the larger individuals, thereby reducing the density of
susceptible hosts below that needed for parasite transmission, which became extinct.
This is an example of 'physical pest control' (the physical removal of pests).
However, in the words of Simberloff (2003), rapid responses to recent invaders
will often 'resemble a blunderbuss attack rather than a surgical strike'. Another
marine invader provides a graphic illustration. Within 9 days of the discovery of
the Caribbean black-striped mussel ( Mytilopsis sallei ) in a small bay near Darwin
in Australia, the area was quarantined and treated with 160,000 liters of liquid
bleach and 6000 tonnes of copper sulfate. The mussel population was eradicated
(Bax et al., 2001), but so was everything else. A blunderbuss approach indeed, but
the secret to success was the knowledge that native species would recolonize from
nearby source populations while the invader could not. Early action using brute-
force methods was also successful for a string of successful eliminations of small
populations of weeds such as pampas grass ( Cortaderia selloana ) and ragwort
( Senecio jacobaea ) on New Zealand's offshore islands (Timmins & Braithwaite,
2002). Eradication of a recently established species known to be a problematic
invader elsewhere cannot (and should not) wait for new population studies to be
performed.
Occasionally, long-established pests have also been successfully eliminated. The
global effort to exterminate the smallpox virus provides an outstanding example,
and a similar effort to drive the poliomyelitis virus to extinction also looks set to
succeed. We can point to more mundane examples too. For example, an eradication