Landscape management - Ecological Applications: Toward a Sustainable World - page 285

Fig. 10.8 In two French
pine plantations the
percentage of trees
attacked by stem-boring
caterpillars is lower (a)
when individual pine
stands are bordered by
a mixture of broad-
leaved trees and (b)
when broad-leaved trees
are closer to the pines
in question. (c)
Mirroring these
patterns, parasitoid
attacks on the stem
borers are more
prevalent when broad-
leaved trees are nearby.
Parasitoid activity was
gauged by purposely
causing standard
damage in fi ve pine
trees in each stand to
encourage stem borers
to invade, and
subsequently counting
the number of
parasitized stem borers
present. (After Jactel
et al., 2002.)

(a)

50

40

Edged by mixed
species stand
of broad-leaved
trees

30

20

Control

10

0

Malakoff Castillonville

(b)

50

40

Castillonville

30

Malakoff

20

10

0

0 200 400 600 800 1000

(c)

6
5
4
3
2
1
0

Castillonville

Malakoff

0 50 100 150 200 250

Distance from the broad-leaved stand (m)

plantation and other trees in the landscape can reduce pine damage can be put to
use when designing future plantings.

10.4.2 Horticulture in
the landscape

An analogous study has involved Brussels sprouts in the Netherlands (Bianchi
et al., 2005). Caterpillars of the moth Mamestra brassicae are signifi cant pests of this
crop but a variety of natural enemies can help depress pest populations. M. brassicae
eggs are eaten by staphylinid and carabid beetles and parasitized by Tr i ch og ra m m a
wasps, while the caterpillars are consumed by beetles and birds and parasitized by
braconid wasps. To discover the relationship between landscape factors and pest
damage, standard egg batches were placed in 42 fi elds of Brussels sprouts. Predation
rates on eggs and caterpillars increased with the extent of woody habitat in the
landscape as a whole, whereas parasitism rates increased with area of pasture. Once
again you can see how landscape confi guration may infl uence the probability that
predators and parasitoids will co-occur with target pests in a metacommunity asso-
ciated with a monoculture. Structurally complex landscapes with substantial
amounts of woody habitat and pasture hold the most promise for sustainable pest
control by natural enemies.