Pest management - Ecological Applications: Toward a Sustainable World - page 165

SE)
percentage of diamond-
back moth caterpillars
parasitized by the
parasitoid Cotesia
plutellae in a glass-
house. Each bar
represents eight
replicates with 16
plants per replicate. The
caterpillars were
feeding on control
cabbage plants, or on
plants treated with a
botanical pesticide
extracted from the
syringa tree (S) ( Melia
azedarach ) or the neem
tree (N) ( Azadirachta
indica ). (After
Charleston et al., 2005.)

Fig. 6.13 Mean ( ±

80

70

60

50

40

30

20

10

0

Control S N

unthinking application of pesticides in the 1940s and 1950s. The IPM philosophy
thus considers all possible control actions before one is adopted and, in most cases,
integrates several control measures in a compatible manner.
The key word here is 'compatible'. You have already seen how the natural control
of potential pests can be disrupted by chemical attack aimed at the pest by dispro-
portionately affecting their natural enemies. This can also apply to an imported
biological control agent. Thus, the fi rst use of DDT in Californian citrus orchards
in 1946-47 led to an outbreak of the (by then) rarely seen cottony cushion scale
insect, when the DDT almost eliminated ladybirds (Section 6.3.1) t h at h ad succe s s -
fully controlled this previously devastating pest. However, careful study can reveal
combinations of biological control agents and particular pesticides that are compat-
ible or even work better together than alone. This is the case for diamondback moths,
a pest of cabbage crops, attacked by a biological control agent, the parasitoid Cotesia
plutellae , in concert with application of a botanical pesticide (Figure 6.13).
IPM relies heavily on natural mortality factors, such as weather and enemies, and
seeks to disrupt the latter as little as possible. The aim is to control pests below the
economic injury level, and IPM invariably depends on monitoring the abundance of
pests and their natural enemies so that sensible decisions can be taken about
whether and when to apply control. Broad-spectrum pesticides are used very spar-
ingly or not at all, and the use of any chemical is minimized. The essence of the
IPM approach is to make the control measures fi t the pest problem, and no two
problems are the same—even in adjacent fi elds. Thus, IPM often involves the devel-
opment of computer-based expert systems that can be used by farmers to diagnose
pest problems and suggest appropriate responses.
To illustrate the way that managers design and implement integrated pest manage-
ment I present two cases - the fi rst against an insect pest (Section 6.5.1) and the
second against an invasive weed (Section 6.5.2).

6.5.1 IPM against
potato tuber moths in
New Zealand

The caterpillar of the potato tuber moth ( Phthorimaea operculella ) is a pest of potato
crops in New Zealand. An invader from a warm temperate subtropical country, it is
most devastating when conditions are warm and dry (i.e. when the environment
coincides closely with its optimal niche requirements - Chapter 2). There can be as
many as eight generations per year and different generations mine leaves, stems and
tubers. The caterpillars are protected both from natural enemies (parasitoids) and