and Integrated Pest Management - part - usaid

34 PEST1CIDE MANAGEMENT AND IlM INSOUTHEAST ASIA
Statement II presents the fact of sporadic outbreaks and assumes disruption
to natural enemy control on the basi of all the other factors. This particularly
draws attention to the probabilistic nature of many of the consequential events.
An outbreak might, for example, be attributed to a weather influence, but similar
weather prevails over a wide area which is not affected, or which has several
separate outbreaks (of the same or different pests). The effect must occur at a
particular stage in the dynamic balance bckween the pests and the enemies.
Similarly, BSLRCs may often cause a resurgence but they will not necessarily
do so at every application. On the other hand, an insecticide with selective
characteristics might occasionally lead to an outbreak, suggesting that it has just
tipped a delicate balance in favor of the pest.
There are many events illustrating statements 16 and 17. The long-term
effect of a well-timed aerial spray of a selective chemical in indefinitely
eliminating an outbreak, but with a tendency for further reverberations where kill
is incomplete, is shown in Figure 2.
Cocoons / frond
40
35 E,,,
Larvae/frond
8
7
30 A 6
25 5
20 P,.O,,.. eneoh 4
15 3
I 0 oon dCo 2
5 1-0,0.l~
0
JJ A SO0 N D J F
'MA
M A m 7'
J i
s
AS0
od''S 0
45 9
40 E.g.. B 8
30 fl,ma,", on /* c o o o t6
5 7
0 1 r-n "A'­
30 968 1969 da
Fig'ure 2. Aeria spraying of trichlorfon (at c. 1.5 kg/ha) against the bagworm
Maha.sena (:or/etti on oil palms. In A, the timing was correct and there was no
repercussion. In B, timing was slightly early, before all eggs hatched. In B,
there was some further resurgences antI limited grounqd spraying, but the attack
came under natural control eventually (after Wood 1971).