and Integrated Pest Management - part - usaid

[IM ON ESTATE CROPS IN MALAYSIA 33
Statements 3, 6, and 13 are crucial. Circumstantial evidence is
c,verwhehling and there is an accumulation of more objective proof. Whenever
a :pontaneous decline of an outbreak, whcther coinpictely unaided or after an
intervention, is monitored closely, .he build-up of natural enemies can be seen.
One proof using the insecticidal check technique was carried out. In ihis, an
insecticide is applied so as to deliberately cause a pest upsurgCnce (DeBach
1958). The technique has been mostly used for quite static pests (e.g. scale
insects), otherwise there is a spread effect. In the present case, it effectively
demonstrai,-d an induced buildup of a Iagworm (Aletisa plana) on oil palms
(Figuirc I),
Stlatements 8, 9 and 10 are related to observable phenomena, but the
undcrlyiig causes and imllic;itions may )be less apparent. Frequently, the pest in
miithrcak; is seen to be in 1DGM and parasites build up at times, but then may
(dcinc again because they caUnno iind enough suitable hosts (which itself helps
to maintain DGM). A well-studied example is that of the hispid leaf miner
(Coelaetwi enoderaLelaidis)and its parasites, in partictular an egg parasite, on oil
palmis in West Africa (Maria', 1976).
Larvae / 1rond
12 ­
area sprcijed
o>oprecojnf (Dec63)
1o. tgo ,inoln(dJan64)
I 0 4th gawwai.-0064
6­
4­
2
0Y
1-10 11-20 21-30 31-40 41-5o 51-60 61-70 71-80 81.9o 91-100
Posilon
Figure I. Insecticidal check technique, as applied in oil palns starting with a
low level population of the bagworn Metisa plana. The horizontal axis
represents the total count at corresponding points on three count lines of length
c. 900 ni, which pass through c. I ha plot subject to dieldrin application
(representod by the stippled band). There is a build-up in the sprayed area, but
(fire to the pest mloving, it gradually spreads from the upset area (after Wood
1971).