and Integrated Pest Management - part - usaid

ROLE OF CULTURAL TECHNIQUES IN RICE IPM
SYSTEMS
I. N. Oka
Agency for Agricultural Research and Development
Bogor Research Institute for Food Crops
Cimanggu Kecil 2, Bogor, Indonesia
Experience indicates that the use of resistance alone in rice varieties may not
be an adequate control tactic, particularly in coping with highly mutable pests
such as the brown planthopper (BPH), the green leafhopper (GLH), the
whitebacked planthopper (WBPH), rice tungro virus (RTV) and rice blast. The
pest populations quickly undergo selection and develop new biotypes/races
capable of breaking down the resistance in existing varieties. For example, IR26
and other varieties with the same gene for resistance to BPH were infested and
hopperburned in two widely separated small areas in the Philippines (Anon
1975a). In the Solomon Islands all resistant selections including IR26 became
susceptible (Stapley 1975). The same happened in Indonesia when IR26 and
other varieties with the same BPIl-resistant genes became susceptible in North
Sumatra, East Java, and Bali due to the development of biotype 2 (Oka 1977).
New varieties with biotype 2 resistance lasted only for 5-8 crop seasons, e.g.,
1R42 in North Sumatra and Central Sulawesi (Oka & Bahagiawati 1985, Shagir
Sama ct al. 1983). A number of local modern varieties, Cisadane, Kruengaceh,
and JR42 possessing biotype I and 2 resistance genes have also recently become
susceptible in parts of Central Java.
With the breakdown in resistance, natural control agents of key pests may
then not be able to catch up with the population buildup of the pest and largescale
severe outbreaks would become unavoidable. Frequent sprays with
pesticides have proved to be futile because the pest quickly develops resistance to
the pesticide(s), resulting in the well-known "pest resurgence" phenomenon.
Cultural methods such as synchronized planting and crop rotation,
sanitation, and water and fertilizer management play an important role in helping
to suppress pest populations. Therefore, in rice IPM systems, the first line of
defence against certain rice pests should be a Lumbintion of nonchemical
methods - cultural methods, varietal resislaace, and natural control (e.g., using
parasites, predators, and insect pathogeins). These will :,erve to maintain pest
populations well below damaging Ikvels. Cultural methods should also be the
basis of natural control and the use of resistant varieties. Cultural methods, if
carried out properly, prolong the life span of resistant varieties. Moreover, it is
entirely compatible with the proper functioning of the natural control agents.
Cultural methods may not give immediate and spectacular results when compared
to pesticidal control, but they are cheap, highly dependable, non-polluting,
ecologically sound and easily understood by farmers.