and Integrated Pest Management - part - usaid

84 PFS'I1CID MANAGEMFN'I AND IPM IN SOU'II[EAST ASIA
Cultural methods are as old as agriculture itself. A cultural method may be
defined as the modification of certain farm operations to make the environment
less favorable for the development and multiplication of pests, but favorable for
crop production.
Certain cultural methods may be aimed at destroying the pest population,
such as flooding the field after harvest, plowing under the stubbles, or burning
the stubbles and straw after harvest. For example, the larvae and pupae of the
white stemborer Scirpophagainnotata (Walker) (Goot 1925), and all stages of
BPI-l, GLH, and WBPH and the ibroe rice viruses SGV, RSV, RTV will he
destroyed. Oilier methods !ikc synchronized planting and crop rotation, plant
spacing, and fertilizer nanagemcnt are aimed at preventing further buildup of the
pest population. Planting synchrony and crop rotation carried out over wide
areas are highly dependable for preventing continuous bu'.ldup of BPH, GLH, and
WBPI1 (Oka 1983). The practices prevent development of overlapping
generations of pests.
Types of cultural methods ,obe carried cut should be based on thorough
knowledge of pest eco-biology and rice agronomy. For example, a sanitation
program against BPH may only require that infested rice plants be c!iminated
since rice is the only real alternate host of the insect.
SYNCHRONIZED PLANTING AND CROP ROTATION
In well irrigated areas in Indonesia, traditional rice farming systems used old,
long-duration local varieties (5-6 months) planted once or twice a year. Wet
season rice was planted during December-May/June and dry season rice during
July-November. In areas of limited water supply the farmers planted rice only
once a year during the wet season. Thereafter non-rice crops (soybean, peanut,
sweet potato, vegetables, etc.) were raised. There was some degree of
simultaneous iice cropping and rotation with non-rice crops covering relatively
extensive acreages. Relatively mild attacks of endemic rice pests occurred, such
as by the white stemborer S. innotata. No serious outbreaks of BPH, GLH,
WBPH, and rice viruses were recorded.
However, since the massive introduction of the rice intensification program
in 1968/69, when short duration modern rice varieties were introduced, there, was
room for planting rice three times a year or even five times in two years. Due to
socioeconomic fictors (labor shortagcs, market prices), staggered rice planting
became unavoidable. This situation was ideal for continuous development of
pests. Staggered planting with short idle intervals appeared to stimulate the
buildup of BPH populations and resulted in serious outbreaks (Chatterji 1975,
IRRI 1972, Mochida 1976, Oka 1975, Otake & Hokyo 1976). Outbreaks of the
rice dwarf virus in Japan were also attributed to mixed rice cropping, which
increased the abundance and varied patterns of the virus vector, the green
leafhopper N.virescens (Nakasuji 1974). In Indonesia, from 1974 until recendy,
large-scale outbreaks of BPH, RTV (transmitted by GLH), and WBPH occurred
in fields with staggered planting patterns such as in the Western part of West
Java, Yogyakarta, Southern parts of Central Java, Eastern parts of East Java,
coastal areas of North Sumatra, South Bali, Central Lombok, Central Sulawesi,