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Species Page

white rice stem borer

Scirpophaga innotata
This information is part of a full datasheet available in the Crop Protection Compendium (CPC);www.cabi.org/cpc. For information on how to access the CPC, click here.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Host plants / species affected

Main hosts

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Cyperus (flatsedge)
Oryza sativa (rice)

List of symptoms / signs

Growing point - internal feeding; boring
Stems - dead heart
Stems - internal feeding
Whole plant - dead heart

Symptoms

Newly hatched larvae bore inside the young rice plant, travelling downward between the leaf sheaths and causing death of the young tip (dead hearts) in the vegetative stage, and empty panicles (white heads) in the generative stage. First-instar larvae may use silken threads to move to other plants.

Prevention and control

Introduction

Integrated pest management on the white stem borer has been practised traditionally, before the current interest in the philosophy of IPM. Prior to 1945 insecticides were not available to rice farmers in Indonesia and elsewhere (van der Goot, 1925). The effectiveness of insecticides for control of this pest is still uncertain, sometimes application may reduce infestation but on other occasions no effect is seen. As the larvae stay almost all of the time within the stem, foliar application is unsuccessful, and systemic insecticides are only effective during the vegetative stage. The most effective controls are therefore those related to cultural practices. See van der Laan (1951); Kalshoven and van der Laan (1981); Hendarsih (1992).

Agronomy

Previously, in chronically affected areas such as the northern part of west Java, rice was planted once a year. Cultivars were late-maturing and took 5-6 months to reach harvest, and the area was rainfed. After rice cropping the land was left fallow, leaving white stem borer larvae in the stubble. Since 1970 this area now has a good irrigation system over 250,000 ha, and with the introduction of medium-maturing rice cultivars (135-140 days), a rice-rice-fallow cropping pattern has been practised. This has led to a reduction in the dominance of white stem borer over other pest species: in 1972 the population of S. innotata accounted for only 50% of the pest population, the remainder being the yellow stemborer. Since 1987, the medium-maturing cultivars (e.g. Cisadane), which were susceptible to brown planthopper infestation, were gradually replaced by still faster-maturing cultivars (110-115 days, e.g. IR 64), and since 1988 the white stem borer resumed its dominance. The practice of growing fast-maturing rice cultivars meant a longer fallow period, allowing the white stem borer sufficient time to diapause. In some part of west Java, farmers are now planting medium-maturing cultivars in the dry season, and the S. innotata infestation has decreased again.

The white stem borer has become less important in Australia since the introduction of direct seeding; diapausing larvae are destroyed during land preparation.

Regulating Planting Date

When rice was planted only once per year, regulating the planting date was a commonly used method of control (van der Goot, 1948). The time of planting was adjusted to the rainfall at the beginning of the wet season: rainfall up to 10 mm triggers the termination of diapausing larvae. As the white stem borer is a monophagous insect, postponing the seed bed meant that the first flight of moths could not find host plants to lay eggs (Aunu Rauf et al., 1992a). This method must be carried out over a large area. Adjustment of the planting date could also avoid the susceptible phase of late-maturing rice cultivars coinciding with the peak of S. innotata moth flight. Under the present cropping pattern, infestation is reduced on rice varieties with a duration of 110-115 days if planted very early and late in the wet season. Heavy infestation occurs if the susceptible phase of rice development coincides with the third peak of moth flight. However, this method is not easy to adopt, as there may be other demands on the water allocation for each location.

Cultural Practices

Closed plant spacing or direct seeding give a dense plant population, which does not reduce white stem borer infestation, but does help to reduce yield loss (Hendarsih and Kertoseputro, 1991). Applying nitrogen fertilizer at the appropriate time may also reduce yield loss: tillers affected during the vegetative phase could recover and compensate for the damage. Under the same degree of S. innotata infestation, application of urea granules (slow release) gives a higher yield. Early flooding prior to wet-season planting also reduces infestation as diapause is ended out of synchronization with the availability of the host crop.

Host-Plant Resistance

There are no cultivars available which are specifically resistant to S. innotata. In the field the degree of infestation is determined by the duration of the rice variety, the date of planting and the stem borer population. See Baco et al. (1992); Hendarsih et al. (1992); Hendarsih and Sanusi Wityanara (1994).

Mechanical Control

Infestation may be reduced by cutting the stubble very low during harvest, destroying larvae before they move to the lower part for diapause; however, at harvest 40-85% of larvae have already reached the lower part of the stem. Ploughing the stubble immediately after harvest could destroy the larvae; however this may not be economically feasible unless the field is to be planted again. Attracting the moth using lamps has also been suggested; but experiments show that mass trapping by petromax lamps is not effective as the majority of moths attracted had already laid eggs in the field, and it required many lamps to be effective (Aunu Rauf et al., 1992b). Egg collection in the seed bed was recommended by van der Goot (1925), but not in the field, as this practice is very labour-intensive.

Biological Control

Natural control is by parasitoids and predators (see Notes on Natural Enemies). Egg parasitoids are more important than larval or pupal parasitoids, and egg parasitism may reach up to 90% at harvest. In order for the populations of egg parasitoids to build up early in the season, early insecticide application should be avoided.

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Impact

In Java, prior to 1945 the average area of rice attacked by the white stem borer was 20,000 baus (ca 15,000 ha). The degree of damage in the Indramayu region was around 11%, and in some years as high as 37%. In some areas the harvest failed completely due to heavy infestation, causing famine in several locations. In the late 1980s in the Indramayu region, 2000 ha of rice were attacked by the white stemborer, with a peak in 1990 when 65 040 ha were infested (15,000 ha at 100% infestation) (Ibrahim Manwan et al., 1990), with a yield loss was estimated at 210,000 tons of unhulled rice. In west Java, 10,000-20,000 hectares of rice are infested each year (S. Hendarsih, Sukamandi Research Institute for Food Crops, Indonesia, personal communication, 1995).

Yield losses depend on stem borer populations and the stage of the rice plant. If rice is attacked in the vegetative stage, the yield loss varies, but if the infestation happens during the booting stage the yield loss could be as high as 90-95%. In Australia, yield reduction due to the white stem borer was estimated at 30% in the summer crop, while the winter crop was free from infestation (van der Goot, 1925).