Philippine rice stemborers: a review

Issue Date

4-2011

Abstract

Scirpophaga spp are the most prevalent rice stemborers in the Philippines regardless of location and ecosystem. The yellow stemborer Scirpophaga incertulas (Walker) (YSB) is the most prevalent rice stemborer in Luzon while in the Visayas and Mindanao, the white stemborer S. innotata (Walker) (WSB) predominates. From tiller dissections in over 12 sites, Scirpophaga spp. represented 53% of all borers in dryland, 79% in rainfed wetland, and 83% in irrigated ecosystems. The prevalence of the striped Chilo suppressalis (Walker) (SSB), found throughout the Philippines, has declined since the introduction of narrow-stemmed (< 5mm), modern rices because its large body size does not allow it to colonize a younger crop. Two other stemborers round out the prevalent species: pink Sesamia inferens (Walker) (PSB) and gold-fringed stemborer C. auricilius Dudgeon (GFSB). The success of YSB and WSB is due to their being monophagous to rice and their slender body size that allows them to colonize modern rices and young rice crops, even in the seedbed. The comparative advantage of YSB is its ability to survive flooding during the pupal stage, thus it is highly adapted to a monsoon climate. WSB, on the other hand, is highly adapted to the El Niño-prone, equatorial Inter-tropical Convergence Zone (ICZ) climate as it can remain in diapause for a year, long enough to survive droughts. YSB is more widely adapted as it can encroach into the ICZ climatic zone in between El Niño events, but there is no evidence that WSB encroaches into the monsoon climatic zone. Double-cropped, irrigated rice has the potential to greatly increase stemborer densities, but natural enemies likewise benefit from the same ecosystem and keep stemborer densities in check along with stubble plowdown after harvest. In fact, damage levels were higher on traditional, single-crop rice than on irrigated, double-crop rice. Average loss per crop was estimated for each rice ecosystem from stemborers in the Philippines to be 6% in irrigated, 11% in rainfed wetland, and 0% in dryland. Modern rices have a great potential to compensate from stemborer damage, but on the other hand crop stresses accentuate stemborer losses. The interplay between these two countervailing forces of compensation and stress determines yield loss in a particular field. As a management strategy, farmers should undertake cultural practices which increase the crop's ability to tolerate injury. Rather than use insecticides that suppress natural enemies, the farmer is best served by sowing medium maturing varieties and using his scarce resources to remove existing crop stresses such as weeds and nutrient deficiencies.

Source or Periodical Title

Philippine Entomologist

ISSN

0048-3753

Volume

25

Issue

1

Page

1-47

Document Type

Article

Frequency

semi-annually

Physical Description

graphs ; tables

Language

English

En – AGROVOC descriptors

SCIRPOPHAGA; STEM EATING INSECTS; PEST OF PLANTS; ECOLOGY; ADAPTATION; YIELD LOSSES; INTEGRATED PEST MANAGEMENT; PHILIPPINES

Link to Full Text

Share

COinS