Evaluation of action thresholds for chronic rice insect pests in the Philippines. IV. Stemborers

Published source details Litsinger J.A., Bandong J.P., Canapi B.L., dela Cruz C.G., Pantua P.C., Alviola A.L. & Batay-An E.H. (2006) Evaluation of action thresholds for chronic rice insect pests in the Philippines. IV. Stemborers. International Journal of Pest Management (formerly PANS Pest Articles & News Summaries 1969 - 1975, PANS 1976-1979 & Tropical Pest Management 1980-1992), 52, 195-207.
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This study is summarised as evidence for the following.

	Action	Category
	Use pesticides only when pests or crop damage reach threshold levels Action Link

Use pesticides only when pests or crop damage reach threshold levels

A 13-year randomised, replicated, controlled study in the Philippines (Litsinger et al. 2006b, the same study as Litsinger et al. 2005 and 2006a) found greater rice Oryza sativa yield (by 130-299 kg/ha) when sprays were based on thresholds of stem borer Scirpophaga spp. egg abundance and rice plant damage compared with no treatment. Thresholds based on moth abundance resulted in similar yields to untreated controls (17-65 kg/ha difference). The most effective thresholds assessed deadhearts (percentage of leaves killed by stem borers) and enabled correct decisions to spray/not spray on 90-99% of occasions. The most effective threshold level depended on the stage of crop growth (5%, 25% and 10% deadhearts for initial, flowering and ripening stages, respectively). At best, insecticides (endosulfan, chlorpyrifos or chlorpyrifos and BMPC) controlled 36% of plant damage and at worst they increased damage by 5% (at three weeks after planting). Thresholds were studied at 4-9 farms/year in each of four sites, totalling 68 rice crops overall. Thresholds and unsprayed controls were tested in 100-200 m² plots. Decisions were considered correct if deadhearts reached 5-15% per 20 plant hills, and if yield loss exceeded 250 kg/ha (in additional control plots). Comparisons to a conventional spraying regime and effects on natural enemies were not presented.