Effect of multiple infestations from insect pests and other stresses on irrigated rice in the Philippines: I. Damage functions

Abstract

Artificial infestation methods were employed to generate damage function graphs for guilds of three rice insect pests. In the vegetative stage, infestation of whorl maggot (Hydrellia philippina Ferino) and defoliators (a mixed population of Naranga aenescens Moore and Rivula atimeta [Swinhoe]) was applied as a combined or single pest attack. Infestation of yellow stemborer (Scirpophaga incertulas [Walker]) and leaffolder (Cnaphalocrocis medinalis [Guenée]) each were infested in one or two crop growth stages. Combinations of three stresses (four N application rates, solar radiation from the wet or dry season, and/or the presence or absence of weeds) were applied to each guild to develop more holistic economic injury levels (EILs). Slopes on the linear portion of damage curves of each pest guild became steeper with each additional stress applied, whether from multiple insect pest attack, low N, low solar radiation, or weeds. EILs can be developed by pest managers from the graphs of the damage functions for the variables quantified in this study.

Keywords:

• rice insect pests
• yield loss
• damage functions
• multiple pest infestation
• weeds
• nitrogen fertilisation
• solar radiation
• artificial pest infestation
• damage compensation

Acknowledgements

For both the papers in this series, we appreciate the generous cooperation provided by the farmers in the study sites. Many locally hired project staff were responsible for conducting the trials and their invaluable contributions are acknowledged. Those assisting in Zaragoza were Catalino Andrion and Rodolfo Gabriel and in Guimba George Romero. The assistance and advice from scientists at IRRI: Dr. Serge Savary, Francisco A. Elazegui, and Nestor G. Fabellar of the Plant Pathology Department and Ernesto G. Castillo in the Agronomy Department and Grace L. Reyes in the Statistics Department are gratefully appreciated.