Parasites of Lepidopteran Stem borers of Tropical Grarnineous Plants

Abstract

This publication is primarily intended for biological control practitioners in the tropics, particularly those involved in managing stemborers of gramineous crops. It includes not only information gleaned from the sCientific literature, but also draws on the experiences and personal knowledge the authors have gained through years of involvement with biological control of stemborers. A wealth of information on the biology and ecology of both stemborers and their parasites-as well as hi trophic-level interactions between plants, pests and parasites is included in the text. Particular attention is given to the generalized hierarchical steps involved in successful parasitization and to the various foraging strategies employed by stemborer parasites. A user-friendly key that incorporates parasite biology and taxonomy is provided to help the user detennine the foraging strategy used by the parasites. The key encompasses the primary parasites that are most likely to be encountered when sampling stem borers. The key is not intended to be all inclusive, but rather is a guide that is restricted to those taxa most likely to be found. The intent of the key is to provide tentative identification of the parasite to a use able level, by maximizing the use of ecological information and observational skills, while minimizing taxonomic expertise. Rearing techniques, which acquire their foundation from the foraging strategies, are addressed in the last half of the text. This publication is intended to be a fairly detailed review of stemborers and their parasites, but is not meant to be the final word. Rather, we intend this to be an initial attempt towards organizing the available information on stemborer parasites in a generalized structure that emphasizes the tritrophic interactions between a gramineous plant, a stem borer, and its parasites. Emphasis is placed on grouping parasites into similar foraging strategies to provide a biological structure for understanding the relationships between taxonomy and biology. Thus, the tables listing parasite genera and the text references to parasite species are not all-inclusive, but representative of the taxa likely to be encountered in field surveys for stemborer natural enemies. The broad presentation of material has been followed because the authors feel strongly that a basic knowledge of the biology of the hosts and parasites is a prerequisite to pursuit of biological control, and that this basic knowledge is the foundation for successful biological control intervention. Without first presenting the basic knowledge of planthost- parasite biology and ecology, this publication would result in no more than a cookbook for rearing parasites with limited application. Moreover, we demonstrate that, by knowing the biology and taxonomy of the hosts and parasites, certain generalizations can be made regarding foraging strategies and appropriate rearing procedures. Through the application of these generalizations, practitioners should acquire the knowledge necessary to make field collections of parasites and rear them, regardless of whether specific methods for rearing that species are included. However, whenever generalizations are made there will be exceptions. We have attempted to point out these exceptions whenever possible, but the readers will undoubtedly discover others. The references supplied at the end of sections are not intended to be exhaustive, but rather represent suggested reading for speci fie information on the subject. Often, citations are made in the text to direct the reader specifically. We have attempted to minimize citations in the text to save space. Undoubtedly we should have made more citations to document the wealth of outstanding information in the literature. We apologize in advance for those omissions.