Contributions to an integrated control programme of Hypsipyla grandella (Zeller) in Costa Rica

The shootborer Hypsipylagrandella (Zeller) (Lep., Pyralidae) is the main obstacle to the artificial regeneration of valuable meliaceous tree species such as mahogany ( Swietenia spp.) and Spanish cedar ( Cedrela spp.) in Latin America. On the other hand, the natural regeneration of these species is endangered due to depletion of the naturally existing resources and burning in colonization projects.This dissertation concerns the development of several fields of research, which when incorporated in a programme of integrated control may contribute to a solution of the Hypsipyla problem.Chapter 1 contains a general introduction on this insect pest and its host plants in Costa Rica. In addition, a review is provided of the economic importance of the pest in tropical forestry and of the previous and contemporary investigations on the possibilities of its control.The research carried out in the framework of the Inter-American Working Group on Hypsipyla at the tropical Research and Training Centre of the Inter-American Institute of Agricultural Sciences at Turrialba, Costa Rica, is dealt with in Chapter 2.These investigations refer to the natural resistance of Meliaceae, host selection, development of an artificial rearing technique for H . grandella and to a survey of parasites in Costa Rica which might be employed in a biological control of the shootborer.The main results are:a. Two exotic Meliaceae, African mahogany ( Khayaivorensis ) and the Australian cedar ( Toonaciliatavaraustralis ) were introduced and were found to be immune against attacks of the shootborer. Biological and chemical screening for the basis of resistance of the Australian cedar led to the location of two toxic components in the aqueous fraction of young leaves and shoots of this tree species. The toxicity of Toona can be translocated to Cedrelaodorata grafted on the Australian cedar.b. Experiments on the host selection of H . grandella point at the existence of a host selection mechanism in which the female adult orients itself towards the host by means of olfaction. Fourth instar larvae of the borer prefer native hosts to exotic species as food sources.c. An artificial rearing technique was developed for H . grandella . A diet (Vanderzant) used for rearing Heliothiszea appeared to be a suitable medium for mass rearing Hypsipyla . Although initially mating of adults could only be obtained in outdoor cages in Costa Rica, subsequent rearing in Wageningen, under completely artificial conditions, proved to be perfectly feasible. Larval and pupal periods of H . grandella reared on artificial and natural diets were determined, and compared. Female adults are generally larger than males and live longer. Artificially reared females still restrict oviposition to meliaceous host plants.d. A survey of biological control agents of -the shootborer resulted in the following new records of H . grandella parasites in Costa Rica: Trichogramma f asciatum , T . pretiosum , T . near pretiosum , T . semifumatum , Hypomicrogasterhypsipylae sp. n., Brachymeriaconica and Braconchontalensis ; an Agathis sp. has to be identified yet. In addition the nematode Hexamermisalbicans was found to parasitize larvae of the shootborer in Swieteniamacrophylla and Cedrela spp. The egg parasite Trichogrammasemifumatum could be reared easily on eggs of H . grandella .