During 1990 and 1992 speciesofthe white grubs complex Phyllophaga, Anomala and Cyclocephala) were found associated to agricultural crops and to different groups of soils, in cultivated arcas of the Central Valley and Dry Pacific of CostaRica.White grubs raster and male genital, observed with the scanning electron microscope (SEM), were used to identify genera and species. Larvae and adults were identified as Phyllophaga menetriesi, P. obsoleta, P. zunilensis, P. elenans, P. vicina and P. valeriana; Cyclocephala lunulata, C. castaniella and C. sanguinicollis; and Anomala cupricollis and A. granulipyga. The distribution in agricultural crops was: P. menetriesi and P. vicina on coffee (Coffea arabica); P. menetriesi on asparagus (Asparagus officinalis); P. menetriesi, P. obsoleta, P. zunilensis, Anomala spp., Cyclocephala spp., Cyclocephala lunulata on strawberry (Fragaria anannas); P. zunilensis, P. elenans on sugar cane (Saccharum officinarum); P. valeriana on potatoe (Solanum tuberosum) and tomatoe (Lycopersicon esculentum); P. obsoleta, C. castaniella, C. sanxuinicollis and A. granulipyga on kikuyu grass (Penissetum clandestinum) P. menetriesi larvae were found in Andisols grand groups: Melanudands, Hapludands and Haplustands. P. obsoleta in the Melanudands grand group. P. vicina in Hapludands. P. valeriana in the Inceptisols grand group of Ustropepts. Anomala spp. in Hapludands and Cyclocephala spp. in Hapludands and Melanudands.

Concentrations of Colony Forming Units (CFU) were determined for two entomopathogenic bacteria (Pantoea agglomerans and Bacillus cereus), at the egg, larval, pupal, and adult stages of agriculturally important Phyllophaga and Cyclocephala white grubs, which were collected in five agroecosystems in Costa Rica. L2 and L3  larvae of Phyllophaga elenans collected in all regions where the study was conducted were extensive carriers of Pantoea agglomerans and Bacillus cereu. L2 and L3 larvae of Phyllophaga obsoleta, Phyllophaga menetriesi, Cyclocephala sanguinicollis and Cyclocephala castaniella found in the Central Valley and Central Pacific regions were carriers of Pantoea agglomerans and Bacillus cereus bacteria. In 60% to 90% of larvae in all white grub varieties studied, Pantoea agglomerans showed greater concentrations of CFU than Bacillus cereu, which showed the lowest CFU concentration. Egg, pupal, and adult mortality in all Phyllophaga species was due to Pantoea agglomerans in 62%, 80% and 22.5% of the cases, respectively. A possible antagonistic interaction between Pantoea agglomerans and Bacillus cereus is also discussed. In general, it was noted that light and larval manipulation were the main stress factors affecting these scarabids.