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Resumen El cambio de uso del suelo por la intensificación de la agricultura contribuye a la fragmentación de los bosques tropicales y la pérdida de la biodiversidad. En este sentido, a diferencia de los sistemas agroforestales (SAF) tradicionales, los SAF modernos son considerados de poca importancia para la conservación de la biodiversidad de los fragmentos de bosque. Sin embargo, existe una tendencia al establecimiento de SAF modernos. Debido a la sensibilidad a los cambios ambientales, se evaluó la diversidad de mariposas en SAF modernos de Coffea arabica y Erythrina poeppigiana (CP) y en combinación con Musa spp. (CPM) o Cordia alliodora (la única especie nativa de los SAF) (CPL), además de fragmentos de bosque muy húmedo premontano (FR) en el Corredor Biológico Volcánica Central-Talamanca, Costa Rica. En seis sitios representativos de cada sistema se establecieron tres transectos paralelos de 80 m cada uno y distanciados a 25 m entre los mismos. Cada cafetal y fragmento de bosque fue muestreado durante 1.5 horas en total para el registro de mariposas. Durante tres fechas de muestreo, se obtuvo un esfuerzo de muestreo de 4.5 horas/sitio y 27 horas en cada SAF y en FR. CP y CPM juntos tuvieron una composición de especies de mariposas diferente a la de CPL y FR. CP y CPM juntos resultaron con las especies de áreas abiertas Hermeuptychia hermes y Anartia jatrophae como indicadoras. CPL resultó con las especies de bosques secundarios Heliconus erato petiverana y Pareuptychia ocirrhoe como indicadoras. Por el contrario, FR resultó con diversas especies indicadoras típicas de bosques continuos tales como Pierella helvina incanescens, Caligo eurilochus y Morpho peleides limpida. Además, la riqueza de especies en FR fue mayor en relación a los SAF. Sin embargo, entre los SAF, CPL resultó con la mayor diversidad (Exp(H')) de especies de áreas cerradas que CP. Así mismo, CPM tuvo una mayor abundancia de mariposas frugívoras que CP y CPL. En bosques fragmentados, los cafetales con sombras exóticas pueden ser mejores hábitats para mariposas de bosques si se combinan con árboles nativos y/o frutales.

Abstract Land use change by the intensification of agriculture contributes to tropical forest fragmentation and biodiversity loss. In this sense, in comparison with traditional agroforestry systems (AFS), modern AFS are considered irrelevant for the conservation of biodiversity of tropical forest fragments. However, there is an increasing trend toward the establishment of different types of modern AFS. Owing to the sensitivity to environmental changes, we evaluated the biodiversity of butterflies in AFS with Coffea arabica and Erythrina poeppigiana (CP), and intermixed with Musa spp. (CPM) or Cordia alliodora (the only native species of AFS) (CPL), as well as premontane very humid forest fragments in the Volcánica Central-Talamanca Biological Corridor, Costa Rica. In six representative sites of each system we set up three parallel 80 m line-transects, separated by a distance of 25 m. Each coffee farm and forest fragment (FR) was surveyed during 1.5 hours to record butterflies. All sites were sampled once a month from May to July 2007. We obtained 4.5 hours of sampling/site, and 27 hours of sampling/habitat. Both CP and CPM together had a butterflies' species composition which differed from CPL and FR. The indicator species of both CP and CPM together were Hermeuptychia hermes and Anartia jatrophae which are typical of open areas. CPL resulted with the species of secondary forests Heliconius erato petiverana and Pareuptychia ocirrhoe as indicators. In contrast, FR resulted with several indicator species typical of closed canopy forests such as Pierella helvina incanescens, Caligo eurilochus, and Morpho peleides limpida. Moreover, the richness of species was similar among coffee AFS. Furthermore, the richness of species of each coffee AFS was lower in comparison with FR. However, among coffee AFS, CPL harbored higher diversity (Exp(H')) of forest butterflies than CP. Also, CPM was higher in abundance of frugivorous butterflies in relation with CP and CPL. In fragmented forests, coffee farms with exotic shade species combined at least with a native tree or fruit species, can be a better habitat for forest butterflies than those dominated by an exotic monospecific shade. Rev. Biol. Trop. 66(1): 394-402. Epub 2018 March 01.

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Weeds and their influence on pest and natural enemy populations were studied on a commercial ornamental farm during 2009 in the Atlantic Zone of Costa Rica. A baseline survey of the entire production plot was conducted in February, along a 5 by 5 m grid to characterize and map initial weed communities of plants, cicadellids, katydids, and armored scales. In total, 50 plant species from 21 families were found. Seven weed treatments were established to determine how weed manipulations would affect communities of our targeted pests and natural enemies. These treatments were selected based on reported effects of specific weed cover on herbivorous insects and natural enemies, or by their use by growers as a cover crop. Treatments ranged from weed-free to being completely covered with endemic species of weeds. Although some weed treatments changed pest abundances, responses differed among arthropod pests, with the strongest effects observed for Caldwelliola and Empoasca leafhoppers. Removal of all weeds increased the abundance of Empoasca, whereas leaving mostly cyperacaeous weeds increased the abundance of Caldwelliola. Weed manipulations had no effect on the abundance of katydid and scale populations. No weed treatment reduced the abundance of all three of the target pests. Differential responses of the two leafhopper species to the same weed treatments support hypotheses, suggesting that noncrop plants can alter the abundance of pests through their effects on arthropod host finding and acceptance, as well as their impacts on natural enemies.

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Importation of live nursery plants, like Dracaena marginata Lamoureux (Ruscaceae), can provide a significant pathway for the entry of foliar pests from overseas into the United States. We studied the abundance of foliar pests of quarantine importance found on Costa Rican-grown D. marginata. These include five genera of leafhoppers (Heteroptera: Cicadellidae, Oncometopia, Caldweliola, Diestostema, Cypona, and Empoasca), Florida red scale (Heteroptera: Disapididae, Chrysomphalus aoinidum (L.)), katydids (Orthoptera: Tettigoniidae), and a snail (Succinea costarricana von Martens (Gastropoda, Stylommatophora, Succineidae)). In our first study, we examined the rationale behind size restrictions on Dracaena cuttings imported into the United States from Costa Rica. When comparing plant size, no differences were found in the abundance of quarantined pests on small (15-46 cm), medium (46-81 cm), and large (81-152 cm) propagules. In a second study, we estimated monthly abundances of pests in production plots for 1 yr to determine their relationship to rates of interception at U.S. ports. In any given month, < 6% of the marketable shoots standing in the field were infested with at least one quarantine pest. There was no relationship between the average monthly frequencies of pest detection in the field and in U.S. inspection ports. Pest detections increased during the 1 mo when average monthly shipments were abnormally high. Our data suggest that off-shore postprocessing efforts to remove pest-infested material from the market stream need to be adjusted to accommodate sharp increases in the volume of shipped plants.

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To mitigate risks of invasive pests, international nursery exporters may soon be expected to participate in clean stock programs that reduce the probability of shipping crops that contain pests of quarantine significance. We worked with Costa Rican producers of Dracaena marginata Lam. (Ruscaceae) to identify critical pests, as well as the field conditions and production practices that could be explored for lowering pest abundance in a clean stock program. We sampled the abundance of leafhopper and katydid eggs, armored scales, and snails on leaves using a 10- by 10-m grid in a total of 34 production plots located in two distinct growing regions during the rainy and dry seasons of 2006. Growers were surveyed to determine the production practices in each field. Populations of leafhoppers and snails increased during the rainy season, whereas armored scale populations reached higher densities in the dry season. Fertilizer applications were associated with a greater abundance of leafhoppers, the keystone pests in the system. In contrast, abundances of armored scales and katydids were somewhat lower in fertilized fields. Insecticide applications targeting leafhoppers succeeded in reducing their populations, but secondary outbreaks of armored scales and katydids were observed. Increased frequency of herbicide application was associated with lower populations of leafhoppers with no significant effects on the other herbivores. Although effects of specific production practices in a given plot are confounded, the effects of fertilizer, insecticide, and herbicide use on leafhoppers are consistent with those predicted by literature on this pest. For this reason, the 10- by 10-m sampling grid is sensitive enough for use in controlled studies that evaluate effects of specific practices on pest abundance. As such, it is likely to be a useful tool for developing a clean stock program for D. marginata in Costa Rica.

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