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Distribucin y abundancia de la prosapia (Homoptera: Cercopidae) en las fincas de la zona de Monteverde
Distribution and abundance of Prosapia (Homoptera: Cercopidae) in Monteverde-area farms
Prosapia spp. commonly known as spittle bugs, froghoppers, or la Prosapia, are pasture pests for dairy farmers in the Monteverde region of Costa Rica. The adults eat pasture grass, disturb plant growth, as well as reduce nutritional and palatability values of the pasture grass for dairy cattle, and are responsible froghopper burn. This study examined the relationship between altitude and Prosapia abundance in cattle pastures of farms surrounding Monteverde in Costa Rica. It was hypothesized that abundance will differ with altitude. A total of 11 farms in the Monteverde region of Costa Rica ranging from 825 m to 1510 m in elevation were surveyed between July 18, 2008 and July 30, 2008. At each farm, the owners were questioned about the number of cows, hectares of pasture grass, days of grazing before rotating cows, use of pesticides, chopping and/or burning of grass, and type of pasture grass. Prosapia adults and nymphs were counted by hand within three randomly chosen 1 m2 plots of pasture grass of the same farm and the grass was identified as either burned or not burned. Burned pastures were almost completely yellow and dying; while not burned pastures were almost completely green. A significant difference in Prosapia abundance was found between burned and not burned pastures with a higher average abundance of Prosapia in the burned pastures. A significant difference in the average altitude ofburned and not burned pastures was found, with burned pastures having a higher average altitude. Overall, while no significant trend was found between abundance and altitude, the data strongly suggest that Prosapia abundance increases with altitude.
La Prosapia spp. se conoce comnmente como salivazos o la Prosapia, y es una peste en los potreros de las fincas en Monteverde. Los adultos se alimentan del zacate de los potreros, afectando as el crecimiento de la planta y reduciendo los valores nutricionales del pasto para el ganado lechero, siendo responsables de la quema del zacate por los salivazos. Este estudio examino la relacin entre la elevacin y la abundancia de la Prosapia en los potreros de Monteverde, Costa Rica.
Text in English.
Cercopidae--Costa Rica--Puntarenas--Monteverde Zone
Pastures--Diseases and pests
Cercopidae--Costa Rica--Puntarenas--Zona de Monteverde
Potreros--Enfermedades y plagas
Tropical Ecology 2008
Ecologa Tropical 2008
t Monteverde Institute : Tropical Ecology
1Distribution and Abundance of Prosapia (Homoptera: Cercopidae) in Monteverde-area farms Ryan Brower Department of Zoology, University of Wisconsin-Madi son ABSTRACT Prosapia spp. commonly known as spittle bugs, froghoppers, or la Prosapia, are pasture pests for dairy farmers in the Monteverde region of Costa Rica. The adults eat pasture grass, disturb plant growth, as well as reduce nutritional and palatabil ity values of the pasture grass for dairy cattle, a nd are responsible froghopper burn. This study examined the relationship between altitude and Prosapia abundance in cattle pastures of farms surrounding M onteverde in Costa Rica. It was hypothesized that abundance will differ with altitude. A total of 11 farms in the Monteverde region of Costa Rica rangin g from 825 m to 1510 m in elevation were surveyed bet ween July 18, 2008 and July 30, 2008. At each farm, the owners were questioned about the number of cows hectares of pasture grass, days of grazing before rotating cows, use of pesticides, chopping and/or b urning of grass, and type of pasture grass. Prosapia adults and nymphs were counted by hand within three randomly chosen 1 m2 plots of pasture grass of the same farm and the grass was identified as either b urned or not burned. Burned pastures were almo st completely yellow and dying; while not burned pas tures were almost completely green. A significant difference in Prosapia abundance was found between burned and not burn ed pastures with a higher average abundance of Prosapia in the burned pastures. A significant difference in the average altitude ofburned and not burned pastures was found, wit h burned pastures having a higher average altitud e. Overall, while no significant trend was found betwe en abundance and altitude, the data strongly sugges t that Prosapia abundance increases with altitude. Resmen Prosapia spp se conoce comnmente como salivazos o la Prosapi a, y es una pestes en los postreros de las fincas en Monteverde. Los adultos se alimentan del zacate de los postreros, afectand o as el crecimiento de la planta y reduciendo los valore s nutricionales y del gusto del pasto para el ganad o, siendo responsable de la quema por salivazos. Es te estudio examino la relacion entre elevacin y abundancia de Prosapia en los postreros de Monteverde, Costa Rica. La hip otesis es que la abundancia aumentara conforme aumenta la altitud. Once fincas en la regin de Monteverde fueron estudiadas entre los 825 y 1510 m de elevacin durante el perodo de 18 de Julio al 30 de Julio 2008. En cada finca, los du eos fueron consultados sobre el nmero de vacas, hectar eas de pasto, nmero de das de pastoreo antes de r otar las vacas, el uso de pesticidas, prcticas de contr ol, y el tipo de zacate. Adultos y ninfas de Prosapia se contaron en tres caudrculas, de un metro, ubicadas azarosamente en el mismo postrero y cada una se identific como quemada o no quemada. Una diferenci a significativaen la abundancia de Prosapia se encontr entre los pastos quemados y los no quemado s, presentando los pastos quemados una mayor abundancia promedio. Una diferencia significativa en el promedio de altitud de pastos quemados y no quemados se encontr tambin, con los pastos quemad os presentando una mayor altitud. Aunque no se encontr ninguna diferencia significativa entre la abundancia y la altitud, los datos sugieren una fue rte tendencia de que la abundancia de Prosapia aumenta con la altitud. INTRODUCTION
2 Prosapia spp. (Homoptera: Cercopidae) are commonly known as Spit tle Bugs, la Prosapia, or froghoppers and are pasture pests to the dairy farmers of Monteverde nearly bringing an end to the dairy industry in the 1960s (Peck 1996). Adults feed off the pasture grass, disturbing the growth of the grass a s well as reducing the nutritional and palatability values for dairy cattle. Furthermore, the saliva of adult insects induces phytotoxemia in the grass causing it to turn yellow and die, which is referred to as froghopper burn. Large infestations of Prosapia can burn entire fields and have a major impact on dairy farmers (Peck 1996). In a stu dy done by Holmann and Peck (2002) of pastures in Colombia, it was found that the stoc king rate, milk, and meat productivity decreased from 1 to 54% depending on the abundance of spittlebugs. The reproductive life cycle of Prosapia leads to seasonal population fluctuations (Peck 1996). Eggs are laid in the soil at the base of the grass and diapause throughout the dry season, hatching near the beginning of the wet season. The nymphs give the insect its name (Spittle Bug) because they create protective spittle at the base of the grass and remain hidden in it. The nymphs go through five ins tars before molting to the adult form, which takes six weeks overall (Peck 1996). This stu dy was done after the nymphs have presumably gone through there instars. While much h as been studied on the reproductive cycles and abundance of Prosapia in the Monteverde region, information is lacking o n the relationship between altitude and abundance. A previous study on Prosapia abundance and management practices in Monteverde by Jewett (2006) noted a possible relati onship between abundance and altitude; however, this was not the focus of his st udy and results were tentative. My study further investigates this pattern by examining the relationship between altitude and Prosapia abundance in cattle pastures surrounding Monteverde in Costa Rica. I also compared the nymph and adult densities of Prosapia I found to those that Jewett (2006) in the dry season. My hypothesis was that abundance of Prosapia would vary with altitude and that a different density of nymphs and adults of Prosapia would be found when compared to the study done by Jewett (2006). I expected to see abundance increase with altitude and to find more adults and fewer nym phs than Jewett (2006) due to the time of year (Peck 1996). METHODS STUDY SITE .This study, conducted between July 7, 2008 and July 30, 2008, surveyed 11 farms in the Monteverde region of Costa Rica ran ging from 825 m to 1510 m in elevation. Eight of the 11 farms surveyed were thos e used in the previous study done by Jewett (2006). The elevations measured by Jewett (2 006) were reused for those eight farms, and those of the remaining farms were measur ed with an altimeter. At each farm, the owners were questioned about the number of cows hectares of pasture grass, days of grazing before rotating cows, use of pesticides, ch opping and/or burning of grass, and type of pasture grass. (see Appendix I). Prosapia adults and nymphs were counted by hand within three randomly chosen 1 m2 plots of pasture grass at each farm. The pasture grass was identified as either burned or not burned by visual observation and grass height of each plot was also recorded. Pastures were consi dered burned if all of the pasture was more yellow than green.
3STATISTICAL ANALYSES.Average densities were calculated for each farm an d were used as an abundance indicator. Mean densities of a dults and nymphs of the eight farms of my study and Jewetts (2006) study were compared respectively using a t-test. Three separate ANCOVA tests were performed to compare abu ndance and elevation with hectares, cows, and grass height as the respective covariates. Rank Sum Tests were used to test for significant differences between the bu rned and not burned populations with regard to abundance and elevation. RESULTS Prosapia were counted at 11 farms ranging from 825 m to 151 0 m in elevation with average densities ranging from 0 to 4.66 adults/m2. Mean density of adults of the eight farms shared by Jewett (2006) and this study was 1. 37 adults/m2 and 2.25 adults/m2 respectively and did not differ significantly (t = 3.6, df = 7, p = 0.221). Mean density of nymphs of the eight farms shared by Jewett (2006) a nd this study was 6.79 nymphs/ m2 and 0.00 nymphs/ m2 respectively and did differ significantly (t =-2.7 df = 7, p = 0.037). The number of cows ranged from 1 to 30, the number of hectares from 1.5 to 79, and grass height from 8 cm to 50 cm. There were six far ms identified as burned and five as not burned. A significant difference in Prosapia abundance was found between burned and not burned pastures, with an average of 3.11 1. 48 (N = 6) adults/ m2 in burned pastures and an average of 0.33 .47 (N = 5) adult s/ m2 in not burned pastures (Figure 1, Rank Sum Test, T = 15, p < 0.05, n = 6 (burned), n = 5 (not burned)). A significant difference was also found between the mean altitude of burned and not burned pastures (Rank Sum Test, T = 18, p < 0.05, n = 6 (b urned), n = 5 (not burned)). Burned pastures had a higher average altitude of 1382 m 120 m (N = 6) where as not burned pastures had an average altitude of 1108 m 235 m (N = 5) (Figure 2). 0 0.5 1 1.5 2 2.5 3 3.5 4 burnednot burnedAvg. Number of Prosapia FIGURE 1. Mean number of Prosapia adults/m2 in burned and not burned pastures in the Monteverde area of Costa Rica. (n = 6, 5 respec tively)
4 0 200 400 600 800 1000 1200 1400 1600 burnednot burnedAltitude (m) FIGURE 2. Mean altitude of burned and not burned pastures in the Monteverde area of Costa Rica. (n = 6, 5 respective ly) The data suggest that Prosapia abundance may increase with elevation, but due to a small sample size a linear regression analysis wa s not used (Figures 3 & 4). Elevation was not found to be significant when grass height w as controlled for (ANCOVA, F1,10 = 1.97, P = 0.21) and number of hectares was controll ed for (ANCOVA, F1,10 = 3.50, P = 0.078). Elevation was found to be significant when the number of cows was controlled for (Table 1, ANCOVA, p = 0.03). -1 0 1 2 3 4 5 6 700900110013001500 Altitude(m)Abundance (#/m2) FIGURE 3. The abundance of Prosapia adults per m2 vs. Altitude in the Monteverde area in Costa Rica (n = 11).
5 0 1 2 3 4 5 6 700900110013001500 Altitude (m)Abundance (#/m2) No Pesticide Pesticide FIGURE 4. The abundance of Prosapia adults per m2 in farms that used pesticides and farms that did not use pesticides vs Altitude in the Monteverde area in Costa Rica. TABLE 1. ANCOVA: The effects of altitude, number of cows, and their interaction on the number of Prosap ia adults. There is a significant overall model effec t but no single effect was significant. Effect DF F Ratio Prob > F Altitude 1 2.803 0.14 Cows 1 3.861 0.09 Alt+Cows 1 1.0998 0.33 Model 5.2 0.03 DISCUSSION The data appears to support my hypothesis, suggesti ng that Prosapia abundance may increase with altitude as illustrated in Figure 1, however, the relationship did not prove to be statistically significant. Furthermore, when far ms were categorized by pesticide use (Figure 2) and graphed, this relationship only appe ared in farms that did not use pesticides. Pesticides lower the abundance of Prosapia and while we do not know whether a statistically significant difference exis ts when insects are controlled for, Figure 2 suggests that there may be a difference.
6 The data indicated that the number of hectares and grass height did not significantly affect Prosapia abundance, but did show the number of cows as a significant factor. More cows imply heavier grazing which disrupts the nymphs habitat, increases mortality rate and therefore, decreases a dult abundance (Sotomayor-Rios and Pitman 2000). Prosapia abundance in pastures was also examined by determi ning whether or not the pastures were burned. Pastures appear burned if a sufficient abundance of Prosapia is or recently had been present. Greater abundance of Prosapia found in the burned pastures supports this claim. Following th is line of logic, it seems that there may be a higher abundance of Prosapia at higher altitudes due to the fact that the avera ge altitude of the burned pastures was significantly higher than that of the not burned pastures. Altitudinal climate variations may explain the hig her abundance of Prosapia at higher altitudes. A study done by Sujii et al. (200 2) on a different genus and species of spittlebugs, Deois flavopicta found that a larger number of dormant eggs began embryonic development when exposed to increased per iods of moisture. They also found that extended dry periods and higher temperatures a fter egg development begins resulted in higher embryonic and nymphal mortality rates. In the Monteverde area, higher altitudes have more precipitation in the form of wi nd-driven cloud water (Clark et al. 2000). Also, the higher altitudes have cooler tempe ratures than the lower altitudes (Clark et al. 2000). With the more favorable conditions of more moisture and cooler temperatures in the higher altitudes of Monteverde, it makes sense that there would be a higher abundance of Prosapia Consequently, mortality rates of the embryonic and nymphal stages of Prosapia may be higher in the lower altitudes due to the un favorable conditions of less moisture and extended dry period s. The comparison of dry season and wet season popula tions of Prosapia were found to agree with the seasonal patterns of previo us studies (Peck 1996). In comparing the eight farms shared by both my study and Jewett (2006), although not significantly different for adults, I found more adults and fewer nymphs during the mid-wet season than what he found in the dry season. This is due t o the fact that by this time of year nymphs have been able to go through their five inst ars and molt into their adult form. Overall, the findings of this study merit further investigation into the relationship between altitude and Prosapia abundance in the Monteverde region of Costa Rica. Even with such a small sample size, the data still sugge st a greater abundance of Prosapia at higher altitudes. Further studies with higher sampl e sizes are needed. Another study that should be done is to compare reproductive success r ates of Prosapia at different altitudes. The understanding of where and why Prosapia are most abundant in the Monteverde region is important so that farmers can use managem ent practices more efficiently to control this pasture pest. ACKNOWLEDGMENTS I would like to thank Karen Masters for all her har d work in contacting the farmers and assisting me o n my project. I would also like to thank Pablo Allen Mon ge and Moncho Calderon for being very helpful with answering my questions. Thank you to Rafa for drivi ng me to all the farms and helping with the intervi ews. Finally, I would like to extend my thanks to the fa rmers for allowing me to visit their farms and givi ng me some of their time.
7 LITERATE CITED CLARK, K.L., LAWTON, R.O., and BUTLER, P.R. 2000. The Physical Environment. In: Monteverde, Ecology and Conservation of a Trop ical Cloud Forest Nadkarni, N.M., Wheelwright, N.T., ed. Oxford University Press, New York, NY. pp. 15-30. HOLMANN, F., AND D.C. PECK. 2002. Economic Damage Caused by Spittlebugs (Homo ptera: Cercopidae) in Colombia: A First Approximation of Impact on Ani mal Production in Brachiaria decumbens Pastures. Neotropical Entomology. 31(2): 391-398. JEWETT, G. 2006. Management practices and Prosapia (Homop tera: Cecropidae) in Monteverde area farms. CIEE Spring Semester 2006. PECK, D.C. 1999. Seasonal Fluctuations and Phenology of Prosapia Spittlebugs (Homoptera:Cercopidae) in Upland Pastures of Costa Rica. Environmental Ent omology 28: 372-386. PECK, D.C., 1996. The Agroecology of Prosapia: Spittlebugs, Froghoppers, and Pasture pests. In: Monteverde, Ecology and Conservation of a Tropi cal Cloud Forest Nadkarni, N.M., Wheelwright, N.T., ed. Oxford University Press, New York, NY. pp 409-410. PECK, D.C. 1996. The Association of Spittlebugs With Gr asslands: Ecology of Prosapia (Homoptera: Cercopidae) in Upland Dairy Pastures of Costa Rica. PhD Dissertation Cornell University. SOTOMAYOR-RIOS, A., AND W.D. PITMAN. Tropical Forage Plants: Development and Use. CRC Press 2000. pp 208. SUJII, E., GARCIA, M., FONTES, E., PIRES, C., ONEIL, R. 2002. Effects of Meteorological Variation on Mortality in Populations of the Spittlebug Deois flavopicta (Homptera:Cercopidae). Environmental Entomology 31: 299-305. APPENDIX I. Interview used for each farm owner. Cuestionario sobre Prosapia 1. Cmo se llama Ud. y cmo se llama su finca? 2. Cuntas vacas tiene? 3. Cuntas hectreas tiene? 4. Que tipo de zacate tiene usted? 5. Est teniendo problemas con insectos que mantan el pasto en su finca? 6. Cuntos das se le permite al Ganado permanecer en el mismo potrero antes de rotarlos? 7. Qe tipo de plaguicidas usa? -Jade -conter -desis -tamaron -Otro: por favor escriba el nombre 8. Qu tipo de hongos usa para contrala a la Prosa pia? Circle one El Metarhizium anisopliae Fusarium camptocera Bauveria spp
8 Otro: por favor escriba el nombre 9. Cmo aplica el hongo?, Directamente o mezclado con agua y aceite? 10. Cunto le cuesta por ao, en colones, el produ cto para controlar la prosapia? 11. Usa Ud. incendios controlador en sus portrero s? Si o no. 12.Usted corta el pasto para controlar el prosapia ? a. 13. Puedo contar los insectos en 1 metro quadrado en su postrero? APPENDIX II. The owners of the eleven farms surveyed for this s tudy and their location. 1-Alberto RojasLa Cruz 2-Hermanos Brenes La Cruz 3-Gerardo Vargas Marin La Cruz 4-Xinia Araya Leiton San Luis 5-Rafael Leiton Mendez San Luis 6-Benito GuindonMonteverde 7-Martha CampbellMonteverde 8Randall BelloLa Cruz 9 Norman Santamaria La Cruz 10 Wilbert Mata Leiton Bajo San Luis 11 Jose Louis Sampos Bajo San Luis