Abundancia de chisas rizófagas (Coleoptera: Melolonthidae) en agroecosistemas de Caldono y Buenos Aires, Cauca, Colombia = Abundance of whitegrubs (Coleoptera: Melolonthidae) in two Colombian agroecosystems

Al examinar la composición y variación de la abundancia del problema de plagas subterráneas tipo chisa (larvas de Coleóptera Melolonthidae) en Caldono y Buenos Aires, dos localidades agrícolas del departamento del Cauca (altitud: 1.400 a 1.500 msnm; T°: 21,5°C (promedio); precipitación: 2.192 mm/año), se registró la presencia de varias especies, integrando un complejo de especies cuya abundancia es variable y depende del medio agrícola y el clima Con la finalidad de determinar si la cantidad de las chisas estrictamente rizófagas es una variable importante en el daño ocasionado, se desarrollaron muestreos en cuatro circunstancias agroecológicas en parcelas de media hectárea, así: cultivo de yuca, pastizal, cafetal (sombrío), bosque (área media Ha), que se visitaron cada 15 días (12 excursiones). Adicionalmente, durante un año, se colectaron adultos en trampas de luz para complementar el estudio. Se obtuvieron 12.512 adultos y 10.261 larvas representativas de 32 especies de la familia Melolonthidae. Los análisis estadísticos de cuatro muestreos simultáneos, revelan diferencias significativas en la abundancia de individuos entre las dos localidades (F= 248,83; p= 0.0), entre muestreos (F= 20,27; p= 6,02) y entre los cuatro tipos de habitat (parcela) combinando los dos sitios muestreados (F= 34,43; p = 4,7). Se concluye que existe semejanza entre las estructuras del complejo chisa de las dos localidades de estudio, aunque al analizar en detalle la abundancia se revelan diferencias significativas entre localidades, muestreos y tipos de habitat explicadas en términos de las variaciones climáticas, edáficas y sistemas de manejo agrícola existentes entre las localidades. La sola abundancia del complejo no permite determinar el efecto nocivo en cultivos, ya que ello está dado por la abundancia de las chisas estrictamente rizófagas. = The composition and variation in frequency of soil pests, especially the whitegrub (larvae of Coleoptera, family Melolonthidae) was studied in Caldono and Buenos Aires. These are two agricultural locations in the Department of Cauca (elevation ranges from 1.400-1.500 meters above sea level, temperature of 21.5°C and precipitation averaging 2.192 mm/year). This study showed that the whitegrub complex was composed of several species, in different stages of development. Samples were taken to determine the number and influence of root feeding whitegrubs on plant damage. This was done in four different agro-ecologies: cassava, pasture, coffee under shade, and forest fields. Each plot had an area half an hectare and samples were taken every 15 days, with 12 samples dates, from which four were used for the statistical analysis. A total of 12.512 adults and 10.261 larvae were collected, which represented 32 species within the family Melolonthidae. The statistical analysis of the selected data revealed significant differences in number of individuals from localities (f =248,83; p=O.0), between samples (f =20,27; p=6,02) and between the four types of habitat when the two localities were combined for analysis (f=34,43; p=4.7). In conclusion, there were similarities in the structure of the complex of whitegrubs in Caldono and Buenos Aires (Cauca), however when abundance of whitegrubs was analyzed in detail, statistical differences were noted between the four ecologies selected for the study, which are explained by variations in climate and soils between localities. The data obtained allow us to conclude that the damage caused by whitegrubs is more severe in Caldono than in Buenos Aires

Riqueza del complejo chisa (Coleoptera: Melolonthidae) en cuatro agroecosistemas del Cauca, Colombia

La composición y variación de la riqueza del complejo de larvas Melolonthidae se examinó en cuatro circunstancias agroecológicas en los municipios de Caldono y Buenos Aires, Cauca (1400 a 1500 m.s.n.m, 21,5ºC. y 2000 mm/año de precipitación promedio). Quincenalmente, durante un año, se visitaron parcelas de media hectárea de yuca, pastizal, cafetal y bosque, en cada parcela y ocasión se realizaron 10 muestreos ( 1m2 por 15 cm de profundidad). Se colectaron 10.261 larvas pertenecientes a 32 especies y 12 géneros de Melolonthidae, así: Phyllophaga, Plectris, Astaena, Macrodactylus, Ceraspis, Barybas, Isonychus, Anomala Callistethus, Strigoderma, Leucothyreus, Cyclocephala. La riqueza de especies presentó variaciones estadísticamente significativas entre localidades (F=87.24 p =2.72-18), muestreos (F=22.29 p =5.18-13), parcelas (F= 23.39 p=1.40-13) así como entre la mayoría de interacciones. Los promedios de riqueza fueron: yuca (4.5 ), pastizal (3.6), café (2.1) y bosque (2.2), cada uno con grandes fluctuaciones que hicieron la diferencia. Se discuten las curvas de isodensidades de cada parcela y sus implicaciones en el programa de manejo. = Richness of the white-grub complex (Coleoptera: Melolonthidae) in agroecosystems of the Cauca province, Colombia. The composition and variation in the richness of the complex of rhizophagous Melolonthidae larvae was examinated in four agroecological zones in the Municipality of Caldono (1400-1500 m, 21.5ºC, average rainfall 2000 mm/yr) with complementary surveys in the neighbouring site of Buenos Aires, Cauca. Half-hectare plots (cassava, pastures, coffee and wooded areas) were selected and visited every 15 days (total of 15 visits per plot), and a total of 10 samples were taken (1 m2 by 15 cm deep). In total, 10,261 larvae of 32 species were collected: Phyllophaga, Plectris, Astaena, Macrodactylus, Ceraspis, Barybas, Isonychus, Anomala Callistethus, Strigoderma, Leucothyreus, Cyclocephala. The richness of species varied significantly among sites (F=87.24; p =2.72-18), samples (F=22.29; p=5.18-13), plots (F=23.39; p=1.40-13). In most cases, the average rates for richness were: pastures (3.6), cassava (4.5), coffee (2.11) and wooded areas (2.2). They all had substantial fluctuations, which accounts for the differences. The isodensity curves for each plot are presented and discussed

Structure and composition of the white grub complex (Coleoptera: Scarabaeidae) in agroecological systems of Northern Cauca, Colombia

The larvae of some species of Scarabaeidae, known locally as chisas (whitegrubs), are important pests in agricultural areas of the Cauca, Colombia. They form a complex consisting of many species belonging to several genera that affect the roots of commercial crops. The objective of the present study was to identify the members of the complex present in two localities (Caldono and Buenos Aires) and collect basic information on their biology, economic importance, and larval morphology. The first of two types of sampling involved sampling adults in light traps installed weekly throughout one year. The second method involved larval collections in plots of cassava, pasture, coffee, and woodland. Each locality was visited once per month and 10 samples per plot were collected on each occasion, with each sample from a quadrants 1 m2 by 15 cm deep, during 1999-2000. Light traps collected 12,512 adults belonging to 45 species and 21 genera of Scarabaeidae within the subfamilies Dynastinae, Melolonthinae, and Rutelinae. Members of the subfamily Dynastinae predominated with 48% of the species (mostly Cyclocephala), followed in decreasing order by Melolonthinae (35%) and Rutelinae (15%, principally Anomala). Melolonthinae comprised 60% of the specimens (Plectris spp. 59.5% and Phyllophaga spp. 35.9%). A total of 10,261 larvae of 32 species was collected, including 12 species each of Melolonthinae (Phyllophaga, Plectris, Astaena, Macrodactylus, Ceraspis, Barybas, and Isonychus), Rutelinae (Anomala, Callistethus, Stigoderma, and Leucothyreus) and Dynastinae (principally Cyclocephala). At least a third of the species sampled as larvae are rhizophagous pests. Taken together, adult and larval sampling methods permitted a more precise definition of the whitegrub complex in Caldono and Buenos Aires