Life cycle, agricultural importance and integrated management of the rhizophagous whitegrub, Phyllophaga menetriesi Blanchard (Coleoptera: Melolonthidae), in Cauca and Quindío, Colombia Ciclo de vida, importancia agrícola y manejo integrado de la chisa rizófaga Phyllophaga menetriesi Blanchard (Coleoptera: Melolonthidae), en Cauca y Quindío, Colombia

The life cycle of Phyllophaga menetriesi was studied under laboratory conditions using samples taken from different crop systems in the departments of Cauca and Quindio, Colombia. The life cycle is annual and the developmental stages of this species were as follows: egg, 2–3 weeks; first instar, 3–4 weeks; second instar, 6–8 weeks; third instar, 20–25 weeks; prepupa, 2–3 weeks; pupa, 4–5 weeks; and adult, 4–6 weeks for males and 4–8 weeks for females. Cephalic width as well as body width and length (mm) were measured in the three instars, with the following results: first instar: 1.85– 2.04, 1.05–2.02, and 14.3–19.2, respectively; second instar: 3.3–3.95, 4.02–5.1, and 24–35, respectively; and third instar: 5.8–6.02, 6.1–7.6, and 56–67, respectively. The reproductive period of these insects was short and coincided with the rainy season (October–November), based on the results of weekly catches of insects using light traps in Caldono, Cauca (2° 81' N, 76° 55' W, 1450 m.a.s.l., and an annual pluvial precipitation of 2191 mm). To assess the economic impact of the insect, monthly samples were taken in quadrats (1 m 2 and 25 cm deep) in Quimbaya, Quindío (04° 38´ 02"; N, 75° 47´ 47";W, 1274 m.a.s.l., and an annual precipitation of 2000 mm). Results showed that 5 larvae/m 2 produced total loss of maize and cassava plants less than 2 months old. Incidence ranged from 0 to 8 larvae/m 2 , showing an irregular distribution. The highest densities were detected in pastures and in cassava crops. Plots with a history of incidence should be closely monitored using light traps as an early warning system. The presence of larvae should be determined immediately after the October rains and a microbiological control treatment has to be applied as preventive measure. Levels of 4 larvas/m 2 or above could exact soil removal, localized use of chemicals, and incorporation of phytomass to promote saprophagous grubs, trophic diversity, and natural enemies. La biología e importancia agrícola de P. menetriesi , especie rizófaga, fue ...