Abstract

PARDO-LOCARNO, Luis Carlos  and  MONTOYA LERMA, James. Life cycle, agricultural importance and integrated management of the rhizophagous whitegrub, Phyllophaga menetriesi Blanchard (Coleoptera: Melolonthidae), in Cauca and Quindío, Colombia . Acta Agron. [online]. 2007, vol.56, n.4, pp.195-202. ISSN 0120-2812.

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 m² 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/m² produced total loss of maize and cassava plants less than 2 months old. Incidence ranged from 0 to 8 larvae/m², 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/m² or above could exact soil removal, localized use of chemicals, and incorporation of phytomass to promote saprophagous grubs, trophic diversity, and natural enemies.

Keywords : Phyllophaga menetriesi; Coleoptera; Melolonthidae; biology; integrated management; Colombia.

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