Abstract

BUENO, JUAN MIGUEL  and  CARDONA M, CÉSAR. Action threshold for Thrips palmi (Thysanoptera: Thripidae) on snap beans in the Cauca Valley, Colombia. Rev. Colomb. Entomol. [online]. 2003, vol.29, n.1, pp.51-55. ISSN 0120-0488.

Since its introduction to Colombia in 1997, the melón thrips, Thrips palmi Karny, has become one of the main pests of snap beans in the Cauca Valley. At present, this species is the target of excessive use of insecticides. One way to rationalize the use of pesticides is to apply them at critical infestation levéis, known as action thresholds. To develop an action threshold for T. palmi, two complete randomized blocks triáis and one in Latin square design were conducted in Pradera (980 meters above sea level, 23 °C). In these experiments, snap bean response to increasing infestation levéis (1-17 adults/leaflet) was measured. A negative relationship was found between infestation levéis and yields that can be explained by the regression y = 12926 - 695.9x, average of three triáis. Usinga loss function of 695.9 kg/ha per adult/leaflet, an average action threshold of 7.0 adults per leaflet was calculated. When infestation levéis were maintained below this threshold, actual infestation levéis through the crop cycle ranged from 3 to 4 adults/leaflet. The potential use of this action threshold in a management system is discussed.

Keywords : Management system; Critical level; Control; Phaseolus vulgaris.

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