Abstract: A portable trench barrier is capable of greatly reducing the number of beetles migrating into a cultivated area, such as a field of potato plants. The device comprises a series of linear barrier sections and connector pieces joined together to enclose and protect a cultivated area. Each linear barrier section comprises an extruded plastic section having (a) an elongated floor section, (b) a pair of continuous leg portions extending downwardly from the side edges of the floor portion. The leg portions are adapted to penetrate the soil and form a continuous sub-surface barrier. A pair of opposed upwardly inclined elongated ramp portions extending upwardly and inwardly from the side edges of the floor portion, these ramp portions terminating in downwardly curved free edge portions having smooth outer surfaces with the curved free edge portions of the opposed ramp portions forming therebetween a gap having a width of up to about 20 mm.