The efficacy of intercropping with birdsfoot trefoil and summer savoury in reducing damage inflicted by onion thrips (Thrips tabaci, Thysanoptera, Thripidae) on four leek cultivars

Abstract

Onion thrips, Thrips tabaci (Thysanoptera, Thripidae), are an important pest of leek (Allium porrum) in Slovenia, and their control is becoming increasingly difficult for several reasons (e.g., increased resistance, specific life cycle). Therefore, intercropping, whereby the seeds of a different plant species are sown amidst the primary crop, represents a promising method to prevent pest damage. Our field experiments were conducted in 2009 and 2011, during which we studied the suitability of two different intercrops for reducing the extent of the damage inflicted by onion thrips on the leaves of four different leek cultivars. For the first time, birdsfoot trefoil (Lotus corniculatus, Fabaceae) and summer savoury (Satureja hortensis, Lamiaceae) were chosen as intercrops. Both intercrops significantly reduced the extent of damage in both years when compared to the control plots, in which an intercrop was not sown. We found no noteworthy differences among the cultivars regarding the extent of damage. We also studied the effect of these intercrops on the leek yield. Consistent with previous studies, when grown with these intercrops, the leek yield was lower than that of the control plots; however, we conclude that this reduction is acceptable in light of the advantages of intercropping, especially when utilizing birdsfoot trefoil.