Phytotoxicity of clopyralid at high rates on seed germination of mediterranean pines

Abstract

Black pine (Pinus nigra J. F. Arnold), maritime pine (P. pinaster Aiton), Scots pine (P. sylvestris L.), and Turkish red pine (TRP, P. brutia Ten.) are ecologically and economically important conifers of the Mediterranean Basin, and in particular for Turkish forestry. They are commonly used for the regeneration and restoration of degraded ecosystems in Turkey. Weeds compete with tree seedlings for vital site elements such as soil moisture and nutrients and solar radiation, substantially reducing tree establishment and growth. Herbicides can offer the practitioner efficient and cost-effective weed control compared to other methods. Rapid herbicide seed screening allows testing of crop-safe herbicides and application rates at much lower costs in a very short time-frame when compared to lengthy field trials. Clopyralid is a systemic herbicide used to rid pine seedlings of competing vegetation. The present study examined the effect of clopyralid phytotoxicity on these pine species using a rapid herbicide seed screening test in order to compare different application rates on seed germination and to identify crop-safe rates. Clopyralid was not phytotoxic to any of the pine species at low rates (i.e., <2%, v:v); however, pine sensitivity to the herbicide increased with increasing rates, especially for rates higher than 3%. Moreover, at high rates, clopyralid reduced the germination speed. This herbicide can be used at low rates for degraded areas and nursery sites in which sowing is used as the main regeneration or restoration method. Field confirmation of the obtained results is also recommended.