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ŠUMARSKI LIST 1-2/2022 str. 54     <-- 54 -->        PDF

(e.g., drought, erosion) and anthropogenic pressure (Genç 2012; Boydak and Çalıºkan 2014; Yildiz et al. 2018).
Weeds compete with tree seedlings for vital site elements such as soil moisture and nutrients and solar radiation, substantially reducing tree establishment and growth (Wagner et al. 2004; Radosevich et al. 2007). Consequently, effective weed control on natural forest regeneration and afforestation sites becomes essential (Radosevich et al. 2007). Herbicides can offer the practitioner efficient and cost-effective weed control compared to other methods (Eºen and Yıldız 2000; Wagner et al. 2004; Eºen et al. 2005, 2006; Radosevich et al. 2007).
“Rapid herbicide seed screening” is a method wherein tree seeds are pretreated with herbicide formulations before germination assessments. This method allows screening for crop-safe herbicides and application-rates at much lower costs within a very short time frame (i.e., 30 days or less) compared to the expensive and lengthier tests in the field (i.e., 10 months) (Zedaker and Seiler 1988; Bunn et al. 1995; Blair et al. 2006; Stanley et al. 2014; Dağlar et al. 2016, Bakan et al. 2018; Türedi et al. 2018; Bakan 2019). Recently, this method was employed in black pine, Scots pine, and maritime pine to assess the phytotoxicity of glyphosate (Türedi et al. 2018) and methsulfuron methyl (Dağlar et al. 2016) on the seed germination of the species. Herbicide sensitivity of these pines to these herbicides was found to vary substantially according to species and herbicide application rates (Dağlar et al. 2016; Türedi et al. 2018). Additionally, the rapid herbicide seed screening test using black, Scots, and maritime pine seeds pretreated with glyphosate (Türedi et al. 2018) successfully predicted the results of a longer field trial using 1-3-year-old seedlings of the same pine species in terms of glyphosate sensitivity (Cap and Eºen 2018), thus confirming previous reports of the high correlation between short herbicide seed screening and longer field screening trials (Zedaker and Seiler 1988; Bunn et al. 1995; Blair et al. 2006; Stanley et al. 2014; Dağlar et al. 2016; Türedi et al. 2018).
Clopyralid is a growth-regulating, post-emergence herbicide belonging to the pyridine carboxylic acid group (Monaco et al. 2002; Dixon et al. 2005). It is mainly applied to plant foliage and then roots and is easily translocated to the meristematic sites. Clopyralid effectively controls many broadleaf herbaceous and some woody weeds (Monaco et al. 2002; Dixon et al. 2005) and is reported to be safe for young seedlings of many pine species including longleaf pine (P. palustris Mill.), slash pine (P. elliottii Engelm. var. elliottii), and loblolly pine (P. taeda L.) (South 2000) as well as Scots pine (P. sylvestris L.) (Vea and Palmer 2009).
Clopyralid phytotoxicity on black pine, maritime pine, Scots pine, and Turkish red pine (TRP) at low rates was studied in a recent, preliminary rapid seed screening test in Turkey (Bakan et al. 2018; Bakan 2019). In this preliminary test, clopyralid demonstrated no significant phytotoxic effects on the listed pine species at low rates of 0-1% (v:v). Further testing of the phytotoxicity of this herbicide at higher rates on these pine species was recommended (Bakan et al. 2018; Bakan 2019).
Consequently, as a continuation of the study of Bakan et al. (2018) and Bakan (2019), the present study, in a separate rapid seed germination test, examined black pine, maritime pine, Scots pine, and TRP for clopyralid phytotoxicity at higher rates. The study aimed to determine the clopyralid sensitivity of the pine species at high rates and to help develop a tree-safe pre-emergence herbicide weed control treatment for pine regeneration and/or restoration sites and forest nurseries where sowing is the principal basis of propagation. Considering the high correlation between the results of the rapid seed screening test and those of the field herbicide screening trial, the findings of the present study could also be used for the post-emergence control of herbaceous weeds in the field.
MATERIAL AND METHODS
METODE I MATERIJALI
Prior to the experiment, pine seeds were obtained from the Bolu Forest Nursery situated in Bolu, Turkey, in the autumn of 2015 and stored in air-tight plastic bags in the refrigerator (4-6 ºC) at the Duzce University Forestry Faculty (Dağlar et al. 2016; Bakan et al. 2018; Bakan 2019). The seeds of black, Scots, and maritime pine were collected from their native distribution areas in Bolu-Mengen, Bolu-Aladağ, Izmit-Kefke, and Sakarya-Geyve-Taraklı in the Western Black Sea Region of Turkey in 2014, 2016, 2016, and 2011, respectively. For more detailed information on seed collection and storage, please refer to Bakan (2019). The seeds of these pine did not require pretreatment (i.e., stratification) before germination (Genç 2012).
The present study followed a procedure similar to that of Blair et al. (2006), and more specifically to Dağlar et al. (2016), Bakan et al. (2018), Türedi et al. (2018), and Bakan (2019). Seeds from each of the four pine species were independently presoaked in 100-mL clopyralid (Phaeton 100®, 100 g L-1 a.i., HEKTAª T.A.ª., Gebze Organize San. Bölgesi, İhsan Dede Cd. 700, Sk. 41480, Gebze-Kocaeli, Turkey) solutions at differing rates of 0-5% (v:v) in deionized water in separate plastic containers for 24 h (Table 1) (Bakan 2019). A 0.4% (v:v) Izolcaptan® 50 WP (Metropol Kimya Sanayi ve Ticaret Ltd. ªti., Istanbul, Turkey) was added to the solutions of each rate to prevent the fungus infestations that had occurred in the preliminary test with the lower rates of clopyralid (Bakan and Eºen 2018; Bakan et al. 2018; Bakan 2019). The seeds were then taken from the containers and placed on dry filter paper in 9-cm Petri dishes. For each