Physiological Basis for Triazine Herbicide Tolerance in Bermudagrass, Seashore Paspalum, and Zoysiagrass

Abstract

Atrazine and simazine control weeds in warm‐season turfgrasses, but excessive injury limits applications to sensitive species. The objective of this research was to evaluate the physiological basis for differential tolerances of bermudagrass (Cynodon dactylon (L.) Pers.), seashore paspalum (Paspalum vaginatum Sw.), and zoysiagrass (Zoysia japonica Steud.) to atrazine and simazine. In greenhouse experiments, hierarchical shoot mass reductions from the nontreated by species were: seashore paspalum > bermudagrass > zoysiagrass for atrazine and seashore paspalum > bermudagrass = zoysiagrass for simazine. Atrazine and simazine treatments to soil only or foliar plus soil reduced shoot mass similarly, averaging 45% from nontreated, while foliar‐only treatments reduced shoot mass 22% from the nontreated. Species rank for root absorption of both herbicides after 48 h from high to low was seashore paspalum > bermudagrass > zoysiagrass. All species had acropetal translocation of 14C‐atrazine and 14C‐simazine, but bermudagrass and zoysiagrass translocated ∼10% more 14C than seashore paspalum after 48 h. Hierarchical species rank for nonmetabolized 14C‐atrazine translocation to shoots after 8 h from high to low was seashore paspalum > bermudagrass > zoysiagrass. All species metabolized 14C‐atrazine to hydroxyatrazine and two unidentified metabolites in root and shoots. All species metabolized simazine to hydroxysimazine and two other metabolites in shoots. Seashore paspalum had less total metabolism of 14C‐simazine than bermudagrass and zoysiagrass and produced fewer metabolites in roots. Results suggest bermudagrass and seashore paspalum susceptibility to atrazine is associated with greater absorption and translocation of the parent herbicide to shoots than zoysiagrass. Seashore paspalum susceptibility to injury from simazine is associated with differences in absorption and metabolism from tolerant turfgrasses bermudagrass and zoysiagrass.

Target and Nontarget Resistance Mechanisms Induce Annual Bluegrass (Poa annua) Resistance to Atrazine, Amicarbazone, and Diuron

“…Absorption was similar across harvests suggesting radioactivity was not lost after returning plants to the hydroponic tank at 24 HAT. Reduced absorption of DR3 agrees with findings of Singh et al (2015) showing increased metabolism coupled with reduced absorption results in higher simazine tolerance for zoysiagrass (Zoysia japonica Steud.) and bermudagrass when compared with the more sensitive seashore paspalum (Paspalum vaginatum Sw.).…”

Physiological Basis for Bermudagrass Control with Ethofumesate in Seashore Paspalum and St. Augustinegrass

“…The susceptibility of turfgrasses to herbicide injury has also been correlated with levels of root absorption. Singh et al (2015) reported seashore paspalum had greater root uptake of 14 C‐atrazine and 14 C‐simazine than turfgrasses with greater tolerance levels, bermudagrass and zoysiagrass ( Zoysia japonica L.). Yu et al (2013) reported annual bluegrass ( Poa annua L.) had greater root absorption of 14 C‐amicarbazone than creeping bentgrass ( Agrostis stolonifera L.) and tall fescue ( Festuca arundinacea Shreb.).…”

First Report of Pronamide-Resistant Annual Bluegrass (Poa annua)

“…Reduced levels of root absorption have been attributed to annual bluegrass resistance to atrazine in the absence of a mutated D1 protein (Svyantek et al 2016). Root absorption levels also contribute to the selectivity of herbicides used for annual bluegrass control and the susceptibility of turfgrass species to injury from applications (Lycan and Hart 2006; McCullough et al 2016; Singh et al 2015; Yu and McCullough 2016; Yu et al 2013).…”

“…Plant counts for the nontreated averaged 9 (±1.7 SE) and 6 (±1.5 SE) per pot for the R and S biotypes in Experiment 3, respectively, and 15 (±1.5 SE) and 25 (±2.7 SE) in Experiment 4, respectively. turfgrass species to injury from applications (Lycan and Hart 2006;McCullough et al 2016;Singh et al 2015;Yu and McCullough 2016;Yu et al 2013).…”