Herbicide control of swamp titi (Cyrilla racemiflora) in restoration of ephemeral wetlands

Abstract

Swamp titi (Cyrilla racemiflora L.) is a vigorous native shrub or small tree found in poorly drained areas of the southeastern U.S. Coastal Plain. In the absence of fire, it creates dense thickets that prevent herbaceous groundcover in ephemeral wetlands, degrading habitat for uncommon and endangered amphibians and other genera. In our study, aquatic herbicides and methods of application were examined at two forests in north Florida for restoration of ephemeral wetland habitat to benefit wetland‐breeding amphibians. Glyphosate, imazapyr, and combinations of glyphosate and imazapyr were tested in four study protocols that included an operational standard (triclopyr), treatment method control, and untreated control where appropriate. Results of foliar protocols (targeting rootstocks less than 1.5 m tall) demonstrated that glyphosate provided better titi control than imazapyr (average of 79% vs. 12% mortality), there was no strong improvement with the addition of imazapyr to glyphosate (84% mortality), glyphosate treatments had titi mortality as high or higher than the triclopyr operational treatment (57% mortality), and that methylated seed oil surfactant improved glyphosate efficacy but might have been antagonistic for combination treatments. Glyphosate and imazapyr cut stump treatments did not provide higher efficacy than the triclopyr standard treatment (60% mortality). Cut stem treatments (targeting rootstocks greater than 1.5 m tall) provided the highest level of control averaging 97, 90, 97, and 80% mortality for glyphosate, imazapyr, combination treatments, and triclopyr standard, respectively. Only directed foliar sprays reduced total groundcover and graminoid cover, with triclopyr treatment giving the least reduction of desired herbaceous groundcover.