Burning and 2,4,5-T Application on Mortality and Carbohydrate Reserves in Saw-Palmetto

Abstract

On the flatwoods of the southeastern United States control of saw-palmetto (Serenca repens (Bartr.) Small) is an important step in the improvement of native pastures. This study, conducted at the Ona Agricultural Research Center in south Florida, measured fluctuations in total available carbohydrates (TAC) in rhizomes of burned and unburned saw-palmetto which received a June or October application of 8.9 kg/ha (acid equiv.) of 2,4,5-T. Palmetto kill, change in palmetto cover, and grass canopy cover were evaluated. Burning reduced TAC concentration in rhizomes from 48.8% in March to 14.3% in July as compared to a drop from 47.2% to 37.4% for unburned plants. Applying 2,4,5-T caused a further significant decline in TAC concentration. Both burning and 2,4,5-T resulted in lower rhizome percent dry matter indicating that treatment stress caused metabolism of carbohydrate which was replaced by water. After 1 year there was higher mortality on palmetto receiving 2,4,5-T in June, but after 2 years there was no difference in mortality between June (48%) and October sprayed (39%) plants. Burning was not found to have a significant effect on mortality of sprayed plants. Burning and 2,4,5-T decreased palmetto cover, and burned plants treated with 2,4,5-T in June had less cover than burned plants treated in October with 2,4,5-T. Burning followed by 2,4,5-T application in June increased grass cover from 29.4% at the beginning of the study to 67.5% at the end.