~7 jp U. S. DEPT. OF AGRICULTURE 



U.|. N 5F0REST SERVICE 



CURRENT SEKIAL fttoo^S 



RESEARCH NOTE LS-37 



LAJ^E STATES FOREST ^EXPERIMENT STATION -U.S. DEPARTMENT OF AGRICULTURE 



"7 ' 7i? 





A Test of Concentrated Silvicides on Sugar Maple 



^ 



In a recent test of silvicides by the Lake 

 States Forest Experiment Station in cooperation 

 with the Diamond-National Corporation, 2,4-D 

 amine salts applied in frill girdles produced 

 greater mortality of cull sugar maple trees than 

 did any of the other treatments tested. 



A series of unpublished earlier trials, using 

 both esters and amines of 2,4, 5-T and 2,4-D, 

 indicated more rapid killing could be obtained 

 with amine salts than with esters. Consequently 

 it was decided to test concentrated amines of 

 these two chemicals applied at full strength (4 

 pounds acid equivalent per gallon) and diluted 

 50 percent with water. 1 Two methods of appli- 

 cation were employed: (1) sprayed into freshly 

 cut frills made by axe girdling and (2) injected 

 with a tree injector at 1-inch spacings around 

 the root collar. Thus, eight treatments — two 

 chemicals, two concentrations, and two methods 

 of application — were tested. Each treatment 

 was randomly assigned to a group of 10 trees 

 ranging from 7 to 14 inches in diameter at 

 breast height. These treatments were repeated 

 in three separate blocks, making a total of 240 

 trees in the study. 



The study was installed in northern Minne- 

 sota on July 24, 1961. The treatments were 

 appraised on June 13, 1962, and a final exami- 

 nation was made on June 21, 1963. 



1 The two chemicals used in this test, triethylamine 

 salts of 2,4,5-T and alkanolamine (ethanol and 

 isoproponol series) salts of 2,4-D, were supplied 

 through the courtesy of the Dow Chemical Company. 



The results in 1962 showed that 2,4-D had 

 killed a greater proportion of the trees than had 

 2,4,5-T. A greater proportion of the trees were 

 also three-fourths or more defoliated with 2,4-D 

 than with 2,4,5-T (table 1). An analysis of vari- 

 ance showed both these differences significant at 

 the 5-percent confidence level. These same dif- 

 ferences were still significant in 1963, and in 

 addition the application of the chemicals in 

 frills proved more effective than with the tree 

 injector. There was no significant difference be- 

 tween the two concentrations of chemicals used. 



Application of the concentrated silvicides 

 into freshly cut frills was facilitated by a pres- 

 sure oil can. It is possible that the frill girdling 

 itself contributed some to the success of this 

 method. The effects of girdling alone, however, 

 were not tested in this study because of extremely 

 slow results obtained in the past. 



The chemicals had the least effect on domi- 

 nant trees, which averaged only 30 percent dead 

 compared to 49 percent of the codominant, 68 

 percent of the intermediate, and 75 percent of 

 the suppressed. 



During the field examination it was noted 

 that many of the trees classified as living had no 

 live tissue around their stem below where the 

 silvicide was applied. Two possible explanations 

 are: (1) Some trees are able to keep their crowns 

 alive for a considerable length of time with food 

 reserves stored in the root system. (2) The 

 sample trees are. scattered throughout a stand of 



MAINTAINED AT ST. PAUL'1, MINNESOTA, IN COOPERATION WITH THE UNIVERSITY OF MINNESOTA 



