No. 120 

1961 

KILLING CULL TREES WITH AMMATE CRYSTALS 

--A CASE STUDY 

The use of amrnate (ammonium sulfamate) as a treekilling agent has become widespread during recent years; it 

is well established as an effective and economical silvicide. 

The purpose of this report is to supplement present knowledge and also to present a case study on the use of ammate 

in practical application. 

Ammate has been used for the past 10 years as a silvicide on the Fernow Experimental Forest, Parsons, W. Va. 

The deadening of undesirable trees is an integral part of 

the stand treatments in many timber management studies on 

the Fernow. The data presented here deal with costs of application and percents of kill with time. 

Methods 

In all treatments in this study, ammate in crystalline form was applied in notches cut into the tree trunks at 

convenient chopping height above the ground, usually about 

24 feet. One tablespoon of the crystals was placed in each 

notch. Notches cut by expert axmen were spaced about 4 

inches apart, edge to edge, or in practice about an ax-blade 

width apart. Thus, for a tree 6 inches in diameter at breast 

height, 2 notches usually were cut; for a 10-inch tree, 4 

notches; and for a 20-inch tree, 7 to 9 notches. 

Three areas--A, B, and C--were included in the study. 

The cull trees on one area (C) were treated in 1957, on 

another (B) in 1958, and on the last (A) in 1960. All treating was done during the growing season. In 1960, about 30 

days after the last treatment was applied, a sample of ap- 
proximately 240 trees on each area was examined and tallied. 

Effects of treatment were appraised on the basis of defoliation; only completely defoliated trees were tallied as 

killed. 

Results 

Percentages of kill were based on numbers of trees 

sampled. On Area A, where treating had been done only 30 

days before the examination, 45 percent of the sampled trees 

were completely defoliated. Kills progressed with time: 

Area B, 22 months after treatment, showed a 66-percent kill, 

while Area C, 37 months after treatment, showed a 91-percent 

kill (table 1). 

Treatments were somewhat more effective, however, 

than the kill percentages indicated. With the exception of 

one 6-inch beech on Area C, every tree examined on the three 

areas exhibited foliar damage. The treated trees that still 

lived showed the following average percents of crown kill, 

based on an ocular estimate of each tree: Area A - 84, Area 

B - 95, Area C - 97. These almost dead trees offer little 

competition for moisture, nutrients, and growing space. The 

ammate crystals, as here applied, were highly effective the 

first season, and by the third year were almost totally effective in eliminating the competitive influence of the 

treated trees. 

Ammate has been highly effective in killing beech 

root suckers. When cull beeches are killed ' by girdling, 

worthless root suckers often replace the parent trees and 

little, if any, stand improvement results. Observations 

made on 25 ammate-treated beeches 2 months after treatment 

showed an average of three root suckers affected and one 

killed for each tree treated. Past experience indicates 

that most of such affected sucker stems eventually die. 

Twenty different hardwood species were treated. In 

the tabulation below, the species that were sampled in appreciable numbers are divided into three groups based on 

apparent ease of killing by the ammate-notch method. 

Easy to kill Intermediate Difficult to kill 

Black gum Red oak group Birch 

Sour wood White oak group (black and yellow) 

Service berry Beech Sugar maple 

Cucumber magnolia Red maple 

Black locust Hickory 

Basswood 

Sassafras 

This grouping, however, is presented with reservations because species are confounded with average tree 
Table 1.--Eents of kill for three time intervals after treatment, 

arid averze diameters of the trees bv areas 

Table 

r I 

Average 

Date of Elapsed Trees Average 

Area Date of Trees 

treatment observation time examined observed 

d.b*h* Of d.b.h. of killed 

trees dead trees 

Months Number Inches Inches Percent 

A May 1960 June 1960 1 244 13.7 10.8 45 

B August 1958 June 1960 2 2 235 16.4 14.6 66 

C May 1957 June 1960 3 7 238 14.9 14.5 91 

--Costs of ammate treatment, by areas, based upon labor at $1.20 per hour and ammate at $0.245 per pound 

Aver age 

Treated Labor 'Ostof Cost Trees Tree d.b.h. Cost Cost per 

Area Size trees time o f labor and per inches Per d.b.h. d.bmh. Of 

treated ammate material acre acre tree inch trees tree 

per 

per acre1 

Acres Number Man Pounds Dollars Inches - Cents - Number Number Dollars Dollars 

hours 

A 23 328 4 5 12 0 83 13.2 25.3 14.3 189 3.61 0.019 

B 158 1,023 122 255 2 09 12.8 20.4 6.5 83 1.32 .016 

C 76 766 84 240 160 12.7 20.9 10.1 12 8 2.11 ,016 

W 

'computed as the product of the average number of trees per acre times average d.b.h. 
Table 3.--Tree diameter-inches treated per man-hour 

and mr DOU~~ of ammate 

sizes: species in the easy-to-kill group mostly are represented by comparatively small trees, whereas the difficultto-kill group mostly comprises the largest trees. Since 

kills among the smaller trees of a given species tend to be 

greater than among the larger ones, the grouping probably 

reflects some differences due to tree size that may have led 

to erroneous rating of certain species. The correlation between ease of killing and size is shown in table 1 by the 

smaller average diameters of all dead trees than of all 

treated trees. 

Area 

Costs of treatment vary with a number of factors including season of the year, size and accessibility of the 

area, tree size, number of trees per acre, competence of 

labor, and so forth. In this study, the same methods and 

same crew were used on all areas. The labor rate applied in 

computing costs was $1.20 an hour and the cost of ammate was 

$0.245 per pound. Supervisory costs and cull-marking costs 

were not included. Six to 15 culls were treated per acre; 

per-acre costs ranged from $1.32 to $3.61 (table 2). Average 

cost per inch of tree diameter at b. h. for the three areas 

was $0.017. 

Since labor costs vary greatly and since the price of 

ammate may vary also, costs have been computed on the basis 

of number of tree diameter inches per man hour and number of 

diameter inches per pound of ammate (table 3). On the average, 108 tree diameter-inches were treated per man-hour, and 

44 inches were treated per pound of ammate. These rates offer a good method of estimating costs where travel time to 

the woods is not a big factor, and where trees are not more 

scattered than in our study areas. 

A 23 4,347 97 36 

B 158 13,114 107 5 1 

C 76 9,728 116 41 

Aver age -- - - 108 44 

--HARRY W. YAWNEX 

Research Forester 

Northeastern Forest Experiment Station 

Forest Service, U.S. Dept. Agriculture 

Tree inches 

per pound 

of ammate 

Acres 

Tree 

inches 

Tree inches 

Per man hour