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AUGUST 1950 

NORTHEAST 

NORTHEASTERN+OREST.MP~RIMENT STATION 

UPPER DARBY , PA. V. L . HARPER , DIRECTOR 

WEED K1LI;ERS MAY BE USEFUL 

IN REFORESTING OLD BURNS 

MORE THAN 6 million acres in the 12 Northeastern and Riddle Atlantic States need to be 

reforested, according to Forest Service estimates. Yet many of the sites that need planting 

are rocky and steep and hard to plant. In many 

places there is a dense cover of grasses, weeds, 

and shrubby growth. Old burns in the northern 

hardwood-hemlock forests and spruce-fir forests 

are especially hard to plant. 

Part of the problem is to release the newly 

planted seedlings from competition, so they can 

get the light and soil moisture they need. They 

also need to be protected from competing growth 

that bends down under snow cover and smothers or 

breaks them. 

A test of chemical herbicides 

TO FIND OUT if chemical plant killers can 

be used in preparing planting sites, preliminary 

tests were made with four chemicals: ammate, 

2,4-D, (2,652, and comnon salt. The test area 
was in the Allegheny National Forest, on a lower 

south-facing slope that was covered with bracken ._ .I fern, goldenrod, and bush honeysuckle. 

Three questions were considered: (1) Would 

the herbicides kill these competing plants?; 

(2) Would the planted trees live on treated 

areas?; (3) How long would the chemicals prevent reinvasion by weeds and shrubs? 

Six treatments were used, each on three 

1-milacre quadrats, as follows: 

'Ammonium sulfamate. 2~odium salt of 2,4-Dichlorophsnoxyacetic acid. 3~ethyl ester of 

2,4-Dichlorophenoxyacetic acid. 

Chemical used 

The chemicals were applied by spraying, on 

August 4-5, 194'7, under calm afternoon conditions. Some of the 2,4-D solutions may have 

been diluted by a light shower. 

Ammate' (~u~ont) 0.5 lb. 218 gal. 

Ammate (DOW) 1.0 lb, 435 gal. 

2 ,4-II2 (~u~ont ) 6 level tsp. 200 gal. 

2,443 (Dow) 8 level tsp. 200 gal. 

~,652~ 8 level tsp. 200 gal. 

Common salt 2.7 lb. 75 gal. 

Concentration 

per gallon 

of water 

Rate of 

application 

per acre 
Results, 1947 to date 

ONLY AMMATE proved effective. 

The other chemicals had slight effects on 

leaf tissue and caused terminal shoots to curl, 

but did not lessen the density of plant growth. 

During the 1948 growing season, no differences 

could be seen between untreated areas and areas 

treated with the other chemicals. 

Ammate killed some aspen, black cherry, and 

serviceberry seedlings as well as shrubby and 

herbaceous growth. Two weeks after spraying, 

all vegetation on the treated plots had turned 

brown, and aerial portions were dead. Six weeks 

later (at end of the 1947 growing season) these 

quadrats were still bare, except one treated 

with the weaker anmate solution. Here a few 

sheep sorrel seedlings and sickly bracken shoots 

appeared. 

At the end of the 1948 growing season, the 

quadrats treated with the stronger ammate solution were still completely open. A scattered 

low cover of sheep sorrel, grass, sedge, and 

bush honeysuckle had reinvaded the three lightly 

treated quadrats. 

At the end of the 1949 growing season, the 

heavily treated quadrats were still fairly open. 

The others were filling in with plant growth, 

but it was not nearly so dense as in ad Jacent 

untreated areas. 

To test the effect of the chemicals on 

planted seedlings, two test trees of red 

and black locust were planted (in April 1948 pine in

each of the six quadrats treated with ammate. 

These trees all survived and grew well through 
the 1948 growing season. They apparently were 

not affected by ammate toxicity in the soil. 

However, the black locust suffered some damage 

from animals. 

By the end of the 1949 growing season, the 

black locust seedlings had all died; but this ' 

was attributed to rodent damage. The pines had 

also suffered some damage from animals, but grew 

well. They were still alive and free to grow. 

during the 1950 growing season. 

Practical use indicated 

RESULTS FROM this preliminary study indicate that ammate, applied as spray at the height 

of the growing season, may be useful for preparing planting sites and reducing competition for 

at least two growing seasons. However, damage 

by animals may prove to be the limiting factor 

in such planting. 

At present, the most successful ammate 

treatment tested would cost about $50 per acre 

for full coverage of planting sites. Further 

studies should be aimed to reduce costs to a 

more reasonable level by determining the effects 

of ammate at different periods during the growing season, the lowest effective concentration, 

and the smallest spot needed to permit successful survival and growth of planted stock. 

-- A. F. HOUGH 

Silviculturist 

AGRICULTURE-FOREST SERVICE-UPPER DARBY 

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