9^/1Jo

ELEASING CONIFERS

in the Lake States

With Chemicals "^^

Umted States Department of Agriculture^

^Agriculture Handbook No. 185 V

Forest Service,

January 1961
4

PREFACE

Tliis publication deseriljes the present status of various usable chemical

methods for releasing ])ine and otlier conifer stands in the Lake States

from tlie competitioji of undesirable hardwoods and brush. The information presented is based on the firsthand experience and the research results

obtained by the authors in noi-thern Minnesota and lower Michigan.

8ince most research I'esults and experience on release in tlie Lake States

have been related to planted stands of high value, emphasis is often placed

upon the eliemical release of conifer plantations. However, the chemical

techniques for controlling brush and undesirable hardwoods are equally

useful in the release of naturally established conifers.

Each release job requires an individual ¡prescription, depending on the

species, density, and the degree of control desired. Moreover, since chemical control of woody vegetation is relatively new, some of the techniques

described may be improved or refined from time to time as more research

results become available. The techniques outlined here are therefore

necessarily general. By giving careful attention to the general prescriptions set forth, each forest manager should be able to adapt them to his

local release problem. Until the forest manager has learned the capabilities and limitations of the various herbicides from his own experience, he

should of course use caution when applying them to control undesirable

hardwoods and brush in conifer stands.

CONTENTS

Page Page

Introduction 1 High release by herbicide treatTypes of release 1 ments __ _ 12

Chemical herbicides-the modern p^üage spraying from aircraft 13

release tool 2 -r^,-

2,4,5-T esters 3 Foliage sprays with mist

2,4-D esters 4 blowers 15

Mixtures of 2,4-D and 2,4,5-T Basal cut-bark treatments 15

esters 4 Chemical frill girdles _ 15

Other selective herbicides 4 Cutstumps_._ 16

JNonselective herbicides 4

Selecting the proper herbicide-. 4 Tree injectors 17

Methods of application 5 Costs 17

Foliage spraying 5 TJ i u i • ,-.

Basal cnt-bark treatments 6 Basal bark spraying 17

Basal spraying 6 Release of Christmas tree plaiitaLow release by herbicide treatment- 7 tions _ 18

Foliage spraying-__^ : I Preplanting release 19 With ground equipment 7 „

From aircraft 10 Safety measures 21

Basal bark spraying 12 Species sensitive to foliage sprays. _ 22

Note.—A small preliminary edition of essentially the same material was

issued in April I960 under the title, How To Release Conifers in the Lake

States With Chemicals.
/ Releasing Conifers in the Lake States

With Chemicals

¿^¿y John L. Arend and Eugene I. Roe^

INTRODUCTION

Erusli iind lo\v-v;i]ne liardwoods

are often obstacles to the satisfactory establishment and growth of

conifers in botli |)hinted and natural stands. Once established,

most conifei's in the Lake ¡States

need full sunliiiht for best crowtii.

For this reason, brush, undesirable

trees, and other competin<i' vegetation must be l^ept from overtopping

these more valuable trees (fi,<i'. 1).

The job of keepinu; such competitors from interferino- with the satisfactory development of conifers

is called release.

This report describes the princi-

\)A\ types of release needed in the

Lake States region and how they

ai'e accomplished with the aid of

chemical herbicides. It gives detailed information on the types of

herbicides used, and on techniques

of application suitable for various

kinds and conditions of competition.

^ Re.-siiectively, leader of the East Lansing, Mich.. Research Center, and forester at the Grand Rapids, Jlinn., Research Center. I.al^e States Forest Kxlierinient Station. The station is maintained at St. Paul 1, .Minn., h.v the Forest

Service, F.S. Department of Agriculture.

in cool'>eratioii with the Fniversit.v of

Minnesota. The Fast Lan-sinK Research

Center, in turn, is maintained b.v the station in cooperation with Michigan State

University.

FiGUHE 1.—This S-ye.-ir-old red ¡jliie is

completel.v (jvertopped by brush and in

urgent need of light.

TYPES OF RELEASE

Tlie conifer release jolj in the

Lake States falls into two main

tyi)es, depending on the size of the

brush and other competitors to be
AGRICULTURE PIANDBOOK NO. 1S5

( ()iitr(.)lk'(l. AA^lit'ii llicsi» coiiiiit'l it(ii-s ai'i' ('(iiiiixiscd oí low slinilts,

luM'lis, ;iii(l oilier VCüCI;il ion, cillici'

su|)|)n'ssin,i;' oi- thrcateiiiiiii' (lie di'-

N'ciopincnt of (lie conifers. Hie job

of reinoN'iii^' siidi \'ei;'etati()ii is ofI en

ciilled loir rclciixc. (ienei-ally llic

( oni])etilors aie about as lall ;is I lie

conifers, or a lidie taller.

AVlien the competition comes

from tall brush and lo\v-\-aIue liai'dwoods that are much lar^'er than

and com]>letely overtoppina' the

I'onifers, the "job is known as liiç/li

i-clfttHc. Sometimes the interfei-inii'

woody <ii-()wth may foi'in a double

overstory or one tliat is lit) or more

feet taller than the conifers ( H^-.

2). Some hiii'h-release jolis are the

result of plantinii' conifers under

already established stands such as

asi)en, bii'ch, or oak. Most liiahrelease o])erations, ho\\evei', are

made necessary by ])ast neglect or

poor low release, or by plantiiii>- in

sparsely stocked hardwoods. Since

early and adequate low release will

reduce both moi'tality and loss of

ii'rowth of conifers to a mininnini,

its im])ortance to the forest manager is obvious; and usually it can

be done at a lower cost than high

i-elease.

Another imiiortant operation

that will reduce the size, of the release job in plantations or even

eliminate it altogether consists of

treatments used to control the competing vegetation before the conifers are ]ilanted. This is called

planting-sile preparation, or prephniflju/ release.

The control of vegetation crowding conifers that have been planted

for Christmas tree production requires special attention in order to

l^romote satisfactory form development as well as growth. This suliject is covered in a special section.

Nearly complete control of undeFii.riiH 2.—Red pine nvertopped l),v aspen. Uulcss flic pines are released

scjon, tliey will lie eliminated liy i(iiiilielil ion.

sirable brush and hardwoods is

nsiially re(|uired.

In conifer stands other than

tliose established for Christmas

trees, complete kill of roots and

tops of all competing vegetation is

seldom needed, IKU' is it desirable

from the site i)rotection standpoint.

All that is needed is to set back the

brush so that the conifers can get

ahead and develop.

CHEMICAL HERBICIDES—THE

MODERN RELEASE TOOL

F)efore "World War II, all release

opei'ations in conifer stands,

whether low release, high release,
KELEASING CONIFE.RS IN THE LAKE STATES WITH CHEMICALS 3

preplaiiting release, or care of

Christmas trees, were carried on by

laborious and costly handtool methods. Sprout regrowth followingsuch methods was often so great as

to require successive operations.

Later develojiment of the chemical

herbicides has completely changed

this situation and the use of handtools alone to release conifers is becoming less common. It still has

a place, however, in plantations and

natural stands that are too small or

scattered to make release with herbicides practical.

Chemical herbicides can be used

either alone or in conjunction with

cutting to kill the tops of midesirable vegetation and to reduce sprout

regrowth. They are usually more

effective and less costly than hand

cutting.

Various chemicals, available in

commercial quantities, can be used

as herbicides to kill trees, brush,

and other vegetation. However,

for control of undesirable hardwoods and brush in conifer stands

only the .select/vc or ''honnone" type

herbicides are recommended; those

of the 7io».seIect/ve type are toxic to

lioth conifers and broadleaf vegetation. The most common of tlie selective herbicides are 2,4:,5-T and

2,4:-D. But it must be remembered

that the selective propei'ties of these

two general herbicides are relative.

E.rtremeJy heavy do><ages tvill kill

all vegetation; )rhe» properly diluted, they a-ill kill ■■<oate speeiex

and ncjt othern.

2,4,5-T Esters

(2,4,5-trichlorophenoxyacetic acid)

The herbicide now most widely

used to control brush and undesirable hardwoods is 2,4:,5-i. liie

most effective formulations ot tins

herbicide for brush control contain

one of the esters; - these are miscible in diesel oil, fuel oil, or kerosene

and emulsiliable in water and in oilwater. Such ester fonnulations are

produced by a number of chemical

companies in 1-gallon, ,5-gallon, and

55-gallon lots. They usually have

an acid equivalent ( 2,4,5-T)' of 4.0

pounds per gallon. Forunilations

with a different acid equivalent are

also available, however, particularly in smaller size lots.

The cost of low-volatile ester formulations of 2,4,5-T containing a

4.0-pound acid equivalent varies

from al)out $6 to $12 per gallon, depending on the quantity purchased.

Since tlie price per gallon of this

and other herbicides will depend

largely on the amount of their acid

equivalent, it is important to check

the latter ñgure when purchasing

such herbicides.

"When properly diluted and applied, ester formulations of 2.4,5-T

will kill tlie tops of most broadleaf

brush and hardwood species in the

Lake States and reduce sprouting.

This herbicide should be used for

controlling such species as rose,

raspberry, oaks, maples, and other

species resistant to some of tlie other

common herbicides. It can also

damage conifers if applied in heavy

quantities, especially during the period of new growth.

Recent experiments with invert

emulsions of 2,4,5-T indicate that

they may have some use for controlling unwanted brush with less

- These are of two types : the lowvolatile ester.s recognized by the U.S. Departnieiit of Asriciilture (the propyleiie

«îlycol butyl ether group, butoxyethanol,

iso-oc-tyl, ete.) and the older volatile

esters'(methyl, ethyl, Isopropyl, butyl,

pentyl, etc.). The former are somewhat

more expensive and are reputedly more

effective on brush. They do not vaporize

as do the volatile esters and hence are

safer to u.se where conifers may be adjacent to agricultural crops.
AGRICULTURE HANDBOOK NO. 185

drift effect. Dosages for invert

emulsions, liowe\'er, liiive not been

Avorkecl out for ü,enei'ii1 Held applications.

2,4-D Esters

(2,4-dichlorophenoxyacetic acid)

The fírst of the hormone herbicides to be used for brush control,

2,4-D, can be used to kill shrubs

and hardwood trees such as hazel,

alder, sumac, willow, and aspen.

Like ¿i,4,.5-T, it is marketed in lowvolatile ester formulations which

usually have a 4.0-pound acid

equivalent per gallon, and in volatile ester formulations ranging

from 2.7- to 6.0-poimd acid equivalent. The cost of 2,4-D per pomid

of acid equivalent is only about half

that of 2,4,.5-T; it will therefore be

the preferred choice where shrubs

or trees equally sensitive to both

herbicides are to be controlled.

Mixtures of 2,4-D and 2,4,5-T Esters

Also available are many different

brands of so-called chemical "brush

killers." These are mixtures of various esters of 2,4-D and 2,4,5-T,

usually 50-50 but occasionally %-

I/3. Many of these products are

composed of the low-volatile esters

of the two herbicides, but others

contain only the older volatile esters. "Brush killer" mixtures have

been Avidely used, particularly with

the vieAv of reducing costs of brush

control on areas containing a. mixture of species, some of which are

resistant to 2,4-D. HoAvever, there

is as yet no reliable evidence that

the tAvo chemicals combined are any

more effective than either alone.

For species resistant to 2,4-D, the

effectiveness of the 2,4,5-T will

probably be the same when used

alone or wdien the equivalent

amount is mixed with 2,4-D. In

some cases at least, it would be actually less costly and just as effective to apply the equivalent amount

of 2,4,5-T alone.

Other Selective Herbicides

Other selective herbicides, notably 2,4,5-TP (2-(2,4,5-trichlorophenoxy) propionic acid) and

amitrol (3-amino-l,2,4-triazole),

are on the market, but so far these

appear to have no advantages over

the less expensive herbicides, 2,4-D

and 2,4,5-T, for use on the common

brush species and weed trees needing control in stands of Lake States

conifers. Moreover, amitrol causes

injury to some conifers.

The water-soluble'amine formulations of 2,4-D and 2,4,5-T have

been found to be more effective in

minute quantities in killing unwanted hardwoods and reducing

sprouting when applied directly to

cut surfaces of the tree than are the

oil-soluble esters. This herbicide is

less expensive than the esters. Oilsoluble amine formulations have

been developed, but to date their

effectiveness has not been demonstrated.

Nonselective Herbicides

Other herbicides that are very effective for killing both herbaceous

and woody vegetation include : Ammate (ammonium sulfamate), monuron, and other urea derivatives.

However, these herbicides are nonselective in that they will injure

conifers as well as the competing

A^egetation. They therefore have

A^ery limited use in conifer release

operations except for careful applications directly on the competing

A'egetation and not on the conifers.

Selecting the Proper Herbicide

Selection of the type of herbicide

to be used should depend entirely
JiKLEASING CONIFE.RS IN THE LAKE STATES WITH CHEMICALS

on the composition of the brush

and hardwoods to be controlled. If

all species are susceptible to '2,-1-D,

then this herbicide should be used.

If a majority of the species are resistant to 2,4-D, then á,4,5-T alone

should be used. A mixture of these

herbicides should be used only for

areas of brush containinji a few

scattered stems of species resistant

to 2,4-D. A partial list of species

sensitive to foliage sprays of 2,4:-D

and 2,4:,5-T is given at the end of

this handbook.

METHODS OF APPLICATION

The chemical herbicides described in this report can be applied in several different ways for

the release of established conifer

stands or the prerelease of conifer

plantations. These include foliage

sjiraying, basal cut-bark ( ical iiicnl s.

and liasal l)ark spraj'ing.

Foliage Spraying

Foliage s()raying consists in applying solutions or enudsions (dejjending on the carrier)'^ of herbicide

esters directly on the leaves of the

brush or other unwanted plants by

means of ground equipment (fig.

3) or from aircraft. For release

purposes foliage spraying is limited

to the latter part of the growing

season when the broadleaf species

are still sensitive to the herbicides

but the conifers have hardened off.

At this stage of growth the conifers

= Hei-bieides of 2,-4-D and 2,4,.5-T are

diluted with either oil, water, or oil and

water. The e.ster formulation.s are soluble in oil and form au emul.sion when

mixed with water.

JA.

P.O.K. 3.-H.drauUe spra. ecui.nent can he used to apply folia.e spra.s for control
6 AGRICULTURE HANDBOOK NO. 18.5

ai-e resistiuit (o liglit iii)i)lieatioiis

of the selective herbicides, wliereus

the broiulleaf species ai-e still sensitive to tlie same applications.

Even in the latter part of the

<¡;rowi]i<T season, folia<i'e sprays must

be applied so that only very small

quantities will hit the conifers directly. Aerial applications durin<i

this time rarely injure the conifers

because the total volume used is low.

Occasionally, red pines will show a

strong; recurving of the needles at

the end of the new growth as a result of foliage spraying; but this

permanent ''set" does not seeiu to

affect the future development of the

trees.* On the other hand, if conifers are sprayed during the active

growing season, even with .small

quantities, the needles will die and

the trees may be killed entirely or

the current growth malformed.

Of the pines commonly planted

in the Lake States, jack pine and

Scotch pine ai'e the mo.st susceptible

to injury from foliage spraying

with herbicides. Somewhat less

easily damaged are white pine and

red pine. White spruce and black

spruce are seldom injured by light

applications of selective herbicides

after active growth is complete; but

Norway spruce is more easilj'

damaged.

Basal Cut-Bark Treatments

Basal cut-bark methods involve

the use of hand or power tools to

prepare freshly cut surfaces, which

are then treated with either 2,4,5,-T

ester in oil or the amine of 2,4-D

or 2,4,5-T diluted in water. Such

treatments are of two general types :

1. Cut-stump treatment, more

commonly used for small trees

and occasionally for brush.

^ This type of injury closely resembles

the condition known as needle droop ;

the latter is apparently due to drought.

2. Cut-bark treatments, used on

trees larger than 3 to 4 inches

in diameter by means of frill

girdles or tree injectors.

In tlie cut-stump treatment, immediately after the stem has been

cut with an ax or saw, the top.s,

sides, and root collar of the stump

are thoroughly di-enched with 2,4,5-

T mixed with oil (12 to 16 pounds

AHG). AHG is an abbreviation

for acid equivalent per hundred

gallons of solution.

Cut-bark ti-eatments are used to

kill individual trees larger than ?>

to 4 inches in diameter. The diluted herbicide is applied to the

sapwood through fresh cuts in the

bark. The cut may be a frill girdle,

or a tree injector (see p. 17) may

be used. A frill girdle is a continuous troughlike incision made

completely around a tree, deep

enough to penetrate the bark and

extend one-fourth to one-half inch

into the sapwood. The incision is

thus one-half to one and one-half

inches deep de])ending on the thickness of the bark. It is made as close

to the base of the tree as is practicable. Frill girdles are made by a

series of overlapping downward

cutting strokes with an ax; the

chips are not removed, hence the

name "frill." A solution of either

2,4,5-T in oil or the amine of 2,4-D

or 2,4,5-T in water is then applied

to insure top kill and reduce sprouting. (See p. 15 for details.)

Basal Spraying

The basal bark spray method—

spraying the base of trees with an

oil solution of 2,4,5-T—is used

mainly for controlling hardwoods

and brush that sprout prolifically,

such as aspen, red maple, moimtain , maple, and speckled alder. Ordinarily it is used for stems Ze« than

4 inches in diameter. Large trees

can also be killed with basal sprays,
ïiELEASING CONIFERS IK THE LAKE STATKs WiTTl rrrE:\irCAl,:

but. since this requires ix large volume of herbicide, it is seldom practical except along roads and in

other accessible places where adequate supplies can be transported

by truck or jeep.

The chief advantages of basal

sprays are that they kill small trees

and brush more completely (less

sprouting- follows) and that they

require less labor, as compared with

cutting or girdling. The principal

disadvantage is the lai'ge volume of

chemical needed.

2,4,5-T ester mixed with fuel oil

or kerosene is the only herbicide

that has been etîective for general

basal-spray work in the Lake

States. The oil carrier is essential ;

it enables the chemical to penetrate

the bark, whereas water does not.

Basal sprays applied at any season of the year will give good control of most hardwood species with

very little resprouting. The most

sprouting follows if trees are

sprayed before growth starts in the

spring; the least, if sprayed immediately after full leaf development

when root reserves are low. P'oiexample, aspen trees that are basal

sprayed immediately after full leaf

development seldom sprout; at

other seasons of the year sprouts

and suckers still develop.

LOW RELEASE BY HERBICIDE

TREATMENT

^- The control of low brush, small

weed trees, and herbs that are approximately the same height as the

conifers is accomplished mainly by

foliage sprays applied with aircraft

or occasionally with ground equipment.' For certain special low-

= Release from grass and herbaceous

plants is a special t.ype of low release for

which no satisfactory che.aical methort

has so far been worked out on a practical basis. However, certain new che.nicals such as siniazin, ma.y prove usetul

for c-ontrolling such vegetation.

.fi.í4::45°—61 2

bnisli conditions <;!' Iimilçil ;n-c;i,

tlie coiiqieting vegetation r;iii In.

controlled by ItasaJ s])raying, or Ijy

cutting and basal spraying the

freshly cut stum])s.

Foliage Spraying

Foliage spraying for the low release of conifers can be done with

either ground equipment or from

aircraft, depending on the size of

the area to be released, its accessibility, character of the terrain, and

the landowner.ship pattern.

The new growth of all vegetation,

including conifers, is easily injured

during the period of active growth

by herbicides ajjplied in light quantities and even by drift. The release job therefore nuist be delaj^ed

until the new growth has hardened

otï. In tests in Lower Michigan,

foliage sprays of 1 and 2 pounds

acid equivalent in the form of esters

of both 2,4-D and 2,4,5-T in 21/2

and 5 gallons per acre were applied

directly on conifers at 2-week intervals during one entire growing season. Such applications caused injury t-o the new growth until July

15 for white spruce, August 1 for

red pine, white pine, and Norway

spruce, and August 1 for red pine,

white pine, and Norway spruce, and

August 15 for jack and Scotch

pines. But since the factor governing such injury is the stage of development of the plant, these dates

will likely vary not only with location l>ut also with season.

With Ground Equipment

The type of ground spraying

equipment selected for low-release

work depends largely on the condition and character of the local terrain, size of the control operation,

and the density and height of the

brush and other vegetation to be

controlled.
8 AGRICULTURE HANDBOOK NO. 185

BacJcpach xprai/cfK.—To release

small conifers from scattered low

brush, use backpack-type sprayers

of 3- to 5-gallon capacity (fit;. 4).

With sucTi equipment, foliage

sprays can be carefully directed

^Yith little waste of materials and

damage to the conifers.

Satisfactory top kill of common

brush, such as hazel, alder, willow,

and sumac, and of many common

herbs can be obtained with 40 to 50

gallons per acre of a water emulsion containing 2 to 3 pounds of

2,4-D AHG (this is 2 to 3 quarts

of an ester having a 4-pound acid

equivalent). For stands of species

that are resistant to 2,4-D, substitute 2,4,5-T.

If the brush includes a small proportion of stems of species that are

resistant to 2,4-D and a uniform

top kill is desired, use a mixtui-e of

esters of these two herbicides. Buy

such mixtures in the form of the

standard brush-killer formulations,

composed usually of 2,4-D and

2,4,5-T in 50-50 mixtures (see p.

4), or make them up in the proFIGURE 4.—Backpack spray equipment

can be used to control patches of low

brush by means of foliage sprays.

portions desired. Ester formulations of a single manufacturer are

more likely to be readily miscible

than those of different manufactui-ers.

Wet the foliage thoroughly but

avoid drip from the leaves—this

wastes herbicide materials. No

special effort need be made to spray

both sides of the leaves.

For larger tracts of conifers that

are readily accessible and are on

fairly level, firm terrain, use either

(1) power sprayers equipped with

200- to 40()-gallon tanks mounted on

trucks or trailers pulled by tractors,

or (2) mist blowers.

Povx'/r uprnyerx.—Power pumps

apply droplets, which can be varied

in size from fog to coarse, at pressures ranging from fiO to 400 pounds

jier square inch ; the lower j^ressures

use less herbicide materials and

cause fewer mechanical failures

(fig. 5).

Power sprayers, because of their

higher operating pressure, typically

apply larger volumes than do hand

pumps. Therefore the concentration of herbicide should be reduced

somewhat below that recommended

for hand pumps to prevent damage

to the conifers, particularly those

growing in oi:)enings. If the tops of

the conifers are exposed, apply not

more than 75 to 100 gallons per

acre of a water emulsion containing

1.25 to 1.5 pounds AHG: somewhat

higher volumes can be used where

the trees are completely overtopped.

To reduce loss through drip,

spray only when the foliage of the

brush is relatively dry. Windy

days should be avoided if there are

farm crops on neighboring lands

that might be injured by drift.

Mist hloioers.—The main advantage of mist blowers lies in their

ability to apply low voliunes of

herbicide mixtures per acre fairly

uniformly over dense brush, re-
l.l-LEAyiNC! CONIKKRS IX THE LAKE S'lAUKS \V]\\\ rTIEMITM.S 0

FiGUKE .1.—Spraying dense alder brush with 2,4-lJ prior to phiiitiiig.

gardless of its size, for dist;iiices

ranging- from 50 to 200 feet (ñg. 6).

Mist blowers come in a variety of

sizes ; the largest ones are mounted

on trucks or trailers; the smallest

one, weighing less than 40 pomids,

is of the Ijackpack type."

Mist blowers Avill not ajjply small

volumes of herbicide as uniformly

as aircraft because they cannot be

towed or transported at a constant

rate of speed over rough terrain.

Where the spray is manually directed, however," it can be applied

as needed, depending on the density

of the biush.

Where the conifers are partly exposed, use 5 gallons per acre of a

water-oil emulsion of one of the

"For description of some of the mist

l.lowers availahle, see Potts, S. F Equipment for pest aud disease control. I uasrlvi 13 ( ') • S!>-1(»1. ilUii^- l'*-'''*- '^111-

-ie copv Iirice <;.l cents, avaihihle from

e^iunUa' rniv. Press In.ernafonal

Doenments Serv.. 2!.C,() P,r..adwa.v. ^e^A

^-orl- -^7 N Y ) Another reference :

Potts Sa'n.uel Frederick, Concentn.ted

sprav eauipment. n,i.xtures. aud^tpphcation'method.s. -^l'^'--^

Books, f-.Udwell. -N.J. 1!>-^

ilhw. Durland

herl.)icide esters containing 20

pounds AUG. Where the conifers

are completely overtopped, increase

the volume to 10 gallons per acre.

These volumes are equivalent to 1

or -! pounds, respectix-ely, of liei'bicide per acre.^ Since the high-velocity mist will penetrate the brush

and hit the overtopped conifers, do

not aim the blower directly at the

brush; instead, direct it higher so

that the mist falls on the brush.

Because the spray can travel a considerable distance, mist blowers

must be carefully handled. This

is especially true in conifer .stands

adjacent to farmland. In such

areas, do not use mist blowers on

days when winds are blowing at

more than -J to '.'> miles i)er hour.

f'o.'<f.—Cost of foliage spraying

with ground equipment will range

from $5 per acre upward depending

on the kind and amount of herbicide applied and the type of etjuip-

^ Follow spray recommendations provided liy manufacturer. Spray mixtures

used sticcessfuUy in Lower Michigan

have been 1 part chemical, 4 parts No. 2

fuel oil. and 1." pai'ts water.
10 AGRICULTURE HANDBOOK NO. 185

-. J kv iV;' Á>...\, .^ .(, \V

il'*

:-:P^^.&<

FIGURE 6.—One type of mist blower that can be effectively used to control hardwoorls

for conifer release. Such a mist blower can be used for both low and high brush

and trees.

ment used. Hand applications will

naturally cost more than those

made with power pimips and mist

blowers.

From Aircraft

When the conifers needing low

release occupy a ti'act 5 aci'es or

more in size, rectangular in outline,

and so located that there would be

no danger of drift damage to adjoining cropland, explore the feasibility of controlling the brush by

aerial spraying. Large areas of

conifer stands, regardless of their

accessibility and the density of

their brush competitors, can be released by aerial spraying in just a

few hours' time and at a much lower

cost than with ground equipment.

In aerial spraying, the same

amount of herbicide (acid equivalent) is used per acre as in ground

applications, but the total volume

applied is low.

The following tabulation will

serve as a guide to the amount of

herbicide and volume of mixture to

apply to brush stands of different

degrees of density.

Brush density Number of stems per acre

Low 2,000-8,000

Medium 8,000-25,000

Heavy 25,000 and up

Pounds of Gallons of

hertjicide mixture

per acre per acre

1 2

IH 2

2 3
I;I-:LEASING C0NirE,RS IN THE LAKE STATES WITH CHEMICALS 11

Wliat the best type of caiTier is

needs fiu'ther study; water alone

has been found to be satisfactory,

but good results have also been obtained with mixtures containingsmall amounts of No. 2 fuel oil or

diesel oil.® The addition of oils to

the carrier should, therefore, be

continued until research or experience pi'oves them unnecessary. Typical mixtures used are: li/o quarts

herbicide ester, 1 quart oil, and öVi;

quarts water; or 2 quarts herbicide,

2 quarts oil, and 12 quarts water.

To avoid trouble, mix the oil and

herbicide needed for a planeload

and then add this slowly to the water required to complete the load,

stirring vigorously all the while.

Do not add the v:ater to the herhicide-oil mixture.

Carriers composed entirely of

fuel or other oils have been used in

foliage spraying. In some aj^plica-

• tions damage to jack pine and even

death has been reported. General

recommendations cannot be given

until further tests have determined

the conditions under which oil carriers can be safely used.

Make aerial applications for low

release at about the same time of

year as ground foliage sprays.

Since the volumes applied with aircraft are much lower and are less

well distributed, such spraying can,

however, begin 1 to 2 weeks earlier

than applications made with

ground equipment, especially where

none of the conifers are exposed.

1: To minimize drift, ñying should be

' done when the general wind velocity is less than 6 miles per hour

Little is kno\ATi about the eiiect oí

temperature conditions; Ray'' recommends a tein¡)erature range of

65° to 80° F. with high humidity.

The higher temperature limit is

presumably set so that turbulent air

conditions will be avoided.

Because the volumes applied

aerially are small, it is not important that foliage be dry. This is

fortunate because early morning •

and early evening, both periods

tending to have heavy dew, are generally the best times of day for

aerial spraying. At these times

quiet air and favorable temperature

and humidity usuallj^ prevail.

Tracts needing low release usually can be marked with simple devices so that they are readily

identified from the air. Mark corners or boundaries with flags, with

captive orange or yellow balloons

3 to 4 feet in diameter and 15 to 20

feet above the bi'ush, or with reflectors made of aluminum foil,

freezer grade. Where oil-water is

used as the herbicide carrier, balloons should be of the oil-resistant

type. Helium can be used to inflate

the balloons ; hydrogen, besides having greater buoyancy, is easier to

obtain and less expensive. Hydrogen, howevei\ is dangeroufdy explosive and must he handled loith

great care. Tracts fairly regular in

outline can of course be sprayed

with less ground marking and supervision than those with irregular

boundaries. In some areas of irregular shape, it may be more practical to spray certain portions with

ground equipment.

Planes commonly used are the

lio-hter craft, such as those em-

» vo \ fuel or diesel "il shoulil never

I,P used Besides beiuK m'-.-e expensive

than X". 1 oil, it is "-'i-e '"junous to

conifer;-.

° Ray, Hurlon C. General information

on herbicides and aerial application for

hardwood suppression. I)i Chemical

Control of Range AVeeds, Unnumbered

liandbook, U.S. Deiits. Agr. and Int.

Range Seeding Equipment Committee.

(96PP-) Rev. 1950.
12 AGRICULTURE HANDBOOK NO. 185

ployed for íI<íI'ÍCU1(UI'íI1 crop spraying'. Helicopters have been used

only to a minor extent in the Lake

States but will likely be used more

in the future. Ivight conventional

aircraft commonly have a. 40- to

200-g-allon storaoe tank feeding the

nozzles through a wind-driven

pump. Most planes are equipped

with a series of from 20 to 25 nozzles, evenly spaced along a boom

extending the width of the plane

and operated at pi-essures i-anging

from 2.5 to 50 p.s.i. More research

is needed to determine the best nozzle arrangement.

Where topography and the shape

of the tract to be sprayed permit,

flying should preferably be done in

a grid pattern, alternating the

swaths in opposite directions. In

rough country, flying gridwise may

be impossible. Here it will be safer

to fly either along the contours or

downslope, making the swaths all

in the same direction.i" Planes usually fly from 25 to 75 feet above the

brush canopy; the latter elevation

is the minimuni height permitted

for reasons of human safety, in all

U.S. Forest Service aerial brush

control operations.

The costs of low release by means

of aerial foliage sprays vary with

the herbicide usecl, its concentration, the volume of mixture applied

per acre, the size of the area

sprayed, and type of aircraft used.

For sizable tracts, total costs will

range from $3 to $5 per acre for the

recommended mixtures of 2,4-D and

$4.50 to $7 per acre for the 2,4,5-T

mixtures with fixed-wing aircraft.

Helicopter costs for herbicide

spraying have been re2)orted to

range from $7 to $15 per acre.

r

"U.S. Agricnltural Research Senice.

How to spray the aircraft way. U.S.

Dept. Agr. Fanners' Bui. 2062," 32 pp.,

illu,s. 19.54.

Basal Bark Spraying

Although foliage spraying is the

chief method of applying herbicides

in the low release of conifers, basal

bark spraying can be used to control low brush in the dormant season as well as at other seasons of

the year. The basal portion of the

stems is thoroughly soaked at the

ground line and up to a height of

about 1 foot with a solution of

2,4,5-T in fuel oil.^^ For general

application, u.se 12 ¡rounds AHG (a

3-percent solution of an ester having a 4-pound acid equivalent) until local experience shows that lower concentrations will provide the

desired degree of control. For example, on the Superior National

Forest, 4 pounds AHG of this herbicide has been used successfully to

control upland alder {Alnus crispa) clumps in a jack pine plantation.

HIGH RELEASE BY HERBICIDE

TREATMENTS

Natural and planted conifers that

have been overtopped by aspen,

oaks, or tall brush may be released

most efficiently by two principal

herbicide methods. These are (1)

foliage spraying with either aircraft, or mist blowers, and (2) basal

cut-bark treatments. Basal bark

spraying can also be used for special high release conditions of limited area. Foliage spraying is a

blanket treatment, whereas the

other two methods permit the selection of the trees to be controlled.

The choice of method depends

mainly on the size of job and the

time of year selected to do the work.

Overtopped conifers on tracts of 5

acres or more and of fairly regu-

" Use the cheaper No. 2 oil as the carrier for 2,4,.5-T for basal spraying and

all basal cut-bark treatments.
rjELEASlNG CONIFERS IK THE LAKE STATES WITH CHEMICALS 13

lar iiiitline can be released duriiiothe lutter part of the growing season by spraying the foliage of the

competing vegetation with lierbicide mixtures applied from aircraft. Smaller or very irregular

areas can more feasibly be released

by spraying the foliage of the competitors with a mist blower or by

one of the two ground methods using hand labor—basal cut-bark

treatments and basal bark spraying.

Although basal cut-bark and

basal spray methods are generally

most effective immediately after

full leaf development, they will

also give good results during tlie

winter months when labor is relatively easy to hire. These methods,

being applied on an individual tree

basis, can control composition and

density in overtopped plantations

where it may not be desiral)le to remove all of the hardwood competition. In aerial foliage spraying, selectivity is of course not possil)le.

Foliage Spraying From Aircraft

The same details given for aerial

spraying under low release apply

to high release with but little modification (fig. 7). Since the competitors are taller, however, somewhat

larger amounts of herbicide and

greater volumes of mixture per acre

will be required.

For alder, paper birch, and willow, use li/o to 2 pounds of 2,4-D ni

4 gallons of oil-water emulsion per

acre; for aspen, o pounds of 2,4-D

in 4 o-allons of water emulsion per

acre; for oaks, one-half to 1 pound

of 2,4,5-T in 2 to 21/2 gallons of oilwater emulsion per acre. In l^ower

Michigan red pine has been successfully released from aspen with an

application of 2 pounds of 2,4-D in

4 crallons of No. 2 fuel oil solution

per acre, and 15-year-old jack pine

from scrub oak competition with

one-half to 1 pound of 2,4,r)-T in 2

gallons of fuel oil solution par acre,

with no api)ai-eiit damage to the

pines. In Maine M'hite pine has

been successfully released with 1 to

3 pounds of 2,4,5-T in 21/0 gallons

of fuel oil. But in northern Minnesota lierbicide applications with

an oil carrier have damaged or killed jack pine of pulpwood size. Further testing with oil carriers is

needed before general conditions

for its use can be prescribed.

Marking the boundaries of tracts

to be aerially sprayed for high release also needs special consideration. This job must be done in

advance of the spraying time so the

boundaries will be plainly visible

from the air. Mark the corners

with either flags or colored balloons that float at least 15 to 20 feet

above the general canopy. Or, in

oak stands where the trees to be

spraj'ed are 4 inches or more in diameter, selected trees on the boundaries of the tract may be killed by

frill girdling (see pp. 6 and 15) 2

or ?> weeks before the aerial

spraying. The bright brown foliage of the freslily killed trees can

be seen for distances of 2 to 4 miles

as the pilot approaches the tract.

It will also help the pilot to mark

the boundaries parallel to the line

of flight Avith flags or balloons at

about l,00()-foot intervals. Sometimes swath widtlis are also set off

by flagmen as the job progresses.

Ill rough topography, as in the

northern part of the Lake States,

such extra marking is not feasible,

and many pilots clo not feel it is

necessary.

Pilots on large aerial release jobs

should be given good maps with

which they can become thoroughly

familiar before the work is started.

Two-way radio communication between pilots, the loading base, and
14 AGRICULTURE HANDBOOK NO. 185

VAIS h-^^-'-^h.. am¿%

(^.-.

^li

^^^u^T^j^^^^y

FIGURE 7.—Airplanes can be used to apply foliage sprays to control both high and /

low brush and trees for conifer release.

ground observers is also of much

help.

Since hi¿,h r&l^nse generally requires the use of stronger concentrations and larger volumes of

herbicide mixtures per acre, costs

will be somewhat higher than those

given for aerial low release on page

10. However, large areas of red

pine plantations are being released

from overtopping scrub oaks in

Lower Michigan by one aerial

spraying costing less than $4 per

acre. Tliis mocterate cost is due to

several favorable factors, mainly

the relative ease of controlling oak
RELEASING CONIFERS IN THE LAKE STATES WITH CHEMICALS 15

and I he sizable tracts sprayed,

makiuo- it feasible to use bi<>-^ "fust

planes with large tank capacities.

Costs for hig-h-release jobs normally range from $4 to $7 i)er acre

with fixed-wing aircraft, and $7 to

$15 per acre witli helicopters.

Foliage Sprays With Mist Blowers

Foliage spray applied by ground

equipment has limited use for high

release. Where ground eijuipment

can operate, mist blowers with

manually directed mist streams can

be used on tall brush and low-value

hardwoods for conifer release.

This type equipment will require

about 10 gallons of oil-water emulsion per acre, varying with the

height and density of the brush.

For an application of 10 gallons per

acre, the emulsion should contain 2

quarts of herbicide estei^—2 pomids

acid ecjuivalent. Follow manufacturers directions for carrier dilution or try 1 part chemical, -Í parts

No. 2 fuel oil, and 15 parts water.

Theoretically, mist bloweis can

apply low spray volumes at a uniform rate like aircraft sprays.

I^ut most blowers operate over fair1}' rough terrain wiiere it is difficult

to apply uniform low rates. A uniform rate of application may not

be necessary, however—especially

in high release work. Instead, the

spray should be directed where

needed to cover the high brush and

undesirable h a r d w o o d s. Care

should be taken not to blast the

conifers directly with mist-blower

sprays.

Basal Cut-Bark Treatments

Basal cut-bark treatments have

been used extensively in the Lake

States to control individual hardwoods for high-release purposes.

Several cutting techniques and

herbicide mixtures can be used, deiiendinc- maiidy on the size of the

hardwoods and personal preferences. These include cliemical frill

girdles, cut stumps, and chemical

tree injectors.

Chemical Frill Girdles

In the Lake States, frill cuts

around the base of the tree are commonly treated with an ester of

2,4,5-T at 4 to S ])ounds AHG (1-

to 2-percent solution by volume) in

No. 2 fuel oil or die.sel oil. The

chemical is applied to the frill cut

preferably within an hour or two

after the ax work is completed

(fig. 8)._

A variety of different containers

can be used to apply this herbicide

solution to frill girdles. A backpack type sprayer with a built-in

pressure jnnnp and a nozzle that

sprays a fine straight stream for a

distance of only a few inches has

pro\-ed satisfactory. With this

sprayer only a few jiounds of pressure should be maintained to avoid

waste of the solution. The incision

is filled once by walking or reaching around the tree. This will require about a teaspoonful (4 to 6

milliliters) of solution for everj' 3

inches of tree circumference (approximately 1 inch of diameter).

One gallon of mixture will treat

800 to" 1,000 indies of tree diameter.

Since the individual ax cuts usually form an irregular line, spraying the herbicide directly into a

frill is often difficult and time consuming. A better technique is to

spray the chemical-oil mixtiu'e on

the tree trunk about one-half inch

above the girdle, so that it rims

down into the cut trough. Not only

is this faster, but also it conveniently marks the trees that have

been treated, since the oil mark on

the tree is visible for several days.

An oil »oh/hle dye, such as para red

or National Oil Red O, can also be

used in the solution to stain the

frills and identify treated trees.

Aïiother herbicide that can be

used for treating frill girdles is the
16 AGRICULTURE HANDBOOK NO. 185

V'V^

^ ^^ -^-7 ^ ;\K' '

w

^^ ¿vj"'*

FIGURE S.—Chemical frill girdling is useil to control inflividnal hardwoods for conifer

release.

amine salt of 2,4-D and 2,4,5-T.

This type of herbicide, applied in

vei-y small qnantitieg (1 milliliter

of a 50-percent water solution per

1 inch of diameter) to frill girdles,

gives both effective tojî kill and reduced sprouting. One gallon will

treat -i:,000 inches of diameter or

four to five times the coverage given

by 2,4,5-T ester in oil. Since the

volume of herbicide needed is so

small, the amine form can be very

useful in basal cut-bark treatments.

The amine of 2,4,5-T is effective on

most hardwoods. The amine of

2,4-D works equally Avell on oaks

and aspen.

To keep sprouting to a minimmn,

chemical treatment of frills is most

effective wlien the work is done close

to the root collar and immediately

after full leaf development, Avheii

root reserves are lowest. Unless the

conifers being released are less than

3 or 4 feet in height, however, the

greater sprouting which follows

frilling done at a more convenient

and safe working height or during

the dormant season will be of little

importance.

Cut Stumps

Competing tall brush and hardwoods too small to girdle should be

cut right along with the girdling.

Whei-e only an occasional small

sapling is cut, the stump can be
EELEASING CONIFERS IN THE LAKE STATES WITH CHEMICALS 17

treated with the same concentration

of 2,4,5-T recommended for the

frill girdles—i to 8 pounds AHG.

If the cut trees are numerous, use

12 pounds AHG throughout the

stand. Thoroughly spray cut

stumps with 2,4,5-T and oil around

the root collar or ground line to

effectively reduce sprouting.

tree Injectors

Tree injectors '^ may be used to

make cuts through the bark into the

sapwood aromid the base of the tree.

The herbicide is injected into the

tree through the cutting head

(either automatically on some models or by a trigger release) before it

is withdrawn. These tools apply

the herbicide close to the root collar of the tree and are safer to use

than an ax. The herbicide mixture

generally recommended for tree injectors is 16 to 20 pounds AHG of

2,4,5-T ester in fuel oil. The amine

salts of 2,4,5-T diluted with an

equal part of water should also be

effective for controlling hardwoods

when applied by means of tree injectors.

Costs

Costs of high release by basal cutbark treatments have been fomid to

range as follows :

Labor for frilling and chemical

treating—$4.50 to $6 per 1,000

inches of tree diameter treated (3

to 4 man-hours). A satisfactory

work unit is a three-man crew, with

two men cutting frills and the third

man applying tlie herbicide.

Chemical for frill girdles—$0.25

to $0.50 per 1,000 diameter-inches

treated with 8 pomids of 2,4,5-T

^= Current manufacturers and dealers

include Reuel Little Tree Injection Co.,

Madill Okla. ; Forestry Suppliers, Jackson Miss.; and Ben Meadows Co., Atlanta, Ga. Prices currently range from

,$13 to $53.

AHG (2-percent solution by volume) in fuel oil or a 50-percent

amine-water solution. For stronger

solutions of 2,4,5-T, costs will increase proportionately.

Cut-stump treatment—can be expected to cost more than frill

girdling, mainly because of the use

of somewhat larger amounts of a

slightly stronger solution of 2,4,5-T.

Tree injector—no cost data available but costs are likely to be comparable with chemical frill girdling

costs.

Basal Bark Spraying

Basal sprays for high release have

possibilities on small jobs and for

controlling species that sprout

abundantly, such as aspen, red

maple, mountain maple, and speckled alder. Bark spraying is especially effective when clone in the

period just after full leaf development.

Apply basal sprays of fuel oil

containing 12 pounds 2,4,5-T AHG

so as to drench the bark to a height

of 1 to 2 feet completely around the

base of the tree (fig. 9). Apjily

FIGURE 9.—Basal sprays are an effective

method of controlling small brush and

trees that are prolific sprouters.
18 AGRICULTURE HANDBOOK NO. 185

just eiioii<>h spray to wet tlie bark

thoroui>hly and cause runoff to appear aroiuid tlie root collar. Trees

with tliick, corky bark leciuire heavier applications than smoothbarked ones sucli as aspen, beecji,

and red maple; ])aper birch, however, is difficult to kill with basal

sprays. The larger the tree, tlie

more volume of chemical herbicide

ne«ded to kill it.

Basal sprays can be applied with

various types of hand-operated

equipment. Especially satisfactory

is a 3- to 5-gallon sprayer of the

backpack type with a pump operated by a side handle and maintaining a low pressure (less tlian 15

pounds). A nozzle producing a

fan-shaped spray is more efficient

than one producing a cone-shaped

spray.

A 4-gallon backpack sprayer can

be emptied in 30 minutes on basal

spray work and the delay time to

refill it depends on the walking time

to source of su])ply. One cost test

in lower Michigan required 2 manhours per 1,000 inches of diameter

to basal spray oaks ranging from 1

to 12 inches d.b.h. This included

time s])ent in refilling the sjirayei's

(delay time) which for a three-man

crew amounted to 25 percent of the

total time.

The volume of herbicide solution

used for basal sprays varies considerably with tree diameter; trees

ranging from 1 to 4 inches in diameter will require only about 4 gallons of solution per 1,000 inches of

diameter treated compared with

about 12 gallons for trees ranging

from 1 to 12 inches.

RELEASE OF CHRISTMAS TREE

PLANTATIONS

The control of undesirable hardW'oods and brush in Chi'istmas tree

plantations requires more care than

that in plantations for timber production. A high degree of sprout

control is neecled, and only very

slight damage to the conifers can

be tolerated. Browned foliage and

malfoi-med branches on even a few

conifers per acre caused by improper application of herbicides can be

e.xti-emely costly in Christinas tree

plantings.

The safest and most effecti^'e release method is to cut the undesirable brush and hardwoods and

spray the freshly cut stumps with

2,4,.5'-T in oil. Use an ester of

2,4,5-T at 8 to 12 pounds A TIG (2-

to 3-percent solution by volume) in

No. 2 fuel oil.

The second most effective method

is basal sprays. Drench the bases

of the trees to a height of 2 feet

with an ester of 2,4,ñ-T in fuel oil

at 12 pounds AHG. On prolifically

s])routing species, such as aspen,

cherry, and red maple, api")ly such

sprays immediatelj^ after full leaf

develojiment.

To eliminate large trees, use the

basal cut-bark methods described

on pages 6 and 15. Since complete

sprout control is desired, do this

work immediately after full leaf

development.

Foliage sprays, at the rates listed

under Low Release, can also be used

for brush control in Christmas tree

pi antings. They must, however, be

aj)plied late in the growing season

and carefully directed so that only

very light volumes fall on the conifers.

Backi)ack pump sprayers are useful for treating low brush or scattered dense patches of low brush.

Power spraj'ers and mist blowers

can also be nsed on dense brush, but

their use in Christmas tree plantations is not generally advisable because they are likely to damage the

trees.

The larger Christmas tree ¡îlantations, like plantations for other

products, can be released by aerial
RELEASING CONIFERS IN THE LAKE STATES WITH CHEMICALS 19

spraying. In fact, this nictliod is

fiUdird beciiuse hei'bicide can be

more easily applied iinifonnly by

airplane than with ground eijuipment.

Complete control of all undesirable brush is seldom achieved by

one application of folia,i>T sprays.

In dense brush one aerial spray

treatment will seldom ])rovide more

than 90 percent release—especially

from the tall brush and trees. The

remainino- release can be obtained

the followino- year with around

treatments designed for coni])lete

control of the undesirable low

brush.

PREPLANTING RELEASE

Preplanting release r.ims at prior

control of brusli and undesirable

hardwoods to reduce the need for

release of conifers aftei' they are'

planted. It is also called plantingsite preparation. Formerly this

operation was performed only with

heavj^ equipment such as disk ])lows

whicii uprooted much of the brush

and temporarily slowed its growth.

Such mechanical treatment, however, is slow and costly and is restricted to firm, fairly even ground

without much slojie.

In the last few years, foliage

spraying of brush in advance of

planting has proved an effective

and much cheaper substitute for

mechanical preplanting release (hg

' 10) Through the proper use ot

this method, the need of subsequent

release of plantations on brushy

sites can be greatly reduced aiid in

. some cases eliminated Where

brush regrowth overtakes tlie plant-

, ed conifers, a good job «f io^I /j^^

- lease with hei'bicides should set tlie

unwanted vegetation back so that

the trees will be free to grow.

Areas scheduled for preplantuig

release usually have no conifers

prêtent to be injured by the herb.-

cide. Spraying llicreforc can be

done at the ideal time for the prevention of resprouting—iinuiediately following full leaf develoj)-

ment, normally after July 1 in the

Tjake States. In this active

growth i)eriod, all vegetation is sensitive even to minute amounts of

herbicide, so special care must be

taken to prevent damage on adjacent areas.

Like foliage spraying for low release and for high release, the job

can be done from the ground with

hand or power equipment or from

aircraft, applying 1 to 2 pounds per

acre ^-^ acid equi\'alent of 2,4-D or

2,-l:,r)-T, depending on the density

and species of trees or brush to be

controlled. Detailed prescriptions

are gi\'en on jxiges 10 and V).

The volume of mixture used

will vaiy with the equipment used.

Suggested are the following applications and carriers: ^^

Aircraft—2 to -i gallons per acre

of an oil-water emulsion.

:Mist blowers—5 to 10 gallons per

acre of an oil-water emulsion, depending on density and height of

brush.

liackpack pumps—50 gallons per

acre of water emulsion.

Power pumps—50 to 200 gallons

per acre of water emulsion.

The beneñts of prerelease spraying are exemplihed by a plantation

of red pine and white spruce planted

during May 1955 on the Superior

National Forest. The site, a 20-

acre tract of rough land covered

with dense hazel, upland alder, willow, and mountain maple, was

sprayed from the air with 2 pounds

of combined 2,4-D and 2,4,5-T in 4

gallons of oil-water emulsion per

acre in late July 1954, the year before planting. Three growing sea-

' ' Large a.spen may require as much as

3 pdUiuis of 2,4-D per acre.

" Use oil soliitidDs wliere oak or large

aspeii Is to be sprayed from aircraft.
20 AGRICULTURE HANDBOOK NO. 185

4

F-4n2S4i)j 402S54

Figure 10.—Chemical spraying Idwers tlie cost of preplantiiig treatment. A, Dense

brusli of hazel, willow, and nKJuntain maple on area otherwise siiitable for planting.

B, Same area 5 years after aerial spraying: note the good reduction of brush in

foreground.
IIKLEASING CONIFE,RS IN THK LAKE STATES WITH CHEMICALS 21

sons lut er, only 12 percent of the

plunri'd conifers in the sprayed area

needed release, compared with 85

percent where the same species were

planted on adjacent unsprayed

land. Moreover, the trees on the

sprayed area were making better

growth. These results were obtained by site preparation which

cost only $7.50 per acre, whereas

$15 to $20 per acre would have been

spent had the work been done by

disking.

The possibilities of aerial spraying for the preparation of brushy

land for planting, both on lowland

and upland sites, are therefore

promising, not only from the standpoint of cost reduction but also

from that of making progress toAvard restocking the millions of

acres of Lake States land now unproductive. Chemical methods

other than foliage sprays can also

be used, where applicable, for preplanting release. The section on

Basal Cut-Bark Treatments gives

details on these methods.

SAFETY MEASURES

Chemical release of conifere, except for the special accident hazards associated with aerial spraying, is a relatively safe operation.

Both hand and power sprayers

should be operated at pressures

within safe limits. Hose clamps on

hand sprayers are often flimsy and

should be replaced by more substantial ones. The oils used to prepare

herbicide solutions for cut-surface

treatments and basal spraying may

cause burns to the body of the operator. Leaky tanks, hose, or shutoff valves should therefore not be

used. A tight-ñtting gasket of neoprene rubber will prevent leakage

from around the filler cap of backpack sprayers. Since the herbicides

and oil carriers are toxic to tlie skm

of some persons, gloves and goggles

sliould be woni by crews mixing the

spray materials. Manufacturers"

recommendations of precautionai'y

measures should be followed in all

handling and mixing operations.

The usual precautions taken with

handtools—use of luird hats, sliinguards, safety shoes, sheaths for

axes, etc.—should be taken on highrelease operations employing basal

cut-bark treatments.

Aerial release jobs, on the other

hand, involve considerable hazard.

If the balloons used for marking

are inflated with hydrogen, wliich

is readily flammable and dangerously explosive, great care must be

taken to avoid igniting it. Absolutely no smoking is permissible

within a radius of 100 feet while

the balloons are being filled or

within a distance of 50 feet from

tanks of hydrogen at other times.

At least the minimum requirements of the Federal Aviation

Agency concerning the safety of

pilots should be followed. Otlier

safeguards, such as plane-to-ground

radios in the plane and at the base

and, if possible, also at the scene ol

the spraying would be vei-y desirable. The same is true of certain

types of weather instruments, such

as anemometei-s. When water-based

planes are used, a boat and other

lifesaving equipment should be

available at the loading dock

throughout the flying period of the

job.

To avoid possible legal difficulties, all aerial release jobs should be

done under a contract that clearly

defines the responsibilities of the

interested parties. Some States

have laws regulating the use of

herbicides. These should be thoroughly reviewed and applicable

provisions of them made a part of

the contract.
22 AGRICULTURE HANDBOOK NO. 18.5 _.: : ' ; '

SPECIES SENSITIVE TO FOLIAGE SPRAYS

tiiiccie.1 kiUcJ hti liuth 2,J,-D anil .i,l,,r>-T^ Gviipe {Vitu liparia)

A1 der (-1 In u.s crispa, A. ritgom ) Hazel. ( Corylm amencana, C. cor-

\i>\\,hhidi (Frit.ri/nt.'i/ligni) mtta) .„ ,. • ?

Aspens (/'o/mhis qnnKlUhnfata, Locust, black {holnma pseucloF. tremuJo'nha) ' . ncicra)

Birch, paper {BetvJa papynfem) Sumacs (Rhm sp)).)

Cherry, black {Prunus serótina) Willows (Salix spp.)

Cherry, pin (/^ pensi/llumica) . .,,,,,,.,. , ., , r -r

, „ , ', ' /,> •• ^ KiiccHu re.tixtiint to 2,J,-rj but nut to :i,!i,5-T ( hokeclierry (/ . virc//n/anu)

VAm (fUmusspp.) " Hlackbeiries (Ru.bus up]).)

Juneberries (Ainelanch/'er spp.)

'Kill refers to rtejith of fdliase (nily: ^[ai)les ( Are/' spp.)

iiianj- woody plants will ivsproiit at or ,'j.'L //0//^/r-i/l «nn Í

near the groniul line (h.rius the .season \)<^}^^ i'^'tetrusspp }

following hei-bicidal spraying of foliage Prickly-ash (Aanf/wxijlum ameneven though their tops .are dead. canu.m)

Only the two common herUicides ¡ire iîas|)be] ries (Rvhus ¡dueus, R. occicoiisidered in this list. Of cour.se it does ,' , j- .

not include all plant species in the le- r,"'"?n''

gion that are sensitive to these chemicals. Ivose {IiOHa spp.)

'«•,

us GOVERNMENT PRINTtNG OFFICE; 1961

For sale b.v the SuporinteiKleiit of iJui-iuiieiits, I'.S. (jiivernuieiit Printing Office

Washington 25, D,C'. Price 15 cents