Control of Dogfennel (EupaforiumCapillifolium (Lam.) Small)

Does Not Increase Loblolly Pine Yields1

James D. Haywood

SUMMARY

Control of dogfennel alone did not increase

height or cubic-foot volume of newly planted loblolly pines. Of five treatments - check, removal

of dogfennel in the 1st year only, removal of all

dogfennel yearly, removal of a!1 competing vegetation biannually, and yearly spraying of all compet.ing vegetation with chemicals-only biannual

removal of all competing vegetation produced

significantly better pine height and cubic-foot

yields.

Additional keywords: Weed control

INTRODUCTION

Mechanical site preparation on upland sites in

the West Gulf Region is often followed by a rapid

proliferation of both annual and perennial plants

that compete with newly planted pines. Controlling all competing plants can increas,e theI cubicfoot yields of, pines, but such,,measures may be

impractical and prohibitively ‘expensive. So we

must find out if controlling only certain plant populations will significantly increase pine yields.

This study determined whether controlling one

major competitor-dogfennel (Eupatorium capillifolium (Lam.) Small)-in a newly planted loblolly

pine (Pinus taeda L.) plantation would increase

pine survival, height, and volume.

Dogfennel is a short-lived perennial commonly

found on pine sites in Louisiana. It grows in colonies from thick woody roots, averages 4-5 ft tall

when mature, and may have thousands of stem

clusters per acre.

METHODS

The study area is located in central Louisiana

on a moderately well drained Beauregard silt

loam soil that originally supported a scattered

.,

,

*This publicationreports research involving pesticides It does

not contain rec’ommehdations for th’eir use, nor does’it imply

that the Uses’discussed here have been regiatered.“AWuses of

pesticides must be registered by appropriate State and/or

Federal,agancies before they”can,‘be recommended,.

CAUTION: Pesticides can be,injurious. to humans; domestic

animals,, desirable plants; and fishor oth.er wildlife4f they are

not handled or applied properly. Use.all pesticides selectively

and carefully. Follow recommended practices for the disposal

of surplus pesticides and pesticide containers.

Southern Forest Experiment Station/T-10210 U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Servtng Alabama, Arkansas, Louisiana, Mississippi, Eastern Oklahoma, Tennessee, Eastern Texas.
stand of loblolly pine. The site was chosen for its

large dogfennel population.

Harvesting of the pine in 1974-75 left a dense

mixture of hardwoods that were mainly understory trees before the cutting. The predominant

species included oaks, sweetgum, blackgum, and

flowering dogwood (see table 4 for,scientific

names). These hardwoods numbered several

thousand per acre, ranged up to 17 inches in diameter, and averaged about 7 inches in d.b.h.

(diameter at 4.5 ft aboveground). In the summer

of 1975 the residual stand was sheared, windrowed, and left unburned. In February 1976 the

area was machine-planted with l-0, bare-root loblolly pine seedlings at a 6 x i 2 ft spacing.

In July 1976 the most numerous plant species

on the site, excluding grasses, were inventoried.

Dogfennel averaged 21,600 plants (clusters from

common rootstock) per acre. The major vine and

brush species were smilax (6,500 stems per acre),

American beautyberry (6,000 stems per acre),

and shining sumac (2,800 stems per acre). Many

forb species and a mixture of scattered oak, hickory, sweetgum, b.lackgum, flowering dogwood,

tree sparkleberry, and muscadine grape also

grew on the area.

Plots were established in a completely randomized block design with four replications. Each plot

contained one row of 10 loblolly pines. All plots

were at least 12 ft from a windrow, and no plot

touched another.

Five different degrees of competition control

were maintained over three growing seasons

starting in July 1976:

(1) Check-no post-planting control of competing vegetation;

(2) Removal of dogfennel by digging up roots

in the 1 st year only;

(3) Removal of dogfennel yearly;

(4) Hemoval of all competing vegetation by

hoeing twice a year;

(5) Control of all competing vegetation by annual spraying with a mixture of 2,4,5-T

(2,4,Wrichlorophenoxyacetic acid) and

MSMA (monosodium acid of methanearsonate) in water solution.

For treatment 5, pines were shielded in 1976

and 1977 so they would not suffer chemical injury. Trees were not shielded in 1978. During July

1976, each chemical was applied at 8-lb acid

equivalent (ae) per acre in 3 gal water. The rates

were halved for the May 1977 and May 1978 treatments. Even the 4 lb ae rates, however, were excessive for treatment among young loblolly pines

because the chemicals pruned the lower

branches. Chemicals probably also caused less

evident injuries that might have decreased pine

survival, height, and volume. So damage from

chemicals compromised treatment-5 results, and

they were excluded from further analysis.

No treatment could be devised for controlling

all competing vegetation except dogfennel.

Tip moths (Rhyacionia frustrana Comstock) infested the plantation during March 1977. Pines

were treated in March 1977 and 1978 with pellets

that were 10 percent carbofuran. This treatment

prevented confusion of insect damage with damage caused by dogfennel. Pellets were broadcast

by hand around individual pines at a rate of 10 g

per tree in 1977 and 20 g per tree in 1978. Pines

suffered little evident tip moth damage.

As a measure of treatment response, total

heights to the nearest 0.1 ft and diameters atonehalf of total height to the nearest 0.1 inch were

taken each fall on all surviving pines. Diameters

at the groundline were also taken in 1978 to the

nearest 0.1 inch. Total cubic-foot volume per tree

was calculated with the equation from Perry and

Roberts (1964)?

where V =

H =

D =

v = 10.62 D2*H

volume per tree in cubic inches

height per tree in feet

diameter per tree at one-half of total height in inches.

For each plot, single-tree ,volumes were averaged.

On May 1 and 2, 1978, all competing vegetation

within a 1-milacre circle around tree number 5

was cut to a 1 -inch stub and bagged for drying on

the treatment-3 and -4 plots. For each check plot,

a 1-milacre sample was taken from an adjacent

row so that check plots would not be disturbed.

This inventory was taken before cultural treatZPerry, T. 0. and A. Y. Roberts. 1964. Volume formulas for

loblolly pine seedlings in the vicinity of Raleigh, North Carolina. J. For. 62:182-187.

Haywood is Assistant Silviculturist, Southern Forest Experlment Station, Forest Service-USDA, Pineville, Louisiana.

2
ments were applied. Samples were ovendried at

70” C to a constant weight.

During the first four growing seasons after

planting, an inventory of the dogfennel was conducted before cultural treatments were applied.

This inventory was done on 3 milacres per plot,

with pine seedling numbers 2, 5, and 8 as center

points.

In October 1979 I inventoried competing plants

again to determine the most numerous species

on the study area at stand age 4 (table 4).

Average pine survival, diameters at groundline,

total heights, and cubic-foot volumes were tested

by analyses of variance. Differences among

means were determined by Duncan’s Multiple

Range Test (0.05). Survival percentages were

transformed into arcsin \/proportions before

analysis.

RESULTS AND DISCUSSION

Pine Survival, Growth, and Yield

Loblolly pine survival was high on all plots, and

survival did not differ statistically among treatments (table 1).

By stand age 2, pines on treatment-4 plots were

significantly taller than trees on check plots. This

difference was maintained through the 3d year

when loblolly pines on treatment-4 plots were 23

percent taller than pines on the check plots (table

1). Pines on treatment-2 and -3 plots where only

dogfennel was controlled were not significantly

taller than trees on check plots.

After 3 years, loblolly pine on treatment-4 plots

had significantly larger diameters than did pines

in the other three treatments (table 1).

Differences in the cubic-inch volume per pine

developed during the second growing season.

This difference increased during the third growing season; by stand age 3, trees on treatment-4

plots had over twice the average volume of trees

on check plots (table 1). This large increase in

yield occurred even though most competitors

were herbaceous plants.

Competing Vegetation

The 21,600 dogfennel clusters per acre noted

on the check plots at the beginning of the study

had declined to 9,500 per acre by the fourth

growing season after planting (table 2). And stem

vigor and number per cluster had declined. By

the fourth growing season, dogfennel numbered

only 250 and 400 clusters per acre on treatment2 and -3 plots where just dogfennel was controlled. No clusters were noted on treatment-4.

plots.

Dogfennel seedlings were more common on

treatment-2 and treatment-3 plots than on check

and treatment-4 plots. Pines on treatment-4 plots

had well developed crowns that shielded the plot

surface, thus reducing encroachment, germination, and development of seedling dogfennel.

Most dogfennel seedlings had disappeared by

July on all plots. The few remaining seedlings

were poorly developed and under severe moisture stress.

Evidently dogfennel can successfully pioneer

an area, but then declines over the years under

competitive pressure from strong perennials, like

the grasses. As established dogfennels fade from

the site, the other plants keep the seedling dogfenneis from becoming established. The mechanism of suppression might be moisture stress or

shading from overtopping plants. Removing dogfennel was ineffective because other herbaceous

plants quickly replaced it, thus maintaining constant competitive pressure on the pines.

In May 1978, ovendry weights per acre of all

competing plants were significantly less on treatment-4 plots than on check and treatment-3 plots

(table 3). Treatment-2 plots were not sampled because these plots were intermediate to treatment1 and treatment-3 plots.

Field evaluation in 1979 clarified May 1978

data. On check plots the woody competition was

developing slowly, and herbaceous plants were

still the major competitors of loblolly pine four

growing seasons after planting. The major competitors on check plots were panicums, bluestems, common carpetgrass, purple lovegrass,

composites, American beautyberry, blackberry,

shining sumac, hypericums, and smilax (table 4).

In 1979 no difference was evident in level of

competition on the check, treatment-2, and treatment-3 plots (except in number of dogfennel).

By the fourth growing season, pines dominated

treatment-4 plots and were suppressing competition. In 1979, then, herbaceous plants were

sparse, and despite the stopping of treatment in

1978, brush was limited to a few small shining

sumac and a few small blackberry canes.

3
.

Table 1 .-Survival md growth of loblolly pine at shnd age 3, by treatment

Total

Treatments Survival height

Peroent Pert lnchra

Check 98 a’ 5.2 a 1.5 a

Dogfennel removed 1 St year only 88a 4.8 a 1.3 a

Dogfennel removed yearly 100a 5.3 a 1.3a.

All vegetation removed by hosing 96a 8.4 b 2.0 b

/Iv

.32.0 a

‘23.2 a

28.4 a

r1.2 p

Weans followed by the same letter are not slgnlflcantly dlffsrent (Duncan’s Multiple Range Test,

0.05).

Table 2.--Dogfennel Inventories

July 1678 before treatments began May 1979 efter final treatment

\

Residual stem W 1879

Treatments de&dual *em rrlusten oluEter6 Iv3 totals

-a

-------------I------Numb~rof~~~m~p~rac~--..,--.---------.--

Chaek

Dogfennel removed 1 at year only

Dogfennel removed yearly

All vegeWon removed by hoeing

\ Pl ,@ou 9,500 18,500 28,000

W430 250 81,250 51,500

23,900 400

23,560 ’

ps2,100 52,500

0 ‘I 24,500 24,500

Table 3.-Own& weight per acre of competing wgeWonIn

>) Mayam

_/ ,, ?@&fmnr Mean i .‘X ..

.~ Tons

Check , . n,: 0.85 b*

Dogfennel removsd’$&rly 0.88 b

All vegetetlon rem&W#yho@ng -07 a

:, : ,Z’ ;‘”

*Means followed I@ t~~q$@@tter are not signlflcantly differant (Duncan’s Uuftiplr mt, 0.05). ..)“* -1 ‘,

.1 , ,

.
Table 4.-Abbreviated listing of the competitors of planted loblolly pine; field data were collected

in October 1979, four growing seasons after planting

Major competitors

Grasses ~ ./ / 1 i ,, , :,\ 5” I’ , ‘.‘>j _, ;I -,.:. j: ’

” Panicums

, I ‘~,s@sjstem~“~ , g :

Panlcum spp.

Common carpetgrass

,: ”

~~~~opogon spp.

Axonopus affinis Chase

.! _a!;,.:

Purple lovegrass, ., _,. Eragrostis spectabilis (Pursh.) Steud. .

Composites

. Maryland goldaster Heterotheca mariana (L.) Shinners ~(

Bushy aster ,&r&r dumosus L.\,; : I’, ! +., . - ; ‘c’. . - _, :

Skydrop aster .’ ’ Aster patens Ait. : ’ .: j , _ ,,., :; ,:, 8

I Rogfennel ,. Eupatorium capillifolium (Lam.)Smalt~~~.

Tall goldenrod Solidago altissima L.

Brush ~

! + . ,( ,. ( ,-.1,-,1 ;.-;,i ‘be:, ;/! ‘,:’ I” i _J<,‘l, : I, . ,

Shining sumac Rhus copailina L.

Smilax Smilax spp.

Blackberry Rubus Spp.

American beautyberry Callicarpa americana L.

Hypericum Hypericum spp.

Other competitors

Grasses

Fringeleaf paspalum’

Arrowfeather threeawn

,: Campwit& i_ ‘ ~

,~ ,:‘.‘- ..‘Swamp FUPIf,c~I’

Horseweed ‘, I ’

’ HyssQpleaf eupator’ium

Mistflower

Roundleafeupatorliiin

,.Purple cudweed,<, ,:

i:. Fragrant cudweed

,~;ti~iry elephantfqet

,.,c$@ded goldywod

Frigrant goldenrod

Forbs

Woolly croton

Maryland meadowbeauty

Whiteleaf mountainmint

Downy lobelia

Southern bracken

Brush ,. ,_

Muscadine grape

Carolina jessamine ,

Eastern baccharis

Southern bayberry ,.:.

Tree sparkleberry, ‘:,.

Flowering dogwood

Persimmon

Blackgum ,:, (~(I

Sweetgum?

Water oak2 .

Southern red oak2

Blackjack oak

Chinquapin

Hickory

Paspalum ciliatifolium Michx. _. ‘,t. .’

Aristida purpurascens PQir.

,,‘,i,‘, ,: 8.:

.‘S ( . :.,i:;. ‘,

Helianthus angustifolius L.

Erigeron cana,densis L.

“’ ” Eupatonum:‘~~~sopifolium L.

i : 21

Eupatorium coelestinum L.

Eupatorium rotundifolium L.

Gpaphalium purpureum L.

Gnaphalium obtusifolium L. , .“, . , b . ;: ‘,^, , .y

Bfephantopus tomentosus L. 1, ^I ,r. s./ 6 “; ,,, , ?

Sotrdago rugosa Ait. I:.:.. i “ : - ’ ;. ” ,‘,>

Salidago odora Ait.

Croton capitatus var. lindheimeri (Engelm

and Gray) Muell. Arg.

Rhexia mariana L.

Pycnanthemum albescens T&G

Lobelia puberula Michx.

Pteridium aquilinum (L.) Kuhn var.

pseudocaudatum (Clute) Heller

,.?, in -~,~“.),i.“...,.’ f.,,

Vitis rotund/fofia’Mibtk

Gelsem&m sampervirens (L.) Ait.

Baccharis halimifolia L.

Myrica cerifera L. . ,

Vaccinium ,arbqr;eum Marsh,

Cornua.f@rida L: : i’ _:, ,!, * ‘.,

Diospyros virginiana L. ”

, :,: . ,: ,, :Nyssa sylvatiad Marsh. v&C aflatica

‘. Liquida~berst~~a~fflua’ L:.’ v :I

Quercus nigra L.

C?. falcata Michx.

Q . marilandica Muenchh.

Castanea alnifolia Nutt.

Carya spp.

‘Fringeleaf paspalum was actually rare on the study site; no other paspalums were evident.

2These species will probably develop into the major understory trees beneath the pine canopy.

:.5 *U.S. GOVERNMENT PRINTING OFFICE: 1980-671-180