‘1 United States

: a Department of

$i@ Argriculture

m

w

us*s Forest Service

 Southern Forest

Reseath No@

SO-299

Experiment Station August, 1983

Effect of Cut-And-Leave and Cut-And-Top Control Treatments on

Within-Tree Southern Pine Beetle Populations

G. D. Hertel and H. N.. Wallace

SUMMARY

Effects of the cut-and-leave and cut-and-top treatments on within-tree populations of the southern

pine beetle were evaluated in seven active infestations in central Louisiana. Beetle populations were

significantly reduced only in December by felling

freshly attacked trees.

Additional keywords: Control, sampling, Dendfoctonus frontalis Zimmermann.

INTRODUCTION

In 1970, at the height of the most recent outbreak

of the southern pine beetle (SPB) (Dendroctonos

frontalis Zimmermann), the pest was found on more

than half the region’s pine land. Records show that

8.5 million cords and 2.5 million board feet of beetledamaged pine timber were salvaged from 1980

through 1978. This timber has been valued at $200

million (Price and Doggett 1978). It was estimated

that only one-third to one-half of the beetle-affected

timber was salvaged.

Currently, four suppression methods for SPB are

recommended: (1) salvage removal, (2) cut-andspray, (3) pile-and-burn, and (4) cut-and-leave. A

fifth method, cut-and-top, has had limited use in

Texas. Salvage removal is the most widely used of

these methods. Often inclement weather conditions,

administrative delay of sales, low volumes of timber,

inaccessibility of spots, or a poor timber market

severely limits the effectiveness of the salvage removal programs. During such times, the other suppression methods offer advantages.

Two alternatives that are relatively easy to apply

are cut-and-leave and cut-and-top. It has been

shown that cut-and-leave reduces SPB population

survival (Ollieu.1969), disrupts natural aggregation

behavior (Gara 1967), promotes dispersal, and reduces subsequent tree mortality (Billings and Pase

1979).

The cut-and-leave treatment involves felling all

infested trees into an opening created by dead

“black- and red-topped” trees. This usually results

in a large pile of infested trees. When the crowns

are left intact, the inner bark (phloem) molsture is

naturally dissipated through transpiration.

The cut-and-top procedure is applied in the same

way as cut-and-leave, except that the tops are

severed from the bole. Proponents of the procedure

believe that removing the top In the winter prevents

transpiration and thus maintains abnormally high

moisture levels that adversely affect developing

broods.

In both the cut-and-leave and cut-and-top methods, a buffer strip of green pines (equal in width

to the height of infested trees) is cut in front of

recently attacked trees to prevent further attacks

on adjacent trees (Coster and Johnson 1979). The

disruption of the natural pheromone source apparently encourages beetles to disperse at a time

when they may not be physiologically ready to do

so (Hedden and Billings 1977).

This note describes the influence of cut-and-leave

and cut-and-top on beetle numbers.

Southern Forest Experiment Stallowl-10210 U.S. Postal Servicea Bldg., 701 Loyoir Avenue, New Orleans, La. 7Ol13

Forest Service, U.S. Department of Agriculture.

Serving Aiabama, Arkansas, Louisiana, Mlssksippi, E. Oklahoma, Tennessee, E. Texas, fuerto Rico, U.S. Virgin islands

1
METHODS

From 1975 to 1976, evaluations were conducted

in Louisiana to determine the effect of the cut-andleave and cut-and-top treatments on beetle numbers.

The study areas were in the Catahoula and

Evangeline Ranger Districts of the Kisatchie National Forest, located in Grant and Rapides Parishes. All trees were loblolly pines (Pinus taeda L.)

and ranged in diameter from 13 to 46 cm. Treatments were started on November 1, 1975, and

ended on September 10,1976. Seven separate spots

were located and treated. In all cases, the cut-andleave and cut-and-top trees were felled and exposed

to full sunlight. The standing untreated trees were

shaded on all sides, and none of the residual vegetation was removed. Treated and untreated trees

were located within the same group of infested

trees (spot).

The population sampling techniques and equipment used for taking the lOO-cm2 bark samples were

similar to those reported by Coulson et al. (1975).

The first set of bark samples was taken on the first

day of treatment, prior to tree felling, from all the

infested trees in that spot. Two sample disks (north

and south) were collected at 1.4 m intervals, starting

1.4 m from the ground, along the infested bole.

The cut-and-leave and cut-and-top trees were immediately cut after sampling and exposed to full

sunlight. A second set of bark samples was taken

just prior to beetle emergence. Two samples at

each sampling interval (1.4 m) were taken on each

untreated tree, and four samples were taken at

each sampling interval from the cut-and-leave and

cut-and-top trees. These samples were incubated

in rearing cups for 30 days to collect emerging

adults.

Total numbers of insects on each tree for each

sample date were estimated’ by the topological

mapping technique (Pulley et al. 1976). Two variables were analyzed - survival and numbers of

offspring per attacking adult. A one-way analysis

of variance was performed using the actual data to

conduct a multiple range test on the treatment differences. A two-way analysis of variance was done

for the survival data. Duncan’s Multiple Range Test

was used to determine if pairs of plots were significantly diiferent from each other.

RESULTS AND DISCUSSION

Survival

For trees with late brood stages (large larvae,

pupae, callow adults), there were no significant

diyferences (P > 0.05) in survival among treatments,

dates, and treatment by date interactions. Survival means for different treatments were variable

throughout the year. Table 1 presents average

beetle survival by treatment and date. Overall

averages show that the two treatments reduced

survival 11 and 15 percent over survival in the untreated trees. However, survival in the untreated

trees was greatest for only three of the five dates.

In cut-and-top trees, average beetle survival

ranged from 8 to 48 percent. The largest survival

percentages, in March and September, reflect a

majority of pupae and callow adults in the study

trees as compared to other treatment months,

December and August, when primarily larvae were

present. Beetle survival in untreated trees in July

(32 percent) was similar to the July results (34

percent) of Palmer and Coster (1978).

Palmer and Coster found July survival in cut-andleave trees to be 17 percent compared to this evaluation’s 18 percent. In this evaluation, cut-and-leave

beetle survival ranged from 13 to 52 percent. The

high (September) and low (December) seasonal

values in beetle survival were comparable to the

findings of Hodges and Thatcher (1976), which had

been completed 1 year prior to the present evaluation.

Cut-and-leave resulted in the lowest average survival for all seasons. Average survival was 24 percent for cut-and-leave, 28 percent for cut-and-top,

and 39 percent for controls (table 1). This compares

to the results of Hodges and Thatcher (1976), where

survival was 32, 17, and 35 percent far cut-andleave, cut-and-top, and untreated trees, respectively.

Number of Offspring

Instead of survival, the number of offspring per

attacking adult was compared in the trees containing recent attacks. In this set of experiments, there

were significant dif,erences (p < 0.05) in offspring

for treatments within treatment dates (table 2).

0. D. Hertei is Applications Coordinator, integrated Pest Management Program, USDA Forest Service, 2500 Shreveport Highway,

Pineviiie, LA 71350. When this evaluation was conducted, he was Staff Specialist, Forest Pest Management, State and Private

Forestry, Southern Region, USDA Forest Service, Pineviiie, LA, H. N. Wallace is Biological Technician, Forest Pest Management,

State and Private Forestry, Southern Region, USDA Forest Service, Pineviiie, LA. This study was supported by the Expanded Southern Pine Beetle Research and Applications Program. The findings, opinions, and conclusions are the responsibility of the authors.

2
Table l.-Average survival of southern pina beetle brood in untreated, cut-and-leave, and cut-and-top pines

Dqc. 1975 Mar. 1976 July 1976 Aug. 1976 Sept. 1976 Average

Treatment Trees Brood WI T- &Ood SD Trees Brood

sampled survival sampled survival sampled survival SD Trees Brood sD Trees Brood SD Brood

sampled survival sampled survival survival SD

number percent number percent number percent number percent number percent percent

Untreated 4 20 7 3 76 1 3 3 3 2 11 3 3 4 2 6 5 39 2 3 39 24

Cut-and-top 4 6 3 3 36 1 0 3 36 31 3 1 0 1 4 46 21 26 22

Cut-and-leave 4 1 3 1 0 0 101 3 1 6 4 3 16 21 3 5 2 3 0 24 22

Average . . . . I4 6 49 25 . . 29 1 9 21 21 .-.. 44 2 3 30 23

Standard Deviation.

ZData missing/not available: estimation done by regression analysis.

Table P.-Average number ot offspring per attacking adult trom recently attacked pines

Treatment

Dec. 1975 15 June 1976 29 June 1976 Sept. 1976 Average

Trees Trees Trees Brood

sampled Offspring’ W sampled Offapring SD sampled Offspring SD survival SD

Untreated ‘

Cut-and-top

Cut-and-leave

Average

_......number______

3 3.30

1 1.29

3 1.60

. . . . 2.30

1.103

b

l.lOb

l.lOa

________number___

____

3 0.45

3 .lO

3 -04

20

0.32

.04

.02

.26b

_______num&______

3 1.30

3 .%I

3 .90

1.09

0.40

.07

A0

.35b

. . . . . . number._.___

1 3.70

2 .95

3 1.03

. 1.45

35

.49

1.1 b

number

1.90

-70

30

1.15a

.15b

.69b

‘Per attacking adult.

‘Standard deviation.

‘Means followed by the same letter in each column are not significantly different (P < 0.05).
c

There was no significant treatment-by-month interaction at the 0.05 level. This greater effect on early

broods supports the findings of Ollieu (1969), but

not those of Hodges and Thatcher (1976).

When compared to untreated pines, the number

of offspring per attacking adult was significantly

less for the cut-and-top and cut-and-leave treatments. Either lower egg production or higher brood

mortality accounted for this difference. The number

of December offspring per adult was significantly

larger than those of the other three sampling dates.

In this evaluation, cut-and-leave and cut-and-top

treatments significantly reduced SPB populations

only in limited situatlons. When the felled trees were

freshly attacked In the winter, populations were

adversely affected. It appears that microenvironmental changes have a greater opportunity to affect

the beetle in these trees. Population survival is reduced by different amounts, depending on treatment and date of application; however, it is impossible to eliminate the entire brood.

It is not known how much beetle population must

be reduced to prevent the breakout of a controlled

spot. In the summer, controlled spots may break out

but few new ones are initiated, indicating that slgnificant beetle mortality can probably be attributed

to the dispersal phase. This assumption is based

on the belief that when cut-and-leave and cut-andtop are applied, the broods are placed in a less than

desirable environmental situation and produce adult

beetles that are not physiologically capable of flying

for very long distances and thus are not able to

initiate new spots (Billings and Pase 1979).

Billings, R. F.; Pase, H. A., Ill. Spot proliferation

patterns as a measure of the area-wide effective

ness of southern pine beetle control tactics. In:

Coster, J. E.; and Searcy, J. L., eds. Evaluating

Control Tactics for Southern Pine Beetle: Symposium Proceedings, 1979 January-February;

Many, LA. Tech. Bull. 1613. Washington, DC: U.S.

Department of Agriculture Forest Service, Combined Forest Pest Research and Development

Program; 1979: 8%97.

Coster, J. E.; Johnson, P. C. Characterizing flight

aggregation of the southern pine beetle. Environ.

Entomol. 8: 381-337; 1979.

Coulson, R. N.; Hain, F. P.; Foltz, J. L.; Mayyasl,

A. M. Techniques for sampling the dynamics of

southern pine beetle populations. Texas Agriculture Experiment Station: 1975. Misc. Pub.

1185.18 p.

Gara, R. I. Studies on the attack behavior of the

southern pine beetle I. The spreading and col”

lapse of outbreaks. Contr. Boyce Thompson Inst.

23: 349-354; 1967.

Hedden, R. L.; Billings, R. F. Seasonal variations

in fat content and size of southern pine beetle

in east Texas. Ann. Entomol. Sot. Amer. 70: 87%

880; 1977.

Hodges, J. D.; Thatcher, R. C. Southern pine beetle

survival in trees felled by the cut and top - cut

and leave method. U.S. Department of Agriculture

Forest Service, Southern Forest Experiment Station; 1976. Res. Note SO-219.5 p.

Ollieu, M. M. Evaluation of alternative southern pine

beetle control techniques. Texas Forest Service;

1969. Pub. 104.6 p.

Palmer, H. C., Jr.; Coster, J. E. Survival of southern

pine beetles in felled and standing loblolly pines.

J. Ga. Entomol. Sot. 13: 1-7; 1978.

Price, T. S.; Doggett, C. A history of southern pine

beetle outbreaks in the southeastern United

States. Georgia Forestry Commission; Macon, GA

1978.31 p.

Pulley, P. E.; Mayyasl, A. M.; Foltz, J. L.; Coulson,

R. N; Martin, W.. C. Topological mapping to estimate numbers of bark inhabiting Insects. Environ.

Entomol. 5: 640-843; 1976.

Texas Forest Service. Cut-anddleave, a method to

reduce losses from the southern pine beetle.

Texas Forest Service, College Station, TX, Cir.

223; 1975.6 p.

4

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