United States

Department of

Agriculture

Forest Service

Southern Forest

Research Note

SO-342

Experiment Station November 1997

Southern Pine Beetles Attack Felled Green Timber

John C. Moser, Robert A. Sommers, Peter L. Lorio, Jr.,

J. Robert Bridges, and Jeffrey J. Witcosky

SUMMARY

Southern pine beetles attacked green, uninfested

downed trees and logs, as well as nearby standing

trees. Beetles infesting horizontal trees and decked

logs reproduced sufficiently to indicate that in some

circumstances freshly cut, green trees may provide a

utilizable resource for beetle populations.

Keywords: Dendroctonus frontalis, dispersal, Ips

calligraphus, southern pine beetle.

INTRODUCTION

Although Hopkins (1909) briefly mentioned that the

southern pine beetle (SPB) (Dendroctonus frontalis

Zimmermann) will breed in felled pines (Pinus spp.),

this behavior has been thought to be uncommon (Gara

and others 1965). MacAndrews (unpublished MS thesis

1926)’ first reported SPB completing a generation in

felled logs of shortleaf pine (Pinus echinata Miller) in an

“epidemic”situation. In summer and fall he noticed that

the logs were attacked simultaneously by SPB and Ips

calligraphus (Germar) within 2 days after felling and

that the bottoms of logs were colonized more heavily

by SPB than the tops. Highest emergence:attack ratio

(E/A) (10.4) was in the butt logs where bark was

thickest. The average number of beetles was 21 .4/cm2

(198/ft2). In standing timber, the VA was lower (about

8.0), but numbers of emerging SPB were higher (32.41

cm2 or 300/ft2).

‘MacAndrews, A.H. 1926. The biology of the southern pine beetle.

Unpublished M.S.thesis. N.Y. State College of Forestry. 103 p.

Craighead and others (1927) (cited by Dixon and

Osgood 1961) also noted that SPB attacked downed

material, but discounted its importance. St. Georgeand

Beal (1929), however, noted that “blow downs” during

the summer, and large quantities of timber normally cut

at that time, created conditions that were a menace to

the surrounding healthy trees because the freshly cut

or damaged timber was frequently attractive to the

beetles. Beal and Massey (1945) viewed the phenomenon as occurring during non-outbreak conditions, but

included a photo revealing Ips galleries in the upper

portion of a downed log with SPB colonizing the side

and bottom. Gara and others (1965) reported that the

SPB prefers to land on vertical rather than horizontal

objects under any condition. Subsequent SPB literature did not dispute this statement, and in one recent

article it is stated that, “SPB won’t touch trees that are

on the ground” (Anon. 1987).

We report here observations of SPB attacking logs

cut from green uninfested treesand stacked horizontally in a log deck, as well as freshly cut green trees

adjacent to a spot in which infested trees were felled

and not removed. Results indicated that beetles may

land on, attack, and reproduce in felled green trees

much more commonly than generally thought.

MATERIALS AND METHODS

Horizontal Trees

This study was conducted on the Kisatchie National

Forest, Catahoula Ranger District, about 5 km (3 mi)

north of Williana, Louisiana. The test area was in a

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.

Serving Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands .

1 ”
35year-old mixed stand of loblolly pine (Pinus taeda

L.) and shortleaf pine, with a mesic understory of mixed

hardwoods.

TheSPB infestation was located by District personnel

on November 12, 1985, when it contained 20 infested

trees. By the first week of December, trees containing

SPB brood in various stages of development and 89 noninfested trees were felled but not removed (fig. 1). The

uninfested trees were felled to ensure that no infested

trees were overlooked, and to provide a buffer strip at

the advancing front of the infestation. East of and adjacent to this area, about 40 infested trees, cut but not

removed, remained from a previous control operation.

One hundred meters (328 ft) to the northeast was an

active infestation with 50 trees containing SPB brood,

and within a 0.4-km (0.25mi) radius of the infestation

were hundreds of additional infested trees.

Starting January 10,1986, we examined the downed

trees at weekly intervals to determine which were

attacked by SPB or Ips spp. and for evidence of parent

adult emergence.

On March 24, each of the downed trees infested with

SPB was destructively examined to determine the stage

of the most advanced brood. Five of the most heavily

infested trees were sampled intensively. Trees selected

for sampling had SPB brood in the pupa-callow adult

stage and were 20 to 25 cm (8 to 10 in) or greater in

stump diameter (fig. 2). Using a hole-saw, lOO-cm*

(15.5-in*) samples were taken at 1.5-m (5-ft) intervals

from the tree butt to the base of the live crown. Four

samples were taken at each sample interval-one from

each side and one from the top and bottom of the tree.

To obtain bottom samples, trees were cut into bolts and

rolled over. Samples were examined as they were removed to record any larvae and pupae not in the outer

bark.

In the laboratory, samples were examined to determine 1) the number of emergence holes and 2) the

number of SPB attack sites (Linit and Stephen 1978).

The samples were then placed in rearing containers to

collect emerging brood. Total emergence included the

number of emergence holes, plus the number of brood

adults that emerged, plus any larvae and pupae exposed

on the inner bark surface when collected. The E/A ratio

was calculated as total emergence divided by 2 times

the number of attack sites (Thatcher and Pickard 1964).

Analysis of variance tests for the downed trees were

designed to compare (PI 0.05) attack density and total

Figure l.-Aerial photo of study area showing majority of green trees in a buffer strip adjacent

to standing frees. The arrow (also see figure 2) points to the first mfested standmg tree m

the plot.

John C. Moser isresearchentomologist, Robert A. Sommers isforestrytechnician, Peter L. Lorio, Jr., is principal research forester, and J. Robert

Bridges is supervisory research entomologist, at the Southern Forest Experiment Station, Forest Service-USDA, Pineville, LA 71360. Jeffrey

J. Witcosky is entomologist, USDA Forest Service, Forest Pest Management, State and Private Forestry, Pineville, LA 71360. The authors thank

J. Russell Flowers, Jr., of Cenla Forestry of LaSalle, Jena, Louisiana, for his assistance in securing the log deck for the period of study and also

the following manuscript reviewers of an earlier draft: R.F. Billings, A.H. MacAndrews, and F.M. Stephen.

2
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e Green buffer pines

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l-5 Sample trees (brood production)

ft Aerial photo marker points to

first infested tree. Length is

5m (16.4 ft.).

w Figu Ire 2.-Diagrammatic sketch of the felled buffer-strip trees, subsequently infested by SPB, and adjacent inventory plot.
emergence among top, bottom, and side samples.

Significantly different means were identified by Duncan’s new multiple range test. To stabilize the variance,

attack data were transformed using log(X+O.S).

Starting January 10, we checked the adjacent stand

for infested trees to a depth of 1 chain (66 ft) along the

infestation perimeter (fig. 1). A 0.16-ha (0.4-ac) plot

was installed encompassing 15 infested trees adjacent

to this perimeter. This was a loo-percent inventory tally

of all pines and hardwoods equal to or greater than 9.2

cm (3.6 in) in diameter (fig. 2). The basal area of the plot

was compared with the basal area of SPB spots within a

radius of 0.8 km (0.5 mi).

Infestations treated by using the cut-and-leave method (Swain and Remion 1981) werechecked during May

through October for evidence of SPB attack and brood

development in buffer-strip trees. Spotsexamined were

treated in May (five spots; Grant Parish, LA), June (six

spots; Grant Parish, LA), and October (nine spots;

Lafayette County, MS). Five or more buffer-strip trees

were examined in each infestation. Bark samples having SPB galleries were returned to the laboratory where

the number of larval mines and frass-filled larval feeding cells were tallied.

Log Deck

This study was conducted in the Kisatchie National

Forest, Catahoula Ranger District, about 6.5 km (4 mi)

northeast of Ball, LA. The test area was in a35-year-old

stand of loblolly pine with a dogwood-waxmyrtle (Cornus florida L. - Myrica cerifera L.) understory. The

infestation was located by District personnel in early

December, and about 800 trees were cut for salvage

December 17 through 27. One group of 32 logs

trimmed to lengths of 5.5 and 8 m (18 and 27 ft) was

piled in a log deck adjacent to the cut area and not

removed immediately (fig. 4).

On December 31,1985, we observed SPB attacking

three fresh logs in the deck. Beetles were observed

entering and exiting from pitch tubes in attempts to

establish egg galleries. Apparently, eight logs in the

deck had been attacked by SPB before cutting because

they contained extensive gallery systems. However, the

three logs attacked after being felled had little or no

gallery systems. Each log was numbered and the length

and diameters of the upper and lower ends measured.

Thereafter, the logs were examined weekly to document new attacks and parent adult emergence and to

determine stage of brood development. Starting on

March 24, each log was destructively examined to

determine when sampling for brood production should

begin. Ips spp. attacks were also monitored.

Five logs ranging from25 to38 cm (10 to25 in) d.o.b.

(small end) with SPB in the pupa-callow adult stage

were sampled intensively to determine numbers of

emerging brood adults. Using a hole saw, lOO-cm2

(15.5-in*) samples were taken at 1.5-m (5-ft) intervals

from the log base to the top (fig. 4). Ideally, three

samples were taken at each sample interval-one from

each side and another from the top. Because the logs

could not be turned, only the exposed areas were

sampled. The samples were examined and the beetles

reared as for the horizontal trees.

The trees surrounding the log deck were examined

weekly to determine if SPB attack had occurred.

Analysis of data for the log deck was the same as for

horizontal trees. Likewise, comparison of means for

horizontal trees with those for the log deck were limited

to top and side samples.

RESULTS AND DISCUSSION

Horizontal Trees

Of the89 unattacked trees felled in December 1985 in

the controlled infestation (fig. 2), 32 were attacked by

one or more pairs of SPB. Of these, five were colonized

by January 10, another 21 by January 28, and six more

by February 18, which was the last date that new attacks

were seen. All 32 attacked trees were in the middle third

of the area (fig. 2). The trees most heavily attacked were

those over 25 cm (10 in) in stump diameter and those

elevated above the ground, but none less than 18 cm (7

in) in stump diameter were infested.

Field observations that fewer SPB galleries were on

the top half of felled trees than on the sides or bottoms

(fig. 3) were supported by survey data. Of the five trees

sampled, mean numbers of SPB attacks per 100 cm*

(15.5 in’) were greater (Pr0.5) on the bottom (5.23) and

sides (4.67) than on the top (2.60). Mean square error

(MSE) for transformed attack data was 0.249. Similarly, brood adult emergence per 100 cm*( 15.5 in*) was

significantly higher (P10.05) on the bottoms (15.74)

and sides (12.12) than on tops (7.55) (MSEz93.85). This

suggests that attacking adults selectively oviposit most

often on the sides and bottoms of downed trees (fig. 3).

Emergence:attack ratios (E/A)* were not significantly

different (P> 0.05) among tops (1.66), sides (1.47), and

bottoms (2.21) (MSE-3.49).

Attack densities in this study were higher than the

average of 19/ft*(=2.04/100 cm*) given by MacAndrews

(1926). Conversely, our maximum emergence figure of

15.74/100 cm2(=146/ft2) was less than his average number of 198/ft2. Thus, his average E/A of 10.42 was far

higher than our maximum of 2.21.

Although no standing trees in the area were examined, in 223 trees sampled during the summers of 1983

and 1984, emergence averaged 21.8/100 cm2 (range

2.9-52.5) (Bridges, unpublished). In standing trees

‘E/A here is an average on a per sample basis and cannot be

obtained by dividing the overall emergence average by the overall

attack average.
emergence among top, bottom, and side samples.

Significantly different means were identified by Duncan’s new multiple range test. To stabilize the variance,

attack data were transformed using log(X+O.5).

Starting January 10, we checked the adjacent stand

for infested trees to a depth of 1 chain (66 ft) along the

infestation perimeter (fig. 1). A 0.16-ha (0.4-ac) plot

was installed encompassing 15 infested trees adjacent

to this perimeter. This was a loo-percent inventory tally

of all pines and hardwoods equal to or greater than 9.2

cm (3.6 in) in diameter (fig. 2). The basal area of the plot

was compared with the basal area of SPB spots within a

radius of 0.8 km (0.5 mi).

Infestations treated by using the cut-and-leave method (Swain and Remion 1981) werechecked during May

through October for evidence of SPB attack and brood

development in buffer-strip trees. Spotsexamined were

treated in May (five spots; Grant Parish, LA), June (six

spots; Grant Parish, LA), and October (nine spots;

Lafayette County, MS). Five or more buffer-strip trees

were examined in each infestation. Bark samples having SPB galleries were returned to the laboratory where

the number of larval mines and frass-filled larval feeding cells were tallied.

Log Deck

This study was conducted in the Kisatchie National

Forest, Catahoula Ranger District, about 6.5 km (4 mi)

northeast of Ball, LA. The test area was in a35-year-old

stand of loblolly pine with a dogwood-waxmyrtle (Cornus florida L. - Myrica cerifera L.) understory. The

infestation was located by District personnel in early

December, and about 800 trees were cut for salvage

December 17 through 27. One group of 32 logs

trimmed to lengths of 5.5 and 8 m (18 and 27 ft) was

piled in a log deck adjacent to the cut area and not

removed immediately (fig. 4).

On December 31,1985, we observed SPB attacking

three fresh logs in the deck. Beetles were observed

entering and exiting from pitch tubes in attempts to

establish egg galleries. Apparently, eight logs in the

deck had been attacked by SPB before cutting because

they contained extensive gallery systems. However, the

three logs attacked after being felled had little or no

gallery systems. Each log was numbered and the length

and diameters of the upper and lower ends measured.

Thereafter, the logs were examined weekly to document new attacks and parent adult emergence and to

determine stage of brood development. Starting on

March 24, each log was destructively examined to

determine when sampling for brood production should

begin. Ips spp. attacks were also monitored.

Five logs ranging from 25 to38 cm (10 to 25 in) d.o.b.

(small end) with SPB in the pupa-callow adult stage

were sampled intensively to determine numbers of

emerging brood adults. Using a hole saw, lOO-cm2

(15.5-in2) samples were taken at 1.5-m (5ft) intervals

from the log base to the top (fig. 4). Ideally, three

samples were taken at each sample interval-one from

each side and another from the top. Because the logs

could not be turned, only the exposed areas were

sampled. The samples were examined and the beetles

reared as for the horizontal trees.

The trees surrounding the log deck were examined

weekly to determine if SPB attack had occurred.

Analysis of data for the log deck was the same as for

horizontal trees. Likewise, comparison of means for

horizontal trees with those for the log deck were limited

to top and side samples.

RESULTS AND DISCUSSION

Horizontal Trees

Of the89 unattacked trees felled in December 1985 in

the controlled infestation (fig. 2), 32 were attacked by

one or more pairs of SPB. Of these, five were colonized

by January 10, another 21 by January 28, and six more

by February 18, which was the last date that new attacks

were seen. All 32 attacked trees were in the middle third

of thearea (fig. 2). The trees most heavily attacked were

those over 25 cm (10 in) in stump diameter and those

elevated above the ground, but none less than 18 cm (7

in) in stump diameter were infested.

Field observations that fewer SPB galleries were on

the top half of felled trees than on the sides or bottoms

(fig. 3) were supported by survey data. Of the five trees

sampled, mean numbers of SPB attacks per 100 cm2

(15.5 in2) weregreater (Pr0.5) on the bottom (5.23) and

sides (4.67) than on the top (2.60). Mean square error

(MSE) for transformed attack data was 0.249. Similarly, brood adult emergence per 100 cm*(15.5 in*) was

significantly higher (PsO.05) on the bottoms (15.74)

and sides (12.12) than on tops (7.55) (MSEz93.85). This

suggests that attacking adults selectively oviposit most

often on the sides and bottoms of downed trees (fig. 3).

Emergence:attack ratios (E/A)2 were not significantly

different (P~0.05) among tops (1.66), sides (1.47), and

bottoms (2.21) (MSEz3.49).

Attack densities in this study were higher than the

average of 19/ft2(=2.04/100 cm2) given by MacAndrews

(1926). Conversely, our maximum emergence figure of

15.74/100 cm2(-146/ft2) was less than his average number of 198/ft*. Thus, his average VA of 10.42 was far

higher than our maximum of 2.21.

Although no standing trees in the area were examined, in 223 trees sampled during the summers of 1983

and 1984, emergence averaged 21.8/100 cm2 (range

2.9-52.5) (Bridges, unpublished). In standing trees

‘E/A here is an average on a per sample basis and cannot be

obtained by dividing the overall emergence average by the overall

attack average.

4
Figure 3.-Section of horizontal tree about0.3 m (1 ft) above ground, stripped of bark and showing

gallery distribution of beet/es shortly after attack. Most SPB galleries are on the sides and

bottom of tree, whereas Ips calligraphus (arrows) is starting to occupy the top. Gallery

pattern on this tree is typical of those m other buffer-strip trees. The free was cut about 76

km (10 mi) from the area discussed in this article. The tree was felled May 1 , 1986 and

photographed May 13. Ambient temperature was about 34” C (93” F) at time photo was

taken, indicating indentical patterns of attack in both cool and hot weather. A similar

photograph appears in Beal and Massey (1945).

MacAndrews found a much higher average emergence

of 32.3/100 cm2(=300 ft2). The highest VA found by

Bridges (unpublished) was 3.9, much lower than the

average of 7.9 found by MacAndrews.

SPB attack termination was apparently due to competition by Ips calligraphus, ancl to a lesser extent by 1 .

grandicollis Eichoff and I. avulsus Eichhoff. A few Ips

spp. were seen in the first observations in early January

(fig. 3), but colonization became intense by February 6

when all but 6 of the 89 trees were attacked by 1 or more

Ips sp. By February 18, all of the larger diameter trees

were infested so heavily that little, if any, bark surface

was available for incoming SPB.

Re-emergence holes of parent adult SPB were seen

February 18 in 7 trees, and a total of 14 trees were tallied

by March 24. Examination of the outer bark on March

24 revealed mature brood adults ready to fly from six of

the downed trees.

Fifteen standing trees were attacked by SPB between

January 13 and February 5, but the attacks were unsuccessful in five trees (fig. 2). The infestation failed to

continue to enlarge, perhaps for several reasons.

Although the attacked trees were closely grouped on

the edge of the treated area, other pines in the immediate area were more widely spaced and were interspersed with hardwoods (see 0.16-ha (0.4-ac) plot in

fig. 2). These conditions could constitute a barrier to

continued spot growth. The basal area at the center of

this plot was 1.8 m2(20 ft2) of pine and 2.8 m2(30 ft*) of

hardwood, while the average basal area of nine active

spots within 0.8 km(0.5 mi) was 10.1 m2(l 10 ft2) of pine

and 2.8 m2(30 ft2) of hardwood, with extremes of 5.5 to

12.9 mz(60 to 140 ft2) of pine and 1.8 to 4.6 m2(20 to 50

ft2) of hardwood.

Another factor could have been a limited population of beetles in the immediate vicinity, some of which

attacked the downed, green trees in the buffer strip.

However, a significant portion of the emerging population may have dispersed to other areas because the

literature suggests that beetles have a tendency to do

so at this time of the year (Billings 1979).

Examination of buffer-strip trees in spots controlled

by the cut-and-leave procedure showed that trees in

some of the infestations were attacked by SPB. Trees in

four of five spots cut in May, one of six spots cut in June,

and three of nine spots cut in October became infested

with SPB and Ips spp. In these spots, SPB colonized 20

to 35 percent of the green horizontal trees examined.

Again, Ips spp. were observed on the upper surface of

the downed trees and SPB on the sides and lower

surface. Examination of bark samples revealed that

SPB development was poorer in June-compared to

May-treated spots. Poor brood development was apparently associated with poor food substrate because the

5
Figure 4.-The log deck. Technician is removing circular disks of

bark for determination of attack and emergence data.

The three flagged standing trees were attacked (unsuccessfully) by a few SPB.

larval mines were abnormally long and narrow. This

suggests that in hot weather, downed trees may act as

a sink for SPB.

Log Deck

When we first discovered the log deck on December

31 (1 week after logs were cut and stacked), the eight

trees attacked before felling were still under active

attack; hence, they probably were still attractive at this

time. Also, at this time three fresh logs were under

attack. Many attacks resulted in large pitch tubes, with

many beetles being pitched out. Temperatures on

December 31 ranged as high as 24°C (75’F), and the

adult SPB and their clerid predators [Thanasimus

dubius (F).] were actively flying in the area, occasionally hitting us. They were also actively running about on

the logs. Although the beetles were attacking the logs,

they did not immediately attack the numerous standing

trees adjacent to the log deck.

By January 10, seven logs had been attacked; by

January 21,12 more; and by February 6 all but one log

had been attacked at least once. The latter log was on

the bottom of the deck and mostly covered by other

logs. As might be anticipated, those logs on the top of

the deck and nearest the previously attacked logs were

attacked by SPB first and received the most attacks.

Although most attacks ceased after February 6,

weekly.observations after this date revealed occasional attacks. The last fresh pitch tube was seen March 24.

Parent adults began re-emerging from one of the

pre-attacked logs on January 21, and by March 3, parents had re-emerged from all eight logs. In the fresh

material, parent adults began re-emerging March 3

from the first log, and by March 24 had re-emerged from

six more.

Samples taken on March 24 revealed that six preattacked logs and at least one of the fresh logs

contained callow adults. Brood development in most of

the other logs had still not progressed past the midlarval stage.

In contrast to the downed green trees, Ips spp.

(mostly 1 . calligraphus) may not have been a major

factor in SPB attack termination within the log deck.

Ips attacked later than SPB and then in relatively few

numbers. The first Ips attacks were not seen until

March 3, but by March 21 a total of 21 of the35 trees had

been attacked at least once. In a similar study of the

spruce beetle, D. rufipennis (Kirby), Nagel and others

(1957) also noted that few Ips spp. attacked downed

spruce. Ips spp. preferred the tops of the logs, whereas D. rufipennis preferred the sides and bottoms. Five

standing trees surrounding the log deck were attacked

by SPB between January 21 and March 11. All beetles

were pitched-out, and the trees survived the attacks.

Of the five logs sampled, mean numbers of SPB

attacks per 100 cm2 (15.5 in*) were significantly greater

(PsO.05) on the sides (3.22) than on the tops (1.47)

(MSE=O.613). Mean emergence was 9.30/100 cm2 for

the sides and 5.24/100 cm2 for the tops (MSE-107.97);

mean E/A was 1.69 for the sides and 1.42 for the tops

(MSE3.56). These differences were not significant.

The attack and emergence means for the horizontal

trees and those for the log deck were not significantly

different (PbO.05).

The data confirm previous observations by Craighead and others (1927), St. George and Beal (1929),

and Beal and Massey (1945) that downed timber can be

attractive to SPB. This is common behavior for many

species of Dendroctonus, such as D. rufipennis and

the Douglas-fir beetle, D. pseudotsugae Hopkins, and

occasionally occurs for others, such as the mountain

pine beetle, D. ponderosae Hopkins (Wood 1982). ln

fact, Amman (1983) suggested a strategy for trap log

cutting and removal to reduce mountain pine beetle

populations in ponderosa pine forests because of the

beetle’s strong attraction to felled ponderosa pine

(Pinus ponderosa Douglas).

6
CONCLUSIONS

This study shows that attacks of downed material by

SPB are much more common than previously thought

(Billings 1980, Gara and others 1965, Swain and

Remion 1981, Thatcher and others 1982). Bufferstrip

trees felled during a cut-and-leave operation were

attacked, either by beetles emerging from infested

trees in the controlled infestation or from trees in the

surrounding area known to have emerging brood, or

both. When a SPB spot is controlled during midwinter, some downed material may be attacked. Beetles in this infested material are able to reproduce and

possibly provide a source for future SPB infestation.

The study also shows that the SPB may also attack

felled trees in spring, summer, and fall. However, SPB

survival may be poor in hot weather. Research on SPB

behavior and dispersal throughout the year is needed

to determine the likely effects of a variety of control

tactics and strategies.

LITERATURE CITED

Amman, G.D. 1983. Strategy for reducing mountain

pine beetle infestations with ponderosa pine trap

logs. Res. Note INT-338. Ogden, UT: U.S. Department of Agriculture, Forest Service, lntermountain

Forest and Range Experiment Station. 3 p.

Anon. 1987. Rx for SPB: Cut! cut! cut!. The American

Tree Farmer. 6:13.

Beak, J.A.; Massey, C.L. 1945. Bark beetles and ambrosia beetles (Coleoptera:Scolytoidea): with special reference to species occurring in North Carolina. Durham, NC: Duke University School of Forestry Burl.

10.178 p., PI. 1-28.

Billings, R.F. 1979. Detecting and aerially evaluating

southern pine beetle outbreaks. Southern Journal of

Applied Forestry. 350-54.

Billings, R.F. 1980. Direct control. In: Thatcher, R.C.,

and others, eds. The southern pine beetle. Tech.

Bull. 1631. Washington, DC: U.S. Department of Agriculture, Forest Service: 7-28.

Craighead, F.C.; Graham, S.A.; Evenden, J.C. [and

others]. 1927. The relation of insects to slash disposal. USDA Dep. Cir. 411. 32 p.

Dixon, J.C.; Osgood, E.A. 1961. Southern pine beetle. A

review of present knowledge. Pap. 128. Asheville,

NC: U.S. Department of Agiiculture, Forest Service,

Southeastern Forest Experiment Station. 34 p.

Gara, R. I.; Vi&, J.P.; Cramer, H.H. 1965. Manipulation

of Dendroctonus frontalis by use of a population

aggregating pheromone. Contribution of Boyce

Thompson Institute. 23: 55-56.

Hopkins, A.D. 1909. Practical information on the SCOIytid beeties of North American forests. Bark beetles

of the genus Dendroctonus. U.S. Department of

Agriculture, Bureau of Entomology Bull. 83, Part 1.

169 p.

Linit, M.J.; Stephen, F.M. 1978. Comparison of methods for estimation of attacking adult populations of

Dendroctonus frontalis. Journal of Economic Entomology. 7 1: 732-735.

Nagel, R.H.; McComb, D.; Knight, F.B. 1957. Trap tree

method for controlling the Englemann spruce beetle

in Colorado. Journal of Forestry. 55: 894-898.

St. George, R.A.; Beal, J.A. t929. The southern pine

beetle. USDA Farmers Bull. 1586. 18 p.

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