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Experimen Station July, 1963

Lightning Strike Simulation for Studying Southern Pine Bark and

Engraver Beetle Attacks

Mitchel C. Miller

SUMMARY

Endemic populations of the southern pine beetle

(Dendroctonus frontalis Zimm.) and Ips spp. attacked loblolly pilnes (Pinus taeda L.) on which lightning strikes were simulated with detonating cord

in the field. Southern pine beetles were reared in

successive generations in these trees from fall 1981

through spring 1982; only Ips spp. attacked treated

trees through December 1982. Lightning strike

simulation provides an alternative means of studying

bark beetle attack and opens the way for comparisons with nat;ural lightning strikes.

Keywords: Lightning strike simulation, southern

pine beetle, Ips, Dendroctonus frontalis.

INTRODUCTION

Lightning strikes have a significant effect on bark

beetle ecology (Komarek 1964; Schmitz and Taylor

1969; Clarke 1970; Taylor 1969, 1974) including that

of the southern pine beetle (SPB) (Dendroctonus

frontalis Zimm.) (Thatcher and Pickard 1964). Lorio

and Bennett (1974) reported that for a 4-year period

an average of 29 percent of active SPB spots were

initiated in lightning struck trees; in any one month

lightning accounted for none to as many as 77 percent of the infestations. In some cases external

lightning damage is not visible (Komarek 1964,

1968; Ducharme 1974), but physiological change

could make the tree suitable for beetle attack.

Therefore, the number of spots (=infestations) attributed to attack by SPB on lightning struck trees

(Hodges and Pickard 1971, Lorio and Bennett 1974)

is probably conservative; actual values could be

considerably higher.

Lightning struck trees may attract SPB with a release of volatile oleoresin fractions from the shower

of finely divided bark and needle particles (Taylor

1973, Lorio and Yandle 1978); struck trees offer a

favorable attack and brood development site for

SPB and Ips spp. as a result of reduced oleoresin

exudation pressure, reduced oleoresin flow, reduced relative water content and increased reducing-sugar content of inner bark (Hodges and Pickard

1971). Anderson and Anderson (1968) associated

successful attack by three Ips species on a lightning struck loblolly pine with reduced oleoresin

exudation rate.

Taylor (1973) simulated lightning strikes with

explosive detonating cord (primer cord) in a study

to evaluate lightning as an ignition source for forest

fires, and Safranyik and Whitney (1980) used detonating cord to destroy mountain pine beetle (Dendroctonus ponderosae Hopkins) brood in lodgepole

pine. In the present study a lightning strike simulation (LSS) technique applied to loblolly pine (Pinus

taeda L.) is described that results in southern pine

bark beetle attack.

METHODS

On the England Air Force Base Ordnance Disposal Range near Alexandria, LA, sections of 50

grain per foot PETN (pentaerythritol tetranitrate)

detonating cord were placed in various patterns and

Southern Forest Experiment Stationfl-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
Figure l.-Results of lightning strike simulation with single

strand 50 grain/foot PETN detonating cord on 12”

diameter lob/o//y pine bolt.

shaped charges on 6-foot loblolly bole sections to

determine the best technique to simulate a lightning

strike effect. A single strand of detonating cord

spiralled tightly around a bolt, maximizing contact

with the bark surface, produced the best effect (fig.

1). The bark was split and the bark and phloem

separated from the wood up to 2 inches on either

side of the detonating cord.

Lightning strike simulation was carried out on

the Catahoula Ranger District, Kisatchie National

Forest in central Louisiana. Five loblolly pines were

tested in 1981, two in mid-September and three in

mid-October. The dbh range was from 10 to 19

inches. In 1982, 32 trees were treated from March

through December at three to five week intervals;

all were 10 to 12 inches in dbh.

A single strand of detonating cord was spiralled

Figure 2.-Lightning strike simulation with 50 grain/foot PETN

detonating cord spiralled 1 Vz times around 10.5

inch dbh lob/o//y pine, Catahoula Ranger District,

Kisatchie National Forest, Mar. 25, 1982. Detonation courtesy Explosive Ordnance Disposal, United

States Air Force, England Air Force Base, Louisiana.

Exposure: l/125 sec,fll, Kodacolor 400 film.

1% times around each of the trees from 30 feet to

3 feet on- the bole, where the cord was brought

parallel to the ground to a small sapling for attachment of the electric blasting caps. Preparation for

blasting, placing of the detonating cord, and detonation (fig. 2) were provided by the Explosive Ordnance Disposal Team, 26th Combat Support Group,

U.S. Air Force, England Air Force Base.

OBSERVATIONS

Observations were made of each tree twice a

week for 30 days in the 12-15 foot areas of the tree

bole for evidence of SPB attack. Within 7 to 10

days after LSS, black turpentine beetles (BTB)

(Dendroctonus terebrans Oliver) attacked at the

base of the tree, followed by Ips calligraphus (GerMitchel C. Miller is Research Entomologist, Southern Forest Experiment Station, USDA Forest Service, Pineville, LA 71360.

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mar) at 20 feet. Southern pine beetle appeared to

be the third insect species to attack the LSS pines,

but after 5 days predominated on the bole from 3

to 25 feet.

Southern pine beetles attacked both trees treated

in September 1981. The first confirmed attack occurred 11 days after treatment. Within 10 days SPB

attack shifted to the second tree. Adult SPB brood

emerged from the first tree 2.3 months later. The

onset of cold weather delayed brood development

in the second tree, and egg though adult development took 3.9 months.

The three trees treated in mid October 1981

“pitched out” a few SPB attacking during the first

10 days, but two of these trees were later successfully attacked. Development of SPB took 3.8 months;

emergence was in early March 1982.

In 1982 two of the three late March LSS trees

were not attacked by any beetles except BTB until

May when 1 . calligraphus became the dominant

beetle in both trees. However, careful inspection

of these trees revealed that a small number of SPB

attack sites and SPB galleries were present (table

1). Three of the 14 loblolly pines, one in March and

two in May, were arbitrarily treated with the SPB

aggregating pheromone frontalure for 24 hours following LSS. They were attacked by SPB within 24

hours. Trees not subject to LSS that were close to

frontalure treated LSS trees were also attacked and

killed by SPB.

Four of the five 1981 LSS trees were successfully

attacked by SPB even though no aggregating

pheromone was used. All three LSS trees on which

aggregating pheromone was used were successfully

attacked by SPB, as were five nearby untreated trees

(table 1). From June through December 1982 none

of the 26 trees upon which LSS was conducted were

attacked by SPB; all were attacked by 1. calligraphua

(Germar).

DISCUSSION AND CONCLUSIONS

In past attempts to induce attack, even with the

use of frontalure, loblolly pines were able to pitch

out SPB. With LSS trees, pitch tubes were few and

inconspicuous, and it may be that fewer beetles are

required for a successful attack than on similar uninjured trees. Observations of the few pitch-outs of

SPB and absence of pitch tubes on LSS trees agree

with those of Hodges and Pickard (1971) and Taylor

(1969). The LSS technique offers the opportunity to

compare natural lightning strikes and LSS for the

study of physiological conditions, oleoresin release

and quality, and attraction to bark beetles.

Those LSS trees not attacked by SPB were attacked by 1. calligraphus. This may have been

because endemic SPB populations are not uniformly

Table I.-Lightning strike simulation on loblolly pines Sep. 1981-May 1982, Catahoula

Ranger District, Kisatchie National Forest, La.

Attacked by:

Treatment

date

LSS’ SPBz fPs

Not Not Not

Treated3

treated Treated treated Treated treated

1981

14 Sep. 2 2 0

14 Oct. 3 2 0

1982

25 Mar. 1 2 l(+v4 0 0 2 5

11 May 2 2 2(+4)4 0 0 2

19 May 2 1 0

24 June-18 Dec. 2 8 2 8

Totals 3 3 7 3(+5)4 5 0 3 0

‘Lightning strike simulation.

ZSouthern pine beetle (Dendroctonus frontalis Zimm.).

%PB aggregating pheromone, frontalure.

4Numeral in parentheses indicates trees close to a LSS-frontalure treated tree.

%vcludes a few SPB galleries.

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distributed across the forest or because the response of each beetle species to LSS trees may

vary with season, host-tree, or site/stand conditions. All trees showed the same sequence of attack

after LSS of BTB, 1. calligraphus, and then SPB.

Anderson and Anderson (1968) observed that

successful Ips attack was associated with low oleoresin exudation rate. Ips grandicollis and 1. calligraphus attacked first at the base of the crown with

mass attack by 1. calligraphus occurring five weeks

after the strike. The size of their subject tree, the

time of year, geographic variation, the type and

extent of the damage, and the endemic beetle

species available for attack could easily account

for differences in time and nature of attack.

All of the trees subjected to LSS were attacked

by southern pine bark or engraver beetles. Our observations with frontalure indicate it may be used as

an adjunct in the study of SPB attack patterns or

responses to LSS.

It was originally thought that LSS would serve as

a means by which attack by SPB could be generated

in the field if a SPB population was present. Following the completion of the 1981 through May 1982

LSS studies a SPB spot that could have been the

source for the attacking SPB was found within 300

yards of the LSS sight. More extensive studies of

this technique and its application are needed to

determine its full relationship to bark beetle attack.

The trees used for LSS were in stands that are

considered to have low risk of SPB attack by the

evaluation of resource data site/stand characteristics (Lorio and Sommers 1981). Since some trees

were attacked more than 10 days following LSS,

suitability or attractiveness of the blasted host tree

may not result from the immediate bark, needle,

or resin particle shower mentioned by Taylor (1969,

1973) or Lorio and Yandle (1978). The frequency and

intensity of beetle attack may be complicated by the

effect of temperature on the release of chemicals

from the tree, the oxidation rate of wound exudate,

or the level of endemic beetle activity.

Lightning strikes may serve as a reservoir of

populations during endemic periods especially in

low risk stands. A study of LSS in high risk stands

would add to our knowledge of population dynamics

of these destructive insects.

Lightning strike simulation is a tool that allows

the researcher to induce attack by bark beetles.

Researchers considering the use of this technique

should seek the services of a properly trained and

certified blaster for the purchase, storage, transportation, application, and detonation of detonating

cord and blasting caps.

LITERATURE CITED

Anderson, N. H.; Anderson, D. B. fps bark beetle

attacks and brood development on a lightning

struck pine in relation to its physiological decline.

Fla. Entomol. 51: 23-30; 1968.

Clarke, E. W. Attack height of the black turpentine

beetle. J. Ga. Entomol. Sot. 5: 151-152; 1970.

Ducharme, E. P. Lightning-a predator of citrus

trees in Florida, In: Proceedings, Ann. Tall Timbers Fire Ecol. Conf., Tallahassee; 1974: 438-496.

Hodges, J. D.; Pickard, L. S. Lightning in the ecology of the southern pine beetle, Dendroctonus

frontalis (Coleoptera:Scolytidae). Can. Entomol.

102: 44-51; 1971.

Komarek, E. V., Sr. Lightning and lightning fires as

ecological forces. In: Proceedings, Ann. Tall Timbers Fire Ecol. Conf., Tallahassee; 1968: 169-197.

Komarek, E. V., Sr. The natural history of lightning.

In: Proceedings, Third Ann. Tall Timbers Fire

Ecol. Conf., Tallahassee; 1964: 139-187.

Lorio, P. L., Jr.; Bennett, W. H. Recurring southern

pine beetle infestations near Oakdale, Louisiana.

Res. Pap. SO-95. New Orleans, La. U.S. Department of Agriculture, Forest Service, Southern

Forest Experiment Station; 1974.6 p.

Lorio, P. L., Jr.; Sommers, R. A. Use of available resource data to rate stands for southern pine

beetle risk. In: Symp. Proceedings, Hazard-rating

Systems in Forest Insect Pest Management. Gen.

Tech. Rpt. WO-27. Washington, DC. U.S. Department of Agriculture, Forest Service, Southern

Forest Experiment Station; 1981; 75-79.

Lorio, P. L., Jr.; Yandle, D. 0. Distribution of lightning-induced southern pine beetle infestations.

South. Lumberman 236(2921): 12; 1978.

Safranyik, L.; Whitney, H. S. Using explosives to

destroy mountain pine beetle brood in lodgepole

pine trees. J. Entomol. Sot. Brit. Columbia 77:

3-l 4; 1980.

Schmitz, R. F.; Taylor, A. R. An instance of lightning

damage and infestation of Ponderosa pines by

the pine engraver beetle in Montana. Res. Note

INT-88. U.S. Department of Agriculture, Forest

Service; 1969. 8 p.

Taylor, A. R. Ecological aspects of lightning in forests. In: Proceedings, Tall Timbers Fire Ecol.

Conf., Tallahassee; 1974: 455-482.

Taylor, A. R. Lightning effects on the forest complex.

In: Proceedings, Tall Timbers Fire Ecol. Conf.,

Tallahassee; 1969: 127-150.

Thatcher, R. C.; Pickard, L. S. Seasonal variations

in activity of the southern pine beetle in east

Texas. J. Econ. Entomol. 57: 840-842; 1964.

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