Southwestern pine tip moth damage to ponderosa pine reproduction

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"76 3^ U Southwestern Pine Tip Moth Damage

to Ponderosa Pine Reproduction

v

Abstract

Lessard, Gene, and Daniel T. Jennings.

1976. Southwestern pine tip moth damage to ponderosa pine
reproduction. USDA For. Serv. Res. Pap. RM-168, 8 p.
Rocky Mt. For. and Range Exp. Stn., Fort Collins, Colo.
80521.

The southwestern pine tip moth deforms young pines by
mining growth tips. Deformities, recognizable several years after
initial attack, are categorized as prune, crook, fork, posthorn,
bush, and spiketop. Combinations of deformities — crook/prune,
bush/crook — are prevalent at Chevelon, Arizona.

As tree height increases, tip moth damage decreases.
Deformities causing the greatest reduction in height growth also
occur most frequently. Only 7 percent of the 5,012 whorls
examined escaped tip moth damage; 89 percent had a signifi-
cant height growth loss of from 13 to 40 percent.

Keywords: Pinus ponderosa, Rhyacionia neomexicana. insect
damage.

USDA Forest Service
Research Paper RM-168

May 1976

ft \?C^

Southwestern Pine Tip Moth Damage
to Ponderosa Pine Reproduction ^

Gene Lessard1 and Daniel T. Jennings2

Entomologist, Division of State and Private Forestry, Southwestern Region, USDA Forest
Service, Albuquerque, New Mexico.
2

Research Entomologist, Rocky Mountain Forest and Range Experiment Station, located at
Station's Research Work Unit at Albuquerque, in cooperation with University of New Mexico;
Station's central headquarters is maintained at Fort Collins, in cooperation with Colorado State
University.

Contents

Page

Introduction 1

Methods 1

Results and Discussion 3

Types of Deformities 3

Frequency of Deformities 6

Effect on Tree Growth 8

Literature Cited 8

Southwestern Pine Tip Moth Damage
to Ponderosa Pine Reproduction

Introduction

Tip- and shoot-feeding insects damage trees by
injuring or destroying the apical meristems or new
growth centers. One such insect, the southwestern
pine tip moth {Rhyacionia neomexicana (Dyar)),
attacks and damages ponderosa pine (Pinus ponder-
osa Laws.) in the central and southern Rockies,
midwestern Plains, and the Southwest. This tip moth
and related species are important pests threatening
the establishment and growth of pine reproduction.

Larvae of R. neomexicana pass through five
instars and have three distinctive feeding stages: (1)
a needle-mining stage before new shoots are at-
tacked, (2) a pitch-tent stage when new needles on
expanding shoots are severed and mined, and (3) a
shoot-mining stage that often destroys the entire new
shoot (Jennings 1975). Both terminal and lateral
shoots in upper and midcrowns of young pines are
susceptible to attack. Destruction of these shoots not
only reduces height growth, but also deforms sub-
sequent tree growth form.

Damage is generally greater on young ponderosa
pines less than 6 to 8 feet tall. Seedlings less than 1
foot in height may be attacked the same year they are
planted (Jennings 1975). Large, open areas with
numerous small trees, such as naturally seeded or
planted burns, seem most vulnerable to persistent
infestations.

Working with the related European pine shoot
moth, R. buoliana (Schiff.), Heikkenen (1960)
grouped tree damage into the following categories:
pruning, crook, fork, posthorn, bush, and spiketop.
Descriptions of these damage categories on red pine,
Pinus resinosa Ait., are given by Heikkenen (1960),
Talerico and Heikkenen (1962), Miller and Schallau
(1963), and Miller (1967). Similar types of damage
are found on ponderosa pine due to feeding by R.
neomexicana.

In 1956, a devastating forest fire, the Dudley Fire,
burned 21,000 acres of ponderosa pine on the
Chevelon Ranger District, Apache-Sitgreaves
National Forest, about 45 miles south of Winslow,
Arizona. Most of the Dudley Burn reseeded natural-
ly with ponderosa pine, but large open areas were
subsequently planted with ponderosa planting stock.
The young seedlings, both natural and planted, soon
became infested with tip moths. Surveys conducted
by entomologists with the Forest Insect and Disease
Management Branch, Southwestern Region, USDA
Forest Service, showed that few seedlings escaped

damage. In 1966, 38 percent of the seedlings
examined were damaged by tip moths.3 By 1969, this
percentage had increased to 82.4

Although tip moths are continuing (1975) to
damage young pines at Chevelon, there is some
indication that thinning naturally seeded areas allows
the remaining trees to grow beyond the height
susceptible to tip moth attack. The smaller planta-
tion trees, including those under heavy grass compe-
tition, are still being heavily damaged.

In 1975, studies were initiated to obtain informa-
tion on how the tip moth affects ponderosa pine
regeneration in the Southwest. These studies were
designed to determine the nature and extent of
damage and resultant deformities to ponderosa pine
reproduction at Chevelon. This paper summarizes (1)
the types of tree deformities found, (2) how frequent-
ly each type occurs, and (3) their possible effects on
tree growth rates.

Methods

In 1968, fifteen 100-acre study plots were estab-
lished on the Dudley Burn.5 Most of the plots were
located in naturally seeded areas, and were originally
established to determine the effectiveness of chemical
treatments for controlling tip moths. Additional
study plots were established the same year in planted
areas of the George, Loop, and Hatchery Burns, on
the Chevelon Ranger District. Within each study
plot on the Dudley Burn, 25 subplots of variable size
(only 10 subplots on the George, Loop, and Hatchery
Burns) were systematically established. The 10 trees
nearest subplot center were then chosen and perma-
nently tagged.

Tip moth survey, 1966, Chevelon Ranger District,
Sitgreaves National Forest. 15 p. (Unpubl. rep. on file at
Southwest. Reg., USDA For. Serv., Albuquerque, N.M.)

4Buffam, Paul E. 1969. Results of the 1969 evaluation
of the southwestern pine tip moth trend study plots.
Sitgreaves National Forest, Chevelon Ranger District,
Region 3. 4 p. (Off. Rep., on file at Southwest. Reg.,
USDA For. Serv., Albuquerque, N.M.)

5Buffam, P. £., and C. J. Germain. 1968. Helicopter
application of Cygon (dimethoate) for control of the
southwestern pine tip moth, Rhyacionia neomexicana
[Dyar). Results-Pilot Control Study, Sitgreaves National
Forest, Chevelon District, Region 3. 8 p. (Off. Rep., on
file at Southwest. Reg., USDA For. Serv., Albuquerque,
N.M.)

1

Since 1968, Forest Insect and Disease Manage-
ment entomologists have measured height growth
and determined tip moth infestation trends on the
George, Loop, Hatchery, and nine of the Dudley
Burn plots (fig. 1). Because these observations and
measurements provide infestation and tree-growth
histories for individually tagged trees, these same
trees were examined for tip moth-caused deformities.

Tagged natural and planted trees were measured
and examined for deformities in September-October

1975. By this time, R. neomexicana larvae had
completed their shoot feeding. Tree heights were
measured with telescoping 12-foot poles. Heights
were measured to the nearest inch from the upper-
most shoot, regardless of intrawhorl position, to
ground level. For example, if the terminal shoot was
destroyed by tip moth feeding, a lateral shoot
generally assumed dominance. Height of this upper-
most shoot aboveground determined tree height.

CHEVELON RANGER DISTRICT
APACHE -SITGREAVES NATIONAL FOREST

Location of southwestern
™ pine tip moth plots

□ Lookouts

i scale

0 12 3 4

A-

Chevelon
Work Center

M0G0LL0N
MESA

George^ Burn

Dutch
Jo<

Loop Burn

Ohaccy

6

\Dudley
Lake

Dudley Burn^

Jarts )
Crossing /

M0G0LL0N

Hatchery
Burn

(

PLATEAU

Figure 1. — Location of study plots on the
Dudley, Loop, George, and Hatchery
Burns.

RIM

2

Individual whorls within trees were examined for
deformities and measured for internodal growth,
starting at the crown apex and working downward
toward the base of the tree. Small trees were
examined for three or four whorls; larger trees for
five or six and occasionally seven whorls. For
analysis, the type and percentage of each deformity
was determined for each 10 inches of tree height.
Mean height growth following each type of deformity
was then determined from the internodal measure-
ments.

Results and Discussion

Types of Deformities

The deformities found on ponderosa pine due to
feeding by R. neomexicana are summarized as fol-
lows:

Prune: one or more lateral buds killed, resulting in
fewer branches per whorl; no crook in main
stem (fig. 2).

3

Crook: a departure from straightness, resulting Posthorn: a severe crook resulting from larval

from complete or partial destruction of the feeding on only one side of the terminal shoot;

terminal shoot. Miller (1967, p. 13) lists four feeding stops before the shoot is killed and the

types. Lateral generally assumes dominance over injured leader bends at the point of attack (fig.

damaged terminal; loss of form depends on 5).
degree of crook and number of lateral shoots
that continue height growth (fig. 3).

Fork: two or more laterals assume dominance (fig.

4). Forking may follow bushing (Talerico and Bush: an increase in the normal number of

Heikkenen 1962); one ultimate effect of forking branches at a whorl; adventitious buds produce

may be a crook, if a competing branch becomes multiple shoots after destruction of terminal and

dominant. lateral shoots (fig. 6).

4

Spiketop: insect attack kills the terminal but
adventitious buds do not develop, resulting in a
dead top (fig. 7).

Frequency of Deformities

We examined a total of 5,012 whorls for tree
deformities caused by tip moths (table 1). Only 7

Table 1 . --D i str i but ion of southwestern pine tip moth tree deformities, by whorl level

Damage
Category

Whorl level

Total

or

7 average

Observat ions

919

919

905

Number
828

664

488

289

5012

Percent

SINGLE:

Norma 1

1 1

0

5

0

6

0

5.1

6

6

6

4

13

5

7

0

Bush

15

3

6

3

6

8

4.2

7

8

9

2

10.

0

8

4

Crook

8

2

9

8

9

7

10.5

10

5

7

8

6

9

9

3

Prune

21

0

15

0

12

5

17.9

18

4

21

1

18

3

17

it

Fork

1

2

2

8

1

9

1.9

1

5

1 .

8

1 .

7

1

9

Sp i ketop

1

1

0

0

0

0

0.0

0

0

0

0

0

0

0

2

Posthorn

1

0

0

0

0

2

0.0

0

3

0

2

0.

0

0

4

DOUBLE:

Prune/crook

25

4

3^

7

31

7

34

3

33

3

32

6

28

0

31

6

Bush/crook

14

1

21

8

27

2

23

2

20

2

18

2

21

1

21

0

Prune/fork

0

9

2

5

2

2

1

8

1

0

1

8

0

3

1

7

Bush/fork

0

5

1

2

1

6

1

0

0

2

0

8

0.

0

0

9

Posthorn/fork

0

0

0

0

0

1

0

0

0

0

0.

0

0

0

0

0

Posthorn/bush

0

5

0.

3

0

0

0

0

0

0

0

0

0.

0

0

2

Posthorn/prune

0

2

0

1

0

0

0.

1

0

0

0

0

0.

0

0

1

6

percent of the whorls were categorized as normal,
that is, without damage and having a complement of
at least three lateral branches (fig. 8). Most whorls
(55 percent) had a combination of two kinds of
deformity, such as crook/prune or prune/fork; 38
percent had only one kind.

The crook, bush/crook, prune, and prune/crook
categories accounted for about 79 percent of the
deformities. The remaining categories made up 14
percent of the total whorls examined, of which only 5
percent were forks, posthorns, and spiketops. In
contrast, Talerico and Heikkenen (1962) found that

most European pine shoot moth damage resulted in
forking, and that most forks were an outgrowth of
bushing. From 60 to 90 percent of the red pine trees
they sampled had forks.

As tree height increased, especially above 61
inches, tip moth damage decreased (table 2). Dis-
tribution of damage by 10-inch height classes indi-
cates that as tree height increases: (1) percentage of
normal and bush whorls increases; (2) percentage of
crook, bush/crook, prune/crook and prune/fork
decreases; and (3) percentage of prune remains
about the same. These percentages possibly reflect

Table 2. --Percent deformity, by tree height class and damage category
Damage Tree height class ( i nches)

Category 1-10 11-20 21-30 M-50 51-60 61-70 71-80 81-90 91-100

Percent

Normal

l.k

k

7

6.5

9

0

7

1

7

3

8

0

9

7

14.9

13

9

Bush

2.7

8

0

7.6

8

3

8

2

8

3

7

h

10

1

12.9

20

3

Crook

3-9

7

k

8.7

9

h

10

8

1 1

3

13

0

1 1

2

9.8

8

9

Bush/crook

25-9

18

9

20.8

21

1

21

7

23

0

21

5

20

h

19-6

16

5

Prune

13.6

19

8

16.0

15

9

17

2

17

7

19

3

16

2

H.9

25

3

Prune/crook

kk.3

37

5

3*».0

32

h

29

6

27

5

25

8

25

0

2k. 2

1 1

k

Prune/fork

3-9

1 .

6

2.3

0

7

1 .

1

1

2

1

1

1

2

0.5

0

0

7

height preferences by ovipositing females. Fewer eggs
are deposited on upper crown needles more than 6 to
8 feet aboveground; consequently, larger trees sus-
tain less tip moth damage.

Effect on Tree Growth

Three distinct deformity classes were established
on the basis of analysis of variance and multiple
range tests (table 3). Mean internodal height growth
was significantly different (P<.05) between each of
the deformity classes, but no differences were found
within classes: Class I, normal and bush; Class II,
crook and bush/crook; and, Class III, prune,
prune/crook, and prune/fork. Deformities not in-
cluded in these three classes were infrequently
observed.

Table 3- "Mean internodal height growth, by
deformity class2

Type of
deform i ty ,
by class

Mean
internodal

Stan-
da rd

Observa-

height
growth

dev i -
at ion

t i ons

Inches

Number

CLASS 1:

Normal (no damage)

7.5

3

3

1 3k

Bush

7.6

k

2

165

CLASS 1 1 :

Crook

3

2

3H

Bush/crook

6.5

8.

0

783

CLASS III:

Prune

5-5

3.

1

520

Prune/c rook

5.0

2

9

1229

Prune/fork

h.5

2

0

59

1 Internodal growth following each deformity
cl ass .

2Classes are significantly different at P<.05.

Mean internodal height growth following fork (6.1
inches) was significantly different from Class I
deformities, but not from Class II or III deformities.
Also, no differences were found following posthorn
(6.8 inches) or bush/fork (6.3 inches), or between
these two damage categories and all other damage
categories.

Height growth following crook and bush/crook
was significantly less than that following the normal
internode. Pruning and combinations of prune/fork

and prune/crook produced even greater departures
from normal. Reduced height growth following crook
is probably a function of the severity of the crook.
Although pruning causes no departure from straight-
ness, loss of height growth may be a function of
reduced photosynthetic area necessary for terminal
growth.

Only 7 percent of the 5,012 whorls examined
escaped tip moth damage; 89 percent of the whorls
had a significant height growth loss of from 13 to 40
percent. Although we have no data on long-term
effects of the southwestern pine tip moth on pon-
derosa pine, Miller (1967) found that red pine
eventually outgrows crook and bush deformities.
In the Southwest, ponderosa pines taller than 6 to 8
feet are less susceptible to attack by the southwestern
pine tip moth. Some deformities probably persist as
the tree matures, however, and may appear later as
defects in merchantable trees. Ffolliott and Barger
(1967) quantified some stem features, including
crook and fork, that reduce quality of southwestern
ponderosa pine. Perhaps some of these defects may
be attributed to earlier tip moth infestations.

Literature Cited

Ffolliott, Peter F., and Roland L. Barger.

1967. Occurrence of stem features affecting qual-
ity of cutover southwestern ponderosa pine. U.S.
For. Serv. Res. Pap. RM-28, 11 p. Rocky Mt.
For. and Range Exp. Stn., Fort Collins, Colo.
Heikkenen, Herman John.

1960. The identification and dating of past attacks
of the European pine shoot moth on red pine.
J. For. 58:380-384.
Jennings, Daniel T.

1975. Life history and habits of the southwestern
pine tip moth, Rhyacionia neomexicana (Dyar)
(Lepidoptera: Olethreutidae). Ann. Entomol.
Soc. Am. 68:597-606.
Miller, William E.

1967. The European pine shoot moth — ecology
and control in the Lake States. For. Sci.
Monogr. 14, 72 p.
Miller, William E., and Con H. Schallau.

1963. Problems in identifying old European pine
shoot moth damage. J. For. 61:677-678.
Talerico, Robert L., and H. J. Heikkenen.

1962. Stem injury to young red pine by the
European pine shoot moth. J. For. 60:403-406.

8

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