Optimizing Ethanol-Baited Traps for Monitoring Damaging Ambrosia Beetles (Coleoptera: Curculionidae, Scolytinae) in Ornamental Nurseries - naldc
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HORTICULTURAL ENTOMOLOGY
Optimizing Ethanol-Baited Traps for Monitoring Damaging
Ambrosia Beetles (Coleoptera: Curculionidae, Scolytinae)
in Ornamental Nurseries
MICHAEL E. REDING,1 PETER B. SCHULTZ,2 CHRISTOPHER M. RANGER,2
3
AND JASON B. OLIVER
J. Econ. Entomol. 104(6): 2017Ð2024 (2011); DOI: http://dx.doi.org/10.1603/EC11119
ABSTRACT The exotic ambrosia beetles Xylosandrus crassiusculus (Motschulsky) and Xylosandrus
germanus (Blandford) (Coleoptera: Curculionidae: Scolytinae) are serious pests in ornamental tree
nurseries. To optimize bottle-traps as a monitoring system for X. crassiusculus and X. germanus in
nurseries, we tested whether increasing the rate of commercial ethanol lures improved captures or
early detection of these species. Experiments were conducted in Ohio (2008 and 2009) and Virginia
(2008), two states that have experienced signiÞcant damage from X. crassiusculus, X. germanus, or both.
There were four treatments: no-lure (unbaited control), 1-ethanol lure, 2-ethanol lures and 1 ⫹
1-ethanol lures (one lure in the trap and one suspended 0.5 m above the trap). Captures of X.
crassiusculus and X. germanus were higher in all ethanol treatments than unbaited controls, and were
generally higher in treatments with two lures versus one. There was no difference in beetle captures
between the 2-lure and 1 ⫹ 1-lure treatments. First detection of X. crassiusculus and X. germanus
occurred more consistently in the treatments with two lures than one lure. Xyleborinus saxesenii
(Ratzeburg), Anisandrus sayi Hopkins, Hypothenemus dissimilis Zimmermann, and Hypothenemus
eruditus Westwood were also more attracted to traps baited with ethanol than unbaited controls. X.
saxesenii was captured in higher numbers in the treatments with two lures than one in Virginia but
not in Ohio. There was no difference in captures of the other species among ethanol treatments. The
current research shows that ethanol release rates inßuence sensitivity of traps for detecting emergence
of overwintered ambrosia beetles.
KEY WORDS Xylosandrus crassiusculus, Xylosandrus germanus, bottle-traps, ethanol concentration
Wood-boring ambrosia beetles bore into the xylem of are subsequently attracted (Ranger et al. 2010). Eth-
trees creating tunnels they inoculate with symbiotic anol is emitted from trees under physiological stress
fungi, the source of food for the larvae and adults (Moeck 1970, Kimmerer and Kozlowski 1982, Kelsey
(Wood 1982). Ambrosia beetles (Coleoptera: Curcu- and Joseph 2001) and acts as a primary attractant for
lionidae: Scolytinae) generally colonize physiologi- ambrosia beetles including X. crassiusculus and X. ger-
cally stressed, unhealthy or dying trees (Wood 1982, manus (Graham 1968, Cade et al. 1970, Moeck 1970,
Kühnholz et al. 2001). Some exotic ambrosia beetles Borden et al. 1980, Montgomery and Wargo 1983,
such as Xylosandrus crassiusculus (Motschulsky) [the Oliver and Mannion 2001, Ranger et al. 2010). Weber
granulate (formerly Asian) ambrosia beetle] and Xy- and McPherson (1984) found that X. germanus were
losandrus germanus (Blandford) have a reputation for more likely to colonize black walnut (Juglans nigra L.)
being more aggressive because they colonize trees with slower growth rates, and concluded that beetles
that appear healthy (Hoffman 1941, Wood 1982, We- could differentiate between slight differences in host
ber and McPherson 1983, Oliver and Mannion 2001, vigor. Furthermore, injection of ethanol into contain-
Kühnholz et al. 2001, Reding et al. 2010). However, erized Magnolia virginiana L. induced attacks by X.
trees that appear healthy might actually be physio- germanus and other ambrosia beetles, but neighboring
logically stressed to the point where ambrosia beetles water-injected or uninjected control trees were not
colonized (Ranger et al. 2010).
1 Corresponding author: USDAÐARS, Horticultural Insects Re- X. crassiusculus and X. germanus are generalists col-
search Laboratory, 1680 Madison Avenue, Wooster, OH 44691 onizing over 200 species of trees and are serious pests
(e-mail: mike.reding@ars.usda.gov). in ornamental tree nurseries (Weber and McPherson
2 Hampton Roads Agricultural Research and Extension Center,
1983, Solomon 1995, Hudson and Mizell 1999, Oliver
Virginia Tech University, Virginia Beach, VA 23455.
3 Otis L. Floyd Nursery Research Center, Tennessee State Univer- and Mannion 2001, Gandhi et al. 2010, Reding et al.
sity, Department Agricultural and Environmental Sciences, McMin- 2010). Adults overwinter in galleries of infested trees
nville, TN 37110. until early spring, then females emerge and disperse2018 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 104, no. 6
by ßight to colonize (attack) new trees (Weber and
McPherson 1983, Oliver and Mannion 2001, Reding et
al. 2010). Emergence of overwintered beetles of both
species appears to be related to climate and weather
conditions (Weber and McPherson 1983, Oliver and
Mannion 2001, Reding et al. 2010).
In ornamental tree nurseries, growers rely on trunk
sprays of insecticides to prevent colonization of trees
by ambrosia beetles. Timing of treatments for control
of X. crassiusculus and X. germanus is usually based on
the calendar and efÞcacy is inconsistent. Because of
the small size and cryptic nature of these species, early
colonization of nursery trees often occurs before
growers realize the beetles are active, and thus trees
may be damaged before preventive treatments are
applied. A reliable monitoring system would enable
growers to synchronize their control treatments with
X. crassiusculus and X. germanus activity.
Ethanol-baited traps have shown potential as tools
for monitoring the ßight activity of ambrosia beetles in
nurseries (Hudson and Mizell 1999, Oliver and Man-
nion 2001, Reding et al. 2010). Oliver and Mannion
(2001) found that captures of X. crassiusculus and X.
germanus in ethanol-baited traps coincided with their
attacks on nursery trees, and thus captures should be
reliable indicators of the beetlesÕ activity. Reding et al.
(2010) demonstrated that bottle-style traps baited
with ethanol effectively captured X. crassiusculus and
X. germanus, were relatively inexpensive to make, and
were most effective when placed within 0.5 m of the
ground. Furthermore, Oliver et al. (2004) captured
more X. crassiusculus in a bottle-style trap than four-
funnel Lindgren funnel traps. Fig. 1. Example of bottle-trap used in the lure concen-
Further research is needed on the release rates of tration experiments.
ethanol from bottle-traps to optimize this system for
monitoring ambrosia beetles in nurseries. Some am- 5506, Sierra Antifreeze/Coolant, Old World Indus-
brosia beetles, including X. germanus, Anisandrus sayi tries, Northbrook, IL) as the killing agent. The lures
(Hopkins), and Xyleborinus saxesenii (Ratzeburg) were commercially available pouch-style dispensers
have shown a positive response to increasing concen- (lures) loaded with 10 ml of 95% ethanol with a release
trations of ethanol in ßight barrier and funnel traps rate of 65 mg/d at a constant 30⬚C (Standard Release
(Klimetzek et al. 1986, Ranger et al. 2011). However, ethanol lures, AgBio, Westminster, CO).
this tendency has not been thoroughly explored for Experiments. Experiments were conducted in 2008
trapping X. crassiusculus or X. germanus in bottle-traps and 2009 in Ohio, and 2008 in Virginia. Both states have
deployed in ornamental tree nurseries. The objective experienced signiÞcant damage to nursery trees from
of the current research was to compare attraction of X. crassiusculus (VA) or X. germanus (OH and VA).
X. crassiusculus and X. germanus to different quantities Traps were deployed from early April through early
and arrangements of commercially available ethanol September in Þve nurseries in Ohio located in Lake
lures in bottle-traps. (three nurseries), Lorain (one), and Wayne (one)
Counties, and from late March through early Septem-
ber in four nurseries in Virginia located in Hanover
Materials and Methods
(one) and Henrico (one) Counties and the city of
Traps and Lures. The traps used in the current Suffolk (two) (no county afÞliation). The experi-
research were constructed of two clear plastic bottles ments were set up as randomized complete block
(0.5 and 1 liter) with the mouth ends connected (RCB) designs with three replications per nursery for
by a plastic threaded tube (“Tornado Tube,” item totals of 15 replications in Ohio and 12 in Virginia.
#WTUB-500, Steve Spangler Science, Englewood, Traps were deployed along the wooded borders of
CO), hereafter referred to as bottle-traps (Fig. 1). The nurseries (within 2 m of the border) with RCB-blocks
1-liter bottle was on top and had two vertical openings within nurseries and traps within RCB-blocks at least
⬇12.5 cm ⫻ 7.5 cm to allow entrance of ambrosia 25 m apart. The traps were suspended from steel rods
beetles. The small bottle (0.5 liter) functioned as the so the opening and the ethanol lure within the trap
collection receptacle and was Þlled with ⬇100 ml of a were ⬇0.5 m above the ground (Reding et al. 2010).
50% solution of propylene glycol (CAS Registry #57Ð There were four different ethanol lure quantity andDecember 2011 REDING ET AL.: OPTIMIZING AMBROSIA, BEETLE MONITORING IN NURSERIES 2019
conÞguration treatments including 1) no lure (un- Þrst captures of X. saxesenii occurred in the 2-lure
baited control), 2) one lure in the trap (1-lure), 3) two treatment in the Lorain (early May), Wayne (late
lures in the trap (2-lure), and 4) one lure in the trap April), and two of the Lake County nurseries (late
plus one lure suspended ⬇0.5 m above the trap (1 ⫹ April), with a Þrst capture in the 1 ⫹ 1 lure treatment
1-lure). Lures within traps were suspended in the in the Wayne County nursery. In the third Lake
1-liter bottle section of the trap (Fig. 1). While the County nursery the Þrst capture occurred in the 1-lure
volumes of ethanol in the 2-lure and 1 ⫹ 1-lure treat- treatment (early June). In 2009 in Ohio, Þrst captures
ments were essentially the same, we surmised that of X. saxesenii occurred in all ethanol treatments in the
ethanol emitted from the suspended lure of the 1 ⫹ Wayne County (late May) and one Lake County nurs-
1-lure treatment would spread over a larger area than ery (late April) and only in the 1-lure treatment in the
treatments with lures located only inside the traps. As remaining nurseries (late April to early May). X. cras-
a result, the 1 ⫹ 1-treatment should be more likely to siusculus captures were not compared among treat-
attract beetles during periods of low beetle activity ments because they occurred in only one nursery
such as initial emergence. (Lorain County) where Þrst captures occurred early
Traps were checked at 6 Ð14 d intervals. At that time May and early July in 2008 and 2009, respectively
the beetles were transported to the laboratory and (Table 1).
stored in 70% ethanol in vials labeled by treatment, Seventeen Scolytinae species were captured in
replication, and date of collection until they were Ohio, 10 of which were captured in all nurseries (Ta-
identiÞed to species. All of the ambrosia beetles cap- ble 1). X. germanus was the most captured species with
tured in Ohio were identiÞed to the species level the native species Hypothenemus dissimilis Zimmer-
(Wood 1982, Rabaglia et al. 2006). Only X. crassius- mann the next most common. Seven exotic species
culus, X. germanus, and X. saxesenii were identiÞed in were captured in Ohio, four of which occurred in all
the Virginia captures. sites (Table 1). Anisandrus sayi, H. dissimilis, and Hy-
Data Analysis. Data were analyzed by analysis of pothenemus eruditus Westwood (all native species)
variance (ANOVA) for a randomized complete block were captured in sufÞcient numbers to compare lure
design (Analytical Software 2003). Following a signif- treatments (Table 1). More A. sayi, H. dissimilis, and
icant ANOVA means were separated using TukeyÕs H. eruditus were captured in ethanol treatments than
honestly signiÞcant difference (HSD) test (␣ ⫽ 0.05). unbaited controls each year (respectively, 2008: F ⫽
Data were log(X ⫹ 1) transformed before analysis to 14.3; df ⫽ 3, 42; P ⬍ 0.001, F ⫽ 98.8; df ⫽ 3, 42; P ⬍ 0.001,
meet assumptions of homogeneity of variances (Zar F ⫽ 5.2; df ⫽ 3, 42; P ⫽ 0.004; 2009: F ⫽ 16.6; df ⫽ 3,
1999). Cumulative captures of X. crassiusculus, X. ger- 42; P ⬍ 0.001, F ⫽ 45.1; df ⫽ 3, 42; P ⬍ 0.001, F ⫽ 14.1;
manus and X. saxesenii through 11Ð16 June (Þrst gen- df ⫽ 3, 42; P ⬍ 0.001) with no differences among
eration) in Ohio and Virginia were compared among ethanol treatments (Fig. 2).
lure treatments. Captures of other species from Ohio Seasonal ßight activity of X. germanus and X. sax-
that totaled ⬎150 individuals for the entire trapping esenii were similar in Ohio (Fig. 3) with the primary
season (through early September) and occurred in all spring peaks in late April and late May and another
nurseries were also compared among lure treatments. peak during late July to mid-August. A. sayi and H.
Capture data were analyzed separately by species, dissimilis had primary peaks of activity in late May
state, and year. each year with very little activity thereafter, while H.
eruditus activity peaked mid-June or early July
(Fig. 3).
Results
Virginia. In Virginia, more X. crassiusculus, X. ger-
Ohio. In Ohio, captures of X. germanus were higher manus, and X. saxesenii were captured in ethanol treat-
in ethanol treatments than unbaited controls in 2008 ments than unbaited controls (F ⫽ 36.9; df ⫽ 3, 33; P ⬍
and 2009 (F ⫽ 199.4; df ⫽ 3, 42; P ⬍ 0.001 and F ⫽ 178.7; 0.001, F ⫽ 20.8, df ⫽ 3, 33; P ⬍ 0.001, and F ⫽ 27.4; df ⫽
df ⫽ 3, 42; P ⬍ 0.001, respectively) (Fig. 2). The 2-lure 3, 33; P ⬍ 0.001, respectively) (Fig. 4). More X. cras-
treatment captured more X. germanus than the 1-lure siusculus were captured in the 2-lure and 1 ⫹ 1-lure
treatment in 2008, but in 2009 there were no differ- treatments than in the 1-lure treatment (Fig. 4). More
ences among ethanol treatments (Fig. 2). First cap- X. germanus were captured in the 1 ⫹ 1-lure than the
tures of X. germanus occurred in all three ethanol 1-lure treatment with the 2-lure treatment interme-
treatments in the Lorain and Lake County (three diate between them (Fig. 4). More X. saxesenii were
nurseries) (late April) nurseries in 2008, and the captured in the 2-lure and 1 ⫹ 1-lure treatments than
Wayne (early May) and Lake County (late April) the 1-lure treatment (Fig. 4). First captures of X.
nurseries in 2009. In the Wayne and Lorain County crassiusculus occurred in all three ethanol treatments
nurseries in 2008 and 2009, respectively, captures of X. on the same date in the Henrico County and city of
germanus occurred in the 2- and 1 ⫹ 1-lure treatments Suffolk nurseries (early April), while Þrst captures in
(late April) 1 wk earlier than in the 1-lure treatment. the Hanover County nursery occurred in the 1 ⫹
In Ohio, more X. saxesenii were captured in the eth- 1-lure treatment (early April) with captures in the
anol treatments than the controls in 2008 and 2009, 2-lure and 1-lure treatments one and 4 wk later, re-
with no differences among ethanol treatments (F ⫽ spectively. First captures of X. germanus occurred in
11.4; df ⫽ 3, 42; P ⬍ 0.001 and F ⫽ 10.3; df ⫽ 3, 42; P ⬍ all ethanol treatments in one city of Suffolk nursery
0.001 for 2008 and 2009, respectively) (Fig. 2). In 2008, (early April), in the 2-lure only in Henrico County2020 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 104, no. 6 Fig. 2. Mean (15 traps) captures ⫾ SE (error bars) of X. germanus, X. saxesenii, A. sayi, H. dissimilis, and H. eruditus from Ohio 2008 and 2009 compared among ethanol lure concentration treatments (untransformed data presented). The data for X. germanus and X. saxesenii are cumulative captures through 11 or 16 June (2008 and 2009, respectively) while the other species are through September (end of the trapping season). Columns within species and years with similar letters (2008 uppercase, 2009 lowercase) are not statistically different (TukeyÕs HSD, 0.05). (late March), in the 2-lure and 1 ⫹ 1-lure treatments Virginia with the second peak the same date as X. in the other city of Suffolk nursery (early April), and crassiusculus and a week later than X. saxesenii (Fig. 5). in the 1-lure and 1 ⫹ 1-lure treatment in Hanover County (early April). First captures of X. saxesenii occurred in all ethanol treatments in the Hanover Discussion County and city of Suffolk nurseries (late March to The exotic species X. crassiusculus and X. germanus early April) and in the 2- and 1 ⫹ 1-lure treatments in were considered the most important ambrosia beetles the Henrico County nursery (early April). to monitor for Ohio and Virginia, because of their In Virginia, ßight activity of X. crassiusculus and X. tendency to attack and damage nursery trees (Hudson saxesenii were similar with primary peaks in early April and Mizell 1999, Oliver and Mannion 2001, Kuhnholz and a second peak in late May or early June (Fig. 5). et al. 2003, Reding et al. 2010). There was a trend The Þrst peak of activity for X. germanus was approx- toward higher captures of X. crassiusculus, X. germa- imately a month later than the other two species in nus, and X. saxesenii in bottle-traps baited with two
December 2011 REDING ET AL.: OPTIMIZING AMBROSIA, BEETLE MONITORING IN NURSERIES 2021
Table 1. Species and cumulative totals of Scolytinae captured
in Ohio nurseries during 2008 and 2009, and the no. of nurseries
in which they occurred
No.
Occurrence
captured
Species
No.
2008 2009
nurseriesa
Native species
Anisandrus (Xyleborus) sayi Hopkins 5 506 234
Hypothenemus dissimilis Zimmermann 5 3,977 5,372
Hypothenemus eruditus Westwood 5 216 424
Monarthrum faciatum Say 1 3 0
Monarthrum mali (Fitch) 4 12 5
Phloetribus limnaris (Harris) 5 29 11
Xyleborus ferrugineus (F.) 2 1 2
Xyleborus pubescens Zimmermann 5 12 5
Xyleborus xylographus (Say) 3 3 1
Xyloterinus politus (Say) 5 12 69
Exotic species
Euwallacea validus (Eichhoff) 5 51 9
Scolytus rugulosus (Mller) 1 0 2
Xyleborinus alni Niisima 3 5 97
Xyleborinus saxesenii (Ratzeburg) 5 252 164
Xyleborus atratus Eichhoff 5 57 39
Xylosandrus crassiusculus (Motshulsky) 1 31 29
Xylosandrus germanus (Blandford) 5 8489 6081
a
Traps were deployed in Þve nurseries each year.
ethanol lures than one or no lure, but differences were
not always detected. In Germany, Klimetzek et al.
(1986) also reported increased captures of X. germa-
nus and X. saxesenii in ßight barrier traps as ethanol
concentration increased. Ranger et al. (2011) re-
ported that increasing the concentration of ethanol
from 27 to 390 mg/d at 20⬚C doubled captures of X.
germanus in funnel traps. In the current research,
captures of X. germanus in bottle-traps increased by
1.1Ð2.3 times by doubling the lure volume (from 10 to
20 ml) and thus the release rate (⬇65Ð130 mg/d at
30⬚C for treatments with one or two lures, respec-
tively) of ethanol. Furthermore, the Þrst time of the
season X. crassiusculus and X. germanus were detected
at a site, they always occurred in the treatments with Fig. 3. Seasonal ßight activity of X. germanus, X. saxesenii,
two lures while occurring 75Ð 80% of the time in the A. sayi, H. dissimilis, and H. eruditus during 2008 and 2009 in
1-lure treatment. These results show that ethanol re- Ohio.
lease rate inßuences sensitivity of bottle traps for de-
tecting emergence of X. crassiusculus and X. germanus.
In Ohio, there was no practical advantage of the 1 ⫹ crassiusculus in the bottle traps were similar or ex-
1-lure versus the 2-lure treatment for detecting emer- ceeded those reported by Oliver and Mannion (2001)
gence of the target beetles. In Virginia however, the and Gandhi et al. (2010) for Lindgren funnel traps
1 ⫹ 1-lure treatment was better at detecting Þrst emer- baited with greater volumes of ethanol. Based on total
gence of X. crassiusculus than the other ethanol treat- captures for the season, Oliver and Mannion (2001)
ments. Reding et al. (2010) reported that captures of captured 77.2 Xylosandrus sp. per trap in Tennessee,
X. crassiusculus were similar in traps deployed at 0.5 Gandhi et al. (2010) captured 81.4 X. germanus per
and 1.7 m above the ground, while captures of X. trap and we captured 161.9 X. germanus per trap in
germanus were always higher in the 0.5 m traps. The Ohio and 76.2 X. crassiusculus per trap in Virginia.
greater sensitivity of the 1 ⫹ 1-lure treatment for Oliver et al. (2004) also captured more Xylosandrus sp.
detecting emergence of X. crassiusculus versus X. ger- in bottle traps than funnel traps in Tennessee.
manus may be related to differences in their ßight Monitoring for X. crassiusculus and X. germanus will
behavior. enable growers to better synchronize their control
The current research indicates bottle traps baited treatments with the beetlesÕ activity. Many nursery
with ethanol are effective tools for monitoring and growers time their controls for these pests based on
early detection of X. germanus and X. crassiusculus in the calendar. However, previous and current research
ornamental nurseries. Captures of X. germanus and X. has shown variation in emergence of X. crassiusculus2022 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 104, no. 6
Fig. 4. Mean (12 traps) captures ⫾ SE (error bars) of X. crassiusculus, X. germanus, and X. saxesenii, from Virginia 2008
compared among ethanol lure concentration treatments (untransformed data presented). The data are cumulative captures
through 11Ð13 June. Columns within species with similar letters are not statistically different (TukeyÕs HSD, 0.05).
and X. germanus between years. Reding et al. (2010) in ethanol-baited traps, appears to be inßuenced by
recorded Þrst captures of X. crassiusculus as early as 13 temperature. Flight activity of X. crassiusculus and X.
March in Virginia and 3 April for X. germanus in Ohio, germanus often has two peaks during spring, and the
while in the current study as late as 4 and 24 April, dip in activity between the peaks usually coincides
respectively. These results show that the calendar is with cool temperatures (Reding et al. 2010; Figs. 3 and
unreliable for timing treatments for either species. 5). Variation in the emergence of X. crassiusculus and
Emergence of Scolytinae that overwinter as adults, X. germanus between years in the current and a pre-
such as X. crassiusculus and X. germanus, probably vious study further supports a relationship between
begins after temperatures reach a certain level or the activity of these species and temperature and/or
threshold (Rudinsky 1962, Daterman et al. 1965, We- other environmental factors (Reding et al. 2010).
ber and McPherson 1991). Flight activity of X. cras- However, further examination of this relationship is
siusculus and X. germanus in spring, based on captures needed.
Fig. 5. Seasonal ßight activity of X. crassiusculus, X. germanus, and X. saxesenii during 2008 in Virginia.December 2011 REDING ET AL.: OPTIMIZING AMBROSIA, BEETLE MONITORING IN NURSERIES 2023
X. crassiusculus was Þrst detected in Ohio in 2007 et al. (2010). Furthermore, Oliver and Mannion
(Lightle et al. 2007, Gandhi et al. 2010). Lightle et al. (2001) found very few attacks on live trees by X.
(2007) and Gandhi et al. (2010) trapped in nine sites saxesenii in Tennessee, compared with X. crassiusculus
in six northern Ohio counties. Lightle et al. (2007) and X. germanus, even though it was the most common
captured X. crassiusculus in Wayne County, OH (N 40⬚ species captured. Consequently, X. saxesenii may not
46⬘53⬙, W 81⬚ 54⬘57⬙), a county sampled in the current be a signiÞcant problem on nursery trees.
study. We captured X. crassiusculus in Lorain County, A. sayi, H. dissimilis, and H. eruditus are native
which was not sampled by Lightle et al. (2007) or species and were captured in relatively high numbers
Gandhi et al. (2010). in Ohio compared with the other Scolytinae captured
Invasive species, including ambrosia beetles, can except X. germanus. These native species are not ex-
spread to new areas through natural dispersal or hu- pected to be a problem in nurseries because they are
man assisted movement (Chen et al. 2005). Because of secondary colonizers attacking damaged or weakened
their wood-boring habits, small size and cryptic na- twigs (Wood 1982, Solomon 1995). However, Anisan-
ture, Scolytinae including ambrosia beetles can go drus pyri (Peck) has been found damaging young fruit
undetected in solid wood packing materials, raw wood and ornamental trees in North America (Mathers
products and nursery stock, which may assist move- 1940), suggesting A. sayi has the potential to be a pest.
ment to new areas (Oliver and Mannion 2001, La- Interestingly, while captures of A. sayi and H. dissi-
Bonte et al. 2005). Some Ohio nurseries regularly buy milis tended to be higher in the treatments with two
stock from southern and western states, where X. lures, H. eruditus was somewhat repelled by the 2-lure
crassiusculus has occurred since at least the 1970s and treatment with numerically higher captures in the 1-
1990s, respectively (Solomon 1995, LaBonte et al. and 1 ⫹ 1-lure treatments. H. eruditus activity peaks in
2005). In Ohio, X. crassiusculus appears to have a early summer, later than the other species we com-
patchy distribution (M.E.R., personal observation), pared among treatments.
which suggests its movement into the state was as- A reliable monitoring system is an important step
sisted by humans. However, extensive surveys of Sco- toward developing an integrated program for manag-
lytinae have not been done in Ohio, and lack of de- ing ambrosia beetles in ornamental tree nurseries.
tection of X. crassiusculus in some areas could be Ethanol-baited traps are promising tools for monitor-
because of low populations. ing ambrosia beetles. However, research was needed
In Ohio, X. crassiusculus occurs in much lower num- to reÞne trapping methods for monitoring ambrosia
bers than X. germanus, while in Tennessee and Vir- beetles in nurseries. This study demonstrated that
ginia, X. crassiusculus generally occurs in higher num- increasing the volume of ethanol increased attractive-
bers than X. germanus (Oliver and Mannion 2001, ness of bottle-traps to key nursery-attacking ambrosia
Gandhi et al. 2010, Reding et al. 2010; Table 1, Fig. 4). beetles and also offered an advantage in Þrst detection
X. germanus has occurred in Ohio since at least 1978, of beetle activity. Additional research on attractants
and X. crassiusculus may occur in lower numbers be- would further reÞne trapping as a monitoring tech-
cause it is a more recent introduction (Anderson and nique for ambrosia beetles. In addition, describing the
Hoffard 1978). Another possibility is that X. germanus relationship between damaging ambrosia beetles and
is better adapted to cooler climates associated with environmental factors might lead to development of a
higher latitudes than X. crassiusculus. In the current model for predicting beetle activity, which would pro-
study, X. germanus was captured at least 3 wk earlier vide growers with another tool to help them synchro-
than X. crassiusculus in Ohio. Trees emerging from nize their control treatments with beetle activity.
dormancy tend to be more vulnerable to attack by
ambrosia beetles (Kühnholz et al. 2001). Conse-
quently, by emerging earlier X. germanus should have Acknowledgments
access to more vulnerable hosts than a later emerging
X. crassiusculus, which could provide a selective ad- The authors thank Betsy Anderson (USDA-ARS), and
vantage. In contrast, X. crassiusculus emergence and M. S. Dills and C. A. Whitaker (Virginia Tech.) for technical
assistance. Mention of proprietary products or companies is
peak activity in Tennessee and Virginia is similar or included for the readerÕs convenience and does not imply any
slightly earlier in the season than X. germanus (Oliver endorsement or preferential treatment by either USDA/ARS
and Mannion 2001, Reding et al. 2010; Fig. 5), which or The Ohio State University.
could shift the advantage to X. crassiusculus in those
states.
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