Seasonal patterns of capture of Helicoverpa zea (Boddie) and Heliothis phloxiphaga (Grote and Robinson) (Lepidoptera: Noctuidae) in pheromone traps in Washington State

2011·4.3 MB·English

by  L Camelo

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J.Entomol.Soc.Brit.Columbia108,December201 3
Seasonal patterns of capture oiHelicoverpa zea (Boddie) and
Heliothisphloxiphaga (Grote and Robinson) (Lepidoptera:
Noctuidae) in pheromone traps in Washington State.
L. CAMELOS T. B. ADAMS^ P. J. LANDOLT^ R. S. ZACK^, and C.
SMITHHISLER
ABSTRACT
In each of the 6 years of this study in south central Washington state, male com earworm
moths, Helicoverpazea (Boddie), first appeared in pheromone traps in late May to mid June,
and thereafterwere present nearly continuously until mid to late October. Maximum numbers
of male com earworm moths captured in pheromone traps occurred in August and early
September. Male Heliothisphloxiphaga (Grote and Robinson) moths first appeared in traps
baitedwith com earworm pheromone and conspecificpheromone inApril, andwere generally
present throughout the season until mid to late September. In some years, two peaks oftrap
capture ofH.phloxiphagamales was suggestive oftwo generationsperseason,with one flight
in April and May and the other in July and August. Although both species were caught
primarily in traps baited with their appropriate conspecific pheromone, smaller numbers of
both species were captured in traps baited with the heterospecific pheromone. Heliothis
phloxiphaga captured in com earworm pheromone traps can be misidentified as com
earworm, resulting in false positives for com earworm in commercial sweet com or
overestimates ofcom earwormpopulations.
Key Words: Seasonal phenology, Helicoverpa zea, Heliothis phloxiphaga, com earworm,
trapping, pheromone
INTRODUCTION
Helicoverpa zea (Boddie), the corn overlapping size and coloration, H.
earworm (CEW), is a pest of many phloxiphaga in CEW pheromone traps may be
agricultural crops, particularly com, tomato, wrongly identified, giving false positive
CEW
and cotton (Metcalf and Metcalf 1993). The indications for andpotentially leading to
moth is monitored in cropping systems with a unnecessary pesticide applications (Adams
four component sex pheromone (Klun et al. 2001, Hoffman et al. 1991). Photographs of
1980). In the irrigated farming areas of south the adult stage ofboth species are figured by
central Washington, the com earworm is the Covell (1984), Powell and Opler (2010), and
key pest of sweet corn, and numerous on the Noctuoidea of Canada Website
pesticide applications are required per season (Troubridge andLafontaine 2011).
to control it. Heliothisphloxiphaga (Grote and Monitoring of the male com earworm
Robinson) is generally not a pest but is moth flight with pheromone traps provides
important as a non-target insect that is information to growers and field scouts that is
sometimes captured in corn earworm used to make pest management decisions.
pheromone traps (Adams 2001, Hoffman etal. Growers ofsweet com in Washington use the
1991). Heliothis phloxiphaga males respond traps to indicate the onset of arrival of com
to the com earworm pheromone, due to the earworm moths, and the need to begin a spray
overlapping chemistries of pheromones of program. In this area, the com earworm has
these two species (Kaae et al. 1973, Klun et one to three generations peryear (Mayer etal.
al 1980, Raina et al. 1986). Because oftheir 1987), while H. phloxiphaga may be
' 2700SeminisInc., Caminodel Sol,Oxnard, CA93030
2OregonStateDepartmentofAgriculture,635 CapitolSt.NE, Salem,OR,USA97302
^ Correspondingauthor,[email protected]
DepartmentofEntomology,WashingtonStateUniversity,Pullman,WA99164
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4 J.Entomol.Soc.Brit.Columbia108,December201
univoltine (Piper and Mulford 1984). Sweet The primary objective ofthis study was to
com is first planted in May in eastern determine the seasonal occurrences ofadultH.
Washington, becomes susceptible to attack by zea andH.phloxiphagain centralWashington.
the com earworm inmid July, and is grown by We determined seasonal pattems of moths
staggered planting dates into October. present as indicated by captures of moths in
Growers need to know when to expect com pheromone-baited traps. In addition, we note
earworm moth flight, and when to be responses of the two species to their
concemed with distinguishing com earworm conspecific and heterospecific sex
from H. phloxiphaga moths in com earworm pheromones. Differences and similarities in
pheromone traps. Seasonal pattems of com the seasonal pattems ofthe two species should
earworm captures in traps have been help with interpretation oftrap catch data and
determined for other geographic and climactic reduce errors caused by the capture of both
areas (Parajulee et al. 2004, Weber and Ferro species in traps used for com earworm pest
1991) but these reports may not be applicable managementprograms.
to irrigated agriculture ofWashington.
MATERIALS AND METHODS
Trapping studies were conducted in 1999 dispensers were stored in glass vials in a
to 2004 in south central Washington. The freezer until placed in traps in the field.
multicolored (white bucket with yellow cone Pheromone lures were placed in the plastic
and green lid) Universal Moth Trap (Great baskets provided at the center ofthe inside of
Lakes IPM, Vestaburg, MI) was used, with a the tops ofthe traps
6.4 cm2 piece of Vaportape™ (Hereon Traps were set up early in the season near
Environmental, Emigsville, PA) stapled to the fields to be planted to com, and were
inside wall ofthe trap bucket to kill captured maintained until the moth flights ended in late
insects. In all cases, traps were checked and autumn. Traps were either hung on fences or
captured insects removed each week, and from stakes put into the ground, at a height of
Vaportape™ and lures were replaced every 4 0.7 to 1.0 m. Traps were checked each week,
weeks. and Vaportape''''^ and pheromone lures were
Com earworm lures were the pheromone replaced each month. Moths in traps were
identified by Klun et al. (1980) consisting of placed in labeled Ziploc® plastic bags for
86.7% (Z)-ll-hexadecenal, 3.3% (Z)-9- transport to the laboratory, where moths were
hexadecenal, 1.7%) (Z)-7-hexadecenal, and sorted, identified, and counted. Voucher
8.3%) hexadecanal in a total pheromone load specimens are deposited in the James
of 1.0 mg per septum, following the methods Entomological Collection, Department of
of Halfhill and McDunough (1985). Entomology, Washington State University,
Pheromone lures forH. phloxiphaga (Raina et Pullman, WA.
al 1986) were 92% (Z)-11-hexadecenal, 0.4% Season-long monitoring of CEW with
(Z)-9-hexadecenal, 4.8% hexadecanal, and pheromone traps. Com earworm moths were
2.8% (Z)-l1-hexadecen-l-ol in a total trapped throughout the seasons of 1999-2004,
pheromone load of 1.0 mg per septum. with from 4 to 9 trap sites used per season
Pheromone was loaded into red mbber septa (Table 1). One trap baited with com earworm
(West Co., Lyonville, PA ) that had been pre- pheromone was placed at each site. Trapping
extracted twice with methylene chloride in a sites were selected based on abundant acreage
tumbler. Pheromone was applied to septa as a of commercial sweet com to be planted
solution in hexane, at a dosage of 200 nearby. At the end of the season, traps were
microliters per septum. Chemicals were recovered fi^om the field, washed with hot
purchased from Farchan Chemicals (Atlanta, soapy water, rinsed with tap water, and
GA) and Aldrich Chemical Co. (Milwaukee, exposedoutside to sun andopen airinwooden
WI), and all chemicals were 95% or greater bins for a minimum of30 days before indoor
purity. The aldehydic pheromone compounds winter storage, to reduce risk of long term
were purified by elution through a silica gel contamination ofthe trapbypheromone.
column with 5% ether in hexane. Pheromone Season-long monitoring of H,
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J.Entomol.Soc.Brit.Columbia108,December201 5
phloxiphaga with pheromone traps. earwormpheromone trap.
Heliothis phloxiphaga moths were monitored We also report H. phloxiphaga moths
CEW
with traps baited with H. phloxiphaga captured in traps baited with pheromone
CEW
pheromone, during 1999-2001. Trapping sites, from 1999-2004, and moths captured in
trapping dates, and trap maintenance were the traps baited with H. phloxiphaga pheromone,
same as those indicated above for com from 1999-2001. Statistical comparisons were
earworm pheromone traps during the same made ofnumbers ofCEW andH.phloxiphaga
years (Table 1). One trap baited with H. moths trapped in response to conspecific
phloxiphaga pheromone was placed at each versus heterospecific sex pheromone lures,
site, more than 90 meters from the com using apairedt-test.
Table 1.
Dates andlures forseasonlongmonitoringofcom earworm.
No. of Pheromones
Year StartDate Site Locations
Sites tested
YakimaCo., Mabton & CEW
1999 17 May
ToppenishBenton Co., Prosser H.phloxiphaga
CEW
2000 20April 5 Grant Co., Mattawa
H.phloxiphaga
Grant Co., Moses L. Franklin Co., CEW
2001 16April 4
Pasco H.phloxiphaga
2002 25 March 4 Yakima Co., Wapato, Granger, CEW
Donald, Toppenish
2003 29 March 4 Yakima Co., Toppenish & Moxee CEW
Benton Co., Prosser
YakimaCo., Toppenish & Moxee CEW
2004 2April 4
Benton Co., Prosser
RESULTS
Generally, first male com earworm moths determine the onset of H. phloxiphaga flight
were captured in late May, and males were and males were captured during the first week
present continuously through the summer into of the study. In all 6 years, there were two
October (Figure 1). In all years, maximum separate periods of flight activity of male H.
numbers of male moths were captured in phloxiphaga. The first period was in lateApril
August. However, in 2002 and 2003, a smaller to early June, and the second period was mid
peak of activity was apparent in June. July to lateAugust. Numbers ofmoths trapped
Numbers of moths per trap per week varied varied greatly from year to year, with a
widely from year to year, with a maximum of maximum ofover 24 male moths per trap per
over 250 per trap per week in 2002, but under weekin 2004, and a maximum offewerthan 5
70 moths per trap perweek in 1999, 2000, and moths perweek in 1999.
2003. Traps baited with CEW pheromone
CEW
For 1999-2001, data for H. phloxiphaga captured primarily moths, and traps
are from traps baited with conspecific baited with H. phloxiphaga pheromone
pheromone, and for 2002-2004, data for H. captured primarily H. phloxiphaga (Table 2).
phloxiphaga are from traps baited with CEW In 1999, 2000, and 2001, when the
CEW
pheromone. Generally, male H. phloxiphaga pheromones ofboth andH.phloxiphaga
moths were first captured in pheromone traps were maintained throughout the season, CEW
in April (Figure 2). In 1999 and 2000, traps moths were captured primarily in traps baited
were not placed in the field early enough to with the CEW pheromone, with relatively few
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6 J.Entomol.Soc.Brit.Columbia108,December201
captured in traps baited with the H. the H. phloxiphaga pheromone compared to
phloxiphaga pheromone. Numbers ofmale H. traps baited with the CEW pheromone
phloxiphaga captured were numerically but (Table 2).
not significantly greater in traps baited with
DISCUSSION
The primary objective ofthis study was to interested in determining periods of risk of
characterize the seasonal patterns of captures misidentifying H. phloxiphaga as CEW, in
CEW CEW
of andH. phloxiphaga moths in traps in relation to pest management. Although
CEW
southcentral Washington as an indicator of numbers of moths captured in
adult moth presence in com fields. Particular pheromone traps varied greatly from year to
aspects of moth seasonal patterns that are year, the cessation, termination, and peak
potentially of interest include the onset of periods of moth activity were similar
moth flight in the spring and cessation in throughout this 6 year period. The period
autumn, peak activity periods, and numbers of during which com earworm moths were active
generation per year. In this case, we are also broadly encompasses the entire period during
Figure 1. Mean (+ SE) numbers of male com earworm moths captured per week per trap, in traps
baitedwith comearwormpheromone, for 1999, 2000, 2001, 2002, 2003, and2004.
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J.Entomol.Soc.Brit.Columbia108,December201 7
Figure 2. Mean (± SEM) numbers ofmale H. phloxiphaga moths captured per week per trap, in traps
baited with H. phloxiphaga pheromone (1999, 2000 and 2001) or com earworm pheromone (2002,
2003, 2004).
which com is grown in this same area. Com is from south to north (Hartstack et al. 1982;
normally first planted after last frost, in mid to Westbrook et al. 1997), there is no
late May, and staggered plantings and documentation ofnorth to south migration. If
harvesting continue into early October. such a migration occurs, it could explain in
However, com is a suitable oviposition site for part the disappearance of the moth in early
CEW
beginning with the silking stage, which autumn in south centralWashington.
starts in late June. Earlier in the season, CEW Mayer et al. (1987) reported 1-3
moths might be infesting altemate host plants, generations of CEW per year in Washington.
possibly weed and wild flower species Our data show nearly continuous moth
(Hardwick 1965, 1996; Neunzig 1963; activity for 5 months, from late May into mid
Robinson et al. 2002). It is assumed that the to late October, without evidence of distinct
end of moth flight in autumn may occur generations. Com earworm may overwinter in
primarily as a result of decreasing the southem Columbia Basin of Washington,
temperatures making moth flight impossible. as pupae in soil (Eichman 1940, Klostermeyer
In contrast to evidence for CEW migrating 1968), first emerging in May. The
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8 J.Entomol.Soc.Brit.Columbia108,December201
interpretation of trap catch data may be capturedinpheromonetraps sporadically from
CEW
complicated by immigration of early June to the end of September (Hayes
populations from the southwestem U. S. In 1991). In Massachusetts, CEW moth flight
other areas of North America, CEW moths appears to begin much later than in south
migrate (Hartstack et al. 1982; Hendrix et al. central Washington despite a similar latitude.
1987; Lingren et al. 1993, 1994; Westbrook et Weber and Ferro (1991) captured CEW moths
al. 1997). Strong increases innumbers ofmale in pheromone traps in Massachusetts from
CEW moths in pheromone traps in August early July into early September, which is a
may have been due to reproduction by earlier seasonal activity period that is nearly 2
emerging moths, and/or migrating moths that months shorterthan seenin our study.
arrive in south central Washington with Piper and Mulford (1984) reported that H.
infrequentweatherfronts. phloxiphaga was univoltine in Washington.
The seasonal activity and abundance ofthe The data presented here indicate consistently
com earworm moth varies geographically, over the 6 years that there were two periods of
probably in response to climactic factors and increased catches ofmoths in traps, indicating
their impact on migration, reproduction, and possibly two generations per year. The
other behaviors, as well as regional makeup apparent two maxima ofactivity indicated by
and abundance ofcrops and crop planting and pheromone traps suggests that a first adult
harvest cycles. The amplitudes ofthe seasonal generation occurred in April/May and a
CEW
patterns of catches of moths in second generation in July/August. However,
pheromone traps in south central Washington Hoffman et al. (1991) did not see more than
were small compared to that observed in one peak of captures of H. phloxiphaga in
Texas by Parajulee et al. (2004). Captures of com earworm pheromone traps in California,
moths inpheromone traps oftenbegan inApril although adult activity was noted over a
in Texas, compared to May in Washington, period of 6 months, from February to
and ended in October as it did in our study in September. Certainly, multiple generations of
Washington. In Mississippi, CEW males were a moth species can occur within a season
Table2
Mean(+SE)numbers ofmale comearworm andH.phloxiphagamoths capturedperseasonpertrap
baitedwithcomearworm andH.phloxiphaga sexpheromones.
Moth species Corn earworm H.phloxiphaga
captured pheromone pheromone
1999
Com earworm 218.3 ±64.2a 1.4±l.lb 9
H.phloxiphaga 6.9±2.4a 12.4±3.9a 9
2000
Com earworm 427.6±52.3a 3.8 ± 1.0b 5
H.phloxiphaga 25.2±6.4a 44.2± 10.9a 5
2001
Com earworm 415.8 ± 144.0a 2.5 ±0.9b 4
H.phloxiphaga 22.3 ±5.7a 16.0±5.8a 4
Means within a row followed by the same letter are not significantly different by a paired t-test at P <
0.05.
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without the appearance of distinct separated summer when both are present, but in
periods offlightindicated inpheromone traps. situations where com earwormpopulations are
In all six years ofour study, the first flight expectedtobe low.
of H. phloxiphaga began about one month Although the chemistry of the H.
before the first catches of CEW moths in phloxiphaga sexpheromone overlaps with that
CEW
traps, and captures of H. phloxiphaga moths of the pheromone, H. phloxiphaga
ended about one month before the last responses to the CEW lure are not consistently
captures of CEW moths. Peak numbers of a problem with CEW monitoring programs in
possible second flight H. phloxiphaga NorthAmerica. Weber and Ferro (1991) found
populations overlapped somewhat with peak 5 non-target species of noctuids captured in
CEW CEW
numbers of in early August, although monitoring traps in Massachusetts, but
the numbers of H. phloxiphaga in H. did not indicate the trapping of H.
phloxiphaga pheromone traps were phloxiphaga. Chapin et al. (1997) reported
considerably less than CEW moths trapped non-target moths captured in com earworm
with com earwormpheromone. Itappears then traps, but captured only one H. phloxiphaga
that CEW monitoring traps in May might moth compared to over 25,000 CEW.
easily provide misleading information from However, in eastern Washington, H.
the capture ofH. phloxiphaga misidentified as phloxiphaga is consistentlypresentthroughout
CEW, but before the expected appearance of much of the com growing season and is
CEW. Also, in August, H. phloxiphaga routinely captured in corn earworm
captured in CEWpheromone traps may inflate pheromone traps (Adams 2001), and Hoffman
counts of CEW trap catch, if misidentified. et al. (1991) trapped it in sweet com fields
However, those numbers would usually be throughout Califomia. Growers can reduce
CEW
minor in relation to the numbers of costs and pesticide used by distinguishing the
moths trapped at that time. It is most two species when captured in com earworm
important to positively identify the two traps, and by recognizing that com earworm
species early in the season, and again in late are unlikely tobepresentbefore late May.
ACKNOWLEDGEMENTS
Assistancewith lures, traps, andmoths was a vehicle for use in this study. This work was
provided by J. Bmmley, P. Chapman, J. supported in part by funding from the
Dedlow, D. Larson, D. Lovelace, and C. Columbia Basin Vegetable Processors
Martin. We thank L. Anderson,A. Bassani, R. Association, the America Farmland Trust
Earl, L. Elder, R. Halvorson, C. Martin, R. Foundation, the Environmental Protection
Martinez, J. Rice, H. Sealock, P. Smith and B. Agency, and a USDA, Westem Region IPM
Thorington for access to their fields. Del grant.
WA
Monte Corporation, Toppenish, provided
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