the red imported fire ant, solenopsis invicta, in the virgin islands

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Wetterer & Snelling: Solenopsis invicta in the Virgin Islands 431
THE RED IMPORTED FIRE ANT, SOLENOPSIS INVICTA,
IN THE VIRGIN ISLANDS (HYMENOPTERA: FORMICIDAE)
JAMES K. WETTERER1 AND ROY R. SNELLING2
1Wilkes Honors College, Florida Atlantic University, 5353 Parkside Dr., Jupiter, FL 33458
2Natural History Museum of Los Angeles County, 900 Exposition Blvd., Los Angeles, CA 90007
ABSTRACT
The best known and most destructive exotic ant species in the US is the red imported fire
ant, Solenopsis invicta Buren. Recently, this species has been reported from several islands
in the West Indies, including St. Croix, US Virgin Islands (USVI) and Guana Island, British
Virgin Islands (BVI). In the present study, we report new records of S. invicta on St. Croix
(13 sites) and the first records of S. invicta from 3 other of the Virgin Islands: St. Thomas,
USVI (7 sites), St. John, USVI (2 sites), and Tortola, BVI (6 sites). Solenopsis invicta appears
to be well established in disturbed open environments on all 4 islands. It is important that
people in the Virgin Islands and elsewhere in the West Indies, particularly healthcare pro-
fessionals, are aware of the presence of S. invicta, can recognize the symptoms of S. invicta
stings, and know proper treatments for adverse reactions to the stings, including rare but
potentially deadly anaphylactic shock.
Key Words: exotic species, fire ants, Solenopsis invicta. Virgin Islands, West Indies
RESUMEN
La especie de la hormiga exótica mejor conocida y muy destructiva en los EEUU es la impor-
tada hormiga roja del fuego, Solenopsis invicta. Esta especie se ha sido reportado reciente-
mente en varias islas en las Antillas, inclusive S. Croix, las Islas Virgenes de EEUU (USVI)
y la Isla de Guana, las Islas Virgenes inglesas (BVI). En el estudio presente, nosotros repor-
tamos nuevos registros de S. invicta en el S. Croix (13 sitios) y los primeros registros de S.
invicta de tres otras de las Islas Virgenes: S. Thomas, USVI (7 sitios), S. John, USVI (2 si-
tios), y Tortola, BVI (6 sitios). Solenopsis invicta aparece ser establecido bien en ambientes
abiertos perturbados en las cuatro islas. Es importante que personas en las Islas Virgenes y
en otras partes en las Antillas, particulamente profesionales de cuidado medico, están avi-
sado de la presencia de S. invicta. Estos profesionales deben de reconocer los síntomas de la
picada de S. invicta, y saber los tratamientos para reacciones adversas a la picada.
Translation provided by the authors.
The best known and most destructive exotic The venom has hemolytic and neurotoxic proper-
ant species in the US is the red imported fire ant, ties and may cause allergic responses and result
Solenopsis invicta Buren, which arrived in Ala- in secondary infections, sepsis, anaphylactic
bama by ship from South America sometime be- shock, and even death (Prahlow & Barnard 1998;
fore 1945 (Buren et al. 1974). Since then, this deShazo et al. 2004).
predatory ant has spread across the US from The earliest known West Indian records of S.
Texas to North Carolina in the southeast and Cal- invicta are from Puerto Rico (Buren 1982), where
ifornia in the west, particularly in open disturbed it is now widespread (Torres & Snelling 1997;
areas, causing ecological and economic damage Davis et al. 2001; RRS & JKW, unpublished data).
(e.g., see Tschinkel 1988, 1993; Allen et al. 2004; More recently, S. invicta has been reported from
Wetterer & Moore 2005). Solenopsis invicta is numerous other islands in the West Indies (Table
well-known for its powerful sting, which causes a 1), including the Virgin Islands, which lie to the
burning sensation in humans, usually followed east of Puerto Rico. Davis et al. (2001) published
within one or two days by the appearance of a records of S. invicta from St. Croix, US Virgin Is-
white pustule. These pustules are diagnostic for lands (in 1997: Fredensborg National Guard facil-
the stings of S. invicta and other Solenopsis sae- ity, and in 2000; Route 66, 0.8 km east of Route
vissima complex fire ants from South America (S. 663) and from Guana Island, a small island north
Porter, pers. comm.). The stings of other ants, in- of Tortola, British Virgin Islands (BVI, in 1996).
cluding the widespread tropical fire ant, Solenop- Solenopsis invicta closely resembles S. geminata,
sis geminata (Fabricius), do not produce pustules. both in appearance and in the pain of its sting.
432 Florida Entomologist 89(4) December 2006
TABLE 1. EARLIEST KNOWN SPECIMEN RECORDS FOR SOLENOPSIS INVICTA ON ISLANDS OF THE WEST INDIES. THE AS-
TERISK (*) INDICATES DATE PROVIDED BY M. DEYRUP.
Island Year Source reference
Puerto Rico 1981 Buren 1982
St. Croix, USVI 1988 present study
San Salvador, Bahamas 1993* Deyrup 1994
New Providence, Bahamas 1995* Deyrup et al. 1998
North Andros, Bahamas 1996* Deyrup et al. 1998
Guana Island, BVI 1996 Davis et al. 2001
Gorda Cay, Bahamas 1997 Davis et al. 2001
Antigua 2000 Davis et al. 2001
Abaco, Bahamas 2000 Davis et al. 2001
Trinidad 2000 Davis et al. 2001
Grand Bahama, Bahamas 2000 Davis et al. 2001
Providenciales, Turks & Caicos 2001 Davis et al. 2001
Berry Islands, Bahamas 2005 M. Deyrup, pers. comm.
St. Thomas, USVI 2005 present study
St. John, USVI 2005 present study
Tortola, BVI 2005 present study
Because S. geminata is common throughout the In 2005, JKW collected S. invicta from 28 sites
West Indies, the presence of S. invicta may be eas- in the Virgin Islands: St. Croix (13 sites), St. Tho-
ily overlooked, even by trained entomologists. mas (7 sites), St. John (2 sites), and Tortola (6
In the present study, we examined museum sites). All sites were in highly disturbed habitats,
specimens and made field collections to evaluate primarily open grassy areas (Table 2). All sites ex-
the distribution of S. invicta in the Virgin Islands. cept one were low elevation (<100 m above sea
level; the site at Parasol, St. Croix was 200 m
METHODS above sea level). JKW collected S. geminata at 83
sites in the Virgin Islands: St. Croix (23 sites), St.
JKW searched the ant collection at the US Na- Thomas (19 sites), St. John (23 sites), and Tortola
tional Museum (USNM) for Solenopsis invicta spec- (18 sites), in a wide variety of disturbed and rela-
imens from the Virgin Islands. Between Oct 1991 tively undisturbed habitats at all elevations.
and Oct 2002, RRS collected ants on Guana Island On St. Croix, Jozef (Jeff) Keularts, an entomol-
during several visits (see Snelling 1993, 2003). ogist with the US Cooperative Extension Service,
From 30 Oct to 21 Nov 2005, JKW collected was aware of the presence of S. invicta on St.
ants on the 4 largest of the Virgin Islands, the 3 Croix. Lesley Hoffman, Administrative Director
main islands of the US Virgin Islands (St. Croix - at the St. George Village Botanical Garden, St.
7 d, St. Thomas - 5.5 d, and St. John - 4.5 d), and Croix, related that in Jan 2005, her husband,
the main island of the British Virgin Islands (Tor- Robert Hoffman, was stung by S. invicta while
tola - 4.5 d). Collection sites included a diversity golfing at the Buccaneer Hotel Golf Course on St.
of disturbed and relatively natural habitats from Croix. He was brought to Juan Luis Hospital,
the coastlines to the mountaintops. We also made where he was treated for anaphylactic shock with
a number of other observations concerning S. in- adrenaline and antihistamines. He now always
victa in the Virgin Islands. carries an auto-injection charged with epineph-
rine because he was told that a subsequent attack
RESULTS could cause even more severe anaphylactic shock,
which could be fatal without immediate treat-
The USNM collection had Solenopsis invicta ment. Once stung the body builds up antibodies
specimens from 2 sites in the Virgin Islands, both and subsequent attacks can result in potentially
from St. Croix in 1988: Kingshill and Concordia. deadly allergic reactions.
These records are earlier than any published On St. Thomas, George Ralish, the superinten-
records from the Virgin Islands. dent at Mahogany Run Golf Course knew of the
RRS did not find S. invicta on Guana Island presence and threat of S. invicta on the course. He
prior to 1996. In Oct 2002, S. invicta was common has been working to control S. invicta on the golf
on the south side of the island: on the playa be- course through spot treatment of nests using two
hind White Beach and in the “plantation” area. insecticides (Extinguish from Wellmark, active
Forested areas of Guana Island were occupied by ingredient = 0.5% Methoprene; Varsity from Syn-
Solenopsis geminata. genta, active ingredient = 0.011% Abamectin).
Wetterer & Snelling: Solenopsis invicta in the Virgin Islands 433
TABLE 2. NEW COLLECTION SITES OF SOLENOPSIS INVICTA IN THE VIRGIN ISLANDS (30 OCT TO 21 NOV 2005).
°N °W Island Site Habitat
17.780 64.770 St. Croix Salt River, entrance to Gentle Winds grass lawn
17.759 64.586 St. Croix Cramer’s Park grass & weeds
17.757 64.817 St. Croix Parasol; Scenic Dr., 0.5 km E of Rte. 69 grass & weeds
17.740 64.842 St. Croix Montpellier, by church grass lawn
17.732 64.813 St. Croix Upper Love, by church grass lawn
17.729 64.865 St. Croix Little La Grange, by Lawaetz Museum grass lawn
17.720 64.798 St. Croix Kingshill, UVI by parking lot
17.717 64.694 St. Croix Longford, Routes 62 & 85 grass lawn
17.715 64.883 St. Croix Fredriksted, waterfront park plantings
17.715 64.830 St. Croix St George, Botanical Garden grass lawn
17.702 64.885 St. Croix Smithfield, south of Cottages by the Sea grass lawn
17.694 64.891 St. Croix Hesselberg, south end of Shore Drive grass lawn
17.694 64.820 St. Croix Betty’s Hope, south of Route 64 scrub forest
18.364 64.923 St. Thomas Magens Bay, end of Route 35 beach weeds
18.359 64.906 St. Thomas Lovenlund, Mahogany Run Golf Course grass green
18.344 64.974 St. Thomas John Brewer’s Bay, UVI by parking lot
18.344 64.937 St. Thomas Charlotte Amalie, Griffiths Park grass & weeds
18.344 64.933 St. Thomas Charlotte Amalie, Creques Alleys plantings
18.344 64.930 St. Thomas Charlotte Amalie, Emancipation Garden grass lawn
18.339 64.969 St. Thomas Brewer’s Bay, airport plantings
18.348 64.713 St. John Coral Bay baseball field
18.343 64.785 St. John Caneel Bay, resort grass lawn
18.447 64.562 Tortola Josiah’s Bay, by hostel grass lawn
18.425 64.619 Tortola Road Town, waterfront weeds
18.425 64.579 Tortola Paraquita Bay, community college grass lawn
18.414 64.589 Tortola Brandy Wine Bay beach weeds
18.412 64.671 Tortola Carrot Bay beach weeds
18.386 64.699 Tortola Sandy Point, boat yard grass & weeds
On St. John, the US quarantine office in the infested with S. invicta. It seems inevitable
main harbor at Cruz Bay had no records of any that S. invicta will soon spread to most other
ants intercepted from in-coming cargo. The per- populated islands of the West Indies as well.
sonnel there were unaware of any threat posed by Solenopsis invicta poses an important threat
pest ant species, including S. invicta. not only to terrestrial invertebrates in the Vir-
On Tortola, a person visiting a beach com- gin Islands and other West Indian islands, but
plained of white pustules and scars from ant also to vertebrates. For example, S. invicta at-
stings he received while working at a boat yard at tacks and kills hatchling sea turtles in Florida
the Sandy Point. JKW found this entire boat yard (Allen et al. 2001; Parris et al. 2002; Krahe et
heavily infested with S. invicta. al. 2003; Krahe 2005), and may pose a similar
hazard to sea turtles in the Virgin Islands. The
DISCUSSION collection site in southwestern Hesselberg, St.
Croix, was adjacent to the Sandy Point Wildlife
In the Virgin Islands, Solenopsis invicta is Preserve, an important nesting beach for the
now well established on all 4 major islands as endangered leatherback sea turtle, Dermo-
well as on Guana Island. Based on specimen chelys coriacea (Vandelli) (Dutton et al. 2005).
records, it appears that S. invicta probably ar- Solenopsis invicta may also represent a threat
rived in the Virgin Islands in the 1980s, first es- to already endangered small vertebrates on
tablishing itself on St. Croix. The first popula- these islands, including many species of Anolis
tions of S. invicta on the other Virgin Islands lizards. Finally, it is important that people in
may be quite recent, dating from the 1990s and the Virgin Islands, particularly healthcare pro-
later. It is not surprising that S. invicta has fessionals, are aware of the threat of S. invicta
spread to St. Croix and the other Virgin Islands, to humans, can recognize the symptoms of S. in-
given the large amount of commercial ship traf- victa stings, and know proper treatments for se-
fic to these islands from Puerto Rico and ports vere adverse reactions to the stings, including
in the southeastern US, sites which are heavily rare but potentially deadly anaphylactic shock.
434 Florida Entomologist 89(4) December 2006
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126: 186-194.
We thank A. Wetterer, M. Wetterer, S. Porter, and M. KRAHE, H. B. 2005. Impact of the red imported fire ant
Lachance for comments on this manuscript; the Na- (Solenopsis invicta) on two species of sea turtle
tional Science Foundation, Florida Atlantic University, hatchlings. M.S. Thesis, Florida Atlantic Univ., 42 pp.
and the Natural History Museum of Los Angeles KRAHE, H., J. K. WETTERER, AND L. D. WOOD. 2003. Im-
County for financial support. pact of fire ant stings on sea turtle hatchling sur-
vival, pp. 211-212 In Proc. 22nd Ann. Symp. Sea
Turtle Biol. Conserv., NOAA Tech. Mem. NMFS-
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Jenkins et al.: Predators and Parasitoids of Plum Curculio 435
INVERTEBRATE PREDATORS AND PARASITOIDS OF PLUM CURCULIO,
CONOTRACHELUS NENUPHAR (COLEOPTERA: CURCULIONIDAE)
IN GEORGIA AND FLORIDA
DAVID A. JENKINS1, RUSS F. MIZELL, III2, DAVID SHAPIRO-ILAN3, TED COTTRELL3 AND DAN HORTON4
1USDA-ARS, Mayaguez, Puerto Rico 00680-5470
2Entomology and Nematology Dept. IFAS, Gainesville, FL 32611
3USDA-ARS, Byron, GA 31008
4University of Georgia, Athens, GA 30602
ABSTRACT
The extent of predation and parasitism on larvae of the plum curculio, Conotrachelus nen-
uphar (Herbst) (Coleoptera: Curculionidae), was measured independently with several dif-
ferent experimental designs at sites in northern Florida and central Georgia. Experimental
manipulation in Monticello, FL, and in Byron, GA, demonstrated equivocal impacts by pre-
dation. However, direct observations in Byron, GA, revealed that ants are the dominant in-
vertebrate predators of plum curculio larvae, causing up to 62% mortality. Primary ant
predators included Solenopsis invicta (Buren) (Hymenoptera: Formicidae) and Dorymyrmex
bureni (Trager) (Hymenoptera: Formicidae). Predation may be more important later in the
season when infested fruit does not abscise and plum curculio larvae must drop to the
ground from the trees and spend a considerable time burrowing into the soil. This contrasts
with the early season when infested fruit abscise and larvae crawl from the fruit directly
into the soil, reducing their exposure to predators. Recorded parasites included Nealiolus
curculionis (Fitch) (Hymenoptera: Braconidae) and Cholomyia inaequipes Bigot (Diptera:
Tachinidae). Parasitism, particularly by N. curculionis, was common in northern Florida but
rare in middle Georgia.
Key Words: Dorymyrmex bureni, Solenopsis invicta, Nealiolus curculionis, Cholomyia
inaequipes
RESUMEN
El nivel de depredación y parasitismo en contra de Conotrachelus nenuphar (Herbst) (Co-
leoptera: Curculionidae), fue medido independientemente usando diferentes diseños experi-
mentales en lugares como el norte de Florida y la zona central de Georgia. Manipulación
experimental en Monticello, FL, y en Byron, GA, demostró que el impacto de depredación no
fue preciso. Sin embargo, observaciones directas en Byron, GA, revelaron que las hormigas
son el invertebrado dominante en la depredación de la larva de C. nenuphar, causando hasta
62% de mortalidad en las larvas. Entre las principales hormigas depredadoras se encuen-
tran, Solenopsis invicta (Buren) (Hymenoptera: Formicidae) y Dorymyrmex bureni (Trager)
(Hymenoptera: Formicidae). La depredación es más importante en la temporada tardia,
cuando las frutas infestadas no han caido al suelo, por lo tanto las larvas tuvieron que llegar
al suelo desde los arboles y pasaron un tiempo considerable tratando de enterarse en el
suelo. Contrario a esto, en la temporada temprana cuando las frutas infestadas cayeron al
suelo y las larvas pasaron de la fruta al suelo directamente, reduciendo el tiempo que las lar-
vas estuvieron expuestas a los depredadores. Los parásitos reportados incluyen Nealiolus
curculionis (Fitch) (Hymenoptera: Braconidae) y Cholomyia inaequipes (Bigot) (Diptera: Ta-
chinidae). Parasitismo, particularmente por N. curculionis, fue común en el norte de Florida
pero raro en la zona central de Georgia.
Translation provided by the authors.
The plum curculio, Conotrachelus nenuphar lis 1989). Adult plum curculios migrate in early
(Herbst) (Coleoptera: Curculionidae), an insect spring from overwintering sites in adjacent woods
native to North America (Quaintance & Jenne to infest peach orchards (Snapp 1930; Yonce et al.
1912), is the primary direct insect pest of peaches 1995). The females oviposit on young fruit, often
in the Southeastern United States (Horton & El- causing it to abscise (Quaintance & Jenne 1912;
436 Florida Entomologist 89(4) December 2006
Snapp 1930). Larvae develop in the fruit and timal conditions” to emergence under field condi-
move into the soil to pupate. In the bivoltine tions in order to estimate overall mortality attrib-
southern strain of plum curculio (Chapman utable to abiotic factors and to predators, parasi-
1938), adults emerge from these pupae the same toids, and pathogens. In May 2004 we exposed 20
summer to continue the infestation, but their off- virgin female and 20 virgin male plum curculio to
spring emigrate from the orchard to overwinter- 360 green thinning apples (Red Delicious variety)
ing sites in adjacent woods or other locations with for 2 weeks. Half of these apples were then ran-
plenty of leaf litter (Quaintance & Jenne 1912; domly selected and distributed equally among 6
Snapp 1930; Yonce et al. 1995). tilled locations (30 apples/location) at the base of
Plum curculio is currently controlled with peach trees and within the rows of an unsprayed
highly efficacious organophosphate insecticides. peach orchard on the grounds of the SEFTNRL.
The use of these pesticides is being restricted as a Each tilled location was 0.6 m2 in area. This or-
result of the implementation of the Food Quality chard had not received pesticide applications in
Protection Act. Recent insecticide losses, e.g., me- the previous 5 years. Six separate locations in the
thyl parathion, have caused the peach industry in same unsprayed orchard were tilled and used as
the southeast to seek more sophisticated inte- negative controls, each receiving 30 uninfested
grated pest management strategies that take into green thinning apples. Each location was covered
account the target pest’s natural history and biol- with a cone emergence trap (Mulder et al. 2000)
ogy. These approaches include soil applications of after 3 weeks. This allowed predators to access
entomopathogenic nematodes and fungi against the infested apples without interference from the
the larval and pupal stages (Shapiro-Ilan et al. cages but was not enough time for adults to
2002; Shapiro-Ilan et al. 2004; Tedders et al. 1982). emerge from the soil. Cone emergence cages were
Although predators and parasitoids are impor- monitored daily for the emergence of adults over
tant components of integrated management pro- 60 days. The remaining apples that had been ex-
grams for other curculionid pests (Stuart et al. posed to ovipositing female plum curculio were di-
2003; Stuart et al. 2002; McCoy et al. 2000), little vided equally among 6 plastic tubs (11.4 L Rub-
attention has been paid to potential predators or bermaid™ storage box). The infested fruit were
parasitoids of the plum curculio. Field efficacy tri- placed upon a hardware cloth supported above
als against plum curculio often have variable the bottom of the tub by four 2-cm long corks. The
mortality rates (Shapiro-Ilan et al. 2004; Quain- tubs were stored in an environmental chamber at
tance & Jenne 1912; Snapp 1930), suggesting 25° ± 1°C and 50% RH (12:12, L:D) (Amis & Snow
that natural sources of mortality may be involved 1985). The tubs were monitored daily for the
and potentially sources of control. Even though emergence of larvae which were then placed into
researchers in the northeastern U.S. concluded pupation jars. Pupation jars were 950-ml glass
that natural enemies of the plum curculio are in- jars 2/3 filled with a moistened mixture of potting
efficient (Van Driesche et al. 1987) we were inter- soil and vermiculite (2:1) that had been sifted
ested in surveying predators and parasitoids of with a 10-mesh sieve to ensure that the soil did
plum curculio in central Georgia. not contain insects and covered with a glass Petri
Our objectives were to assess the effects of var- dish. Pupation jars were monitored daily for the
ious natural enemies on the southern strain of emergence of adult plum curculio. The number of
plum curculio, C. nenuphar, by (1) quantifying the emerging adult plum curculio was compared be-
extent of plum curculio mortality attributable to tween fruits exposed to predators and fruits not
predation and parasitism in northern Florida and exposed to predators using a t-test (SAS 2001).
middle Georgia, and (2) assaying biological con- We monitored plum curculio larvae as they bur-
trol organisms, such as the fungus, Beauvaria rowed into the soil, recording any predation we ob-
bassiana (Bals.) Vuill. (Hyphomycetes) separately served. Between Mar 15 and Aug 1, 2003, labora-
and in conjunction with the application of conven- tory-reared plum curculio larvae (Amis & Snow
tional pesticides (e.g., bifenthrin, thiamethoxam, 1985), within 12 h of emerging from green thinning
and imidacloprid) to the soil targeting late larval apples, were harvested, taken to the field, and
and pupal stages of plum curculio are located. The placed singly at random locations on an orchard
impacts of these pesticides on potential natural floor in Byron, GA, between the hours of 8:00 and
enemies also were assessed. 20:00. Each larva was observed until the larva bur-
ied itself or was carried off by predators. The time
MATERIALS AND METHODS interval between setting the larva on the ground
and its complete burial or removal by predators was
Experiments Conducted at the Southeastern Fruit and noted. Ant abundance (by species) was measured by
Tree Nut Research Laboratory, Byron GA: Predation counting the number of ants in an area of 0.21 m2 at
random locations in the orchard throughout the
At the USDA Southeastern Fruit and Tree Nut summer. An area of 0.21 m2 was chosen because it
Research Laboratory in Byron, GA, (SEFTNRL) was small enough for researchers to survey it inten-
we compared the potential emergence under “op- sively. Results were then converted to ants per m2.
Jenkins et al.: Predators and Parasitoids of Plum Curculio 437
Parasitism NC) at 438.07 mL/ha, or Beauvaria bassiana
(GHA strain, supplied by Emerald Bioagricul-
Abscised peaches were collected at Byron, GA, ture, Butte, Montana) applied at a rate of 1014
in 2004 and placed on trays with mesh bottoms conidia/ha, or with 2 L of water as a control treat-
over a large aluminum funnel (0.3 m high with a ment. All treatments were delivered in 2 L of wa-
slope of 30%). The funnel was positioned over a ter from a watering can. One hundred abscised
collection pan so that larvae emerging from the fruit, gathered from the orchard floor, were depos-
infested fruit could be collected. Larvae were col- ited at each of the 25 sites (5 treatments with 5
lected daily, enumerated and placed in pupation replicates).
jars. Pupation jars were monitored daily for 60 d
for the emergence of adult plum curculio or para-
RESULTS
sitoids.
In addition, wild plum fruit, Prunus angustifo-
Southeastern Fruit and Tree Nut Laboratory, Byron
lia Marshall and P. umbellata Elliott, infested
GA: Predation
with plum curculio (as denoted by the distinct ovi-
position scar, Quaintance & Jenne 1912) were col- Significantly more adults emerged from apples
lected from Peach Co., GA, and placed in plastic stored in the incubator (7.5 ± 1.3: mean ± SEM)
tubs (11.4-L Rubbermaid™ storage box) and than from apples stored in the orchard and ex-
stored, as described earlier in the predation stud- posed to predation, disease, and environmental
ies. The tubs were monitored daily for the emer- factors (3.8 ± 1.0: mean ± SEM) (t = 2.75; df = 5;
gence of larvae from fruit. Larvae were collected P = 0.022). No adult plum curculio emerged from
and placed into pupation jars and were monitored the control plots that contained uninfested ap-
for the appearance of adult plum curculio and/or ples, indicating that it was likely that all of the
parasitoids. curculio emerging in the cone emergence cages in
One hundred abscised peaches collected from the orchard were from the infested apples and not
an unsprayed peach orchard at SEFTNRL were from plum curculio pupae that were in the soil
placed at each of 5 tilled areas (0.6 m2) at the base prior to the experiment.
of randomly selected peach trees in the orchard. In total, 268 m2 were surveyed for ant abun-
The peaches were then covered with a cone emer- dance and 4,038 ants were found. Solenopsis in-
gence trap. The cone emergence trap was moni- victa Buren (Hymenoptera: Formicidae) com-
tored for 60 d for the emergence of parasitoids his- prised 77% of the ants found, Dorymyrmex bureni
torically associated with plum curculio (Krom- (Trager) (Hymenoptera: Formicidae) comprised
bein et al. 1979). 15%, and a Paratrechina sp. (Hymenoptera: For-
micidae) comprised 8%. There was a mean of 15
Experiments Conducted at the North Florida Research (±0.88 SEM) ants of any species in a given m2. Of
and Education Center, Monticello, FL these, 12 (±0.85 SEM) were S. invicta, 2 (±0.26
SEM) were D. bureni, and 1 (±0.10 SEM) was
One thousand peach fruit that had abscised in Paratrechina sp.
response to infestation by plum curculio were All 3 ant species were observed capturing and
gathered at the University of Florida, North Flor- killing larval plum curculio that we had placed on
ida Research and Education Center (NFREC) in the ground. In total, 229 last instar plum curculio
Monticello, FL, in 2003. These fruit were distrib- larvae were observed on the orchard floor. Of
uted among 10 locations (0.5 m2) on an orchard these, 97 were discovered by S. invicta, 26 were
floor, so that each location had 100 abscised fruit. discovered by Paratrechina sp., and 20 were dis-
Bifenthrin (Talstar® EZ, FMC Corporation, Phil- covered by D. bureni. Eighty six larvae were able
adelphia, PA) was applied (1 lb/acre) in a 3.14-m to bury themselves before being discovered by
ring around, but not on, infested fruit at 5 loca- ants. On average, all larvae discovered by fire
tions. Five locations were left untreated as con- ants were discovered in 13.94 min (SEM = 1.34).
trols. The locations were covered with cone emer- All larvae discovered by Paratrachina sp. were
gence traps and monitored daily for the emer- discovered on average in 9.35 min (SEM = 1.54).
gence of adult plum curculio or parasitoids All larvae discovered by D. bureni were discov-
(Krombein et al. 1979). ered on average in 20.10 min (SEM = 5.67). All
Parasitoid emergence also was monitored in a larvae discovered by any species of ant were dis-
separate field trial in 2003 by assaying 5 pesti- covered on average in 13.97 min (SEM = 2.49). All
cides applied to the orchard floor and targeting larvae that successfully buried themselves did so
plum curculio larvae. Twenty five sites (1 m2) on average in 15.41 min (SEM = 1.39).
were selected and treated with imidacloprid (Ad- A mean of 4.2 (SEM = 1.2) adult plum curculio
mire® 2F, Bayer Crop Sciences, Kansas City, MO) emerged from 100 abscised fruit under the 5 cone
at 1.75 L/ha, bifenthrin (Talstar® EZ, FMC Cor- emergence cages. Only 1 specimen of Nealiolus
poration, Philadelphia, PA) at 1.12kg/ha, thia- curculionis (Fitch) (Hymenoptera: Braconidae)
methoxam (Platinum®, Syngenta, Greensboro, was detected from the cone emergence cages.
438 Florida Entomologist 89(4) December 2006
cf5pnrh2uiosi8pmIn a nail ndat titdhraoov eenCta) a o ehjwlra ,o cfarlr9hsoso3.a m mr0rOeyd antai ahrflebe e osidssoncp eirafse reifeconrqdimum u Bipi tetpy ehnareae osnce sndhBae, e c ipGpghsll o Aauwotc. mf e(e WDdNr ce ie.utp hcccrtuooeecllurmrllcaleeu i:ccio lTntt.ieeatoddo-- MCTEDINON- Untreatedcontrol 13.8 (±2.4) a5.8 (±1.6) a 8. For Nealiolus
E 2
NMacf(r3unouo9ldrnIii%tton th in 2 cyoFtie6ifoslle9 lo tilow rnad,i olfedeF,ef radL s1e PtR, ae1r.e de4stua e6ofmrart erasubcdclih eat of l rarlyfrano ie5emtddal4 dE 6tfedwh rdupuee clsilrautaeet mr iolovacf na ocr PeluvCl.)a ere.a cencTutn.tweelgirdouo,. sNltTai.hf rcoveulasiraee- SCISEDPEACHESCOLL Beauvaria bassiana 14at 10conidia/ha 14.8 (±3.7) a7.8 (±1.8) a 05; F= 1.39; P=0.2531; df=
ecetpdhommrifnaefAeevtetrrr er mggoreneeelntescdd t aeea fn(finnrtvr tooode=rmmfd y 101 2o.1b313.f0i.80 58ffi0e 05 (( nr ±;a±ae t2db2 bha.sf.8sr 4cn=ci inStiS sss4 EeEe.;a d MdTMPs fh f)r)=ar e uaau s0iddreit.tiuu 8n irlnli9egttn 9 s tpp u)thtl.lrhluueete mmsau tlwn omcctceuurearrrenetccai utuont llnetoiidooost 100 ERGINGFROMAB Talstar®s a fire ant barrier 12.8 (±2.8) a6.2 (±1.2) a αachelus nenuphar, = 0.
nisT. hTeh eo nplyer pcaenrat soitfo ipdl urmec ocvuerrceudl iwo aisn Nfe.c ctuedrc uwliitoh- SEM a onotr
tcsospnhuiaflot uiyrr3oscme i7 duddp% ils adic,d or u(riat SdarrhsEec neiunctMgyoeloe i,vta od= bep dr afpc2reesoeo.dme7mam d7aorp ) nno3 tan(dso0rTt %erttsadhhaib gt teeloneet nn o i 4fis1 uu7i)cummg.%a nnTnbb,ti heetfirwlrerecyi aatoo phtinffeme taasad ptddn ciauuocc acinolldttvtnt eerpnptsorraul alouar mglamossef---, OLUSCURCULIONI Thiamethoxamat 438.07 mL/ha 11.6 (±0.9) a10.4 (±0.9) a man-Keuls test. For C
LI u
bers of parasitoids in each treatment (Table 1). EA Ne
culTioh meroer wtaalsit ya swighnDeinIfiS cpCalUnuStmS rI OecdNuurccutiloino iwne prelu rme acruerd- NPHARAND Bifenthrinat 1.12 kg/ha 6 (±2.1) a4 (±1.1) a g to a Student-
U n
indoors, in the absence of natural enemies or ad- N di
vtsabamgicdiratgttavogmnnhuiaueineeeeedenttiogedog atltorrsnarle udninreinrte: sastrnttmso l ih nem ,ieeey ta(tbt.b afit, 1 eeom d o srytDuchpo pco t) tore ueon o ntahato omaflit anpnrerip upruutran ennsrmcvdrtes rotrmmlrttpo hthegaiciei erdte ssroutldt eahctlt bc oa yotr idtaocnal almreafietooncoe uuu ildltydrntriref iomdadiro,rn ftestbc oltnflheoecy(ebyehd ghd une2ugafreo a s ea f anbfr) eu olnodeldoswnomp narirtnetrbrlcurd orodlav hban i vceasaaa eit6awil teeteoenseghyflry g r0 eh dtr moiates spi cond% bnivoon neaa brrooneo eesaa gaeig nmrerbstthreo a tot .ces rtto dae sg isrunanefewHodiero mtni,i ecinnm ntsatetw nnpveiaoitp hipatatdtangslseoewtepil,sueourlel.d m nucnde, rl r enreTi mali cn emsanseuoadtrveasnoh,dovy pro tl nide mdei ibacah pe lpcrapainlt(esu ,ualratn,ee l3ps ln ed eofierotsuln rgi w)oce d rohacntf cfrm dtanwons ouiod iusteeh cm btp.teruhrp il rse liihatifi pnstioeFdulmertafoefocht u oehnt e elm m uyut w afbstmnpprll esh otrrstaaeteeeaapr at otelrc u m drrnrhexslysh etceuh ovv st udhac ru rcaeolahwneabaeitaaaggooirrrtnddooeeeeosf----------- T 1. M (±) C ABLEEANNUMBERSEMOFADULTONOTRACHELUSNE, F.TICELLOL Water controlImidacloprid(2 L of water)at 1.75 L/ha 1Conotrachelus nenuphar18.8 (+6.1) a14.2 (±2.3) aNealiolus curculionis9 (±3.1) a11.2 (±3.7) a 1Means followed by the same letter are not significantly different accorαcurculionis, = 0.05; F = 1.87; P = 0.1210; df = 28.
Jenkins et al.: Predators and Parasitoids of Plum Curculio 439
effect of predation by ants. Peaches infested ear- not found in the current study. These include
lier in the season are small and usually abscise Nealiolus collaris (Brues), N. rufus (Riley), Trias-
and drop to the ground when infested with plum pis kurtogaster Martin, Bracon mellitor Say, B.
curculio larvae (Quaintance & Jenne 1912; De- politiventris (Cushman), B. variablilis (Pro-
tjen 1938). The larvae continue to develop in the vancher) (Hymenoptera: Braconidae), Tersilochus
fruit and can burrow directly from the fruit into conotracheli (Riley) (Hymenoptera: Ichneu-
the soil, probably reducing their chances of being monidae), Patasson conotracheli (Girault) (Hy-
encountered by foraging ants. Peaches infested menoptera: Mymaridae), Myiophasia aenea
later in the season do not abscise and larvae must Wiedemann, Cholomyia inaequipes Bigot
drop from the fruit to the ground. Subsequently, (Diptera: Tachinidae), and Pegomyia fusciceps
the summer generation of plum curculio in late Zett. (Diptera: Anthomyiidae) (Riley 1871; Quain-
season peaches may be more susceptible to ant tance & Jenne 1912; Snapp 1930; Armstrong
predation. The lack of significant difference be- 1958; Arnaud 1978; Krombein et al. 1979; Ted-
tween number of adults emerging from infested ders & Payne 1986). All of these species, with the
fruit that were chemically protected from preda- exceptions of T. conotracheli and B. politiventris,
tors and infested fruit that was accessible to pred- have been recorded in Georgia or Florida (Krom-
ators lends credence to the possibility that larvae bein et al. 1979). The vast majority of these para-
moving directly from infested fruit into the soil sitoids utilize a variety of other hosts, although
may suffer less predation than larvae that drop many of their hosts are often found in fruit
from the tree to the ground. (Krombein et al. 1979).
This is the first quantitative study of the impact Historically, percent mortality and percent
of certain predators on plum curculio, although mortality attributable to parasitism has varied
many anecdotal observations have been published greatly. Quaintance & Jenne (1912) report that
(Quaintance & Jenne 1912; Snapp 1930). Plum cur- the percent of adult plum curculio that emerged
culio larvae were monitored in close quarters from larvae ranged from 9% to 60% with a mean
(within 1 m) for accurate identification of predators. of 32% and that parasitism ranged from 0.7% to
Such proximity to the larvae precluded larger pred- 21% with a mean of 8.1%. Snapp (1930) reported
ators, such as birds and carabid beetles, although that the percentage of adults that emerged from
these may be additional and important sources of larvae ranged from 1.7% to 18.7% with a mean of
mortality. Although Solenopsis invicta was not 7.4%. Armstrong (1958) reported a range of para-
present in central Georgia at the time, Snapp sitized plum curculio larvae of 7.5 to 26.6 with an
(1930) and Quaintance & Jenne (1912) report that average of 20% parasitized. Even in our study,
Dorymyrmex bureni (reported as Dorymyrmex parasitism varied greatly between the 2 sites and
pyramica) was an important predator of larval presumably does so from year to year. This broad
plum curculio. Quaintance & Jenne (1912) list host range suggests that the abundance of alter-
ground beetles (Coleoptera: Carabidae) and a sol- nate hosts may play an important role in rates of
dier beetle, Chauliognathus pennsylvanicus (De parasitism of C. nenuphar.
Geer) (Coleoptera: Cantharidae), as important In summary, variation in mortality of plum
predators of larval plum curculio. Unfortunately, curculio is extremely high, as is variation in inci-
the soldier beetle appears to be in decline in Geor- dence of parasitism (Quaintance & Jenne 1912;
gia, perhaps as a result of predation by S. invicta Snapp 1930). The high levels of parasitism ob-
(Jenkins & Matthews 2003). Dissections of spade- served in Florida are possibly important sources
footed toads, Scaphiopus sp., revealed that they are of natural control of plum curculio populations.
consumers of plum curculio (J. Payne, pers. comm.). Further research is needed to elucidate mortality
Parasitism was of minimal importance as a factors and the causes of this variation. Under-
mortality factor in middle Georgia but appeared standing these factors may lead to better pest
to contribute significantly to the mortality of management strategies.
plum curculio in northern Florida. Though we re-
alize the estimates for parasitism in Florida are
ACKNOWLEDGMENTS
necessarily high, the sheer numbers obtained
need no statistical differentiation from those ob- Mention of trade names or commercial products in
tained in the Byron, GA, studies, considering that this article is solely for the purpose of providing specific
of more than 1000 larvae collected from peach information and does not imply recommendation or en-
and wild plums in central Georgia only 2 yielded dorsement by the U.S. Department of Agriculture. We
parasitoids. It is possible that the N. curculionis thank Betsy Stephens for enduring hours at a time star-
individuals collected in cone emergence traps in ing at plum curculio larvae and ants and Dr. Lionel
Stange of the Florida Department of Agriculture and
Monticello, FL, had used hosts other than C. nen-
Consumer Services, Division of Plant Industry for iden-
uphar. Indeed, N. curculionis is known to use
tifying specimens of Nealiolus curculionis. We thank
many other hosts (Krombein et al. 1979).
Drs. Amanda Hodges, Jim Dutcher, Robert Matthews,
There are a number of parasitoids that have and 3 anonymous reviewers for critical reviews of an
been recorded from plum curculio but that were earlier version of this manuscript.
440 Florida Entomologist 89(4) December 2006
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