The use of Neoaplectana carpocapsae (steinernematidae: Rhabditoidea) against adult yellowjackets (Vespula spp., vespidae: Hymenoptera)

JOURNAL

OF IXVERTCBRATE

19, 331334

PATHOLOGY

Neoaplectana Rhabditoidea)

carpocapsae

against spp.,

of Vector

Control and Solid

0.

~S~~i~er~e~a~~~a~~

(VespuE

Yellowjackets Hymen0 POIFXR,

Univmity

of Entomology, AND

Bureau

Adult

Vespidae: GEORGE

Division

(1972)

JR.

of California,

FRANKLIK

Berkeley 94’720

ENNIK

Waste

Management, Berkeley 94704

Received

December

California

Department

of Public

Heailhg

7, 1971

The yellowjacket workers of Vespula pennsylvanica and V. rufa atropilosa from Northern California and Vespula sp. from the Pu’etherlands were all susceptible to attack by the agriotos or Leningrad strain of Xeoaplectana carpocapsae. Infection occurred aft’er the adult yellowjackets ingested the third-stage infective nematodes that had been placed in a fruit concentrate or on sugar cubes. Most of the yellowjackets placed with nematode-infested nourishment died after the juveniles of dY. carpocapsae penetrated into their thorax and liberated cells of dchromobacter newatophiEus into their hemolymph. Since yellowjackets can often be a serious problem resulting in physical discomfort and economic losses, these nematodes offer a promising alternative to our existing chemical methods of controlling these insects. INTRODUCTION

Yellowjackets, or members of the genus Vespula, can be a serious problem because of their at.traction to foodstuffs. Aside from causing general annoyance, they produce painful stings that may result in serious allergic complications. Workers picking fruit, loading merchandise at meat processing plants, tending zoos, feeding molasses to livestock in feed lots, or performing similar tasks are often bothered by these insects. in 1968, an estimated $200,000 loss in California alone was at,tributed to the action of Yespula spp. in agricultural operations (Hawthorne, 1969). Although this figure probably ineludes loss from other wasps as well, it is still considered by us a conservative estimate even for damage by Vespula spp. Also, estimates of losses att’ribut’able to ,the presence of yellow-jackets at’ some privat,e California resorts range up to $5,000 annually . 331 Copyright

Q 1972 by Academic

Press, Inc

These mounting economic losses, in addition to the immeasurable discomfort experienced by people in residential, rurd 1 and recreat(iona1 areas, makes it desirable to have some safe and reliable methods for control of vespid wasps. Control progress have for the most part been direct’ed at destroying nests or trapping the workers. More recent approaches Milize a bail, system where an insect’icide is added to an at’tractive food, which is collected by the foraging workers and taken back tcj l-he nest. Whole nest’s can be weakened and destroyed when the poisons are introduced to developing Vespula larvae. However, this necessitates placing poisoned food, oft,en attractive to other animals, in exposed eavironplaces and risking undesirable mental cont,amination. MATERIALS

AND

M~TEIODS

Adult workers of Yespula ~~~~&nnicre were collected from 3 nests near Martinr*z

332

POINAR,

TABLE MORTALITY FEEDING

Day

Control carton 1

No.

1 pensylvanica WORKERS PUNCH CONTAINING carpocapsaea

OF Vespula ON HAWAIIAN Neoaplectana Nest

JR.,

1

Nest

Nematode treated

Contrn1

Carton 2

Carton 3

0 0 13” 5 3 0 1 0

0 2 12 5” 1 0 3 2

22

25

ton 4

No.

2

Nematode treated Carton 5

Car1ton 6

I-

0 (Nb 1

2 W) 3 4 09 5

6 09 7 Mortality

0 0 3

9

21

O 1C 0 10 1 1 5 7 25

a Number per carton = 25. b Days on which samples were treated with nematodes. c One specimen drowned in Hawaiian punch.

in Northern California by placing a fly emergence cage over the nest opening, anesthetizing the yellowjackets with COz, and then placing them into separate gallon ice cream cartons. The carton lids were replaced with 18 mesh cloth screen and nourishment was placed in a small dish glued to the bottom. The adults were maintained under laboratory conditions established by Keh (1971). The nematodes used were the agriotos or Leningrad strain of Neoaplectana carpocapsae (see Poinar and Veremtshuk, 1970) that originated from the Soviet Union. This strain, which interbreeds with the DD-136 strain of N. carpocapsae, also carries the bacterium Achromobacter nematophilus in the gut lumen of the infective stage juveniles (Poinar et al., 1971). These nematodes were maintained on larvae of the greater wax moth, Galleria mellonella, in the laboratory and infective stage juveniles were stored at 10°C.

AND

ENNIK

For the first set of infection experiments, 6 cartons, each containing 25 specimens of V. pensylvanica, were used (3 cartons with specimens from nest No. 1 and 3 with adults from nest No. 2). A mixture of 0.5 ml of infective stage nematodes (approximately 3,00O/ml) and 0.5 ml of Hawaiian Punch@1 were placed every other day in the small dish in the bottom of 4 cartons. The other 2 cartons served as controls and received a l-ml mixture of distilled water and Hawaiian Punch every other day. In the second set of infection experiments, a sugar cube saturated with a 1 ml suspension of infective stage juveniles in distilled water containing approximately 6,000 nematodes was placed in each of 3 cartons with 25 specimens of V. pensylvanica from nest No. 3. A carton of control wasps contained a sugar cube saturated with distilled water. In the above experiments, observations were made daily for 1 wk after introducing the nematodes. Workers of Vespula rufa atropizosa collected from Pittsburg, California, and Vespula spp. collected during the summer in the Netherlands were also placed in cages containing Hawaiian Punch and sugar water, respectively, and infective stage nematodes. Because of the limited numbers of specimens used, these latter tests simply served to determine if infection could occur. RESULTS

Vespula workers were observed sampling the Hawaiian Punch at various intervals, but appeared more eager to feed on the sugar cubes. The nematodes remained evenly distributed in the Hawaiian Punch, although a sticky crust soon formed on the surface and may have interfered with the normal uptake of nematodes by the yellowjackets. The numbers of dead V. pensylvanica in treated and control cartons are shown in Tables 1 and 2. Nematodes were found in the 1 A fruit concentrate nolds Foods, Inc., New

distributed York, New

by R. J. ReyYork 10017.

Weoaplectana AND Vespula treated yellowjackets at the time of bheir death. When, for some unknown reason, nematodes could not, be found in freshly killed wa.sps, the presence of a septicemia indicated that cells of AchromoDacter n,ematophilus had been introduced. When introduced into the hemocoel, this bactBerium is known to multiply and kill insects (Poinar and Thomas, 1967). In fact, most treatment-killed wasps had only one or two nematodes in their hemocoel, but as long as the bact’erium was liberated, mortalit’y occurred. In several instances, when dead yellowjackets that had remained in a humid chamber for several days were dissected, breeding colonies of N. ca?pocapsae occurred in the cadavers. The nematodes entered the thorax of the yellowjacket’ through the digestive tract. The restricted opening of the intestine in the gaster may have prevented them from being readily passed into the abdomen. Similar results were obtained with V. 7. atropilosa and Dutch-collected Vespula spp. workers. In an experiment set up wit,h 2 cartons containing the former species with nematodes in Hawaiian Punch, 15 out of 18 and 21 out of 21 wasps were killed after 7 dags. Ko evidence of nematodes or a sept,icemia was found in the yellowjackets dying in the control cartons. However, an unidentified braconid, which was recovered from about, 4% of the workers from all samples, contributed to some mortality.

333 TABLE

MORTALITY

Vesp,u!a

OF

2 pensylvanicu

WORI~RS

FEEDING ON SUGARYCUBES COVEREII WITE 3eoaplectana

carpocapsaeQ

Nest No. 3 Day

Control carton 1

0 (N)b 1 2 (N) 3 4 (S) : (N) 7 Mortality

Nematode

treated

Carton 2

Carton 3

0 1

0 1

0

0

3 1 2 0

8 8 3 30

1 11 7 3 0

2 13 6 0 02

1

2 25

1 23

0 23

8

a Number per carton = 25. b Days on which samples were nematodes.

treated

Cartop -1

with

Alt,hough there is no indication that infect’& workers can in turn infect other members of the nest, the well-being of the developing larvae and of the nest in general will suffer if a substant,ial number of workers are removed. There is a possibility that’ honey bee workers may also be attracted to nematodetreated sugar cubes if they are left exposed in the field. IIowever, earlier findings, surnmarized by Niklas (1967), show that X. carpocapsae produces no ill effect,s when added to sugar water given to workers of Apis mellifera.

DISCUSSION

Ko widespread pathogens of Vespula spp. have been reported and the few cases of nematode infections in natural populations of VespuEa spp. indicate that these are only of chance occurrence (Cobbold, 1588; Welch, 1958). Previous reports on the use of neoaplecbanid nematodes to kill Vespula adults are also lacking and, we feel that under certain conditions, these nematodes have potential in the biological control of these insects.

REFERENCES S. 1888. On Ximondsia paradoxa and probable aflinity with Sphaerularia Trans. Linn. Sot. London, 2, 357361. HAWTHORNE, R. M. 1969. Estimat,ed damage and crop loss caused by insect/mite pests-1968; California Department, of Agriculture. Bureau of Entomology, unpublished report, II pp. I&H, B. 1971. Maintenance of captured workers of Vesp~ula pensyEvanica (Hymenoptera : Vespidae) in the laboratory. Cnlij. Vector Views, in press. NIKLAS, 0. F. 1967. Die Kematoden D13-136 (XeoCOBBOLD,

on its bombi.

T.

334

POINAR,

JR.,

sp.) und Neoaplectana carpocapsae Weiser, 1955 (Rhabditoidea) als Insektenparasiten. Eine Literaturtibersicht. Mitt. Biol. Bundesanst. LandForstwirt. BerlinDahlem, 124, 40 pp. PoINAR,G.O.,JR., AND THOMAS, G.M.1967. The nature of AchromoSacter nematophilus as an insect pathogen. J. Invertebr. Pathol., 9, 510514. POINAR, G. O., JR., AND VEREMTSHUK, G. V. 1970. A new strain of entomopathogenic nematodes and geographical distribution of Neoaplectana carpocapsae Weiser (Rhabdiaplectana

AND

ENNIK

tida, Steinernematidae). Zool. J., 49, 966-969. (In Russian.) POINAR, G. O., JR., THOMAS, G. M., VEREMTSHUK, G. V., AND PINNOCK, D.E.1971.Further characterization of Achromobacter nematophilus from American and Soviet populations of the nematode Neoaplectana carpocapsae Weiser. Int. J. Syst. Bacterial., 21, 78-82. WELCH, H. E. 1958. Agamomermis pachysonza (Linstow, 1905) N. Comb. (Mermithidae: Nematoda), a parasite of social wasps. Insoctes

Sot.,

5, 353-355.