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Laboratory infection of terrestrial isopods (Crustacea: Isopoda) with neoaplectanid and heterorhabditid nematodes (Rhabditida: Nematoda)
JOURNAL
OF INVERTEBRATE
Laboratory
PATHOLOGY
45,
24-27
(1985)
infection of Terrestrial lsopods (Crustacea: Isopoda) Neoaplectanid and Heterorhabditid Nematodes (Rhabditida: Nematoda) GEORGE 0. POINAR, JR. AND MICHAEL
Department
qf Entomological
Sciences.
University
of California,
with
PAFF Berkeley,
California
94720
Received January 12, 1984: accepted February 15. 1984 Under laboratory conditions, the nematodes Neoaplectana curpocap.sue and Heterorhuhditis were able to infect and develop inside the hemocoel of terrestrial isopods belonging to the genus Porcellio. Armidillidium vu/gave was also infected by N. carpocapsae, but this host was less susceptible than Porcellio. Results show that. under suitable ecological conditions. it would be feasible to utilize N. carpocapsae as a biological control agent of sowbugs (Porcellio spp.). This is the first report showing the ability of neoaplectanids and heterorhabditids to invade representatives of the Crustacea. 0 1985 Academic PESS, Inc KEY WORDS: Porcellio spp.; Armidilliduim taulgare; Neoaplectana ccwpoc’opsae: N. gltrsuri: Heterorhabditis heliothidis; nematodes: terrestrial isopods; biological control. heliothidis
Entomogenous
nematodes of the genera and Heterorhabditis are being commercially produced as biological control agents to be used against a variety of insects (Poinar, 1983). These nematodes attack a wide range of insects, and have been restricted to this class of invertebrates, except for a single report of infection occurring in the garden symphylan, Scutigerella immaculata (see Swenson, 1966). Tests with N. carpocapsae against mites, millipeds, slugs, crustaceans, and earthworms have proven negative (Poinar, 1979; Capinera et al., 1982). Terrestrial isopods are mainly scavengers, feeding on decaying plant and animal material. However, when their numbers are high, they can cause damage to fruits and vegetables. They may destroy seedlings, especially in greenhouses, of sweetpeas and a number of flowering plants. When they are regarded as pests, various insecticides have been recommended for their control. Laboratory studies reported here show that some species of Neoaplectana and Heterorhabditis will infect and kill terresNeoaplectana
24 0022-201 Copyright All rights
l/85
%I so
6 1985 by Academic Prerl. Inc. of reproduction m any form recerved.
trial isopods of the genera Porcellio and Armidillidium. MATERIALS
AND METHODS
Initial studies tested the susceptibility of terrestrial isopods to three species of nematodes, e.g., N. carpocapsae (a cross between the DD-136 and the Breton strain); N. glaseri; and H. heliothidis. Tests with each of the three nematode species listed above were made with sowbugs (a mixture of Porcellio scaber americanus, P. dilaTABLE PERCENTAGE spp.)
INFECTED
MORTALITY WITH
I OF SOWBUGS
ENTOMOGENOUS
(Porcellio NEMATODES
Percentage Mortality Nematode Neoaplectana carpocapsae Neoaplectana glaseri Heterorhabditis heliothidis
Control
D3”
D4
DS
Dl2
64
80
84
100
0
0
0
4
28
48
68
100
0
0
0
29
U Days after 25 sowbugs were placed together with 50.000 of each nematode species.
LAB INFECTION
tutus, and
OF ISOPODS WITH NEMATODES
P. laevis). The sowbugs were
collected from the field and held in a logallon terrarium containing 5 cm of damp soil on the bottom. They were fed lettuce and dried leaves.
FIG. 1. A parasitic female of Neoapiectnna in the body wall of an infected Porcellio spp. FIG. 2. Dissection of an infected Porcellio aplecrma carpocnpsne 5 days after infection.
25
Infection experiments were conducted in 2-cm-deep, 9-cm-diameter Petri dishes filled to a depth of 1 cm with damp field soil. Each dish contained an area of approximately 62 cm*. Twenty sowbugs were
carpocapsae (arrow) emerging from an opening made 4 days after infection. (35 x ). spp. having released three parasitic females of Neo(20 x ).
26
POINAR AND PAFF
EFFECT
OF DIFFEKENT
TABLE 2 CONCENTRATIONSOF Neoapktunu ctry~oc~lpaue PILLBUGS ~Armidillidium w/.garr)
ON SOWBUGS (Porcellio
spp.)
ANII
Percentage mortality Nematode concentration (nematodes/cm*) 390 1940 3880
Control
Sowbugs
Pillbugs
D2”
D4
D8
D2
D4
DX
17ah 22a’ 52b oc
33a 35a 70b oc
72a 82a 88a
oc 2C SC
3c
5C IOa
22a 38a 63b
6c
oc
IC
8c
a Days after 20 isopods were placed together with nematodes. b Average of three replications. c Means not flanked by the same letter are significantly different at the 1% level.
placed in each dish, respectively, and several small pieces of lettuce were added as food. Approximately 50,000 infective-stage juveniles of each nematode species were added to the containers. Additional experiments tested three different concentrations of N. carpocupsae, which proved to be the most effective of the three nematodes used in the initial experiment. These tests were conducted against sow bugs and pill bugs, Armidillidium vulgare. Three replications of each nematode concentration for each of the two hosts were made. Data were analyzed by two way analysis of variance and Duncan’s multiple range test. RESULTS
The results of infecting
sowbugs with N.
carpocapsae, N. glaseri, and H. heliothidis
are presented in Table 1. After 12 days, all of the sowbugs in the dishes with N. curpocapsae and H. heliothidis were dead and contained developing nematodes in their body cavities (Figs. 1, 2). Cells of the symbiotic bacteria, Xenorhabdus nematophilus from N. carpocapsae and X. luminescens from H. heliothidis, were present in the hemolymph of the infected sowbugs. Results of different concentrations of N. carpocupsae on sowbugs and pillbugs are shown in Table 2. In the case of sowbugs, an increased dosage insured an initial
quicker kill, but the difference between high and low concentrations was insignificant on Day 8. Nematodes developed to the adult stage, mated, and produced a few infective juveniles inside the isopod cadavers. DISCUSSION
This is the first instance where neoaplectanid and heterorhabditid nematodes have been shown to infect and develop in members of the class Crustacea. It is clear that these terrestrial isopods, although killed by the nematodes, are not as suitable hosts as most insects because the intersegmental membranes break down soon after death and the body cavity is quickly invaded by foreign organisms (bacteria and microbotrophic soil nematodes), which restrict nematode development. Thus, only about 30% of the infected isopods produced infective stages of the test nematodes, and the numbers were relatively low (several hundred) in comparison with similarly sized insects (where several thousand would be expected). It is also clear that N. glaseri is ineffective against these and probably other terrestrial isopods. Likewise, it is possible that other species and strains of Neouplectana and Heterorhabditis might be even more effective pathogens of Porcellio and Armidillidium.
LAB INFECTION
OF ISOPODS WITH NEMATODES
ACKNOWLEDGMENTS The authors thank G. Thomas for general assistance and M. A. Miller for identification of the terrestrial isopods.
REFERENCES J. L., BLUE, S. L., AND WHEELER, G. S. 1982. Survival of earthworms exposed to N. carpocapsae nematodes. J. Inl,errebr. Parhol.. 39, 419-421.
CAPINERA,
27
POINAR, G. 0.. JR. 1979. “Nematodes for Biological Control of Insects.” CRC Press, Boca Raton. Florida. POINAR, G. O., JR. 1983. Recent developments in the use of nematodes in the control of insect pests. In “Proceedings, 10th Int. Congress Plant Protection, Brighton, England,” Vol. 2, pp. 751-758. SWENSON, K. G. 1966. Infection of the garden Symphylan, Scurigerella immaculata, with the DD-136 nematode. J. Invertebr. Pathol., 8, 133-134.
OF INVERTEBRATE
Laboratory
PATHOLOGY
45,
24-27
(1985)
infection of Terrestrial lsopods (Crustacea: Isopoda) Neoaplectanid and Heterorhabditid Nematodes (Rhabditida: Nematoda) GEORGE 0. POINAR, JR. AND MICHAEL
Department
qf Entomological
Sciences.
University
of California,
with
PAFF Berkeley,
California
94720
Received January 12, 1984: accepted February 15. 1984 Under laboratory conditions, the nematodes Neoaplectana curpocap.sue and Heterorhuhditis were able to infect and develop inside the hemocoel of terrestrial isopods belonging to the genus Porcellio. Armidillidium vu/gave was also infected by N. carpocapsae, but this host was less susceptible than Porcellio. Results show that. under suitable ecological conditions. it would be feasible to utilize N. carpocapsae as a biological control agent of sowbugs (Porcellio spp.). This is the first report showing the ability of neoaplectanids and heterorhabditids to invade representatives of the Crustacea. 0 1985 Academic PESS, Inc KEY WORDS: Porcellio spp.; Armidilliduim taulgare; Neoaplectana ccwpoc’opsae: N. gltrsuri: Heterorhabditis heliothidis; nematodes: terrestrial isopods; biological control. heliothidis
Entomogenous
nematodes of the genera and Heterorhabditis are being commercially produced as biological control agents to be used against a variety of insects (Poinar, 1983). These nematodes attack a wide range of insects, and have been restricted to this class of invertebrates, except for a single report of infection occurring in the garden symphylan, Scutigerella immaculata (see Swenson, 1966). Tests with N. carpocapsae against mites, millipeds, slugs, crustaceans, and earthworms have proven negative (Poinar, 1979; Capinera et al., 1982). Terrestrial isopods are mainly scavengers, feeding on decaying plant and animal material. However, when their numbers are high, they can cause damage to fruits and vegetables. They may destroy seedlings, especially in greenhouses, of sweetpeas and a number of flowering plants. When they are regarded as pests, various insecticides have been recommended for their control. Laboratory studies reported here show that some species of Neoaplectana and Heterorhabditis will infect and kill terresNeoaplectana
24 0022-201 Copyright All rights
l/85
%I so
6 1985 by Academic Prerl. Inc. of reproduction m any form recerved.
trial isopods of the genera Porcellio and Armidillidium. MATERIALS
AND METHODS
Initial studies tested the susceptibility of terrestrial isopods to three species of nematodes, e.g., N. carpocapsae (a cross between the DD-136 and the Breton strain); N. glaseri; and H. heliothidis. Tests with each of the three nematode species listed above were made with sowbugs (a mixture of Porcellio scaber americanus, P. dilaTABLE PERCENTAGE spp.)
INFECTED
MORTALITY WITH
I OF SOWBUGS
ENTOMOGENOUS
(Porcellio NEMATODES
Percentage Mortality Nematode Neoaplectana carpocapsae Neoaplectana glaseri Heterorhabditis heliothidis
Control
D3”
D4
DS
Dl2
64
80
84
100
0
0
0
4
28
48
68
100
0
0
0
29
U Days after 25 sowbugs were placed together with 50.000 of each nematode species.
LAB INFECTION
tutus, and
OF ISOPODS WITH NEMATODES
P. laevis). The sowbugs were
collected from the field and held in a logallon terrarium containing 5 cm of damp soil on the bottom. They were fed lettuce and dried leaves.
FIG. 1. A parasitic female of Neoapiectnna in the body wall of an infected Porcellio spp. FIG. 2. Dissection of an infected Porcellio aplecrma carpocnpsne 5 days after infection.
25
Infection experiments were conducted in 2-cm-deep, 9-cm-diameter Petri dishes filled to a depth of 1 cm with damp field soil. Each dish contained an area of approximately 62 cm*. Twenty sowbugs were
carpocapsae (arrow) emerging from an opening made 4 days after infection. (35 x ). spp. having released three parasitic females of Neo(20 x ).
26
POINAR AND PAFF
EFFECT
OF DIFFEKENT
TABLE 2 CONCENTRATIONSOF Neoapktunu ctry~oc~lpaue PILLBUGS ~Armidillidium w/.garr)
ON SOWBUGS (Porcellio
spp.)
ANII
Percentage mortality Nematode concentration (nematodes/cm*) 390 1940 3880
Control
Sowbugs
Pillbugs
D2”
D4
D8
D2
D4
DX
17ah 22a’ 52b oc
33a 35a 70b oc
72a 82a 88a
oc 2C SC
3c
5C IOa
22a 38a 63b
6c
oc
IC
8c
a Days after 20 isopods were placed together with nematodes. b Average of three replications. c Means not flanked by the same letter are significantly different at the 1% level.
placed in each dish, respectively, and several small pieces of lettuce were added as food. Approximately 50,000 infective-stage juveniles of each nematode species were added to the containers. Additional experiments tested three different concentrations of N. carpocupsae, which proved to be the most effective of the three nematodes used in the initial experiment. These tests were conducted against sow bugs and pill bugs, Armidillidium vulgare. Three replications of each nematode concentration for each of the two hosts were made. Data were analyzed by two way analysis of variance and Duncan’s multiple range test. RESULTS
The results of infecting
sowbugs with N.
carpocapsae, N. glaseri, and H. heliothidis
are presented in Table 1. After 12 days, all of the sowbugs in the dishes with N. curpocapsae and H. heliothidis were dead and contained developing nematodes in their body cavities (Figs. 1, 2). Cells of the symbiotic bacteria, Xenorhabdus nematophilus from N. carpocapsae and X. luminescens from H. heliothidis, were present in the hemolymph of the infected sowbugs. Results of different concentrations of N. carpocupsae on sowbugs and pillbugs are shown in Table 2. In the case of sowbugs, an increased dosage insured an initial
quicker kill, but the difference between high and low concentrations was insignificant on Day 8. Nematodes developed to the adult stage, mated, and produced a few infective juveniles inside the isopod cadavers. DISCUSSION
This is the first instance where neoaplectanid and heterorhabditid nematodes have been shown to infect and develop in members of the class Crustacea. It is clear that these terrestrial isopods, although killed by the nematodes, are not as suitable hosts as most insects because the intersegmental membranes break down soon after death and the body cavity is quickly invaded by foreign organisms (bacteria and microbotrophic soil nematodes), which restrict nematode development. Thus, only about 30% of the infected isopods produced infective stages of the test nematodes, and the numbers were relatively low (several hundred) in comparison with similarly sized insects (where several thousand would be expected). It is also clear that N. glaseri is ineffective against these and probably other terrestrial isopods. Likewise, it is possible that other species and strains of Neouplectana and Heterorhabditis might be even more effective pathogens of Porcellio and Armidillidium.
LAB INFECTION
OF ISOPODS WITH NEMATODES
ACKNOWLEDGMENTS The authors thank G. Thomas for general assistance and M. A. Miller for identification of the terrestrial isopods.
REFERENCES J. L., BLUE, S. L., AND WHEELER, G. S. 1982. Survival of earthworms exposed to N. carpocapsae nematodes. J. Inl,errebr. Parhol.. 39, 419-421.
CAPINERA,
27
POINAR, G. 0.. JR. 1979. “Nematodes for Biological Control of Insects.” CRC Press, Boca Raton. Florida. POINAR, G. O., JR. 1983. Recent developments in the use of nematodes in the control of insect pests. In “Proceedings, 10th Int. Congress Plant Protection, Brighton, England,” Vol. 2, pp. 751-758. SWENSON, K. G. 1966. Infection of the garden Symphylan, Scurigerella immaculata, with the DD-136 nematode. J. Invertebr. Pathol., 8, 133-134.