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1979 Evaluation of Ooencyrtus Submetallicus (Howard) and Trissolcus Basalis (Wollaston) as Egg Parasites of Nezara Viridula (Linnaeus). Seung Chan Lee Louisiana State University and Agricultural & Mechanical College
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Recommended Citation Lee, Seung Chan, "Evaluation of Ooencyrtus Submetallicus (Howard) and Trissolcus Basalis (Wollaston) as Egg Parasites of Nezara Viridula (Linnaeus)." (1979). LSU Historical Dissertations and Theses. 3340. https://digitalcommons.lsu.edu/gradschool_disstheses/3340
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University M icrofilms International 300 N. ZEEB ROAD. ANN ARBOR. Ml 48106 18 BEDFORD ROW. LONDON WC1R 4EJ. ENGLAND 7921970 LEE, 8EUNG CHAN EVALUATION OF OOENCYRTU8 8UBMETALLICUS (HOWARD) AND TRX880LCU8 BA8ALX6 (W0LLA8T0NJ A S E G G i PARASITES OF NEZARA VXRXDULA (LINNAEUS). THE LOUISIANA STATE UNIVERSITY AND AGRICULTURAL AND MECHANICAL COL.# PH.D.# 1979
University Micninlms International s o o n, z e e b r o a d, a n n a r b o r , m m s i m EVALUATION OF OOENCYRTUS SUBMETALLICUS (HOWARD) AND TRISSOLCUS B ASA LIS (WOLLASTON) AS EGG PARASITES OF NEZARA VIRIDULA (LINNAEUS)
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Entomology
By Seung Chan Lee B.S. , Seoul National University Korea, I960 M. S. , University of Canterbury New Zealand, 1968 May, 1979 ACKNOWLEDGEMENTS
The author sincerely wishes to express his gratitude to his
major professor, Dr. L. D. Newsom, for contributing assistance and supervision throughout the period of research, and especially
for valuable advice and criticism during the writing of this manu
script. Sincere appreciation is expressed to the members of his
graduate committee, Drs. J. B. Graves, C. D. Steelman, J. B.
Chapin and M. C. Rush for their advice and constructive criticism of the manuscript.
Gratitude is extended to Dr. B. R. Farthing for his advice and assistance in the statistical analyses of the data.
The author is indebted to the Office of Rural Development,
Republic of Korea and Institute of International Education, United
States of America, for granting the financial support under the
AID loan plan for his doctoral program.
Special thanks are due his wife, children and all his family for their patience, understanding and constant encouragement throughout this study. TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS...... ii
TABLE OF CONTENTS...... iii
LIST OF TABLES ...... v
LIST OF FIGURES...... vii
ABSTRACT...... viii
INTRODUCTION...... 1
REVIEW OF LITERATURE...... 3
Taxonomic Status of the Parasites...... 3 T. basalis and O. submetallicus as Pentatomid Egg Parasites ...... 4 Effect of Food and Mating on Biology of Parasites 6 Reproductive Behavior of Parasites...... 7 Criteria for the Success of Biological Control A g e n ts...... 9
MATERIALS AND METHODS...... 12
Laboratory Studies...... 12 Source and Maintenance of Parasite Culture...... 12 Developmental Period of Parasites...... 14 Survival and Superparasitism...... 14 Effect of Presence and Absence of Food and Host Eggs on Longevity of Adult Parasites 15 Genetic Strains...... 16 Sex Ratio ...... 17
iii Page
• Host Preference...... 17 Competitive Interaction...... 18 Field Evaluation...... 19
RESULTS AND DISCUSSION...... 23
Laboratory Studies...... 23 Developmental Period...... 23 Survival and Superparasitism...... 27 Adult Longevity...... 30 Genetic Strains...... 34 Sex R a tio ...... 35 Host Preference...... 36 Competitive Interaction...... 40 Field Evaluation...... 40
GENERAL DISCUSSION...... 46
CONCLUSIONS...... 49
REFERENCES CITED ...... 51
APPENDIX ...... 56
VITA ...... 91
iv LIST OF TABLES
TABLE Page
I. Developmer lal period from oviposition to emergence of T. basalis in three successive generations at different temperatures and 14L:I0D...... 24
II. Developmental period from oviposition to emergence of O. submetallicus in three successive generations at different tempera tures and 14L:10D...... 25
III. Mean percent of emergence in five successive generations of T. basalis at different tempera tures and 14L:10D...... 28
IV. Mean percent of emergence in five successive generations of T. basalis at different tempera tures and 10L:14D...... 28
V. Mean percent of emergence in five successive generations of O. submetallicus at different temperatures and 14L:10D...... 29
VI. Mean percent of emergence in five successive generations of O. submetallicus at different tem peratures and 10L:14D ...... 29
VII. Mean adult longevity of male T. basalis in the presence and absence of h o n e...... y 31
VIII. Mean adult longevity of female T. basalis in the presence and absence of honey and host eggs (N. viridula)...... 31
IX. Mean adult longevity of male O. submetallicus in the presence and absence of honey...... 32
v TABLE Page
X. Mean longevity of female O. submetallicus in the presence and absence of honey and host eggs (N. viridula)...... 32
XI. Mean sex ratio of O. submetallicus in nine successive generations at different tempera tures and 14L:10D...... 36
XII. Percent parasitism of the eggs of several pentatomid species by T. basalis...... 39
XIII. Percent parasitism of the eggs of several pentatomid species by O. submetallicus 39
XIV. Competitive interaction between O. submetallicus and T. b a s a lis...... 41
XV. Percent parasitism of host eggs exposed to parasites for three days in preliminary field trials during 1977 ...... 42
XVI. Mean percent parasitism of egg m asses by released parasites with regard to directions from the central release point in the experi mental area during 1978...... 44
XVII. Mean percent parasitism of egg masses by released parasites with regard to distances from the central release point in the experi mental area during 1978...... 45
vi LIST OF FIGURES
FIGURE Page
1. Developmental period of two parasite species in relation to different tem peratures...... 26
2. Influence of temperature on sex ratio of O. submetallicus ...... 37 ABSTRACT
An egg parasite, Ooencyrtus submetallicus (Howard) was imported from Trinidad and was maintained at the Department of
Entomology, Louisiana State University. This species was ' compared with the indigenous egg parasite, Trissolcus basalis
(Wollaston). Some biological aspects of the parasites were investi gated, and their effectiveness as regulative agents of Nezara viridula (Linnaeus) was compared in the laboratory and field.
Developmental durations of both parasite species were greatly reduced when temperatures were increased, whereas change in photoperiod did not have any influence. Successive generations of the parasites were maintained under temperatures of 21, 25 and
29° C with regim es of 14L:10D and 10L:14D.
Males of T. basalis emerged earlier from the host eggs than females, whereas males of O. submetallicus started emerging later than the females but completed emergence before all females had em erged.
Adult longevity of parasites reared in the laboratory was significantly increased (P< 0.01) when they were fed on honey.
Ovipositional stress in the presence of honey decreased their
v iii longevity significantly (P<0.01). O. submetallicus showed super- parasitism. Females of O. submetallicus and T. basalis oviposited m ore than a single egg per host egg on several occasions. When a host egg was parasitized by T. basalis only one parasite emerged, whereas in the case of O. submetallicus a mean of 1.24 parasites/egg emerged. Both species often oviposited in the same host egg.
However, individuals of no more than one species were ever observed to emerge from parasitized eggs. An arrhenotokous strain of O. submetallicus was found in contrast to previously studied thelyotokous populations. In the arrhenotokously reproducing strain, when tempe rature was increased more male progeny were produced. A signi ficantly negative correlation was found between sex ratio and temperature (r = -0.617**).
In preliminary field trials in a 144 m area where 10,000 parasites of both species were released, no significant difference between parasitization of stink bug eggs by the two species was
7 observed (P> 0. 05). However, in a 400 m area, T. basalis para sitized more egg masses than O. submetallicus (P<0.05). Results of these studies indicate that there would be no advantage gained in regulation of stink bug populations by importation and colonization of O. submetallicus. INTRODUCTION
The southern green stink bug, Nezara viridula (Linnaeus), is a polyphagous insect which feeds on three families of mono cotyledons and 29 families of dicotyledons with preference for
Gvamineae and Leguminosae, respectively (Hoffman, 1935). It is cosmopolitan in its distribution (Cumber, 1964; DeWitt and Godfrey,
1972; DeBach, 1974), and causes considerable reductions in quality, germination and yield of soybeans in Louisiana (Jensen and Newsom,
1972).
Insecticides used to control this pest result in a considerable expenditure to farmers, have deleterious effects on beneficial insects, and add to environmental pollution problems. Therefore, there is a need to develop safer and more economical control measures. The use of insecticides could be reduced by integration of various control procedures into a harmonious system. One of the important components in such an 'Integrated Control1 scheme would be the use of biological control agents. The native biological control agents in Louisiana soybean ecosystems provide some control; however, the introduction of new parasites has the possibi lity of giving additional or complete control. 2
Over 253 successful cases of biological pest control programs were recorded through the importation and release of natural
enemies (DeBach, 1974). van den Bosch and Messenger (1973) listed about 75 target species of insect pests which were completely or substantially controlled in this way.
Ooencyrtus submetallicus (Howard), (Encyrtidae : Hymenoptera), is an important egg parasite of N. viridula in Trinidad (Wilson and
Woolcock, I960; Davis and K rauss, 1963). This parasite was imported from Trinidad in 1975 and is being maintained in the laboratories of the Department of Entomology, Louisiana State University, Baton
Rouge, for the purposes of the present study.
The objectives of this study were: (1) to investigate some biological characteristics of the egg parasites, O. submetallicus and Trissolcus basalis (Wollaston), (Scelionidae : Hymenoptera), a parasite that is widely distributed in Louisiana and other southern states; (2) to determine the host preference of the two parasites with regard to five pentatomid species; (3) to investigate the beha vioral interactions between the two species; and (4) to evaluate their effectiveness as control agents of N. viridula, both in the laboratory and field. REVIEW OF LITERATURE
Taxonomic Status of the two Parasites
Ooencyrtus submetallicus, a hymenopterous species, was first described as Encyrtus submetallicus by Howard (1898) from specimens collected in Guanada, West Indies. Gahan (1927) placed the species in the genus Ooencyrtus. He indicated that Syrphagus submetallicus (Ashmead, 1900) was a synonym for O. submetallicus based on an examination of the type of this species in the British
Museum. The species has since been recorded from the adjacent islands of Saint Vincent, Barbados, and Trinidad, and is an endo- phagous egg parasite of the southern green stink bug, Nezara viridula
(Wilson and Woolcock, I960).
Wollaston (1858) described the egg parasite, Trissolcus basalis, from specimens collected on the island of Madeira.
Kamal (1937) stated that T. basalis is a solitary, arrhenotokous parasite which completes development from egg to adult in the host egg. The features of adult reproductive behavior were described by Wilson (1961). Thomas (1972) listed synonyms for T. basalis:
Asolcus basalis (Wollaston), Microphalus megacephalus (Ashmead),
Telenomus basalis (Wollaston), Telenomus maderensis (Wollaston), 4
Telenomus megacephalus (Ashmead) and Telenomus piceipes (Dodd).
T. basalis and O. submetallicus as Pentatomid Egg Parasites
Cumber (1964) reported that T. basalis was a polyphagous
parasite known to adapt to the eggs of five pentatomid species in addition to those of N. viridula. These five species were;
Cermatulus nasalis (Westwood), Oechalia schellenbergii (Guerin-
Meneville), Dictyotus caenosus (Westwood), Glaucias amyoti (White),
Antestia orbona (Kirkpatrick) and Cuspicona simplex Walker. In addition, Thomas (1972) reported that the percentage of parasitism by T. basalis was more or less uniform in the eggs of N. viridula
(L .), Euschistus servus (Say), Thyanta pallidovirens (Stal) and
A crosternum hilare (Say).
Australia was the first country to initiate biological control against N. viridula by using the egg parasite, T. basalis, which was imported from Egypt in 1933. As soon as T. basalis was well colonized in Australia, the importance of N. viridula as a pest was diminished, and outbreaks were less frequent and less severe than they were formerly (Wilson, 1963; Ratcliffe, 1965). Subsequently,
T. basalis was introduced from Australia into New Zealand in 1948
(Cumber, 1951), and from Trinidad and Florida into Hawaii in 1961
(Davis and Krauss, 1963). The successful establishment of this species was recorded with substantial control of the southern green stink bug in both countries (Cumber, 1964; Davis and Krauss, 1966). 5
Similarly, T. basalis was imported into a number of other Pacific islands including Tonga (1941), New Caledonia (1942), and Samoa
(1953) with establishment recorded in each case but the results of control achieved are not available (DeBach, 1974).
An importation of O. submetallicus from Trinidad was made into Australia in 1952 (Wilson, I960), and also into Hawaii in 1963
(Davis and K rauss, 1963), for the biological control of N. viridula.
No detailed results have been reported.
Effect of Temperature on Development of Parasites
Temperature may affect longevity, fecundity and speed of development of an insect. Chapman (1971) stated that an increase in temperature generally increases the metabolic rate of insects. He concluded that longevity is usually greatest at the lowest temperature at which an insect can normally feed, since the basic expenditure of energy is at a minimum . In general, the effects of temperature on development have been clearly described by Busvine (1955), Brust
(1967), and Hanec and B rust (1967).
Sisli and Bosgelmez (1973) reported that generation time of
N. viridula were equal when it was reared at 23°C and a 10 or 18-hr photoperiod. Beck (1966) concluded that although temperature was a major factor affecting the photoperiodic induction of diapause, temperature extremes might lead to a bypassing of the photoperiodic response system, or they might shift the critical daylength to a 6 point lying outside the range of photoperiods to which the insects are exposed.
Clausen (1962) stated that under optimum temperature conditions for Ooencyrtus malayensis Ferriere development from egg to adult was completed in 12 to 13 days in eggs of Pentatomidae.
Effect of Food and Mating on Biology of Parasites
Entomophagous parasites were reported to lay all their eggs in the first few days of life when food was not provided but a similar number over a long period of time when adult longevity was prolonged by intake of food (Ahmad, 1936; Simmonds, 1943). They concluded that the egg laying capacity of T. basalis varied with the individual, feeding sirpply extended the period of oviposition, and that the total number of progeny was not appreciably affected by feeding. Ganesalingam (1966) reported similar egg laying behavior but noted that unfed females oviposited at a rate comparable to those fed honey and water.
Crossman (1925) stated that virgin females of Ooencyrtus kuwanai (Howard) deposited a much smaller number of progeny than did those which were mated. Maple (1937) found that mating had no influence upon the oviposition activities of the females of O. johnsoni
(Howard).
Hokyo et al. (1966) revealed that the mean longevity of the scelionid egg parasites of N. viridula, Asolcus mitsukurii (Ashmead) and Telenomus nakagawai (Watanabe), was 2.5 days, regardless of sex, when only water was available. When honey was supplied the longevity of parasites was three times longer. Thomas (1972) reported a similar results with T. basalis and, in addition, noted that adult longevity was not affected in the presence or absence of host eggs. Hokyo et al. (1966) and Matsumoto (1974) reported conversely that female longevity was significantly reduced when ovipositional activity took place in the host eggs with the presence of honey.
Reproductive Behavior of Parasites
Many parasites have the ability to discriminate between parasitized and healthy hosts, and thus avoid superparasitism.
Cumber (1951) and Wilson (1961) reported that T. basalis usually avoided ovipositing in host eggs which are already parasitized by recognizing the markings made by a previous female. This is in conflict with Noble (1937), Kamal (1937), and Ganesalingam (1966), who stated that several females of T. basalis oviposited simulta neously in a single egg of N. viridula.
In a few cases superparasitism of Ooencyrtus kuwanai took place in the eggs of gypsy moth (Crossman, 1925). Clausen
(1932) reported that under field conditions in Korea the percentage of parasitization of Lecanium kunoensis (Kuwana) by O. infidus
(Rossi) was so high as to give rise to very extensive superparasitis 8
Walker and Anderson (1933) obtained an average of almost three parasites of O. johnsoni from each egg of Murgantia histrionica
(Hahn), whilst Maple (1937) found that the average number developing in an egg was approximately two.
A vast majority of parasitic Hymenoptera reproduce biparen- tally, but uniparental reproduction was recorded in one or more species in excess of 30 genera (Clausen, 1940).
Uniparental reproduction of O. submetallicus by thelyotokous
parthenogenesis was first recorded in Ooencyrtus by Wilson and
Woolcock (I960). Two other well-known species, O. kuwanai
(Crossman, 1925) and O. johnsoni (Maple, 1937)fare arrhenotokous.
Flanders (1939, 1945a) pointed out that if the spermatheca in arrhenotokous species of parasitic Hymenoptera contained sperma tozoa it became a sex change mechanism. The sex of the egg was determined during oviposition and the stimulation of the spermatheca to discharge spermatozoa into the oviduct was usually caused by external conditions. He concluded that the sex ratio in arrhenotokous species was variable because the action of the spermatheca was determined by inconstant environmental factors.
Flanders (1944, 1945b) reported that bisexuality in predomi nantly unisexual Hymenoptera was determined by environmental factors. Moreover, he stated (1944) that certain species consisted of geographical races, reproduction being biparental in one and 9
uniparental in the other.
Wilson and Woolcock (1960) revealed that the sex of O. submetallicus was uniparentally determined by the temperatures to
■which the female was exposed during development and adult life. The unmated females gave rise to female progeny at low temperatures, but produced some male progeny as well at temperatures of 29°C or higher. In his later experiments, Wilson (1962) concluded that temperature regulated certain cytological processes resulting in sex determination. For example, temperatures of below 29°C produced diploid eggs, whereas at 29°C and above haploid eggs were produced.
C riteria for the Success of Biological Control Agents
Previous workers have presented various hypotheses as to why particular natural enemies controlled, or failed to control, certain hosts in particular countries or islands (Taylor, 1955; Doutt, 1959;
Lloyd, I960; Wilson, I960; Turnbull and Chant, 1961; DeBach, 1962;
Beirne, 1975).
DeBach (1962) analysed successes in biological control of insect pests and concluded that the aspects of successful biological control by natural enemies could be considered as follows; (1) para sites are better than predators (or vice versa); (2) many species of enemies attacking one host species are better than one; 10
(3) monophagous enemies are better than polyphagous enemies
(or vice versa); (4) egg parasites acting alone are ineffective;
(5) biological control works better on islands; (6) sessile hosts, particularly Coccidae, are more amenable to biological control than are other types; (7) complete biological control following an introduction must occur rapidly or else will not be complete;
(8) natural enemies should come from the same host in the country of origin; (9) natural enemies should be imported from areas ecologically equivalent to the area of introduction; and (10) immigrant pests offer the best opportunities for biological control. Some of these hypotheses definitely indicate the initial direction for research involving broad biological principles and procedures on new projects.
Wilson (I960) stated that upon reflection, although there are many examples of successful biological control in the world, an adequate explanation could not be given as to why these particular examples were successful.
DeBach et al. (1950) suggested that a fundamental aspect of biological control is the evaluation of effects of entomophagous species on other parasitic species already colonized or newly imported. Fye and Larson (1969) concluded that preliminary tests are required to determine the biological characteristics and the feasibility of certain necessary manipulations, before a biological agent can be released as a population regulator. MATERIALS AND METHODS
LABORATORY STUDIES
Source and Maintenance of Parasite Culture
The parasitic species of Nezara viridula eggs used in tht;
present studies were maintained in the laboratory of the Department
of Entomology, Louisiana State University, Baton Rouge, Louisiana.
A colony of Ooencyrtus submetallicus was imported from Trinidad in 1975. The other parasitic species, Trissolcus basalis, was
obtained from field-collected parasitized eggs of the southern green
stink bug from soybean fields near Krotz Springs, Louisiana.
Eggs of N. viridula served as hosts for parasites. Glass aquaria measuring 55 X 30 X 28 cm were used to rear the stink bugs for production of eggs. The tops of the cages w ere covered with 50 mesh cheesecloth. Folded index cards were placed on the
floor of the cage to provide oviposition sites which allowed for easy
removal of the egg masses. An aveidge population of 300 stink bugs, with a 1:1 sex ratio, was maintained in each of the 10 oviposi
tion cages.
The southern green stink bugs were reared on snap bean
12 13
(Phaseolus vulgaris Linnaeus) and/or corn (Zea mays Linnaeus).
The food source was replaced every 5 to 7 days depending on its
initial quality. Egg masses were collected daily. The number of
eggs/mass ranged from 50 to 100. Egg masses less than 24-hr old
were stored at 4°C. The eggs were killed at this temperature but
the egg contents remained in a liquid stage for five months. As
long as the egg contents were in a liquid stage, they served as
suitable hosts for parasites (Wilson, I960).
Adults of each parasite species were held in 3. 7 liter ice
cream cartons. The cartons were covered with plastic sheets of the
type used in making plastic bags.
Using scotch tape (Scotch ® Magic Transparent Tape No. 810),
egg masses were attached to 2. 5 X 15 cm cardboard strips which were cut from index cards. Ten egg masses (ca 600 eggs) were
placed on both sides of each strip with a space of 2. 5 cm between
egg masses. Four such strips were placed inside a carton holding
ca 80 adult parasites. The inside of the carton was streaked with honey which served as food for adult parasites. Host material
prepared in this way proved to be convenient to use in various studies undertaken. The cartons were held at 25±1°C with a daily photoperiod of 14-hr light:10-hr dark (14L:10D).
Developmental Period of Parasites
This experiment was done to determine the duration of the 14
developmental period from oviposition to emergence of O.
submetallicus and T. basalis at temperatures of 21, 25, and 29°C,
and a daily photoperiod of 14L:10D.
Thirty adult parasites, more than two-day old, were held in
0.93 liter ice cream cartons covered with plastic sheets for the
purpose of parasitizing host material. A cardboard strip holding
four egg masses of N. viridula was placed in each carton. Each
egg mass contained ca 60 eggs. Following a three-day exposure
under each of three different temperatures, the parasites were
removed from the cartons.
A daily record of adult emergence from host eggs was kept and
the adults were sexed. These counts were converted into percentage
of total adult emergence.
The test described above was repeated three times.
Survival and Superparasitism
This test was conducted to determine the possible continuation
of successive generations at temperatures of 21, 25 and 29°C with two photoperiods of 14L»:10D and 10L:14D at each of these tempera
tures. Possible superparasitism was also observed.
The procedure of confining the parasites and parasitizing the host eggs was the same as described in the previous section.
Approximately 300 adult parasites of each species of each generation were maintained as a stock culture in the cartons to 15 carry out this test. Thirty adult parasites out of the stock culture in each generation were used for parasitizing host eggs.
The number of parasitized host eggs, the number of emergence holes and the number of emerged adults were counted soon after completion of parasite emergence from the host eggs. The survival . was converted into a percentage of the total parasitized eggs. This included both the completely developed parasites and partially developed parasites in eggs.
The observation of superparasitism was made after completion of emergence. The counts included the number of emergence holes and the number of emerged adult parasites.
The test described above was continued for five successive generations.
Effect of Presence and Absence of Food and Host Eggs on Longevity of Adult Parasites
This experiment was conducted to determine the effect on longevity of adult parasites when the availability of food and host were maintained under controlled laboratory conditions.
The four treatments used were as follows: (1) absence of honey and host eggs; (2) host eggs without honey; (3) honey without host eggs; and (4) presence of honey and host eggs. For these treatment combinations, 5 X 1. 3 cm plastic petri dishes were prepared. Five freshly emerged adult parasites more than 16 one-hr old were placed into each dish. Males and females were tested separately.
In treatments 2 and 4, a single one-day old egg mass of
N. viridula was placed in each dish. The mass was replaced daily with a fresh one. This process was continued until the death of all
5 adult parasites. All of the test parasites were held at ?5+l°C and 14L:10D photophase with a 50+5% relative humidity. The whole test was replicated five times.
Genetic Strains
Thi- experiment was carried out to determ ine if O. submetallicus reproduced by thelyotokous parthenogenesis (Wilson and Woolcock, I960; Wilson, 1962). Each single parent female which had emerged from individually isolated host eggs was confined in a 5 X 1. 3 cm plastic dish with honey. This excluded any possibility of females being mated. An egg mass (ca 60 eggs) of the southern green stink bug was placed in each of the plastic dishes and exposed to an unmated female. After the 72-hr exposure period the female was removed from each of the plastic dishes. The emergence of parasites required 17 to 31 days depending upon temperatures.
The test was conducted at temperatures of 21, 25 and 29°C with 14L:10D and 50+10% relative humidity.
The experiment described above was replicated ten times. Specimens sent to the British Museum (Natural History) were identified by J. S. Noyes (1978).
Sex Ratio
All the procedures used in the present test were the same as described above, except that a male parasite was introduced into each of the plastic dishes containing an unmated female. Following a 24-hr holding period for mating, the female was exposed to an egg m a s s .
This test was continued for nine successive generations.
Host Preference
The host preference of O. submetallicus and T. basalis for the eggs of 5 phytophagous pentatomid species was evaluated in the laboratory. The species utilized were N. viridula (L. ),
Acrosternum hilare (Say), Euschistus servus (Say), Edessa bifida
(Say) and Thyanta pallidovirens (Stal).
Adult stink bugs of the species tested were collected from various locations in Louisiana, and were confined in 3.7 liter ice cream cartons. Approximately 30 stink bugs were placed in each carton which was closed with 50 mesh cheesecloth. Green snap beans and/or corn were used as a food source. Folded index cards placed in cartons provided oviposition sites.
Egg masses were collected daily. By subtracting or adding 18
eggs to an egg mass, the number of eggs per mass was brought
between 40-50.
Twenty egg masses from 5 species (4 masses/species)
were attached randomly to four holding strips. Next, 50 two-day
old parasites were transferred into a carton in which the host
holding strips had been placed. Following an exposure of 48-hr, the
parasites were removed from the carton. This experiment was
carried out at 25±1°C and a photoperiod of 14L:10D.
The number of parasites that emerged from each egg mass was determined by counting the emergence holes during 22 days
after oviposition. The counts were converted to a percentage of the
total number of eggs parasitized.
The test was repeated four times.
Competitive Interaction
This experiment was undertaken to investigate the possible
behavioral interaction between O. submetallicus and T. basalis.
Three combinations of the two parasitic species were tested. These
were: (1) equal numbers of O. submetallicus and T. basalis;
(2) alternated O. submetallicus and T. basalis at 24-hr intervals;
and (3) the reverse of (2).
Two-day old female parasites were confined per 0.93 liter ice
cream carton for each treatment combination. In treatment one, five individuals of each of the two parasitic species were confined, whereas in treatment 2 and 3, ten per species were used.
Three egg masses of N. viridula were fixed to each holding strip. Each egg mass was less than 24-hr old and contained ca 80 eggs. The strips were placed into a carton holding adult parasites for a period of six days. The exposed egg masses were transferred to another carton.
The experiment was carried out at a temperature of 25+l°C and a photoperiod of 14L:10D. The adult parasites that emerged from the egg masses were sorted into O. submetallicus and
T. basalis, and counted under a binocular dissecting microscope.
These counts were converted to percentage of the total number of parasitized eggs.
The test described above was replicated four times.
FIELD EVALUATION
Preliminary evaluation of the two parasitic species for control of N. viridula was conducted in an effort to determine:
(1) the effectiveness of parasitism in the field, and (2) the behavior of the parasites with regard to dispersion and searching ability.
Field experiments were carried out on the Louisiana State 20
University, St. Gabriel Branch Experimental Station. A soybean field of ca 5 ha was used as the experimental site.
The combinations of releases with the two species were:
(1) O. submetallicus; (2) T. basalis; (3) combined O. submetallicus and T. basalis; and (4) control.
A pattern was m arked off in the field at each release point with radiating arms extending in the four cardinal directions. The extension of the radiating arm was designated in two ways.
(1) To compare the effectiveness of the parasitic species
in 1977, each arm was designated by 5 stations located
at 1, 3, 6, 9 and 12 m, respectively, from the central
point. The total area devoted to the experiment was
576 m . One egg mass of N. viridula, less than 3-day
old, was placed at each station.
(2) To determine the dispersion and searching ability of
both species in 1978, egg masses were placed at 5
stations located at 1, 5, 10, 15 and 20 m, respectively,
from the release point toward each of the cardinal points
of campus. The total area devoted to the experiment 2 was 1600 m . Three egg masses of N. viridula.less than
3-day old, were placed at each station in the field
pattern.
( p v Masking tape (Scotch Drafting Tape No. 230) 2. 5 cm wide was cut into peices 6 cm long. Host egg masses (ca 50 to 80 eggs/
mass) that had been laid on index cards were used. The portion of
the index card with the egg m ass was cut out and placed on the
adhesive surface of the masking tape. A section of the tape to which
an egg mass had been attached was stapled to the upper surface of
individual soybean leaves selected randomly at each station. An egg
m ass affixed in this manner was surrounded by some portion of the
sticky part of the tape. This helped in preventing the predators (i.e. , ants) from reaching the eggs. The number of parasites released
per treatments 1 and 2 was ca 10,000, while in treatment 3, 5,000
parasites of each of the 2 species were released. Following place ment of the egg masses, the parasites were released from the central
point of the experimental area. Three days after the parasites had been released, the egg masses were collected from the leaves, returned to the laboratory and were placed at 25+l°C and a light
regime of 14L:10D. Following a 22-day holding period, the number of egg masses that were parasitized with O. submetallicus or T. basalis was determined by counting either the adults or the emergence holes. Emergence holes of T. basalis were round with smooth edges; those of O. submetallicus were oval with jagged edges.
The experiment was arranged in a completely randomized block design. The test procedure described above was conducted three times each in 1977 and 1978 during the soybean growing season. 22
In considering parasitism, allowance was made for natural parasitization by T. basalis which is endemic in Louisiana. There fore, the percent figures for parasitism were corrected by modifying
Abbott's formula (Abbott, 1925) as follows:
Corrected % parasitism by T. basalis = 0 - n X 100 “ 100-n
where 0 = % observed parasitism
n = % natural parasitism RESULTS AND DISCUSSION
LABORATORY STUDIES
Developmental Period
The developmental periods from oviposition to emergence of
the two parasite species are presented in Tables I and II, and
Figure 1. The detailed data are given in Appendix Tables 1 and 3.
The developmental period was shorter at high temperatures than at low temperatures. Analyses of variance for these data indicate a highly significant difference (P^ 0.01), in developmental periods
due to temperatures (Appendix Tables 2 and 4).
The mean developmental period of the males of Trissolcus basalis was ca 2 and 8 days longer at 25 and 21°C, respectively,
than when reared at 29°C. However, the females required ca 3 additional days at 25°C and 11 additional days at 21°C when
compared with the developmental period at 29°C; the develop
mental period at 21°C was twice that at 29°C.
Table I and Figure 1 show that the mean developmental
period of T. basalis was shorter for males than that for females.
Males began emergence one to four days before females depending
23 Table I. Developmental period from oviposition to emergence of T. basalis in three successive generations at different temperatures and 14L:10D.
Temperature No. test Days from egg to adult Sex (°C) insects a / Mean- Range
21 Male 214 18.7+0.87 17 - 21 Fem ale 401 2 1 .6 + 1 .1 1 19 - 25
25 Male 224 12.6 + 0. 90 11 - 15 Female 434 13.5 + 0.95 12 - 16
29 Male 235 10.4 ± 0.95 9 - 1 2 Female 397 10.9 + 0. 74 10 - 14
a / Mean and standard deviation. Detailed data and statistical analysis are given in Appendix Tables 1 and 2. upon the temperature conditions. The proportion of females emerging gradually increased thereafter. At 21°C, most of the males emerged before the females (Figure 1).
Wilson (1961) reported that the developmental period of
Trissolcus basalis at 25°C was similar to the present results. The majority of the male parasites emerged from the host eggs several days before the females and they remained with the egg masses for mating until all the females had dispersed (Noble, 1937; Cumber,
1951).
Table II shows the mean developmental period of Ooencyrtus submetallicus. Unlike T. basalis, males of O. submetallicus 25
Table II. Developmental period from oviposition to emergence of O. submetallicus in three successive generations at different temperatures and 14L:10D.
Temperature No. test Days from egg to adult (°C) Sex insects Mean—^ Range
21 Male 70 26.6 + 1. 50 24 - 30 Female 408 26.6 + 1.67 23 - 30
25 Male 68 16.9 ± 1. 10 15 - 20 Female 354 16.7 ± 0. 97 14 - 21
29 Male 90 13.8 ± 1. 11 12 - 17 Fem ale 357 13.7 + 0.97 11 - 17
a/ Mean and standard deviation. Detailed data and statistical analysis are given in Appendix Tables 3 and 4.
usually began emergence later than the females, but their
emergence was completed before all the females had emerged. This was true at all the temperatures (Figure 1). Both sexes of O.
submetallicus reared at temperatures of 21, 25 and 29°C required
averages of ca 27, 17 and 14 days, respectively. Thus, the mean
developmental period of both sexes of O. submetallicus from ovipo
sition to emergence required ca 13 additional days at 21°C and 3
additional days at 25°C as compared to 29°C.
Clausen (1962) reported that under optimum temperature
conditions, Qoencyrtus malayensis in the eggs of Pentatomidae
completed its life cycle in 12 to 13 days. Percentage of adult emergence 20 i. . eeomna pro o to aaie pce i rlto t dfeet temperatures different to in relation species parasite two of period Developmental 1. Fig. O'' 10 9 C 29 12 5 C 25 0 Days after Oviposition after Days 18 O - 20 onyts submetallicus Ooencyrtus Trissolrus basalis Trissolrus 426 24 o- 21 C 21 28 30 ' O ro 27
Survival and Superparasitism
The results of percent emergence of parasites from parasi tized host eggs at different temperatures and two photoperiods are presented in Tables III, IV, V and VI. Detailed data used in the analyses are given in Appendix Tables 5, 6, 7 and 8.
The adult emergence of T. basalis at 14L:10D did not increase significantly (P > 0.05) with the increase in temperature (Table III).
At 10L»:14D, the percent adult emergence at 29°C (89.5%) was signi ficantly greater (P < 0.05) than at 21°C (83.0%) as shown in Table IV.
Overall, the adult emergence at 21°C was lower, and it was higher at 25 and 29°C. Thus, the optimum temperature for rearing T. basalis was somewhere between 25 and 29°C.
No significant difference (P > 0.05) was found in percent emergence of O. submetallicus from host eggs held at temperatures of 21, 25 and 29°C and photoperiod of 14L:10D or 10L-:14D (Tables V and VI). The probable optimal temperature for rearing O. submetallicus was similar to that for T. basalis.
The continuation of successive generations in both parasites,
O. submetallicus and T. basalis, without reduction in survival, was observed in all the test conditions. No significant difference in survival was detected when the parasites were reared at different photoperiods. 28
Table III. Mean percent of emergence in five successive generations of T. basalis at different temperatures and 14L:10D.
Temperature Total No. % . No. individuals a / (°C) host eggs em ergence- per egg parasitized
21 1377 84. 3 ns 1 25 1388 89. 1 ns 1 29 1417 88. 3 ns 1
a/ ns P>0.05. Percent of adult emergence from host eggs in which parasites emerged. Computed from data given in Appendix Table 5.
Table IV. Mean percent of emergence in five successive generations of T. basalis at different temperatures and 10L:14D.
Tem perature Total No. % a / No. individuals (°C) host eggs em ergence per egg parasitized
21 1390 83. 0 b 1 25 1379 88.8 a, b 1 29 ' 1140 89. 5 a 1
a/ Values followed by the same superscript do not differ statistically (P>-0.05). Percent of adult emergence from host eggs from which parasites emerged. Computed from data given in Appendix Table 6. 29
Table V. Mean percent of emergence in five successive generations of O. submetallicus at different temperatures and 14L.:10D.
Temperature Total No. No. individuals % a// b/ (°C) host eggs em ergence- per egg-' parasitized
21 1385 82. 0 ns 1.20 + 0.071
25 1389 85. 9 ns 1.29 + 0. 154 29 1406 84. 9 ns 1.30 ± 0. 118
a / ns P > 0. 05. Percent of adult emergenc:e from host eggs in which parasites emerged. b/ Mean number and standard deviation of parasite emergence per host egg. Computed from data given in Appendix Table 7.
Table VI. Mean percent of emergence in five successive generations of O. submetallicus at different temperatures and 10L:14D.
Temperature Total No. % No. individuals a / b/ (°C) host eggs emergence— per egg- parasitized
21 1347 81 . 1 ns 1. 18 ± 0.087 25 1360 84.0 ns 1. 24 + 0. 082
29 1363 85.6 ns 1.27 + 0. 112
a/ ns P >0. 05. Percent of adult emergence from host eggs from which parasites emerged. b/ Mean number and standard deviation of parasite emergence per host egg. Computed from data given in Appendix Table 8. 30
In the case of O. submetallicus the average number of adult parasites emerging from a host egg ranged from 1.18 to 1.30, whereas a single adult of T. basalis developed within the host egg
(Tables III, IV, V and VI).
My observations agree with those of Noble (1937), Kamal (1937) and Ganesalingam (1966) in that several females of T. basalis oviposited simultaneously in a single egg of N. viridula, resulting in superparasitism. Only one parasite developed per host egg. On the other hand, superparasitism in T. basalis did not occur when a single individual was allowed to oviposit, since the parasite discriminated against the parasitized eggs by recognizing its own markings (Cumber,
1951; Wilson, 1961).
In the genus Ooencyrtus, Clausen (1932) reported high super parasitism by Ooencyrtus infidus in eggs of Lecanium kunoensis under field conditions. Walker and Anderson (1933), and Maple (1937) reported that 2 to 3 individuals of Ooencyrtus johnsoni emerged from eggs of the harlequin bug, Murgantia histrionica.
Adult Longevity
The results on studies of adult longevity of O. submetallicus and T. basalis are presented in Tables VII, VIII, IX and X. When adult parasites were not fed, their longevity was drastically reduced and the presence or absence of N. viridula eggs had no effect on this curtailment. The statistical analysis showed that there was no 31
Table VII. Mean adult longevity of male T. basalis in the presence and absence of honey.
§y Food Total No. Mean S. D. Range insects (days)
Honey 24 43.7 ± 1 .9 36 - 50
No honey 25 2.6** ± 0. 1 2 - 4
** P-=0.01 (t = 46.36 >3.76) aJ Standard deviation. Detailed data used in the analysis are given in Appendix Table 9.
Table VIII. Mean adult longevity of female T. basalis in the presence and absence of honey and host eggs (N. viridula).
sL/ Total No. Mean Food Host S. TT^ Range insects (days)
Honey Host eggs 23 36. 1 b ± 1 .3 29 - 44 No host eggs 25 50.4 a ± 1 .9 40 - 57
No honey Host eggs 24 2.6 c ± 0. 1 2 - 3 No host eggs 24 2.7 c ± 0 .2 2 - 3
aJ Values followed by the same superscript do not differ statistically (P > 0.01). fey Standard deviation. Detailed data used in the analysis are given in Appendix Table 10. 32
Table IX. Mean adult longevity of male O. Bubmetallicus in the presence and absence of honey.
Total No. Mean Food s. D y Range insects (days)
Honey 23 14.6 ± 0 .6 12 - 17
No honey 24 2.6** ± 0 .2 1 - 3
** 0.01 (t = 43.69 >3.76) aJ Standard deviation. Detailed data used in the analysis are given in Appendix Table 11.
Table X. Mean longevity of female O. submetallicus in the presence and absence of honey and host eggs (N. viridula).
Total No. M e a n ^ Food Host S. D7^ Range insects (days)
Honey Host eggs 24 33. 3 b ± 2. 3 25 - 42 No host eggs 23 46.9 a + 2. 7 36 - 55
No honey Host eggs 23 2.7 c + 0. 3 1 - 4 No host eggs 24 2.6 c + 0.2 2 - 3
a/ Values followed by the same superscript do not differ statistically (P > 0.01). fc>J Standard deviation. Detailed data used in the analysis are given in Appendix Table 12. significant difference (P > 0.05) in the mean longevities of parasites
without food in the presence or absence of the host eggs as shown
in Tables VIII and X. Thus, when food was absent, nutrition was
the major factor responsible for early death of the adults and any
utilization of energy due to ovipositional activities caused no addi
tional reduction in longevity.
In the absence of host eggs and in the presence of honey, the
parasites of O. submetallicus lived an average of 46.9 days, whereas when the host eggs were available for ovipositional activi ties, longevity of the parasites was reduced to 33.3 days (P-'0.01).
Thus, when honey was provided, ovipositional activity was a major factor in the reduction of adult longevity, i. e. , from 46. 9 to 33. 3 days in O. submetallicus and from 50.4 to 36.1 days in T. basalis.
Thomas (1972) reported that Trissolcus basalis fed on sugar water lived for a mean period of 7.9 days, approximately twice as long as those that were not fed, and that ovipositional activity had no adverse effect on longevity. In the present study the ovipositional activity reduced longevity significantly (P < 0.01).
The results obtained in this study are similar to those reported by Matsumoto (1974). He reported that adults of the ichneumonid parasite, Venturia canescens, lived for an average of 35.0 days when provided with honey, but 2. 5 days without food. When food was 34 provided in the presence of hosts, ovipositional acitivites reduced adult longevity from 35. 0 to 22.6 days.
Increasing adult longevity can influence the effect of parasites as natural control agents. Entomophagous parasites have been reported to lay all their eggs in the first few days of life when food is not available but will lay similar numbers over a longer period when fed (Ahmad, 1936; Simmonds, 1943). Prolonged adult longevity when hosts are abundant is not necessarily an advantage. However, when the host density is low, widely dispersed, difficult to find, or not in synchrony with the parasite, the prolonged adult longevity is certainly advantageous. Also, under these conditions superpara sitism would probably be reduced. Thus, the parasite's capability for exerting maximum efficiency and effectiveness for control of the host population would be enhanced.
Genetic Strains
In this study, unmated females of O. submetallicus were allowed to produce offspring. All the progeny produced were males and the temperatures (21, 25 and 29°C) did not influence the sex.
Thus, this strain of O. submetallicus reproduced by arrhenotokous parthenogenesis.
Wilson and Woolcock (I960), and Wilson (1962) reported that a strain of Ooencyrtus submetallicus they studied reproduced by thelyotokous parthenogenesis (unmated females produce female progeny). However, he observed that sex determination was affected by temperature. At 29°C or above, unmated females produced
some male progeny. He also reported that gynandromorphs occurred in this species. Morphologically, the specimens of O. submetallicus used in Wilson's and the present studies were alike (Noyes, 1978).
Thus, it would seem that there must be at least two strains of this species. The strain used in the present studies differed from
Wilson's in that unmated females produced all male progeny.
Furthermore, exposure of unmated females to 29°C did not cause them to produce female progeny.
Sex Ratio
The mean sex ratio of O. submetallicus in nine successive generations reared at constant temperatures of 21, 25 and 29°C is presented in Table XI. The mean sex ratio ( cf : 9 ) was 1:6.4,
1:5. 6 and 1:4. 0 at 21, 25 and 29°C, respectively.
The results showed that a temperature of 29°C produced more males in the progeny than 21°C with a same photoperiod of 14L:10D.
Conversely, at 21°C more females were produced than at 29°C. Sex ratio and temperature were negatively correlated (r= -0.617**) as shown in Figure 2. As early as 1932, Whiting and Anderson stated that when the parasitic wasp, Habrobracon juglandis (Ashmead), was exposed to low temperature a high percentage of biparental progeny was produced, but few were males. It appeared that at lowered 36
Table XI. Mean sex ratio of O. submetallicus in nine successive generations at different tem peratures and 14L:10D.
Temperature Total No. A v e ra g e ^ S. D . ^ Range (°C) insects ( a : 9 )
21 1350 1:6. 4 a + 1.2 4.9 - 8.0 25 1556 1:5.6 a,b + 0.7 4.0 - 6.2 29 1403 1:4.0 b + 0.5 2. 9 - 4.2
a/ Values followed by the same superscript do not differ statistically (P > 0. 01). b/ Standard deviation. Data used in the analysis are given in Appendix Tables 13, 14 and 15.
temperature more eggs were fertilized and of these a predominance produced females.
Wilson (1962) reported O. submetallicus possessed a tempera ture sensitive mechanism that controlled the cytological processes underlying sex determination, so that the temperature determined whether progeny produced by unmated females were male, female or gynandromorph. He reported that low temperatures produced female progeny only, but high temperatures produced both female and male progeny in the uniparental strain of O. submetallicus . Factors causing this differential response for sex ratio in both the present study strain and Wilson's strain are not fully understood.
Host Preference
The percentage of parasitism and the results of the ovipositional Sex ratio (<*:?) 1:10 1:2 1:8 1:6 i. . nlec o eprtr o sx ai f . submetallicus. 0.of ratio sex on temperature of Influence 2. Fig. 21 23 Temperature Temperature 25 (°C) -0.417** r= 12.915 - 0.304 x 0.304 - 12.915 27
29 J O 38 preference of O. submetallicus and T. basalis for the eggs of five
species of stink bugs are presented in Tables XII and XIII. There were significant differences (P< 0.05) in ovipositional host preference for the pentatomid species by both parasite species.
O. submetallicus accepted the eggs of all five pentatomid species tested, although Edessa bifida was not a preferred host. The eggs of E. bifida were not parasitized by T. basalis. However, E. bifida belongs to the subtribe Edessini instead of the Pentatomini to which the other four species belong.
Except for E. bifida, the mean percent parasitism of eggs by both T. basalis and O. submetallicus ranged from 93 to 97 for A. hilare, T. pallidovirens, E. servus and N. viridula (Tables XII and
XIII). Thomas (1972) found, under laboratory conditions, relatively uniform parasitism of eggs by T. basalis for the same pentatomid species, except E. bifida.
These findings involve several important points. Firstly, alter native hosts are present for O. submetallicus and/or T. basalis in the field when N. viridula is not present or has a low population density.
Under such conditions the parasite population can be maintained on the alternate host species. Secondly, these other species may help to provide the food necessary for building up increased numbers of
O. submetallicus and T. basalis. On the other hand, the presence of alternate hosts that appear to be equally acceptable as N. viridula 39
Table XII. Percent parasitism of the eggs of several pentatomid species of T. basalis.
Host species Replication Mearr^ 1 2 3 4
N. viridula 98.0 97. 1 96.0 95. 5 96. 7 a A. hilare 93.9 95. 7 92.2 91.6 93.4 b E . bifida 0.0 0.0 0.0 0.0 0.0 c E. servus 95.4 96.0 93.9 92.8 94. 5 b T. pallidovirens 93. 5 92.4 96.4 93.4 93.9 b
a/ Values followed by the same letter do not differ statistically from each other by Duncan's Multiple Range Test (P>0.05). Computed from data shown in Appendix Table 16.
Table XIII. Percent parasitism of the eggs of several pentatomid species by O. submetallicus.
cl / Host species ______Replication______Mean— 1 2 3 4
N. viridula 98.2 95. 5 96.8 94.9 96. 4 a A. hilare 88. 8 93.2 95. 6 93.9 92.9 b E. bifida 1. 1 0.8 1. 1 1.0 1.0 c E. servus 97.6 96.0 97.0 95.0 96. 4 a T. pallidovirens 95. 1 98.0 95. 1 92.8 95.3 a ,b
a j Values followed by the same letter do not differ statistically from each other by Duncan's Multiple Range Test (P>0.05). Computed from data shown in Appendix Table 17. 40
may reduce effectiveness of the parasites for control of the latter.
Competitive Interaction
Table XIV shows the mean percent parasitism of the different
combinations of O. submetallicus and T. basalis against the eggs of
N. viridula under laboratory conditions. Analysis of variance for
these data is presented in Appendix Table 19. There was no signifi
cant interaction (P >0.05) between treatment combinations and
species. Overall, O. submetallicus parasitized significantly more
host eggs than T. basalis (P < 0.05) as shown in Table XIV.
Even when the two parasite species were alternated every
24-hr , the mean percent parasitism by O. submetallicus was signi
ficantly higher than that of T. basalis (Table XIV). Females of both
species oviposited in a single egg of N. viridula, resulting in multi
parasitism. However, only individuals of one species, either
O. submetallicus or T. basalis, developed within the host egg. As a whole, the parasitic activity of O. submetallicus was always signi
ficantly dominant to T. basalis in the laboratory tests.
FIELD EVALUATION
The results of experiments for comparing the effectiveness
of the two parasite species in the field during 1977 are given in
Appendix Table 20. These trials were made under field conditions
to observe the efficacy of the egg parasites, O. submetallicus and
T. basalis, against eggs of N. viridula. Table XV shows a Table XIV. Competitive interaction between O. submetallicus and T. basalis .
______Mean % parasitism_by______Rep. . Combined______Alternated at 24-hr intervals Ooencyrtus+ Trissolcus Ooencyrtus /Trissolcus Trissolcus / Ooencyrtus
1 74. 1 25. 9 63.0 37.0 30.4 69.6 2 66. 8 33. 2 73. 7 26. 3 43.8 56.2 3 60.9 39. 1 65.7 34.3 41.9 58. 1 4 67.5 32. 5 72.2 27. 8 34.2 65.8 M e a n ^ 67.3 a 32. 7 b 68. 7 a 31.4 b 37.6 b 62.4 a
a / Values followed by the same superscript do not differ statistically (P >0.05) . Computed from data shown in Appendix Table 18. Table XV. Percent parasitism of host eggs exposed to parasites for three days in preliminary field trials during 1977.—/
Date of Species Release Ooencyrtus Trissolcus Combined ( O. + T. )—/
July 15 37.50 43.75 50.73 (23.53 + 27.20)
July 31 47.06 60.00 48.23 (23.53 + 24.70) Aug. 14 41. 18 50.42 44.32 (17.65 + 26.67) M ean- 41.91 ns 51.39 ns47.76 ns (21.57 + 26.19)
a j Percent parasitism in each treatment was corrected for parasitism by endemic populations of T. basalis in the control plots and computed from data shown in Appendix Table 20. \J Percent parasitism of combined Ooencyrtus and Trissolcus c j ns P>0.05. Statistical analyses are given in Appendix Table 21. sum m ary of the percent parasitism of the two species on host egg masses at each treatment combination.
Controls for the tests (Appendix Table 20) indicated that a mean of 9. 7% of the egg m asses placed in the field was parasitized by endemic populations of T. basalis. Therefore, the percentage of parasitism resulting from released parasites was corrected to account for parasitism by naturally occurring populations of
T. b asalis.
Rates of parasitism in egg masses placed in a unit area of 2 144 m , when 10,000 parasites were released into each treatment 43
combination, w ere 41.9% by O. subm etallicus, 51.4% by T. basalis
and 47.8% by the two species combined. There was no significant
difference (P>0.05) between the treatment combinations (TableXY).
Of the 47.8% parasitism obtained in the treatment with the
combined species 21. 6% were parasitized by O. submetallicus and
26. 2% by T. basalis, and this did not show any statistically signifi
cant difference (P>0.05).
However, under laboratory conditions there was a highly signi
ficant difference between the two species with O. submetallicus para
sitizing significantly more eggs of N. viridula than T. basalis (Table
XIV). Reasons for the difference in perform ance of the two species
under field and laboratory conditions are unknown.
The mean percentage of egg masses parasitized at each location
of the stations and at various distances from the central release
points in the three tests in 1978 are presented in Appendix Table
22. The analyses of the results of these trials are given in Appendix
Table 25. Table XVI shows the mean percentage of egg masses which were parasitized by released parasites with regard to direction from the central release point in the experimental area.
The direction from the release point did not significantly affect the percent of parasitism in any area of the field pattern as shown in
Appendix Table 25. The mean parasitism rates of egg masses placed in an area 400^m, when 10,000 parasites were released into 44
Table XVI. Mean percent parasitism of egg masses by released parasites with regard to directions from the central release point in the experimental area during 19782-/
Direction Ooencyrtus Trissolcus Combined ( O. + T . ) ^
North 24. 3 32. 1 31.6 (10.8 + 20.8) West 23. 3 31.5 29. 8 (12.0 + 17. 8) South 27. 5 33.0 35.0 (13.6 + 21.4) East 26. 1 30. 7 32. 6 (14.5 + 18. 1) M ean-/ 25. 3 b 31.8 a 32. 3 a (12.7 + 19.6)
a_/ Percent parasitism in each treatment was corrected for parasitism by endemic populations of T. basalis in the control and computed from data shown in Appendix Table 22. bJ Percent parasitism of combined Ooencyrtus and Trissolcus. c/ Values followed by the same superscript are not statistically different (P>0.05). each treatment combination, were 25. 3% by O. submetallicus,
31. 8% by T. basalis and 32. 3% by the two species combined. 2 Unlike the tests of the previous year in an area 144 m , a signifi cant difference was found (P<0.05) between treatment combinations with regard to the percentage of egg masses parasitized.
O. submetallicus parasitized fewer egg masses of N. viridula than those parasitized by T. basalis or the combination of T. basalis and O. submetallicus (Table XVI).
Table XVII shows the mean percentage of egg masses which 45
Table XVII. Mean percent parasitism of egg masses by released parasites with regard to distances from the central release point in the experimental area during 1978.
Distance from Species release point Ooencyrtus Trissolcus Combined M ean ^ (m) ( O. + T . )
1 50. 0 56. 3 59.8 55.4 a 5 42. 3 53. 2 47. 0 47. 5 a 10 30. 1 35.4 37.0 34.2 b 15 4. 2 10. 2 17. 6 10. 7 c 20 0.0 4. 2 0.0 1.4 c
aJ Values followed by the sam e superscript are not statistically different (P> 0.01). Computed from data shown in Appendix Table 22. were placed in field and parasitized by released parasites with regard to distance from the central release point in the experimental area. There was a highly significant difference in percentage of eggs parasitized at the various distances from the release point (P < 0.01).
The percentage of parasitism decreased with distance from the release point. Thus, this result disagrees with a report given by
Thomas (1972). He stated that the searching ability and dispersal of
T. basalis were uniform from a central release point in a 144 m experimental area. GENERAL DISCUSSION
Trissolcus basalis and Ooencyrtus submetallicus were similar
in most aspects of their biology. Both species were alike in their
response to temperature and photoperiod, but the developmental
periods of T. basalis were about 6, 4 and 3 days shorter than those of
O. submetallicus at temperatures of 21, 25 and 29°C, respectively.
Longevity of both species was about the same under each of the
conditions to which they were exposed. When they were held without food or provided with honey ad libitum both species lived about 3 and 48 days, respectively, except males of T. basalis lived longer
than males of O. submetallicus when provided food. When provided host eggs and honey, longevity was decreased about 29 percent for both species. This response confirms to Rubner's rule that longe vity is inversely proportional to the intensity of living, a rule that appears to apply well to poikilothermal species.
The two species differed slightly in pattern of adult emergence
from host eggs. Females of O. submetallicus began emergence
earlier than the males. Conversely males of T. basalis began
emergence earlier than the females. In both species, however,
male emergence was completed before all females had emerged.
46 47
There was a significant difference in the number of parasites
produced per host egg. Each egg parasitized by T. basalis produced
only one individual, whereas eggs parasitized by O. submetallicus
often produced more than one parasite.
Two features discovered about the biology of these parasites
were especially interesting. Both species were frequently observed
to oviposit in the same host egg. However, only individuals of one
species were ever observed to emerge from an egg parasitized by
both species. Also, it was found that the strain of O. submetallicus
involved in this study differed from that studied by Wilson and
Woolcock (1960), and Wilson (1962). The former was found to
reproduce by arrhenotokous parthenogenesis. It produced progeny
of different sex ratios, the percentage of females being negatively
correlated with increase in temperature. The latter strain was thelyotokously parthenogenetic.
Both species of parasites accepted eggs of Acrosternum hilare,
Euschistus servus and Thyanta pallidovirens as readily as those of
Nezara viridula. However, T. basalis did not accept eggs of
Edessa bifida as a host but a small percentage of the eggs of this species was parasitized by O. submetallicus. It is difficult to assess the importance of this polyphagous behavior on effectiveness of these parasites as agents in regulating populations of N. viridula.
It might be favorable from the standpoint of providing alternate 48 hosts for maintenance and buildup of parasite populations in situations where a shortage of N. viridula eggs occurred. On the other hand, it could serve to dilute the effect on populations of the target species.
In laboratory experiments, O. submetallicus was clearly
superior to T. basalis in parasitizing eggs of N. viridula in all types of comparisons made. However, a complete reversal occurred under field conditions. In the field, T. basalis was signi ficantly superior to O. submetallicus in dispersion and searching capability. Thus, it appears that O. submetallicus offers little potential as an effective addition to the natural enemies complex of
N. viridula in Louisiana. CONCLUSIONS
Both Ooencyrtus submetallicus and Trissolcus basalis were affected similarly by temperature and photoperiod in laboratory experiments. The latter completed develop ment in a slightly shorter period of time than required by
O. submetallicus.
Adults of both species lived 16 times as long, when provided honey ad libitum, as they did when held without food. When provided both honey and host eggs, longevity was decreased about 29 percent.
Each host egg parasitized by T. basalis produced only one parasite. Eggs parasitized by O. submetallicus frequently produced more than one individual.
Host eggs parasitized by one species were frequently parasitized by the other but in no case did more than one species emerge from the same egg.
The strain of O. submetallicus used in this study repro duced by arrhenotokous parthenogenesis. Progeny produced by mated females were biparental and sex ratios were influenced by temperature. The strain used by previous 50
researchers reproduced by thelyotokous parthenogenesis.
Increase in temperature to which the parent was exposed
was negatively correlated with percentage of female
progeny.
6. Both species readily accepted as hosts the eggs of four
species representing four genera of stink bugs. However,
eggs of a species of a fifth genus, Edessa bifida, were
refused by T. basalis but accepted to a limited extent by
O. submetallicus .
7. O. submetallicus was clearly superior to T. basalis as a
parasite of the eggs of N. viridula in all of the experiments
performed in the laboratory. However, a complete
reversal occurred in field experiments in which T. basalis
was significantly superior in dispersion and searching
capability.
8. Importation and colonization of O. submetallicus appears
to offer little potential for adding to the impact of indigenous
natural enemies on populations of N. viridula in Louisiana. 51
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Wollaston, V. T. 1858. Brief diagnostic characters of undescribed Madeiran insects. Ann. Mag. Nat. Hist. 3:18-28. APPENDIX Table 1. Developmental period in three successive generations of T. basalis at different temperatures and 14L:10D..
No. adults em erged Days after Temperature host eggs Male (generation) Female (generation) (°C) parasitized 1st 2nd 3rd Mean 1st 2nd 3rd Mean
21 17 3 5 3 3. 7 ----
18 25 28 32 28. 3 -- - - 19 25 29 30 28. 0 6 5 4 5.0 20 7 12 9 9.3 22 15 18 18. 3 21 1 2 3 2. 0 49 43 54 48.7
22 - - - - 37 34 30 33. 7
23 --- - 14 18 21 17.7
24 - - -- 7 8 10 8. 3
25 - - - - 1 2 3 2.0
25 11 4 6 9 6. 3 -- - - 12 23 38 30 30. 3 16 18 21 18. 3 13 20 28 35 27. 7 55 64 59 59.3 14 6 8 10 8.0 43 52 48 47.7
(continued) Table 1 (continued)
Days after No. adults emerged Temperature host eggs Male (generation) Female (generation) (°C) parasitized 1st 2nd 3rd Mean 1st 2nd 3rd Mean
15 2 1 4 2. 3 14 18 11 14.3
16 --- - 5 6 4 5.0
29 9 14 20 18 17.3 --- - 10 19 26 23 22. 3 42 48 53 47.7 11 27 31 35 31.0 55 64 59 59.3 12 7 8 10 8.3 13 17 22 19.3
13 -- - - 6 10 8 8.0
14 -- - - 1 2 3 2.0
m 00 59
Table 2. Analysis of variance of developmental period of T. basalis in five successive generations at different temperatures.
Source of Degrees of Sum of Mean square F value variation freedom squares
Replicate 2 0.003 0.002 0. 1 ** Temperature 2 287. 17 143.58 5183.8 ** Sex 1 8. 96 8. 96 323. 5 Temp, x Sex 2 4.91 2.46 88. 8 E rro r 10 0.279 0. 028 Total 17 301.22
** P t 0. 01 Table 3. Developmental period in three successive generations of O. submetallicus at different tem peratures and 14L:10D.
No. adults emerged Days after *— ...... - .------Male (generation) Female (generation) (°c) parasitized 1st 2nd 3rd Mean 1st 2nd 3rd Mean
21 23 .. 4 3 2 3 24 3 2 2 2. 3 10 12 7 9. 7 25 3 3 2 2. 7 16 19 13 16.0 26 6 9 4 6. 3 32 36 27 31. 7 27 8 6 4 6. 0 39 35 31 35.0 28 3 5 4 4.0 17 19 21 19.0 29 1 2 0 1.0 14 18 11 14. 3 30 2 0 1 1.0 8 7 5 6. 7
31 - - - - 1 1 0 0. 7
25 14 --- - 0 2 1 1 15 0 1 2 1 4 7 5 5.3 16 10 6 8 8 38 43 48 43.0 17 7 12 9 9.3 49 58 50 49. 7 18 2 2 1 1.7 9 12 14 11.7
(continued) Table 3 (continued)
No . adults em er ged Days after Temperature host eggs Male (generation) Female (generation) (°C) parasitized 1st 2nd 3rd Mean 1st 2nd 3rd Mean
19 1 1 2 1. 3 4 • 2 4 3. 3 20 1 0 1 0. 7 0 1 1 0. 7 21 0 1 1 0. 7 1 0 1 0. 7
29 11 -- - - 2 0 1 1.0 12 1 0 2 1.0 7 3 5 5.0 13 16 9 14 13. 3 54 43 48 48. 3 14 10 6 13 9.7 48 42 53 47. 7 15 5 2 3 3. 0 13 8 10 10. 3 16 3 2 1 3.0 7 5 3 5. 0 17 2 1 0 1.0 2 2 1 1.7 62
Table 4. Analysis of variance of developmental period of O. submetallicus in five successive generations at different temperatures.
Sum of Source of Degrees of Mean square F value variation freedom squares
Replicate 2 0. 025 0. 013 0. 74 Temperature 2 545. 63 272.82 15598.63 Sex 1 0. 014 0. 014 0. 79 Temp, x Sex 2 0. 11 0.055 3. 14 E rro r 10 0. 17 0.017 Total 17 545. 92
** p < 0. 01 Table 5. Percent emergence in five successive generations of T. basalis at different tem peratures and 14L:10D.
Temp. No. No. No. Individuals a (0 £j Generation host eggs emergence emergence J parasites per egg^/ parasitized holes emerged
21 1 269 223 82. 9 223 2 270 213 78.9 213 3 283 249 88. 0 249 4 274 238 86. 7 238 5 281 239 85. 1 239
Mean - - 84. 3 -
25 1 280 2 49 88. 9 249 2 275 253. 92.0 253 3 283 243 85. 7 243 4 269 250 92. 7 250 5 281 241 85. 8 241
Mean - 89. 1 - (continued) Table 5 (continued)
Temp. No. No. % No. Individuals (°C) Generation host eggs emergence emergence3^ parasites per eggk/ parasitized holes emerged
29 1 281 242 86. 1 212 1 2 287 263 91.6 263 1 3 272 233 85. 7 233 1 4 286 260 90. 1 260 1 5 291 256 88.0 256 1
Mean - - 88. 3 - 1
a_/ Percent of host eggs from which parasites emerged. hj Mean number of parasites emerged per host egg. Table 6. Percent emergence in five successive generations of T. basalis at different temperatures and 10L,:14D.
Temp. No. No. % No. Individuals (°C) Generation host eggs emergence emergence—^ parasites per eggk/ parasitized holes emerged
21 1 278 222 79.9 222 1 00 o !\i 2 269 219 219 1 3 284 213 76. 1 213 1
4 277 246 89. 1 246 1 5 282 248 87. 9 248 1
Mean - - 83.0 - 1
25 1 268 239 85. 1 239 1 2 289 262 89. 1 262 1 3 257 251 87.2 251 1 4 276 270 92.8 270 1 5 282 265 89. 8 265 1
Mean _ _ 88.8 - 1
(continued) Table 6 (continued)
Temp. No. No. No. Individuals % a , (°C) Generation host eggs emergence emergence parasites per egg-' parasitized holes em erged
29 1 269 249 85. 9 249 1 2 278 252 90. 3 252 1 3 286 271 92. 8 271 1 4 281 251 86. 9 251 1 5 279 267 91.4 267 1
Mean - - 89. 5 - 1
a/ Percent of host eggs from which parasites emerged,
bJ Mean number of parasites emerged per host egg. Table 7. Percent emergence in five successive generations of O. submetallicus at different tem peratures and 14L:10D.
Temp. No. No. No. Individuals % a// (°C) Generation host eggs emergence emergence—' parasites per eggk/ parasitized holes emerged
21 1 286 224 78. 9 268 1.20 2 271 225 83.0 247 1. 10 3 279 240 86.0 312 1.30 4 280 210 75.0 252 1.20 5 269 234 87.0 278 1. 19
Mean - - 84.0 270 1.20
25 1 268 225 84. 0 270 1.20 2 283 224 79.2 275 1.23 3 276 245 88. 8 291 1. 19 4 284 244 85. 9 380 1.56 5 278 255 91.8 328 1.29
Mean - 85.9 1.29
(continued) Table 7 (continued)
Temp. No. No. No. Individuals % (°C) Generation host eggs emergence etnergence parasites per egg parasitized holes emerged
29 1 277 229 82. 7 241 1.49 2 281 224 79. 7 269 1. 20 3 290 261 90. 0 339 1. 30 4 275 234 85. 1 304 1. 30 5 283 246 87. 0 295 1.20
Mean - - 84. 9 - 1. 30
a/ Percent of host eggs from which parasites emerged, b/ Mean number of parasites emerged per host egg. Table 8. Percent emergence in five successive generations of O. submetallicus at different temperatures and 14L:10D*
Temp. No. No. % No. Individuals (°C) Generation host eggs emergence emergence— parasites per egg^ parasitized holes emerged
1 258 217 80. 7 284 1. 10 2 281 213 78. 9 257 1.21 3 265 215 76. 0 280 1. 30 4 276 236 86. 1 258 1.09 5 267 235 83. 6 282 1. 20
Mean - - 81. 1 - 1. 18
1 265 232 82. 9 303 1.31 2 278 237 86.2 283 1. 19 3 259 252 89. 1 323 1.28 4 282 221 82. 2 247t 1. 12 5 276 236 84. 0 307 1. 30
Mean _ 84. 9 - 1.24
(continued) Table 8 (continued)
Temp. No. No. No. Individuals % a // (°C) Generation host eggs emergence emergence ' parasites per eggk/ parasitized holes emerged
29 1 276 242 86. 1 361 1.31 2 . 268 253 88. 2 376 1.40 3 281 220 80. 9 265 1.20 4 259 2 40 83. 9 266 1. 11 5 279 259 89.0 338 1. 31
Mean - - 85. 6 - 1. 27
a/ Percent of host eggs from which parasites emerged, b/ Mean number of parasites emerged per host egg. 71
Table 9. Adult longevity of male T. basalis in the presence and absence of honey.
Treatment Rep. No- o£ Longevity (days) Adults Range Mean
Honey 1 5 36 - 47 41.4 2 5 40 - 50 46.2 3 5 38 - 48 43.2 4 5 39 - 49 44.4 5 4 36 - 48 43.5 43.7
Check 1 5 2 - 3 2.6 2 5 2 - 3 2.6 3 5 2 - 4 2. 6 4 5 2 - 3 2.6 5 5 2 - 3 2.6 2 . 6 72
Table 10. Adult longevity of female basalis in the presence and absence of honey and host eggs.
No. of Longevity (days) Treatment Rep. Adults Range Mean
Honey 1 5 45 - 55 50.4 2 5 49 - 56 52.4 3 5 44 - 55 49.6 4 5 40 - 57 47. 6 5 5 47 - 55 51.8 50.4
Honey + host eggs 1 5 30 - 44 37.8 2 5 31-41 36.6 3 4 32 - 39 35. 5 4 5 29 - 40 34.2 5 4 32 - 40 35.8 36.0
Host eggs 1 5 2 - 3 2.6 2 5 2 - 3 2.6 3 5 2 - 3 2.8 4 4 2 - 3 2.6 5 5 2 - 3 2.6 2.6
Check 1 5 2 - 3 2.8 2 5 2 - 3 2.6 3 5 2 - 3 2.6 4 4 2 - 3 2.6 5 5 2 - 3 2.8 2.7 73
Table 11. Adult longevity of male O. submetallicus in the presence and absence of honey.
Longevity (days) Treatm ent Rep. No. of Adults Range Mean
Honey 1 4 12 - 16 13. 8 2 5 13 - 16 14. 8 3 4 13 - 16 14. 5 4 5 13 - 17 14. 6 5 5 14 - 17 15.4
--- 14. 6
Check 1 5 2 - 3 2.6 2 5 1 - 3 2.2 3 5 2 - 3 2. 6 4 5 2 - 3 2. 8 5 4 2 - 3 2. 6 2. 6 74
Table 12. Average adult longevity of female O. submetallicus in the presence and absence of honey and host eggs.
No. of Longevity (days) Treatment Rep. Adults Range Mean
Honey 1 5 40 - 55 47.8 2 4 38 - 50 44. 5 3 5 45 - 58 50.0 4 5 42 - 54 48. 6 5 4 36 - 50 43.8
- - - 46. 9
Honey + host eggs 1 5 25 - 36 30.4 2 5 27 - 41 33.4 3 4 27 - 36 32. 3 4 5 32 - 42 36. 6 5 5 28 - 40 34.0
- - - 33. 3
Host eggs 1 5 2 - 3 2.8 2 5 1 - 3 2.2 3 4 2 - 3 2.6 4 4 2 - 4 2.9 5 5 2 - 3 2.8
- - - 2. 7
Check 1 4 2 - 3 2.2 2 5 2 - 3 2.6 3 5 2 - 3 2.6 4 5 2 - 3 2.8 5 5 2 - 3 2.6
- - - 2.6 75
Table 13. Sex ratio of O. submetallicus in successive generations at temperature of 216C.
Generation No. adults emerged Ratio Male Female ( cr : 9 )
1 24 118 1:4.9 2 16 130 1:8.0 3 22 158 1:7. 3 4 20 136 1:6.8 5 23 90 1:3. 9 6 27 153 1:5. 7 7 20 96 1:4. 8 8 19 136 1:7. 1 9 16 146 1:9. 1
Mean -- 1:6.4
Table 14. Sex ratio of O. submetallicus in successive generations at temperature of 25°C.
Generation No. adults emerged Ratio Male Fem ale ( cT : 9 )
1 40 128 1:3.2 2 13 102 00 3 45 243 1:5.4 4 20 122 1:6. 1 5 23 113 1:4.9 6 22 125 1:5.7 7 22 129 1:5.9 8 41 193 1:4.7 9 24 151 1:6.3
Mean - - 1:5.6 76
Table 15. Sex ratio of O. submetallicus in successive generations at temperature of 29°C.
Generation No. adults emerged Ratio Male Female ( cf : 9 )
1 24 128 1 5. 3 2 41 140 1 3.4 3 52 150 1 2.9 4 21 58 1 2.8 5 35 166 1 4. 7 6 27 101 1 3.7 7 32 133 1 4.2 8 25 131 1 5.2 9 31 108 1 3. 5 Mean 1 4.0 Table 16. Percent parasitism of the eggs of pentatomid species by T. basalis.
______Replication______1______2______3______Mean Species Test No. eggs % No. eggs % No. eggs % % in mass parasitism in mass parasitism in mass parasitism parasitism
N. viridula 1 94 100 86 96. 5 79 97.5 98.0 2 98 96.9 91 100 87 94. 3 97. 1 3 78 91.6 89 97.8 94 98.9 96.0 4 84 94. 1 94 95. 8 90 96. 7 95. 5 hilar e 1 59 96.6 46 93. 5 49 91.8 93.9 2 57 93.0 46 100 50 94.0 95.9 3 45 91. 1 48 93. 8 61 91.8 92.2 4 58 89.4 47 91.5 50 94.0 91.6
E. bifida 1 21 0 19 0 32 0 0 0 2 34 0 27 0 28 0 3 38 0 47 0 34 0 0 4 42 0 39 0 29 0 0 (continued) Table 16 (continued)
Replication Mean Species Test No. eggs % No. eggs % No. eggs % % in mass parasitism in m ass parasitism in mass parasitism parasitism
E. servus 1 34 94. 1 29 100 38 92. 1 95.4 2 43 95.4 30 100 26 92.3 96.0 3 21 90. 5 24 100 23 91.3 93.9 4 35 94. 3 24 91.2 28 92.9 92.8
T. pallidovirens 1 19 100 22 90.9 19 89. 5 93.5 2 26 92.3 19 89. 5 22 95. 5 92. 5 3 27 100 17 94. 1 21 95.2 96.4 4 17 94. 1 21 90. 5 23 95.9 93.4 Table 17. Percent parasitism of the eggs of pentatomid species by O. submetallicus.
Replication 1 2 3 Mean Species Test No. eggs % No. eggs % No. eggs % % in mass parasitism in mass parasitism in mass parasitism parasitism
N. viridula 1 91 95.6 89 98.9 84 100 98.2 2 76 93.4 83 97. 5 69 95.7 95.5 3 75 100 98 93.9 87 96.6 96.8 4 78 98. 7 83 96. 4 68 89.7 94.9
A. hilare 1 46 91. 3 52 92. 3 64 82.8 88.8 2 59 89.8 60 93. 3 56 96.4 93.2 3 49 100 58 93. 1 63 93.6 95.6 4 47 95. 7 64 93.8 52 92.3 93.9
E. bifida 1 23 0 20 0 31 3.2 1. 1 2 31 0 20 2.4 18 0 0.8 3 59 3.4 22 0 37 0 1. 1 4 33 3.0 26 0 19 0 1.0 (continued)
vO Table 17 (continued)
.______Replication ______1______2______3______Mean Species Test No. eggs % No. eggs % No. eggs % % in mass parasitism in mass parasitism in mass parasitism parasitism
E. servus 1 41 95. 1 43 97. 7 28 100 97.6 2 31 100 34 95.8 26 92.3 96.0 3 20 100 19 94. 7 27 96. 3 97.0 4 18 94.4 36 94.4 25 96.0 95.0 pallidovirens 1 18 100 16 93.8 24 91.7 95. 1 2 15 100 21 100 17 94. 1 98.0 3 16 100 22 90.9 18 94. 5 95. 1 4 16 93. 8 19 89.5 20 95.0 92.8
00o Table 18. Number of eggs parasitized by 0. submetallicus and T. basalis in different combinations.
a/ Combination Rep. No. eggs No. adults emerged2- parasitized Total Ooencyrtus Trissolcus
Combined 0. & T. 1 232 216 160(74.1) 56(25.9)
2 192 181 121(66.8) 60(33.2)
3 241 234 123(60.9) 79(39.1)
4 216 207 158(67.5) 76(32.5)
Mean - - - (67.3) -(32.7)
Alternated 0. & T. 1 201 189 119(63.6) 70(37.0) at 24-hr intervals 2 211 195 143(73.7) 51(26.3)
3 191 181 119(65.7) 62(34.3)
4 214 198 143(72.2) 55(27.8) i Mean -- - (68.7) -(31.4)
Alternated T. & 0. 1 195 188 133(69.6) 58(30.4) at 24-hr intervals 2 185 176 99(56.2) 77(43.8)
3 201 186 108(58.1) 78(41.9)
4 219 202 133(65.8) 69(34.2)
Mean - - - (62.4) -(37.6) a/ Figures in the parenthesis are percent emergence of each species from the total adults emerged. 82
Table 19. Analysis of variance of percent parasitism between O. submetallicus and T. basalisf^
Source of Degrees of Sum of Mean F variation freedom squares square value
Replication 3 0 0 Combination 2 0 0 ** Species 1 6246.83 6246. 82 158.51 Combinations x species 2 154.04 77. 02 1.95 E rro r 15 591.09 39. 41 Total 23 6991.96
** P < 0 .0 1 aJ Data used in the analysis are Appendix Table 18.
Table 20. Number of egg masses parasitized in the preliminary field trials in 1977.
Treatm ent T e s t^ (Released species) July 15 July 31 August 14
Ooencyrtus 8(16) 8(17) 7(17) Trissolcus 9(18) 10(16) 9(16) Combined 10(17) 9(17) 9(17) O. + T. (4 + 6) (4 + 5) (3 +6) Control 2(18) 1(16) 2(17)
a/ Figures in parenthesis are number of egg masses collected out of 20 placed in each treatment. 83
Table 21. Analysis of variance of percent parasitism in the preliminary field trials during 1977.^
Source of Degrees of Sum of Mean F variance freedom squares square value
Treatm ent 2 369.10 74. 53 4.47 ns Test 2 149.06 76.69 4. 60 ns E rro r 4 153.39 16.66 Total 8 369.10
ns P > 0. 05 aJ Data used in the analysis is presented in Table 15. Table 22. Mean percent parasitism of egg masses in three trials at each station in the a / experimental area in 1978 .
Station and distance Species from central release Ooencyrtus Trissolcus Combined (O. + T. ) point, m
North 1 50. 0 64. 7 58. 8(25.0 + 33.8) 5 42. 9 39. 5 46.3(12.5 +33.8) 10 28.6 47. 1 24.4(0 + 24.4) 15 0 9.2 28.4(16.7 + 11.8) 20 0 0 0
West 1 57. 1 54.6 62.6(33.3 + 29. 3) 5 42. 9 54.6 39.0(14.3 + 24.2) 10 16. 7 39.4 33.0(12.5 + 20. 5) 15 0 9. 1 15.2(0 + 15.2) 20 0 0 0
(continued) Table 22 (continued)
Station and distance Species from central release point, m Ooencyrtus Trissolcus Combined ( O. + T. )
South 1 50.0 50.0 57.1(28.6 + 28.6) 5 33. 3 57. 1 62. 5(25.0 + 37. 5) 10 37. 5 28.6 42.9(14.3 + 28.6) 15 16. 7 12. 7 12. 5(0 + 12. 5) 20 0 16. 7 0
East 1 42. 9 55.9 60. 7(25.0 + 35. 7) 5 50. 0 61.4 40.8(14.3 + 26.5) 10 37. 5 26. 5 47.6(33.3 + 14.2) 15 0 9.9 14.2(0 + 14.2) 20 0 0 0
aJ Percent parasitism by O. submetallicus and T. basalis. Figures used in the conversion are given in Appendix Table 23. Table 23. Percent parasitism of egg masses at each station in the experimental area in three trials in 1978.
Species Station and Ooencyrtus + Trissolcus— Control central release point, m 1 2 3 1 2 3 1 2 3 1 2 3
North
1 66.7 50.0 33.3 50.0 66.7 66.7 0.0+50.0 50.0+50.0 33.3+33.3 0.0 0.0 0.0
5 50.0 33.3 50.0 66.7 50.0 50.0 50.0+50.0 0.0+33.3 0.0+50.0 0.0 0.0 0.0
10 33.3 50.0 0.0 50.0 50.0 33.3 50.0+0.0 0.0+0.0 0.0+50.0 50.0 0.0 0.0 o o 15 0.0 0.0 0.0 33.3 0.0 0.0 0.0+33.3 0.0+50.0 0.0+0.0 • 50.0 0.0
20 0.0 0.0 0.0 0.0 0.0 0.0 0.0+0.0 0.0+0.0 0.0+0.0 0.0 0.0 0.0
West
1 50.0 66.7 50.0 66.7 50.0 50.0 50.0+50.0 0.0+50.0 50.0+0.0 0.0 0.0 0.0
5 50.0 50.0 33.3 50.0 66.7 50.0 50.0+0.0 50.0+0.0 0.0+50.0 0.0 0.0 0.0
10 33.3 0.0 50.0 50.0 50.0 50.0 0.0+33.3 0.0+50.0 0.0+33.3 0.0 0.0 0.0 o o
• 33.0 15 0.0 0.0 0.0 50.0 33.3 0.0 0.0+0.0 0.0+0.0 0.0+0.0 50.0 0.0 20 0.0 0.0 0.0 0.0 0.0 0.0 0.0+0.0 0.0+0.0 0.0+0.0 0.0 0.0 (continued) Table 23. (continued)
Station and Species distance from central release Ooencyrtus Trissolcus Ooencyrtus + Trissolcus^ Control point, m 1 2 3 1 2 3 1 2 3 1 2 3
South
1 50.0 50.0 50.0 66.7 50.0 50.0 0.0+50.0 50.0+50.0 50.0+0.0 0.0 0.0 0.0
5 66.7 0.0 50.0 100 0.0 33.3 50.0+0.0 0.0+50.0 0.0+50.0 0.0 0.0 0.0
10 50.0 33.3 33.3 0.0 33.3 50.0 33.3+33.3 0.0+0.0 0.0+50.0 0.0 0.0 0.0
15 0.0 50.0 0.0 0.0 50.0 0.0 0.0+33.3 0.0+50.0 0.0+33.3 0.0 0.0 0.0
20 0.0 0.0 0.0 50.0 0.0 0.0 0.0+0.0 0.0+0.0 0.0+0.0 0.0 0.0 0.0
East
1 50.0 50.0 50.0 50.0 50.0 66.7 0.0+50.0 50.0+50.0 50.0+50.0 0.0 0.0 0.0
5 50.0 66.7 50.0 66.7 50.0 50.0 33.3+33.3 0.0+66.7 50.0+0.0 0.0 0.0 0.0
10 50.0 33.3 50.0 50.0 33.3 0.0 50.0+0.0 0.0+50.0 0.0+50.0 0.0 0.0 0.0
15 0.0 0.0 0.0 33.3 0.0 33.3 0.04-50.0 0.0+0.0 0.0+0.0 0.0 0.0 0.0
20 0.0 0.0 0.0 0.0 0.0 0.0 0.0+0.0 0.0+0.0 0.0+0.0 0.0 0.0 0.0
a/ Figures used in the conversion of percent parasitism are given in Appendix Table 24.
b/ Percent parasitism by (). submetallicus and T. basalis. Table 24. Number of parasitized egg masses placed at each station in the experimental area in three trials in 1978.-'
Station a n d ______Species distance from central release Ooencyrtus Trissolcus Ooencyrtus & Trissolcus Control point, m 1 2 3 1 2 3 1 2 3 1 2 3
North
1 2(3) 1(2) 1(3) 1(2) 2(3) 2(3) 0+1(2) 1+1(3) 1+1(3) 0(3) 0(2) 0(2)
5 1(2) 1(3) 1(2) 2(3) 1(2) 1(2) 1+1(3) 0+1(3) 0+1(2) 0(2) 0(3) 0(3)
10 1(3) 1(2) 0(2) 1(2) 1(2) 1(3) 1+0(2) 0+0(2) 0+1(2) 1(2) 0(2) 0(3)
15 0(2) 0(3) 0(3) 1(3) 0(2) 0(2) 0+1(3) 0+1(2) 0+0(2) 0(3) 1(2) 0(2)
20 0(2) 0(2) 0(2) 0(2) 0(3) 0(2) 0+0(2) 0+0(3) 0+0(3) 0(2) 0(3) 0(2)
West
1 1(2) 2(3) 1(2) 2(3) 1(2) 1(2) 1+1(2) 0+1(2) 1+0(2) 0(2) 0(2) 0(2)
5 1(2) 1(2) 1(3) 1(2) 2(3) 1(2) 1+0(2) 1+0(2) 0+1(2) 0(3) 0(2) 0(2)
10 1(3) 0(2) 1(2) 1(2) 1(2) 1(2) 0+1(3) 0+1(2) 0+1(3) 0(2) 0(3) 0(3)
15 0(2) 0(2) 0(2) 1(2) 1(3) 0(2) 0+0(2) 0+0(3) 0+0(2) 1(2) 0(2) 1(3)
20 0(2) 0(3) 0(3) 0(2) 0(2) 0(2) 0f0(2) 0+0(2) 0+0(3) 0(3) 0(2) 0(2) (continued) Table 24. (continued)
Station and Species distance from central release Ooencyrtus Trissolcus Ooencyrtus & Trissolcus Control point, m 1 2 3 1 2 3 1 2 3 1 2 3
South
1 1(2) 1(2) 1(2) 2(3) 1(2) 1(2) 0+1(2) 1+1(2) 1+0(2) 0(2) 0(3) 0(2)
5 2(3) 0(2) 1(2) 2(2) 0(2) 1(3) 1+0(2) 0+1(2) 0+1(3) 0(3) 0(2) 0(3)
10 1(2) 1(3) 1(3) 0(2) 1(3) 1(2) 1+1(3) 0+0(3) 0+1(2) 0(2) 0(2) 0(2)
15 0(2) 1(2) 0(2) 0(3) 1(2) 0(3) 0+1(3) 0+1(2) 0+1(3) 0(2) 0(3) 0(3)
20 0(3) 0(2) 0(3) 1(2) 0(2) 0(2) 0+0(2) 0+0(2) 0+0(2) 0(2) 0(2) 0(2)
East
1 1(2) 1(2) 1(2) 1(2) 1(2) 2(3) 0+1(2) 1+1(2) 1+1(3) 0(2) 0(2) 0(2)
5 1(2) 2(3) 1(2) 2(3) 1(2) 1(2) 1+1(3) 0+2(3) 1+0(2) 0(2) 0(2) 1(3)
10 1(2) 1(3) 1(2) 1(2) 1(3) 0(2) 1+0(2) 1+1(2) 0+1(2) 0(3) 0(3) 0(2)
15 0(2) 0(2) 0(3) 1(3) 0(2) 1(3) 0+0(2) 0+0(2) 0+0(2) 0(2) 0(3) 0(2)
20 0(2) 0(2) 0(2) 0(3) 0(3) 0(2) 0+0(3) 0+0(2) 0+0(3) 0(2) 0(2) 0(3)
a/ Figures in the parenthesis are number of egg masses collected from each station. Initially three egg
masses were placed at each station. 90
Table 25. Analysis of variance of percent egg masses parasitized at each station in the experimental a re a.^
Source of Degrees of Sum of Mean F variation freedom squares square value
* Treatment 2 610.09 305.05 3.74 Direction 3 101. 59 33. 87 0.42 ** Distance 4 25906.92 6476.73 79.44
Treatment x Direction 6 32. 92 5.49 0.07 Treatment x Distance 8 336.85 42. 11 0. 52 Direction x Distance 12 381.99 31.83 0.39 E rro r 24 1956.64 81. 53 Total 59 29327.00
* P < 0.05, ** P-= 0. 01. aJ Data used in the analysis are in Appendix Table’17. VITA
Seung Chan Lee was born in Jindo, Korea on March 6, 1935.
From March, 1955 to September, I960, he attended Agricultural
College, Seoul National University where he received a Bachelor of Science degree in Agricultural Biology. Upon graduation, he was employed as a research officer at the Department of Entomology,
Institute of Agricultural Sciences, Office of Rural Development.
From September, 1965 to October, 1967, he attended the graduate school of University of Canterbury, New Zealand and received a Master of Science degree in Entomology in May, 1968.
He resumed his duties as a senior research officer at the Institute of Agricultural Sciences in November, 1967.
In September, 1975, he entered the graduate school of Louisiana
State University and was awarded a fellowship from the Government of Republic of Korea in collaboration with United States of America.
He is presently a candidate for the degree of Doctor of
Philosophy in Entomology.
91 EXAMINATION AND THESIS REPORT
Candidate: Seung Chan Lee
Major Field: Entomology
Title of Thesis: Evaluation of Ooencyrtus submetalllcus (Howard) and Trissolcus basalis (Wollaston) as Egg Parasites of Nezara vlrldula (Linnaeus)
Approved: ^ 0- w Major'ProfessorMajor 'Professt and Chairman
... _ ^ Deani of of the the Graduate Gr^uate Scho EXAMINING COMMITTEE: Date of Examination: April 24, 1979