The effect of host age ofLymantria dispar larvae [Lep.: Lymantriidae] on the development ofGlyptapanteles liparidis [Hym.: Braconidae]

The endoparasitic development ofG. liparidis was examined in 3 different host stages of gypsy moth larvae. Hatching ofG. liparidis-larvae occurred 3 to 5 days after oviposition in hosts parasitized during their premoulting period, and after 5 to 7 days in those parasitized in the 3^rd midinstar state. The parasites generally moulted to the 2^nd larval instar between the 11^th and 13^th day in the first group, and between the 13^th and 15^th day in the latter, when they had reached a volume of 0.04–0.05 mm³. The positive correlation between host ecdysis and the ecdysis of 1^st stadium larvae to L₂ suggested that host moulting influenced the development of the parasitoid larvae. Emergence from the host larvae occurred at 20°C after 27 days on average, and coincided with the parasites moulting to the 3^rd instar. Five to 7 days after spinning their cocoons near the developmentally arrested host larva, the male, and 1 to 2 days later the female wasps eclosed. Due to the variation in the number of parasites per host, no difference was observed between the hosts parasitized at various stages; however, a tendency for later parasitized hosts to contain more parasite larvae was evident. The nutritional conditions of the moth parental generation influenced both host and parasite development. On the other hand no influence of host age was observed on emergence dates of larvae and wasps.      

Host recognition by the gypsy moth [Lymantria dispar] [Lep.: Lymantriidae] hyperparasite,Eurytoma appendigaster [Hym.: Eurytomidae] of cocoons ofCotesia melanoscela [Hym.: Braconidae]

Artificial and modified natural hosts were exposed to females of the gypsy moth [Lymantria dispar (L.)] hyperparasite,Eurytoma appendigaster (Swederus), to investigate its host recognition behavior on the primary host, which are cocooned larvae of the gypsy moth parasite,Cotesia melanoscela (Ratzeburg). Material(s) which caused drilling behavior by the hyperparasite on host cocoons were extracted with both polar and non-polar solvents. However, cocoons washed with large volumes of solvent still caused substantial drilling activities by females, suggesting that additional cues may be important. Results suggest that host recognition in this hyperparasite involves a variety of host characteristics.      

Biology ofMicroplitis mediator [Hym.: Braconidae] a gregarious endoparasite ofAgrotis segetum [Lep.: Noctuidae]

Microplitis mediator (Haliday) a gregarious endoparasite was recorded for the first time fromAgrotis segetum (Schiff) in Ankara, Turkey. The female parasites found their hosts by responding to the faeces of the caterpillars. An average, females laid 15.5±1.6 eggs in the bodies of their hosts. The newly laid eggs were elongated, oval in shape and 0.23±0.004 mm long and 0.07 mm wide. They hatched in 5, 4 and 3 days at 20±2°C, 25±2°C and 30±2°C respectively when maintained at 60–70% R.H. and 14∶10 light∶dark regime. At the same temperatures, the larval stage lasted for 24.9±0.6, 18.2±0.4 and 17.1±0.5 days respectively. The prepupal stage was completed in 2 days at 25±2°C, whereas the prepupal and pupal (cocoon) stage lasted 10.9±0.2, 7.0±0.1 and 6.2±0.1 days respectively at the temperatures mentioned above. The adults started mating and feeding shortly after emergence. Female parasites started laying after one day, 7–11 hours and 5–7 hours at the temperatures stated above. At these temperatures females lived for 10.8±0.2, 5.4±0.1, 4.6±0.1 days and laid on average 556, 484 and 363 eggs respectively, whereas the males survived 10.5±0.3, 4.7±0.1 and 4.4±0.1 days respectively.      

Biology ofPhanerotoma hendecasisella [Hym: Braconidae] a parasitoid ofDiaphania indica [Lep.: Pyralidae]

Studies were conducted on the solitary egg-larval endoparasitoidPhanerotoma hendecasisella Cam. [Hymenoptera: Braconidae] to determine its biology onDiaphania indica (Saunders) [Lepidoptera: Pyralidae]. Larvae pass through 3 stages as determined by the shape and size of the mandibles. Mean developmental period from egg to adult was 26.51 days at 26.06 °C and 73.88% RH. There is no preoviposition period. The sex ratio was 1∶1.12 (male/female). Mean adult longevity was not different for ♂♂ and ♀♀.      

Oviposition pattern byCotesia ayerzai [Hym.: Braconidae] onAscia monuste [Lep.: Pieridae] under laboratory conditions

Various aspects of the parasitims of caterpillars ofAscia monuste orseis byCotesia ayerzai, were studied in laboratory choice tests. Individual ♂♂ were found to be extremely variable in ovipositional duration, as well as in the number of eggs oviposited. To simulate parasitoid dispersal, or low host density, we isolated ♂♂ for 60 min following initial exposure and compared our tests with ♂♂ which had not been isolated. No differences in (1) the number of eggs oviposited per host instar; (2) the conditional probability of host encounter; (3) host acceptance; and (4) the conditional probability of instar specific parasitism were found between these groups. Held ♂♂ did, however, reject hosts after ovipositor insertions in a higher proportion.      

The effect of parasitism byHyposoter didymator [Hym.: Ichneumonidae] on food consumption and utilization bySpodoptera litura [Lep.: Noctuidae]

The effect of parasitism byHyposoter didymator (Thunb.) [Hym.: Ichneumonidae] on food consumption and utilization bySpodoptera litura (Fb.) [Lep.: Noctuidae] was studied for seven days, during which the parasitoid completed its larval development. Food consumption, weight gained and faeces produced were significantly less in parasitized larvae than in unparasitized larvae after the 4^th day following parasitization. Approximate digestibility was higher in parasitized larvae after the 2^nd day following parasitization. Efficiency of conversion of ingested and digested food into body weight was greater in unparasitized larvae after the 2^nd day of parasitization. There seems to be a definite immediate advantage to the crop on releasing the parasitoid due to the reduced consumption of food. Contribution No. 46004 of Biological Control Centre (NCIPM), Bangalore 560 024.     

In vitro rearing ofLysiphlebus fabarum [Hym.: Braconidae]

In vitro rearing of the aphid endoparasitoidLysiphlebus fabarum (Marshall) (Hymenoptera, Braconidae) was attempted. Successful permanent cultures ofAphis fabae Sc. andMyzus persicae Sulz. cells were not obtained. Therefore, parasitoid larvae were reared in 2 unnatural media rone of which included cells ofCeratitis capitata Wied. (Diptera, Trypetidae). A group of larvae was reared in a substrate to which parasitoid teratocytes had been added. SinceLysiphlebus fabarum females did not oviposit into paraffin droplets including the substrates, the larvae were directly transferred from parasitized aphids into the rearing media. Several larvae reached the final instar, but only 2 out of the 48 tested in the 3 substrates became adults. The meaning of teratocytes inin vitro rearing of Aphidiine, Braconids is discussed. This work was supported by a grant from the italian Ministry of Education (M.P.I. 40%).     

RearingGlypta fumiferanae [Hym.: Ichneumonidae] on a multivoltine laboratory colony of the western spruce budworm (Choristoneura occidentilis) [Lep.: Tortricidae]

Methods were developed for rearingGlypta fumiferanae Viereck on a nondiapausing laboratory colony of the western spruce budworm,Choristoneura occidentalis Freeman. Both host and parasite are univoltine and undergo diapause in nature. In this study, the parasite's voltinism was synchronized with that of a nondiapausing host.G. fumiferanae mated readily in the laboratory, and 5 consecutive generations were reared with an average generation time of less than 8 weeks-much less than the 23 weeks needed for 1 generation to develop in the field. Developmental times are reported, and some aspects of behavior described.     

Effects of temperature and photoperiod on the development and oviposition ofApanteles sp. groupUltor [Hym.: Braconidae], a larval parasite of the carob mothEctomyelois ceratoniae [Lep.: Pyralidae]

Development of the solitary parasitoidApanteles sp. groupultor in larvae ofEctomyelois ceratoniae was investigated at different constant temperatures. Temperature had a significant effect upon parasitoid development during both host-internal and host-external phases. The duration of the host-internal phase varied from 41 days at 15–17°C to 8.6 days at 29°C, the duration of the host-external phase varied from 16.5 days at 16–17°C to 5.4 days at 29°C. Effect of photoperiod upon parasite development and parasitization of hosts were determined under daily photophases, of 24, 16, 12, 8 and 0 hours. No significant differences in oviposition rate were found among the 5 treatments. In any photoperiod studied, the parasite progeny developed normally without entering diapause.      

Effects of bacterial contamination on development ofMicroplitis croceipes [Hym.: Braconidae]

Bacterial contaminants ofHeliothis virescens (F.) influenced the development ofMicroplitis croceipes (Cresson). Among the four bacterial species studied, the most virulent wasPseudomonas maltophilia Hugh and Ryschenkow followed byBacillus subtilis (Ehrenberg) Cohn. Both bacteria caused severe mortality in all stages ofMicroplitis tested.Microplitis larvae were less susceptible toEscherichia coli (Migula) Castellani and Chalmers andLeuconostoc mesenteroides (Tsenkovskii) van Thieghem than toB. subtilis andP. maltophilia. AlthoughE. coli did not affect the number of cocoons produced, adult emergence was lower than in controls. Longevity of adultMicroplitis exposed to bacterially contaminated honey-water was greatly reduced in all bacterial treatments.      

Preference ofPholetesor ornigis [Hym.: Braconidae] for the sap-feeding larvae of its host,the spotted tentiform leafminer,Phyllonorycter blacerdella [Lep.: Gracillaridae]

Significantly more eggs were deposited by the braconid,Pholetesor ornigis (Weed), in the sap-feeding larvae (i.e. instars 1–3), than in the tissue-feeding larvae (i.e. instars 4–5), of its host, the spotted tentiform leafminer,Phyllonorycter blancardella (Fabr.).     

Influence of crucifer cropping system on the parasitism ofPlutella xylostella (Lep., Yponomeutidae) byCotesia plutellae (Hym., Braconidae) andDiadegma semiclausum (Hym., Ichneumonidae)

Field experiments were conducted to study the influence of cabbage monoculture and mixed cropping on the parasitism of diamondback moth,Plutella xylostella (L.), a destructive pest of all crucifers, by 2 larval parasites,Diadegma semiclausum Hellén andCotesia plutellae Kurdjumov. There was no significant difference in parasitism by either species whether cabbage was planted in insecticide-free monoculture or in mixed cropping with 8 noncrucifers which were sprayed twice a week with chemical insecticides mevinphos, methamidophos and permethrin. Population ofP. xylostella increased as the cabbage plants grew older. Parasitism byC. plutellae was higher soon after cabbage transplanting but decreased as the plants grew older. Parasitism byD. semiclausum was very low soon after cabbage planting but increased as the plants grew older. A significant negative correlation was found betwen parasitism byC. plutellae andD. semiclausum. In a caged field study where only one parasite species was used in an individual cage, parasitism ofP. xylostella by both species decreased as theP. xylostella population increased. This is believed to be due to the absence of competition between the two parasites inside the cage. There was no relationship between host-plant age and parasitism ofP. xylostella larvae by either parasite species.     

Development and encapsulation of the endoparasitoid,Microplitis croceipes (Hym.: Braconidae), in six candidate host species (Lep.)

Encapsulation and development of the endoparasitoid,Microplitis croceipes (Cresson), were studied in six atypical lepidopteran host species whose usual host isHelicoverpa zea (Boddie). The candidate hosts examined were: the fall armywormSpodoptera frugiperda (J. E. Smith); the beet armyworm,Spodoptera exigua (Hübner); the cabbage looper,Trichoplusia ni (Hübner); the greater wax moth,Galleria mellonella (L.); the Indian meal moth,Plodia interpunctella (Hübner); and the diamondback moth,Plutella xylostella (L.). BothS. exigua andT. ni were completely unsuitable forM. croceipes development due to the high rate of eggs that were encapsulated within three days after parasitism. Encapsulation inS. frugiperda included mainly parasitoid eggs and was first detected six days after parasitization at 25°C and two days at 30°C. Encapsulation inG. mellonella occurred only in the larval stage of the parasitoid. InP. interpunctella, parasitoid larvae reached the 3rd stadium, but none of them pupated. OnlyS. frugiperda andG. mellonella supported successful development ofM. croceipes from egg to adult. The percentage of parasitoids reaching the adult stage in these hosts was higher at 30°C than at 25°C (13% vs. 4% inS. frugiperda, and 21% vs. 3% inG. mellonella, respectively). However, these percentages were too low to substitute them as a more economical host for rearingM. croceipes. This biological information will be useful in additional laboratory studies directed toward reducing the rate of encapsulation (e.g., manipulation of host rearing temperature) to increase production ofM. croceipes on these hosts.     

Response ofChelonus blackburni [Hym.: Braconidae] to different ages and densities of potato tuber moth eggs

The response of an efficient egg-larval parasitoidChelonus blackburni Cameron to different ages and densities of potato tuber mothPhthorimaea operculella (Zeller) eggs was studied in a laboratory system. The parasitoid accepted 0–1, 1–2 and 2–3 day old eggs for parasitization. However, the eggs belonging to the first two age groups were significantly more acceptable when compared to the last age group. At low host density levels of 2 and 5 eggs per parasitoid, parasitoid emergence was zero. On increasing the host density, percent progeny production increased till a plateau was reached at a parasitoid-host ratio of 1∶50. This ratio thus proves to be ideal for obtaining maximum percent progeny production in the case of 0–1 and 1–2 day old eggs. Further increase in host density did not result in any significant increase in percent progeny production.      

Intraspecific host discrimination and larval competition inMicroplitis croceipes,Microplitis demolitor,Cotesia kazak (Hym.: Braconidae) andHyposoter didymator (Hym.: Ichneumonidae), parasitoids ofHeliothis virescens (Lep.: Noctuidae)

Intraspecific host discrimination and larval competition were studied forMicroplitis croceipes (Cresson),Microplitis demolitor Wilkinson,Cotesia kazak (Telenga), andHyposoter didymator (Thunberg), solitary endoparasitoids of the tobacco budworm,Heliothis virescens (F.). In ovipositional choice tests between unparasitized and parasitized hosts, the mean number of ovipositions for unparasitized hosts was significantly higher than the mean number of ovipositions for hosts parasitized once by a conspecific female forC. kazak andH. didymator, demonstrating that females of these 2 species discriminate against hosts recently (within a few seconds) parasitized by a conspecific female. No significant difference in oviposition occurred between these 2 kinds of hosts forM. croceipes andM. demolitor. Mean percent parasitization by a 2^nd conspecific female was determined at 24, 48, and 72-h delays in time between the 1^rst and 2^nd female attack, and with no delay. Except for the 0 h time delay forC. kazak andH. didymator, percent parasitization by a 2^nd conspecific female generally decreased as the delay in time between the 1^rst and 2^nd female attack increased. When the 2^nd parasitization immediately followed the 1^rst, one parasitoid larva always eliminated the other by physical combat. With a 24 or 48 h delay between the 1^rst and 2^nd parasitization, the younger larva was the victor over the older larva forM. croceipes, M. demolitor andC. kazak in at least 50% of the cases. Elimination of older larvae by younger larvae was by physical attack. However, forH. didymator, the older instar was the victor, and elimination of younger larvae by older larvae was probably through physiological processes. Further, older larvae ofH. didymator apparently killed the eggs of the 2^nd female by physiological processes.      

Host preferences ofTrichogrammatoidea bactrae fumata (Hym.: Trichogrammatidae) an egg parasitoid of leafrollers (Lep.: Tortricidae)

Trichogrammatoidea bactrae fumata Nagaraja is a naturally occurring egg parasitoid of some leafrollers in New Zealand kiwifruit orchards. The parasitoid showed a distinct preference for younger host-eggs ofEpiphyas postvittana, in which it achieved a higher rate of successful development. Such a preference is not as apparent withCtenopseustis obliquana. Host-species preference experiments found that the parasitoid rarely attackedPlanotortrix octo, and successful wasp emergence from parasitised eggs of this host was low.Epiphyas postvittana was the preferred host whenT. bactrae fumata was reared on this species. When reared onC. obliquana, the parasitoid showed no preference forE. postvittana orC. obliquana.     

Larval morphology and development of the parasitoidDacnusa sibirica [Hym.: Braconidae] in the leafminer hostChromatomyia syngenesiae

The development of the parasitoidDacnusa sibirica Telenga within its hostChromatomyia syngenesiae Hardy [Diptera: Agromyzidae] was studied. The three larval stages ofD. sibirica are described. Parasitoid development was found to be influenced by the host stage parasitized. The duration of the egg and 1st instar larval stages, and overall developmental time from egg to adult, decreased with increasing age of the host at parasitization.     

Allorhogas pyralophagus [Hym.: Braconidae], a gregarious external parasite imported into texas,USA, for biological control of the stalkborerEoreuma loftini [Lep.: Pyralidae] on sugar cane

Allorhogas pyralophagus Marsh is a recently discovered doryctine braconid with potential for field trials against stalk borers infesting both large- and small- stemmed Graminacea. This external gregarious parasite was originally reared fromEoreuma loftini (Dyar) larvae infesting Johnson grass [Sorghum halepense (L.) Pers.] and sugar cane (Saccharum officinarum L.) from the states of Sinaloa and Nuevo Leon, Mexico. The parasite is easily reared in the laboratory using a wide range of host larvae [Diatraea spp.,E. loftini, Chilo sp. andTryporyza nivelli (F)]. Hosts are placed in grass stems or paper straws for exposure to ovipositing females.A. pyralophagus has been field released and recovered from the following hosts infesting sugar cane:E. loftini andD. saccharalis (F.) in Texas.Diatraea spp. in Trinidad,D. rufescens in Bolivia andT. nivella in Sumatra, Indonesia. Approved as Contribution No. TA-20743 of the Texas Agricultural Experiment Station.     

Influence of laboratory hosts on the biological attributes ofChelonus blackburni [Hym.: Braconidae]

Among 6 laboratory hosts tested, the egg-larval parasitoidChelonus blackburni Cameron completed its development in only 3;Corcyra cephalonica Stainton,Phthorimaea operculella (Zeller) andAchroia grisella (Fabricius). The parasitoid failed to develop inSpodoptera litura (Fabricius),Galleria mellonella L. andSitotroga cerealella (Olivier). The development period of the parasitoids obtained from permissive hosts correspond to the development period of their hosts. Development period ofP. operculella, A grisella andC. cephalonica were 24.7±2.0, 39.5±2.1 and 50.5±4.1 days respectively while the development period of the parasitoid reared from these hosts were 25.8±1.6, 36.4±3.5 and 42.5±3.5 days respectively. The fecundity of the parasitoids reared onA. grisella, P. operculella andC. cephalonica were 365.2±52.8, 287.9±101.9 and 248.7±50.8 respectively. The size of the parasitoids reared from the above 3 hosts also followed the similar trend. However, no significant difference was observed on the percent parasitism and the longevity of the parasitoids reared on different hosts. This study was conducted at a temperature of 24±2°C and 60±5% RH. Contribution No 46001 of Biological Control Centre (NCIPM), Bangalore.     

Cold tolerance of coccons ofAllorhogas pyralophagus [Hym.: Braconidae]

Cold tolerance studies were conducted under laboratory conditions for coccons ofAllorhogas pyralophagus Marsh, a Mexican parasitoid of graminaceous borers. By storage, developmental time (from cocoon to adult emergence) could be extended by 2 to 6 times. However, cocoons stored for more than 14 days at 2°C failed to survive, while at 5 and 10°C, about 50% emergence was recorded for upto 21 days of storage. With respect to survival and adult longevity, 10°C seemed to be the most suitable storage temperature. Pre-emergence period was also significantly increased by storing cocoons for 21 to 35 days at this temperature. Sex-ratio of emerging adults was not significantly affected by storage. Fecundity was adversely affected in all the treatments except in the case of females emerging from cocoons stored at 5°C for 7 days. The progeny of parasitoids which emerged from cocoons stored at 5 and 10°C for 35 days consisted of only males. It is clear from the present study thatA. pyralophagus cocoons are more amenable to short-term storage. Contribution No. 285/87 of the Indian Institute of Horticultural Research, Bangalore-560 089.