Factitious Host Research Articles

Synergistic control against Asian corn borer (ACB) by Trichogramma vectored Beauveria bassiana infection on survival larvae escaped from parasitism

The combined application of natural enemies and entomopathogens as an alternative pest-control may act synergistically, additively or antagonistically. The objective of this study is to determine the efficacy of the combined application by parasitic Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) carrying insect-pathogenic fungus Beauveria bassiana (Bals.) Vuill. (TCB) against Asian corn borer (ACB), Ostrinia furnacalis (Lepidoptera: Pyralidae). 0.1% (w/v) starch solution was selected from several adjuvants due to its highest ability to carry fungal conidia, over 3.60 × 104 conidia per wasp. The fungal conidia adsorbed on the surface of factitious host, Antheraea pernyi eggs, subsequently adhered on new emerged T. dendrolimi as a vector, which carried the conidia onto eggs’ surface of ACB. The B. bassiana had no influence on T. dendrolimi’s parasitic rate, whereas resulting in fungal conidia adhering on over 60.00% of hatched larvae, which consequently caused 27.00 ± 5.70% percent of muscardine cadaver rate of pest’s larvae in a screen house test. In field trial, it showed significantly lower incidence parameters regarded as number of damaged plants, wormholes, and living pests, per 100 plants in TCB treatment compared to that of sole T. dendrolimi release (non-TCB) and non-treatment as control, respectively, especially the number of muscardine cadaver per 100 plants was 6-fold amount higher than that of non-TCB treatment. In this study, the suitable adjuvant of cost-effective and safe to T. dendrolimi emergence was selected for fungal conidia adhering for TCB, and the fungal conidia transmitting process from host eggs to pest infection was visualized by fluorescence observation, on the basis, it was proved in both screen house and field experiments that the TCB was a synergistic ACB control program with labor saving, low cost and high efficient advantage compared to sole biocontrol agent application.

Impact of Trichogramma parasitoid age on the outcome of multiparasitism in the factitious host eggs of Chinese oak silkworm, Antheraea pernyi

The age of Trichogramma parasitoids could influence biological traits which are of great importance for effectiveness of mass rearing systems. Recent studies demonstrated that Trichogramma ostriniae (TO) could parasitize Antheraea pernyi eggs through multiparasitism along with other Trichogramma species, although few adults could emerge successfully. It is important to characterize the factors modulating the performance of TO on A. pernyi eggs, notably in order to try enhancing its quantitative emergence through multiparasitism for further use in biological control. In this context, irrespective of host age, we tested different ages of TO females (from 0.5-day- to 6-day-old postemergence) in multiparasitism with Trichogramma chilonis (TC) on A. pernyi eggs. The results of the present study confirmed that TO parasitism on A. pernyi eggs was largely age dependent. Higher percentage of multiparasitism and higher number of emerged TO adults were recorded in the treatment where 3-day-old TO females were used for parasitization with TC on A. pernyi host. In addition, we also tested different female ratios of both Trichogramma species to find out an optimal ratio for use in mass production. The highest percentage of multiparasitism, emergence and optimum emerged number of TO (per A. pernyi egg) was observed with the ratio 3:2 (TO:TC) per 1 host egg. This study demonstrated that the age of TO females can significantly affect their performance in multiparasitism of large A. pernyi eggs. These results prompt for more research in order to develop an effective multiparasitism-based production of TO at the industrial scale.

Feeding lifestyles of the Phytoseiidae revisited: searching for a factitious rearing host for Neoseiulus fallacis (Acari: Phytoseiidae)

Several mite species from the Phytoseiidae (Acari) have been successfully developed as products for augmentative biological control. Rearing of mites using factitious prey in grain-based systems can increase the efficiency of production of phytoseiids. This has been done successfully for several species but usually for Type III (generalist predator) phytoseiids. Neoseiulus fallacis (Garman) (Acari: Phytoseiidae) is a Type II phytoseiid (prefers spider mites) that is currently reared in British Columbia (Canada) on Tetranychus urticae Koch (Acari: Tetranychidae) in a plant-based system. Here, we present feeding behaviour and predation data for N. fallacis on T. urticae and three Astigmatid (Acari) mites: Lepidoglyphus destructor (Schrank) (Acari: Glycyphagidae), Aleuroglyphus ovatus (Tropeau) (Acari: Acaridae) and Thyreophagus entomophagus (Laboulbene) (Acari: Acaridae). Our objective is to identify a candidate factitious host for mass rearing of N. fallacis. Although N. fallacis grabbed prey mites of all four species, successful feeding attempts were more frequent for the native host, T. urticae, than for the three Astigmatid species. N. fallacis rejected A. ovatus and T. entomophagus as hosts more often than T. urticae. In predation trials, N. fallacis fed at the highest rate on T. urticae, at an intermediate rate on L. destructor, and at the lowest rates on A. ovatus and T. entomophagus. For the three mites tested, L. destructor is the most promising species for further development as a factitious host for N. fallacis.

Quality control of the parasitoid wasp Trichogramma brassicae (Hymenoptera: Trichogrammatidae) over 45 generations of rearing on Sitotroga cerealella.

Trichogramma brassicae (Bezdenko) is an important biological control agent that has been used widely against many lepidopteran pests. Commonly, colonies of Trichogramma are mass reared on factitious hosts such as Sitotroga cerealella (Olivier) over many generations. In this study, we evaluated the quality and performance of a colony of T. brassicae that had been reared for over 45 generations (G) using two-sex life table parameters and parasitism capacity. We found that female adult longevity was significantly different among sequential generations, ranging from 5.58 ± 2.5 d (at G5) to 3.75 ± 1.42 d (at G45). However, no significant difference was found in male adult longevity among different generations. Although female wasps survived longer until the 15th generation, they allocated more days for egg laying at G5 and G10. The highest values of gross reproductive rate (GRR), net reproductive rate (R0 ), intrinsic rate of increase (r), finite rate of increase (λ) and mean generation time (T) were found in G5 and G10, which also showed significantly higher c0 . No significant difference in the finite parasitism rate (ω) was found among generations up to G15. These results suggest that T. brassicae wasps held under continuous laboratory rearing can be used successfully in biological control programs until the 15th generation without any loss of quality or performance. However, laboratory mass rearing colonies declined in quality after 15 generations and we suggest that they should be rejuvenated regularly by adding field-collected parasitoids periodically.

Goniozus omanensis (Hymenoptera: Bethylidae) an important parasitoid of the lesser date moth Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae) in Oman.

A new species of bethylid parasitoid wasp, Goniozus omanensis Polaszek sp. n., is described based on morphology and DNA sequence data. The species is currently known only from the lesser date moth Batrachedra amydraula, a pest of economic importance, but can be reared on two factitious host species. G. omanensis is compared with G. swirskiana, known from the same host in Israel. We summarise current knowledge of G. omanensis life-history, and its potential as an agent of biological pest control.

The establishment of a rearing technique for the fruit fly parasitoid Baryscapus silvestrii increases knowledge of biological, ecological and behavioural traits

We have evaluated different rearing strategies of Baryscapus silvestrii (Hymenoptera: Eulophidae), a parasitoid of Bactrocera oleae (Diptera: Tephritidae), including the use of a factitious host, Ceratitis capitata (Diptera: Tephritidae), and in the process acquired new knowledge of the parasitoid’s biology. We found that B. silvestrii: (1) parasitizes only puparia and exclusively if they are concealed, (2) is able to parasitize and complete its development on puparia of all ages, (3) prefers to oviposit on the medfly in choice tests, (4) completes development faster if reared on 2–3 day-old puparia, (5) exhibits sex allocation related to host puparium age. This study provides critical information on several biological traits of B. silvestrii, and the new rearing method can be used to establish a parasitoid rearing for augmentative releases.

Factitious host species impact on the outcome of multiparasitism between egg parasitoids

Trichogramma parasitoids are biological control agents of a large number of lepidopterous pests. Mass production of these Trichogramma parasitoids is carried out on different factitious host eggs where the cost for mass rearing is high and the production efficiency is low. Therefore, efficient means and techniques for mass production of these parasitoids are needed. Host eggs of Chinese oak silkworm, Antheraea pernyi, not only proved effective for the mass production of a single Trichogramma species but also showed great potential for simultaneously producing two different Trichogramma species through multiparasitism. Here, we evaluated the outcomes of multiparasitism between Trichogramma chilonis and T. leucaniae reared on the eggs of two factitious hosts, Antheraea pernyi and Corcyra cephalonica. Our study indicated that parental wasps of both Trichogramma species reared on A. pernyi performed outstandingly in all aspects of multiparasitism on A. pernyi eggs. In contrast, significantly low parasitism rates for parental wasps reared on C. cephalonica and subsequently low emergence rates for their offspring were recorded for multiparasitism on A. pernyi eggs. Parental wasps reared on different host eggs significantly affected the emerged offspring numbers for both Trichogramma species per A. pernyi egg. Significantly high numbers of offspring for specific species of Trichogramma emerged per A. pernyi egg when the parental wasps of that species were reared on A. pernyi eggs compared to the other species reared on C. cephalonica eggs. The present study concluded that rearing host species had a great impact on the performance of parental wasps in the multiparasitism of Trichogramma parasitoids on A. pernyi eggs and clearly confirmed that T. chilonis and T. leucaniae parasitoids can be massively produced on A. pernyi eggs through multiparasitism. Our results provide useful information about rearing hosts, which could provide two different Trichogramma species in the field at a time for the suppression of pest populations.

Study on different diets on the biological parameters of rice moth Corcyra cephalonica (Stainton)

The present investigations were undertaken in laboratory on “Study on factitious host Corcyra cephalonica (Stainton) against storage of egg parasitoid Trichogramma chilonis (Ishii) cards under laboratory conditions” during the year 2018 in the bio-control laboratory, Department of Agricultural Entomology, College of Agriculture, Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut (U. P.) India. The effects of different rearing media on some biological parameters of factitious host, C. cephalonica are based on results are most effective performance with T3 (Sorghum + Groundnut + Yeast powder, 50:50 + 5g Yeast), treatments i.e. larval, pupal, male and female moths emergence, and egg production in cc and followed by 17530, 16667, 15131,14875, 13545 and 11830 i.e. T3 (Sorghum + Groundnut + Yeast powder, 50:50 + 5g Yeast), T5 (Sorghum + Soyabeen + Yeast powder, 50:50 + 5g Yeast), T6 (Sorghum + Cowpea + Yeast powder, 50:50 + 5g Yeast), T4 (Sorghum + Gram powder + Yeast powder, 50:50 + 5g Yeast), T2 (Sorghum + Green Gram + Yeast powder, 50:50 +5g Yeast), T1 (Sorghum + Black gram + Yeast powder, 50:50 + 5g Yeast) and T7 (Sorghum alone (check) eggs per cc of Sorghum + Groundnut + Yeast powder, 50:50 + 5g Yeast and wheal), respectively.

Improvements in the Rearing of the Tachinid Parasitoid Exorista larvarum (Diptera: Tachinidae): Influence of Adult Food on Female Longevity and Reproduction Capacity.

Exorista larvarum (L.), a polyphagous gregarious larval parasitoid of lepidopterans, can be mass produced both in vivo, using the greater wax moth Galleria mellonella (L.) (Lepidoptera: Pyralidae) as a factitious host, and in vitro, on artificial media composed of crude components. The present study was focused on another aspect of E. larvarum rearing, namely the influence of adult food on parasitoid performance. The standard food, consisting of lump sucrose and cotton balls soaked in a honey and water solution (1), was compared with other foods or food combinations, namely lump sucrose alone (2), honey and water solution (3), sucrose and water solution either alone (4) or combined with bee-collected pollen (5), and, finally, pollen alone (6). All foods were provided together with distilled water supplied in drinking troughs. Based on the parameters considered (i.e., female longevity, number of eggs laid on host larvae, puparia obtained from eggs, and adults emerged from puparia), pollen alone was deemed to be the most suitable food for adult females of E. larvarum. In particular, the pollen showed a longevity-promoting effect, increasing the number of eggs laid on host larvae throughout the female lifespan. The use of this adult food may also result in a higher flexibility of the management of E. larvarum colonies because it can be replaced weekly, as no desiccation or mold infections were ever found to occur.

Insectary production and synopsis of Fopius caudatus (Hymenoptera: Braconidae), parasitoid of tephritid fruit flies indigenous to Africa

Abstract Fopius caudatus (Szepligeti) is an endophagous koinobiont egg-larval parasitoid native to Africa. It has recently been noted as a candidate for augmentative biological control of several Dacinae fruit fly pests (Diptera: Tephritidae), due to its ability to parasitize the egg stage. Previous attempts to establish this parasitoid in Hawaii, Guatemala, and Costa Rica were unsuccessful due to inability to maintain parasitoid colonies under laboratory conditions. A cohort of F. caudatus collected from Kenyan fruit flies infesting Coffea arabica was successfully colonized in Hawaii at 28 °C and 60–80% RH, resulting in the development of a laboratory-adapted colony amenable for mass production. The parasitoid was successfully developed from eggs of Ceratitis capitata and Bactrocera latifrons as a factitious host. The wasps were propagated for 15 weeks until the rearing stabilized, at which point >10,500 adults were produced with an overall sex ratio of 0.52 females and a mean host parasitism rate of 17.3%. It could parasitize Medfly eggs in fruits other than coffee, including papaya, mango, pear, squash, and sweet pepper. Female F. caudatus oviposited mainly in 24–48 h old Medfly eggs, although occasionally a few individuals eclosed when first instar fly larvae were exposed. Mean developmental time from egg to adult was 19.8 d for males and 21.5 d for females. Mean longevity was 5.2 d for males and 14.2 d for host-deprived females. This study enabled us to maintain a colony of F. caudatus for research and redistribution to other countries for biocontrol programs against Medfly.

Mass‐rearing optimization of the parasitoid Psyttalia lounsburyi for biological control of the olive fruit fly

AbstractThe olive fruit fly, Bactrocera oleae (Tephritidae), is a direct pest of olives that has invaded the Mediterranean Region and California. Psyttalia lounsburyi (Braconidae), a larval parasitoid from Africa, has been approved for release in the USA as a classical biological agent. However, it has been difficult to rear the parasitoid in the laboratory because it is multivoltine, and the host develops only in fresh olives, which are not available for most of the year. A method to rear the parasitoid on the factitious host, Mediterranean fruit fly (Ceratitis capitata) was developed, but it was not very efficient for producing large numbers of parasitoids needed for release. We developed a number of ways to improve the efficiency of rearing, including the frequency and duration of exposure for oviposition, optimizing the density of adult parasitoids, host age, as well as methods to quickly standardize the number of larvae exposed and to count emerging adult parasitoids. We significantly improved the number of progeny produced per female and the sex ratio of progeny. Thanks to these improvements, we produced in 2017 over 119,000 adults and shipped over 53,900 for release in California.

Effect of cold storage of Corcyra cephalonica eggs on the fitness for Trichogramma chilonis

Cold storage of host eggs is important for Trichogramma mass rearing, but the fitness of Trichogramma is affected by the refrigerated eggs. Corcyra cephalonica eggs are frequently utilized as factitious hosts of Trichogramma chilonis. In this study, we investigated the physicochemical property of fresh rice moth eggs (U) and sterilized eggs cold-stored at 4 °C for 0 (CK), 15 (N15), 30 (N30), 45 (N45), and 60 (N60) days and evaluated the effect of cold storage of host eggs on the fitness of T. chilonis. The results showed that the moisture content, dry matter and pH of C. cephalonica eggs decreased significantly with increasing cold storage time. The survival rates of T. chilonis embryos, larvae and pupae decreased significantly when C. cephalonica eggs were cold-stored for more than 15 days. The fecundity rate of adult T. chilonis in refrigerated eggs declined markedly, and a similar result was observed in the rate of black parasitized eggs. However, no clear difference was observed in either emergence rate or sex ratio between the CK and N15 treatment. A fitted linear regression model revealed that the survival rates of immature T. chilonis were positively correlated to the moisture content and pH of host eggs. Thus, cold storage changed the internal environment of C. cephalonica eggs and reduced the fitness for T. chilonis. This finding suggests that the storage period of rice moth eggs sterilized by UV at 4 °C should not exceed 15 days for mass-rearing of T. chilonis.

Laboratory Evaluation of the Effect of Insecticides on Non-target Organisms: 2- The egg parasitoid, Trichogramma evanescens West. (Hymenoptera: Trichogrammatidae)

The present study aimed to evaluate the effect of different groups of insecticides (e.g., Dipel, Dursban, Biover, Malathion and Spintor) on the immature stages and the parasitism rate of the egg parasitoid, Trichogramma evanescens West. (Hymenoptera: Trichogrammatidae) under laboratory conditions. The parasitized eggs of the factitious host, the Mediterranean flour moth, Anagasta (Ephestia) kuehniella Zeller were used. Data were recorded in terms of parasitism rate, emergence rate and female percentages. The calculated values of the Slope (b) of the log-dosage-probit mortality curve, by treating the parasitized A. kuehniella eggs (ranged from 0.6 to 1.34), indicated that the susceptibility of the population was heterogeneous for all the studied insecticides. Results indicated that each of the tested insecticides showed the different degree of toxicity. Malathion was the most toxic insecticide (Toxicity ratio T.R.: 10-39.7), while the bioinsecticide, Dipel was the least toxic one (Toxicity ratio T.R.:0.24-0.47). The parasitoid developmental stage had a significant effect on the toxicity ratio of all the studied insecticides. The eggs treated 7-day post-treatment showed the highest parasitism rate for all insecticides, (65-94%), followed by 5-day old (52-91%), 3-day old (48-90%), and then 1-day old (43-88%). An inverse relationship between the parasitism rate and the insecticide concentration was found. The emergence rate was affected greatly by both the type of insecticide and the treated immature stage. The highest emergence rate, (14-86%) was recorded for the eggs treated 1-day post-treatment, while parasitized eggs, treated after 7 days at all the tested insecticides recorded the lowest rates of adult emergence of T. evanescens (6-49%). The highest emergence rate (42-83%) was found for eggs treated with the fungicide Biover, while the lowest values (7-35%) were recorded for the eggs treated with Spintor compared to a significant high emergence rate for the untreated ones (92%). Sex ratio (female percentage) did not differ significantly between the treated (38-55%) and the untreated parasitized eggs (50-54%).

Intraguild predation of Orius niger (Hemiptera: Anthocoridae) on Trichogramma evanescens (Hymenoptera: Trichogrammatidae)

Intraguild predation of a generalist predator, Orius niger Wolff (Hemiptera: Anthocoridae) on Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae), was determined in choice and no-choice experiments using a factitious host, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), under laboratory conditions. Choice and no-choice experiments were conducted in order to assess the level of intraguild predation of O. niger on E. kuehniella eggs parasitized by T. evanescens. In no-choice experiments, approximately 50 sterile (1) non-parasitized, (2) 3-day-old parasitized, or (3) 6-day-old parasitized E. kuehniella eggs were offered to 24-h-old females of O. niger in glass tubes. In choice experiments approximately 25 eggs of two of the three groups mentioned above were offered to 24-h-old O. niger females. In both choice and no-choice experiments, O. niger consumed more non-parasitized eggs of E. kuehniella. However, intraguild predation occurred, especially of 3-day-old parasitoids, but very few 6-day-old parasitized eggs were consumed. The preference index was nearly 1 indicating O. niger preferred mainly non-parasitized E. kuehniella eggs. A lower level of intraguild predation is expected under field conditions but needs to be investigated using further experiments.

Effect of exposure time on mass‐rearing production of the olive fruit fly parasitoid, Psyttalia lounsburyi (Hymenoptera: Braconidae)

AbstractClassical biological control programmes rely on mass production of high‐quality beneficial insects for subsequent releases into the field. Psyttalia lounsburyi (Silvestri) (Hymenoptera: Braconidae) is a koinobiont larval–pupal endoparasitoid of tephritid flies that is being reared to support a classical biological control programme for olive fruit fly in California. The mass‐rearing system for a P. lounsburyi colony, initiated with insects originally collected in Kenya, was evaluated with the goal of increasing production, while at the same time reducing time requirements for rearing in a quarantine facility. We tested the effect of exposure time of a factitious host Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), on parasitization, adult production, superparasitism, and sex ratio of P. lounsburyi and survival of the host. Parasitization rates were highest (31%) at 3‐ and 4‐hr exposure times, while adult production (i.e., emergence of wasp progeny) was highest (16%) at the 2‐hr exposure time. Superparasitism over the course of the study was 1.5% and did not appear to be a factor affecting parasitoid production. The sex ratio of wasp progeny was male‐biased and did not vary significantly over different exposure times. The rate of stings on host larvae increased with exposure time and was consistent with decreases in pupal eclosion from larvae and emergence rate of adult flies. When compared to current rearing procedures, the 2‐hr exposure time resulted in an overall 2.8‐fold increase in P. lounsburyi production when standardized for time.

An improved foolproof device for eggs’ sterilization of Corcyra cephalonica (Stainton)

Mass rearing of numerous biological control agents depends on large amounts of eggs of factitious hosts like rice meal moth, Corcyra cephalonica (Stainton) (Lepidoptera : Pyralidae). Corcyra eggs sterilization is required before they are used for parasitisation by Trichogrammatids. To meet the requirement of eggs sterilization of this insect, a new innovative device was invented, fabricated and studied. It consisted of an enclosed structure having semi-circular shaped drawer. An ultra violet (UV) tube of 30 W is fixed on the centre of its ceiling to maintain a uniform distance of 35 cm from the eggs to be sterilized. An exposure of 10 minutes to eggs of C. cephalonica was required to get optimum sterilization. As whole body of the device was an enclosed structure, hence, there was no exposure of UV rays to the laboratory workers. The different sized-models (150,100, 50 of “egg cards” required for Trichogrammatids) can be fabricated to meet the diverse requirements. Irradiated eggs were found having no any adverse effects on the abilities of Trichogrammatids parasitisation and its emergence. It can also used for UV sterilization of laboratory materials like glassware, plastic ware, clothes, cotton etc. The period of exposure to the UV light was set using timer. This innovative UV chamber had numerous advantages i.e., the UV rays used had damaged the host embryo. The damaged embryo could not develop into next stage, at the same time damaged embryo found suitable for parasitization of Trichogrammatids. The whole body of the device was made-up of an enclosed struc-ture; hence, there was no exposure of UV rays to the laboratory workers. The different sized-models (150,100, 50 of “egg cards” required for Trichogrammatids) can be fabricated to meet the diverse requirements of clients. As the UV chamber was made up of metal and ply boards, hence, it was durable. The longitudinal flanges provided in the drawer of the device prevented the host egg bearing cards to glide one over other from curved surface. The device was found safe and effective for sterilization of Corcyra eggs and easy to operate.

Innate Olfactory Responses of Asobara japonica Toward Fruits Infested by the Invasive Spotted Wing Drosophila

Insect parasitoids are often manipulated to improve biological control programs for various arthropod pests. Volatile compounds can be a relevant cue used by most parasitoid hymenoptera for host or host microhabitat location. Here, we studied olfactory responses of the braconid Asobara japonica Belokobylskij, an Asiatic endoparasitoid of the invasive pest Drosophila suzukii (Matsumura), toward its host and host substrates. Adult A. japonica displayed an innate attraction to undescribed volatile cues from infested host fruits irrespectively of the juvenile rearing experience, i.e. they respond to a novel cue subsequently used for microhabitat selection. These data suggest that A. japonica parasitoids mass-reared on artificial diet and factitious host (D. melanogaster) can successfully locate their hosts. Naive female parasitoids did not show a preference towards any of the tested host media. However, the enforced adult experience with the rearing host medium modified the olfactory preference patterns toward non-natal host fruits. These findings provide evidence of associative learning during the adult stage of A. japonica, and demonstrate its plasticity in exploiting the volatiles from various fruits infested by D. suzukii.

Modeling adult emergence and fecundity of factitious hosts under different food sources supports massive egg production management.

Ephestia kuehniella (Lepidoptera, Pyralidae) and Sitotroga cerealella (Lepidoptera, Gelechiidae) are important factitious hosts used for production of biological control agents. Their differences in terms of biology and behavior require adjustments in their mass production, particularly when using corn or barley as food in grain or in bran. We modeled adult emergence, oviposition period and egg production along time after emergence, as a function of the food source. Significant differences between hosts or food type were found for these variables and for adult weight but not for sex ratio. Our results confirm the possibility of mass production of these hosts using corn or barley as food source. Integrating adult emergence patterns and age specific fecundity patterns into a single model, it is clear that rearing E. kuehniella on barley would result in the highest egg output in much shorter time than E. kuehniella on corn or S. cerealella on barley.

Effects of Palpita unionalis and Galleria mellonella larval densities on functional response, egg dispersion and progeny sex ratio of Habrobracon hebetor

ABSTRACTTo assess the potential of the hymenopteran ectoparasitoid, Habrobracon hebetor Say as a biological control agent, we evaluated its response to different larval densities of two pyralid hosts, Palpita unionalis Hbn. and Galleria mellonella L. The former host is a serious pest of olive trees, whereas the latter is used as a factitious host in parasitoid mass rearing. In order to study the functional response of the parasitoid, five host densities (1, 2, 3, 5, 7) of either late instar larva per Petri dish were used. The shape of the functional response curve was determined using logistic regression and could be described as a type II response for both hosts, characterised by a monotonic decelerating increase in the number of hosts attacked with increasing host density. Female parasitoids allocated more eggs to the first larva attacked than all the remaining larvae. Aggregated dispersion patterns for parasitoid egg distribution at different host densities were estimated using the Green index. Multiple visits and ovipositions by females did not significantly affect the total number of progeny produced or their sex ratio. This study has generated novel information on egg laying, egg distribution and sex ratio of H. hebetor when reared on G. mellonella and has the potential to be used in the development of sustainable biological control programmes aimed at P. unionalis in olive orchards.

Effect of age dependent cold storage of factitious host Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) for their continuous production and Trichogramma chilonis (Ishii) (Hymenoptera: Trichogrammatidae) rearing

In Asia Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) is widely used as a factitious host for the mass rearing of several bio-control agents viz. chrysopids, braconids, trichogrammatids and anthocorids. The age dependent cold storage amenability of C. cephalonica eggs was evaluated. At 5±1°C with a 24h of scotophase, 0 to 22h old eggs of C. cephalonica could be stored for up to 5days resulting in 83 to 94% hatching. Eggs of C. cephalonica are UV irradiated for mass rearing of T. chilonis. Four, eight, sixteen and twenty four-hour-old C. cephalonica eggs were stored at 5±1°C for different durations prior to and post-UV irradiation and tested for their amenability to parasitism by T. chilonis. Adult females of T. chilonis could parasitise 67–78% of eggs stored for up to 10days prior to UV treatment, while 74–78.2% parasitism was recorded in the case of eggs stored for 10days post-UV. The host eggs of all age groups stored for 20days (10days pre-UV and 10days post-UV) were effectively parasitised providing 83.8–88.4% parasitism. Eight and sixteen hour-old old host eggs stored for 30days (15days of pre-UV and 15days of post-UV) recorded 70–80% parasitism. The host egg storage technique developed through this study would be beneficial for insectaries to stock the host eggs, which can lead to uninterrupted production and supply of ‘Tricho-cards’, especially during seasonal high demand.