Parasitoid Ratio Research Articles

Extrinsic and Intrinsic Competition between Chouioa cunea Yang and Tetrastichus septentrionalis (Hymenoptera: Eulophidae), Two Pupal Parasitoids of the Fall Webworm, Hyphantria cunea (Lepidoptera: Erebidae).

The endoparasitoids Chouioa cunea Yang and Tetrastichus septentrionalis Yang (Hymenoptera: Eulophidae) are both gregarious pupal parasitoids of the fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Erebidae). In order to analyze the competitive interactions between both parasitoids exploiting H. cunea, we assessed both extrinsic and intrinsic competition. The search time, oviposition duration, and oviposition frequency were used as evaluation criteria for extrinsic competition. The number of survival days, female ratio, and number of parasitoids emerging from the host were used as evaluation criteria for intrinsic competition. The results indicated that both parasitoid species were able to parasitize hosts that were already parasitized by competitors. The first released species consistently emerged as the superior competitor in multiparasitized hosts. Both parasitoid release orders and time intervals between oviposition affect the competition of parasitoids and the parasitic efficiency. The results emphasize the parasitic abilities of both parasitoid species and provide a basis for future research on competition mechanisms and biological control of H. cunea.

Side Effects of Single-Transgene or Pyramided Genetically Modified Maize on the Generalist Endoparasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is an agricultural pest native to tropical and subtropical regions of the Americas, with considerable potential for global invasion and seasonal migration. Although genetically modified (GM) plants have shown positive impacts on the economy and the environment as they synthesize proteins that act as natural insecticides and are primarily intended to protect the crops from damage by specific pests, potential effects of Bt toxins on non-target organisms can occur. This experiment aimed to evaluate the potential impacts on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae), using the pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) as hosts, which were fed with transgenic maize genotypes such as Herculex®, expressing Cry1F protein, and PowerCore®, expressing Cry1F, Cry1A.105, and Cry2Ab2 proteins, or their non-transgenic isohybrid. The experiment was conducted in a completely randomized design with ten replicates. Spodoptera frugiperda larvae were fed ad libitum with transgenic and non-transgenic maize until the pupal stage and then individually exposed to six P. elaeisis females for 78 h. The total number of adults, emerged males, tibia size, cephalic capsule size, and parasitoid body size were not influenced by host feeding. However, the number of emerged females from the Herculex® and PowerCore® treatments was lower than that for the isohybrid treatment. The sex ratio and longevity of parasitoids emerging from PowerCore® were 1.05 and 1.26 times lower, respectively, than that of those from the isohybrid. Furthermore, the number of dead P. elaeisis within the host pupa was 10.56 times higher in the PowerCore® genotype. Combining Bt proteins within pyramided genotypes should cause minimal impacts and promote the conservation and integration of beneficial insects. The results of this study provide helpful information for developing effective and compatible integrated pest management (IPM) strategies.

Effects of Food Source Availability, Host Egg:Parasitoid Ratios, and Host Exposure Times on the Developmental Biology of Megacopta cribraria Egg Parasitoids.

Parasitoids forage for hosts in dynamic ecosystems and generally have a short period of time to access hosts. The current study examined the optimal reproductive attributes of two egg parasitoids, Paratelenomus saccharalis Dodd (Hymenoptera: Platygastridae) and Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae), of the kudzu bug, Megacopta cribraria Fabricius (Hemiptera: Plataspidae). The proportion of O. nezarae and P. saccharalis adult offspring that emerged from M. cribraria eggs and the sex ratio of the parasitoid offspring were compared among treatments for the effects of different adult parasitoid food sources, host egg-to-adult parasitoid ratios, and host exposure times. Our results suggest that honey solution as a food source, a 21:7 host-to-parasitoid ratio, and three-to-five days of exposure time optimized the production of female O. nezarae offspring. For P. saccharalis, honey solution as a food source, a 21:7 host-to-parasitoid ratio, and one day were optimal for maximizing female offspring production. These findings provide new information about the biology of these egg parasitoids.

Parasitoid of cassava mealybug, Anagyrus lopezi (Hymenoptera: Encyrtidae): Mummy size, adult emergence, sex ratio, and parasitization level

Abstract. Naimah F, Sartiami D, Maryana N, Anwar R, Pudjianto. 2023. Parasitoid of cassava mealybug, Anagyrus lopezi (Hymenoptera: Encyrtidae): mummy size, adult emergence, sex ratio, and parasitization level. Biodiversitas 24: 1629-1634. The presence of Anagyrus lopezi as a natural enemy can reduce the population of Phenacoccus manihoti. This parasitoid was introduced from Thailand to Indonesia in 2014 to control cassava mealybugs. This research aims to determine the mummy length and width, adult emergence time, sex ratio, and parasitization level. This study was conducted in July-November 2022, while parasitoids and mealybugs were obtained from Bogor, Indonesia. The size of mummies was measured under Dino-light digital microscope; the emergence time was counted for 24 hours within six days, and the sex ratio of parasitoids was calculated based on the number of males and females emergence. The parasitization level was observed from four female parasitoids at 120, 160, and 200 of host population densities. The study showed the length and width of female mummies (n: 100) were 0.71 mm and 1.64, while the length and width of male mummies (n: 100) were shorter than female with 1.00 mm and 2.18 mm. The peak time of adult emergence is A. lopezi, i.e., during the daytime at 09:01-12:00 AM and 03:01-06:00 PM. The sex ratio of parasitoids from the field and laboratory was 1:0.49, 1:1.05, and 1:1.09, respectively. The one-way ANOVA and Tukey's test at a 5% significance level showed that the host population density of 120 nymphs was significantly different from other densities, with a parasitization level of 66.7%.

Biological characteristics and parasitization potential of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) on the whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), a pest of greenhouse crops in north-western Indian Himalayas

BackgroundThe greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) constitutes key pests of greenhouses and field crops, which have developed pesticide resistance over the years. It has emerged as a difficult pest to manage owing to its indiscriminate exposure to higher dosages of insecticides. The use of natural enemies is environmentally safe alternative management tactic. Efficacy of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) was determined by studying its biological characteristics on T. vaporariorum.ResultsParasitization by E. formosa was higher on fourth-instar nymphs of the greenhouse whitefly (GHWF) (37.2%), which was at par with that of third instar (36.4%), both differing significantly to the parasitization observed in second instar (19.6%). Total developmental duration of the parasitoid was longer on second instar (33.2 days) than that of fourth instar (29.9 days). Adult longevity was found significantly higher for the adults that emerged from fourth-instar nymphs of GHWF, which was at par to that of third instar and longevity of E. formosa adults was significantly higher in the absence of parasitoid host. The size of parasitoid that emerged from different instars of GHWF varied non-significantly. T. vaporariorum was reared on brinjal, cucumber, French bean, lettuce, tobacco, and tomato plants for mass production of E. formosa. Among them, French bean and tobacco were found to be the best host plants for mass production of E. formosa based on higher parasitization (37.2%). Total developmental period varied from 26.4 to 27.3 days on different host plants, the variations being non-significant. The maximum adult longevity was observed on cucumber (8.0 days) in the absence of host, and the adult size of parasitoid varied non-significantly. Results on host to parasitoid ratio of 5:1, 10:1, 20:1, 40:1 and 80:1 revealed that parasitization rate varied from 61.2 to 95.0% with maximum parasitization recorded in host–parasitoid proportion of 20:1 and minimum in 80:1. The total developmental duration varied non-significantly among all the proportions (15.1–15.4 days). Adult longevity was higher in the proportion of 40:1 (6.5 days), which was at par to the proportion of 5:1 (6.2 days), 20:1 (6.2 days), 80:1 (6.2 days) and 10:1 (6.1 days) in the absence of the host, respectively.ConclusionThis study suggests that augmentative biological control of T. vaporariorum under polyhouse conditions with E. formosa appears to be an effective strategy for the management of this economic pest.

Induced dormancy in Indian meal moth Plodia interpunctella (Hübner) and its impact on the quality improvement for mass rearing in parasitoid Habrobracon hebetor (Say).

A steady supply of hosts at the susceptible stage for parasitism is a major component of mass rearing parasitoids for biological control programs. Here we describe the effects of storing 5th instar Plodia interpunctella larvae in dormancy on subsequent host development in the context of host colony maintenance and effects of the duration of host dormancy on the development of Habrobracon hebetor parasitoids reared from dormant hosts. We induced dormancy with a combination of short daylength (12L:12D) and lower temperature (15°C), conditions known to induce diapause in this species, and held 5th instar larvae of P. interpunctella for a series of dormancy durations ranging from 15 to 105 days. Extended storage of dormant 5th instar larvae had no significant impacts on survival, development, or reproductive potential of P. interpunctella, reinforcing that dormant hosts have a substantial shelf life. This ability to store hosts in dormancy for more than 3 months at a time without strong negative consequences reinforces the promise of using dormancy to maintain host colonies. The proportion of hosts parasitized by H. hebetor did not vary significantly between non-dormant host larvae and dormant host larvae stored for periods as long as 105 days. Concordant with a prior study, H. hebetor adult progeny production from dormant host larvae was higher than the number of progeny produced on non-dormant host larvae. There were no differences in size, sex ratio, or reproductive output of parasitoids reared on dormant hosts compared to non-dormant hosts stored for up to 105 days. Larval development times of H. hebetor were however longer when reared on dormant hosts compared to non-dormant hosts. Our results agree with other studies showing using dormant hosts can improve parasitoid mass rearing, and we show benefits for parasitoid rearing even after 3 months of host dormancy.

Biology of Apanteles Baoris Wilkinson (Hymenoptera: Braconide) A Larval Parasitoid of Chapra Maathas Fab

ApantelesbaorisWilkinson is potential biocontrol agent of Chapramathias Fab. a paddy pest in Kolhapur. It attacks about 86% caterpillars of C. mathias. In the present paper life cycle, longevity, Sex ratio and behavioral aspects viz; mating and oviposition have been studied in detail. The life cycle of the parasitoid egg to adult emergence have been completed within 17 days. Egg hatching period was 3 days, larval period was 8-9 days and pupal period was 5-6 days. Mating takes place within one hour of their emergence from cocoons. Mating occurred at morning hours. Oviposition is completed within 3 seconds. In a single host the parasitoid can lay on an average 55 eggs of which progeny production obtained was 46 (average). Sex ratio of adult parasitoids was found favoring females. The results are useful for mass rearing of the above parasitoids.

Trichogramma ostriniae Is More Effective Than Trichogramma dendrolimi As a Biocontrol Agent of the Asian Corn Borer, Ostrinia furnacalis.

Simple SummaryThe performance of two egg parasitoids T. dendrolimi and T. ostriniae were compared on Asian corn borer (ACB) Ostrinia furnacalis eggs of different ages under choice and no-choice conditions. Both parasitoid species showed significant preferences in parasitizing ACB eggs of different ages. Younger ACB eggs (0–8-h-old) showed high suitability while eggs older than 8 h were not suitable for T. dendrolimi. The age of ACB eggs did not affect the biological parameters of T. ostriniae. Overall, our results highlighted the T. ostriniae species as the best candidate biocontrol agent for managing ACB populations.The Asian corn borer (ACB), Ostrinia furnicalis, is a serious corn pest in south-east Asia, causing huge economic losses every year. Trichogramma dendrolimi and Trichogramma ostriniae, two egg parasitoids, have previously been identified as key biological control agents. To determine the age impact of ACB eggs on their effective biocontrol potential, herein we compared the biological parameters (i.e., number of parasitized eggs, emergence, developmental time, and sex ratio) of both parasitoids on ACB eggs of various ages (i.e., 0–4, 4–8, 8–12, 12–16, 16–24, 24–36, and 36–48 h old), respectively. Our results showed that the age of ACB eggs had a significant impact on the parasitization activity of T. dendrolimi in both choice and no-choice conditions. Trichogramma dendrolimi preferred to parasitize 0–8-h-old ACB eggs, and its parasitization dramatically declined on ACB eggs older than 8 h under choice and no-choice conditions. On the other hand, T. ostriniae showed high preference to parasitize all tested ACB egg ages. The age of ACB eggs had no significant impact on the parasitization of T. ostriniae under choice and no-choice conditions. Furthermore, the female progeny of T. dendrolimi decreased as the age of ACB increased, while no differences were found in female progeny of T. ostriniae. Trichogramma ostriniae also developed faster on each ACB egg age group in comparison with T. dendrolimi. Overall, the age of ACB eggs had a significant impact on T. dendrolimi performance, leading us to conclude that T. ostriniae is more effective than T. dendrolimi as a biocontrol agent of the ACB.

Optimizing Photoperiod, Exposure Time, and Host-to-Parasitoid Ratio for Mass-Rearing of Telenomus remus, an Egg Parasitoid of Spodoptera frugiperda, on Spodoptera litura Eggs.

Telenomus remus (Nixon) is a dominant egg parasitoid of the destructive agricultural pest Spodoptera frugiperda (J. E. Smith), and so is used in augmentative biocontrol programs in several countries. An optimized mass-rearing system is essential to produce biological control products in a timely and cost-effective manner. In this study, the photoperiod, host egg:parasitoid ratio, and exposure time were evaluated to identify the optimal rearing conditions for T. remus on the alternative host Spodoptera litura (Fabricius) eggs. Results showed that increasing photoperiod above 12L:12D remarkably improved parasitoid progeny yield and life table parameters. Overlong photoperiods shortened female longevity, but within acceptable limits. There was a significant negative correlation between parasitism rate and host egg:parasitoid ratio under exposure times of 12 and 36 h, but not 24 h. Percentage of female progeny increased significantly along with increasing the host egg:parasitoid ratio. A significant negative relationship between the number of emerged adults per egg and the host egg:parasitoid ratio was observed at an exposure time of 36 h. It was concluded that T. remus may be mass-reared most efficiently on S. litura eggs using a photoperiod of more than 12L:12D, a 14-20:1 host egg:parasitoid ratio, and an exposure time of 24 h. These findings can be used to produce T. remus more efficiently and at lower costs.

Developmental Temperature Affects Life-History Traits and Heat Tolerance in the Aphid Parasitoid Aphidius colemani.

Simple SummaryIndividual insects can experience different temperatures across their lives. In consequence, development of immature stages can take place at temperatures contrasting with those that the adult will encounter. In order to study the adaptation of organisms to warm environments, it is interesting to establish the links between developmental temperature and responses of the adult generation, in terms of physiology, morphology, and behavior. We exposed the parasitoid Aphidius colemani to three temperatures during larval development (10, 20, or 28 °C). We then measured the responses of adult parasitoids regarding their traits (physiology, morphology) and their tolerance to high temperatures. Mass, lipid reserves, survival, and heat tolerance of adults were affected by the rearing temperature regime. This means that, overall, developmental temperatures may affect how insects respond to a given temperature once they are adults, which may consequently influence the ability of parasitoids to control their aphid hosts. These results are important in the context of biological control in hot environments, such as the Maghreb, where this species of parasitoid is used in mass release techniques to control aphids in various crops.Developmental temperature plays important roles in the expression of insect traits through thermal developmental plasticity. We exposed the aphid parasitoid Aphidius colemani to different temperature regimes (10, 20, or 28 °C) throughout larval development and studied the expression of morphological and physiological traits indicator of fitness and heat tolerance in the adult. We showed that the mass decreased and the surface to volume ratio of parasitoids increased with the development temperature. Water content was not affected by rearing temperature, but parasitoids accumulated more lipids when reared at 20 °C. Egg content was not affected by developmental temperature, but adult survival was better for parasitoids reared at 20 °C. Finally, parasitoids developed at 20 °C showed the highest heat stupor threshold, whereas parasitoids developed at 28 °C showed the highest heat coma threshold (better heat tolerance CTmax1 and CTmax2, respectively), therefore only partly supporting the beneficial acclimation hypothesis. From a fundamental point of view, our study highlights the role of thermal plasticity (adaptive or not) on the expression of different life history traits in insects and the possible correlations that exist between these traits. From an applied perspective, these results are important in the context of biological control through mass release techniques of parasitoids in hot environments.

Biological traits of Cosmocomoidea annulicornis (Hymenoptera: Mymaridae), an egg parasitoid of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae), a vector of Xylella fastidiosa in citrus orchards

The parasitic ability of Cosmocomoidea annulicornis (Hymenoptera: Mymaridae) was tested on eggs of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae), vector of the bacterium Xylella fastidiosa that causes citrus variegated chlorosis (CVC), among other plant diseases. In the present study, we evaluated biological traits of C. annulicornis such as parasitism and emergence rates, developmental time, longevity and sex ratio in laboratory conditions on leaves of Citrus aurantium, C. limon, Zea mays and Sorghum halepense. In addition, the functional response of C. annulicornis on host egg masses laid on C. aurantium leaves was studied and new distribution sites of the parasitoid in Argentina are reported. The overall parasitism of C. annulicornis was 49.20 ± 2.90%. Of those parasitized eggs, 83.30 ± 6.51% adults emerged. Parasitism of C. annulicornis was significantly lower in host eggs laid on S. halepense and developmental time was longer in C. limon compared to the other host plant species tested. In all host plant species tested, females developed faster than males. Individuals lived on average 5.94 ± 0.23 days and statistically significant differences were found between the longevity of females and males. Sex ratio of parasitoids was balanced in all host plant species tested, excepted for maize plants, in which sex ratio was female biased. Cosmocomoidea annulicornis females exhibited a type III functional response, indicating a greater searching efficiency at high host densities compared to low densities. Previous reports of field parasitism in combination with our results of C. annulicornis performance on eggs of T. rubromarginata are indicators of a potential biological control agent against the vector of X. fastidiosa, though further studies are needed regarding its biology.

First record of the parasitoid Pteromalus puparum L. (Hymenoptera: Pteromalidae) associated with pupae of Pterourus multicaudatus (Kirby) (Lepidoptera: Papilionidae) in Mexico.

Pteromalus puparum L. is recorded for the first time parasitizing pupae of Pterourus multicaudatus (Kirby) in Mexico. Preliminary behavioral and biological aspects of P. puparum were recorded from sentinel pupae of P. multicaudatus. Parasitoid wasps arrived at the pupae beginning on the second day of exposure and interacted with pupae for a period of one to five hours for seven days. A parasitism rate of 39% by P. puparum was recorded on P. multicaudatus pupae. Wasps began to emerge 46.15 days after pupae were exposed to parasitism, with an average of 144 wasps emerging per pupa. The sex ratio of parasitoids was skewed toward females, with a female: male ratio of 4:1

Influences of varying host: parasitoid ratios on parasitism of whitefly by three different parasitoid species

This study reports the effects of different host: parasitoid ratios on parasitic behavior and functional response of three different parasitoid species (Eretmocerus sp. nr. furuhashii, Encarsia bimaculata, and Encarsia sophia) attacking the sweetpotato whitefly, Bemisiatabaci, under laboratory conditions. The parasitic ability of three parasitoid species was significantly influenced by the whitefly density. Increasing host density had beneficial effect on parasite efficiency of Er. sp. nr. furuhashii, E. bimaculata, and E. sophia. The rate of instant attack (a) observed for Er. sp. nr. furuhashii, E. bimaculata, and E. sophia was 0.1649, 0.1113, and 0.0655, respectively. Total parasitic time (Th) observed for Er. sp. nr. furuhashii, E. bimaculata, and E. sophia was 0.0737, 0.2325, and 0.1936, respectively. In the second experiment, the parasitical action was also influenced by parasitoid density. At constant host density, the rate of parasitism increased with parasite density up to a certain density followed by a decrease in rate of parasitism with increasing parasitoid density.

Radiation of Bactrocera dorsalis (Diptera: Tephritidae) Eggs to Improve the Mass Rearing of Diachasmimorpha longicaudata (Hymenoptera: Braconidae).

This study explored the potential for Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) larvae hatched from irradiated eggs as hosts for Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). B. dorsalis eggs of three different ages (12-, 24-, and 36-h old) were analyzed for hatchability, pupation rate, pupal weight, emergence rate, and sex ratio after exposure to different doses of radiation (5 and 10 Gy) at different dose rates (1 and 6 Gy/min). For the eggs of different ages exposed to radiation, only the hatchability and pupal weight of 36-h-old eggs exposed to the dose rate of 1 Gy/min were not affected; therefore, 6 Gy/min was not suitable for irradiating eggs. The viability of the parents and progenies of D. longicaudata when the parents were reared from 36-h-old eggs irradiated at nine different doses (0, 5, 10, 15, 20, 25, 30, 35, and 40 Gy) under laboratory conditions were investigated. The emergence percentage, sex ratio, and longevity of parasitoids developed from irradiated eggs were similar to those reared from nonirradiated hosts. A significant increase in larva mortality was observed for the eggs irradiated at doses above 25 Gy, and no redundant adult flies emerged at doses above 15 Gy. Hence, for B. dorsalis eggs to be applied in the mass rearing of D. longicaudata, the age of 36 h and a dose of 20-25 Gy are the optimal parameters. The results reveal that hosts and parasitoids need not be separated, enabling a reduction in cost, labor, and time and resulting in an improved mass rearing procedure for D. longicaudata.

Field surveys of egg mortality and indigenous egg parasitoids of the brown marmorated stink bug, Halyomorpha halys, in ornamental nurseries in the mid-Atlantic region of the USA

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive species native to regions of China, Japan, Korea, and Taiwan. In its native and introduced range, H. halys is considered a pest of tree fruits, vegetables, legumes, and ornamental trees. The highly polyphagous nature of this insect as well as its vast dispersal capabilities, require an integrated approach to management. Here we focus on the potential impact of indigenous natural enemies on H. halys in woody ornamental nurseries in Maryland, USA. We sampled naturally field laid H. halys egg masses for mortality and parasitism rates in 2012 and 2013. Overall, egg mortality averaged 54% for both years, and increased within season and between years. The largest source of mortality was from egg parasitoids with mean parasitism rates of 30.73 and 39.63% in 2012 and 2013, respectively. Mortality from predation was much lower and averaged 4.61% by chewing and 2.53% by sucking predators. We found seven species of Hymenopteran egg parasitoids attacking H. halys eggs, with Anastatus reduvii being the dominant species comprising 61.17 and 79.12% of all parasitoids in 2012 and 2013, respectively. The observed increase in parasitism over time and female biased sex ratio of parasitoids suggests that native parasitoids may be responding to the novel host, H. halys. Consequently, the use of these native eupelmid egg parasitoids in augmentative or conservation biological control may be a viable H. halys management strategy in ornamental nurseries.

Host species and vegetable fruit suitability and preference by the parasitoid wasp Fopius arisanus

AbstractParasitoids that oviposit in a concealed host inside a plant part need to be able to find both the plant and the host. Egg parasitoids of fruit‐infesting Tephritidae need to assess the oviposition site based both on the host egg and the infested fruit. Infestation by Tephritidae fruit flies threatens fruit and vegetable production. Management methods have been implemented including biological control, using Fopius arisanus Sonan (Hymenoptera: Braconidae). The parasitism by F. arisanus in three Tephritidae flies in vegetable fruits was investigated. Laboratory assays were conducted to assess the parasitoid's preference and survival. Zucchini, sweet pepper, and tomato were artificially infested with eggs of Bactrocera dorsalis Hendel, Ceratitis capitata Wiedemann, and Ceratitis cosyra Walker (all Diptera: Tephritidae), then exposed to mated naïve F. arisanus females in a 20:1 egg:parasitoid ratio. Parasitoid behavioral activities (resting, antennating, probing, ovipositing) were observed on the infested fruits. Parasitism rate was determined by dissection of fruit fly eggs under a stereomicroscope. Behavioral activities of F. arisanus differed between all the fruits when infested with B. dorsalis or C. cosyra eggs but differed only between some of the fruits when infested with C. capitata. Fopius arisanus preferred B. dorsalis over C. capitata and C. cosyra, with a parasitism rate 2× higher on B. dorsalis compared to the Ceratitis species. Preference for fruits was dependent on the infesting fruit fly. The emergence of F. arisanus was higher with B. dorsalis than with Ceratitis spp. Although B. dorsalis completed its development earlier than Ceratitis spp., host fly species did not affect the developmental time of F. arisanus. We discuss the significance of F. arisanus preference in relation to naturally occurring Tephritidae infestations. We also discuss whether some fruits might constitute a refuge for Tephritidae flies and whether this will affect the current biological control efforts against B. dorsalis.

The optimal age and radiation dose for Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) eggs as hosts for mass-reared Fopius arisanus (Sonan) (Hymenoptera: Braconidae)

Fopius arisanus (Sonan) is a dominant egg-pupal parasitoid of many fruit fly pests. Bactrocera dorsalis (Hendel) is one of F. arisanus’ hosts and is the usual host used for mass rearing F. arisanus. To obtain parasitoids without hosts suitable for the release of F. arisanus in the field—skipping the need to separate parasitoids and unparasitized hosts—radiation (15, 20, 25 and 30Gy) was applied to B. dorsalis eggs of five different ages (24, 27, 30, 33, and 36h). Hatch rates, pupation rates, pupae weights, emergence rates, sex ratios, flight abilities, mortality rates and fertilities were analyzed during parasitoid development from irradiated eggs to adults. Irradiation of eggs aged 30–36h at 20Gy might be the optimal age and dosage when using B. dorsalis as hosts for mass rearing of F. arisanus. Furthermore, we investigated the viability of the parents and offspring of F. arisanus when the parents were raised from irradiated eggs under both laboratory and field cage conditions. The parasitism percentage, emergence rate, sex ratio (female: male) and longevity of parasitoids reared with irradiated hosts were similar to those of parasitoids obtained from non-irradiated host eggs. Significantly, the results revealed that unparasitized B. dorsalis previously irradiated with an appropriate dose at appropriate ages do not emerge: a finding that solves the problem of separating unparasitized emerging flies during mass rearing. This experiment also demonstrates that F. arisanus reared on irradiated hosts can find, identify, and parasitize hosts normally—both indoors and outdoors—and that the resulting parasitoids can be directly applied to control pest populations in the field.

The impact of adult diet on parasitoid reproductive performance

Diet is one of the most common influences on parasitoid reproductive traits. The life span, mating ability, fecundity, fertility and sex ratio of parasitoids can be affected by the quality of the adult diet. In the field, parasitoids can rely on different hosts and non-host nutrient sources, such as floral and extrafloral nectar, hemipteran honeydew and pollen, and various artificial diets have been used in mass rearing. In addition, some parasitoid species obtain nutrients by feeding on their host while adult (host feeding). In this review, we summarize current knowledge on the impact of the adult diet on the reproductive behavior of hymenopteran and dipteran parasitoids, with a particular focus on longevity, offspring production and host searching traits. First, we focus on food preferences and learning abilities of parasitoids to discriminate high-quality diets. Second, we analyze the impact of the adult diet on longevity, examining different natural and artificial food sources as well as the effect of their concentration and frequency. Third, we highlight the impact of the adult diet on host foraging. Fourth, we review the impact of adult diet on parasitoid offspring with special reference to (1) egg load, maturation and resorption, (2) parasitism and (3) progeny production and sex ratio. Finally, a number of implications for biological control and integrated pest management are discussed.

Potential use of Beauveria bassiana in combination with Scleroderma guani for improved control of Apriona germari

Beauveria bassiana, an important entomogenous fungus, and Scleroderma guani, a hymenopteran parasitoid, are the two main biological control agents for managing the spread of Apriona germari. The aim of the present study was to assess the potential value of combining the two agents for the purpose of controlling A. germari. First, the relative virulence of B. bassiana against both A. germari and S. guani was determined. The results showed that among the seven strains of B. bassiana, isolate BI05, which was isolated from another cerambycid, was far more virulent against A. germari (mortality, 71.75%) than it was against S. guani (mortality, 34.82%). The parasitic efficiency of S. guani against the larvae of A. germari was significantly affected by the size of the host and the host to parasitoid ratio. In this study, third-instar A. germari larvae and a 1:3 host:parasitoid ratio of inoculation were used to evaluate the parasitization rate achieved by S. guani that were previously exposed to B. bassiana BI05. The mortality of A. germari treated with the previously inoculated S. guani was 73.30%. This was significantly greater than that of S. guani alone or B. bassiana alone (57.20% and 46.21%, respectively). The results indicated that the efficiency of both S. guani and B. bassiana are improved when used in combination, and this is promising for future control of A. germari.

Linear Dispersal of the Filth Fly Parasitoid Spalangia cameroni (Hymenoptera: Pteromalidae) and Parasitism of Hosts at Increasing Distances.

Release of parasitic wasps (Hymenoptera: Pteromalidae) as biological control agents for house flies and stable flies in livestock confinements has had variable success. In part, this may reflect a lack of knowledge regarding the optimal distance to be used between parasitoid release stations. In the current study, we assessed the effect of linear distance on host parasitism by the wasp Spalangia cameroni Perkins. In open fields at distances ranging from 1 m to 60 m from a central point, house fly puparia were placed in a mixture of pine shavings soiled with equine manure, urine, and alfalfa hay. Releases of S. cameroni then were made using a 5:1 host: parasitoid ratio. Host pupae were parasitized at all distances, with the highest rate of total parasitism (68.9%) recorded ≤ 5 m from the release site. Analyses of results using non-linear and linear models suggest that S. cameroni should be released in close proximity to host development areas. Additionally, releases may not be suitable in pasture situations where long-distance flight is required for control. However, further testing is needed to examine the effect of density-dependent dispersal and diffusion of S. cameroni.