Assessment of Ceratitis capitata (Diptera,Tephritidae) pupae killed by heat or cold as hosts for rearing Spalangia cameroni (Hymenoptera: Pteromalidae)

In this work, we study the suitability of using dead medfly Ceratitis capitata pupae, killed by heat- or cold-shock, for the mass rearing of Spalangia cameroni, a pupal parasitoid of key pests. 100% mortality of medfly pupae could be accomplished with cold-shock at –20°C for 60 min or with heat-shock at 55°C for 30 min. Neither parasitism percentage nor sex ratio of the offspring differed significantly among heat-shocked, cold-shocked and untreated pupae. In addition, there was no significant difference in the percentage of parasitoids that aborted (♂♂ or ♀♀) among pupal treatments. Some of the pupae were covered with peat because the third larval instar of the medfly buries itself before pupation. However, the buried pupae were not parasitised at a greater or lesser rate than those not covered with peat. The percentage of parasitism was also unaffected by whether the pupae had been killed recently or had been stored at between 4°C and 6°C over 15 or 30 days. The use of dead hosts and later storage permitted the following: (a) the use of hosts over long periods of time; (b) a rapid increase in parasitoid numbers and (c) the availability of pupae killed at the most suitable postpupation times for the production of parasitoids. Furthermore, in biological control projects, the use of dead parasitised pupae in the field avoids the risk of enhancing the pest and allows an increase in parasitism in the field through the use of pupae treated with cold- or heat-shock.     

Evaluation of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) as a mortality factor of Ceratitis capitata (Diptera: Tephritidae) infesting Citrus species under laboratory and field-cage conditions

Ceratitis capitata (or medfly) is one of the major pests currently affecting fruit crops in northwestern Argentinian Citrus-producing areas. Medfly populations are sustained in large exotic fruits, such as Citrus paradisi, Citrus aurantium and Citrus sinensis, which are known to hinder the activity of almost all native parasitoid species. Therefore, a feasible approach to controlling medfly involves the use of exotic parasitoids such as Diachasmimorpha longicaudata. In this study, the prediction that parasitoid females would be proficient at finding medfly larvae infesting the Citrus species mentioned earlier was tested. Particularly, the variation in fruit species preference by parasitoid females, the efficacy of the parasitoid to kill medfly and the effect of host density on parasitoid performance were determined. Parasitoids were allowed to forage for 8 h on grapefruits and oranges artificially infested with medfly larvae under controlled (laboratory) and uncontrolled (field cage) environmental conditions. Fruit choice and no-choice tests were performed. Results were assessed by comparing the number of female visits to and ovipositor insertions into the fruit, and parasitoid emergence, parasitism and additional host mortality percentages. Parasitoid preference for visiting larger fruits (sour orange and grapefruit) may be related to the increased fruit surface area. Ovipositional activity on fruit was influenced by the variation of the larval host density per unit of fruit surface. The higher parasitism rates recorded from sweet orange would be mainly a result of both increased host density and fruit physical features. Nevertheless, D. longicaudata showed the capacity to parasitise hosts in all Citrus species tested.     

Interaction effects between time and cultivar on the seasonal fluctuations of the safflower fly,Acanthiophilus helianthi (Rossi) (Diptera: Tephritidae) and its parasitoids in the south of Tehran

The safflower fly, Acanthiophilus helianthi is one of the most important pests of safflower in the world that every year puts a lot of loss to the crop. In order to study interaction effect between time and cultivar on seasonal fluctuations and parasitism of the safflower fly on 2012, seven safflower cultivars including Goldasht, Padideh, Zarghan, Varamin, PI, Acataria, Mec163 was cultivated under Completely Randomised Block Design with four replicates in research field of Shahed University research (south of Tehran). Once the prey of adult samples, sampling was started from safflower bolls on weekly basis from late June to late of August. The number of larvae and pupae in each boll were counted separately for each cultivar and recorded in the tables. The highest density of larvae was observed on Goldasht cultivar on 9 July. Aceteria cultivar, on 9 July and Zarghan, Mec163 and PI cultivars on 15 July and Mec163 cultivar was observed the lowest density. The highest density of pupa was observed on cultivar Padideh on 9 July. Also the lowest density of pupa was observed on cultivar PI on 2 July. Goldasht and Aceteria cultivars on 9 July had the highest contaminated bolls, respectively. The lowest density of infested bolls on 25 June was observed on Zarghan and Aceteria cultivars with rank mean of 30.00. The highest natural parasitism of the safflower fly, A. helianthi by Microdontomerus annulatus was observed on the 9 July and lowest on the 19 June. The highest and lowest percentage of parasitism by Ormyrus gratiosus was observed, respectively on the 19 June and the 2 July. In conclusion, using integrated pest management and crop cultivars suitable for early crop up a lot of damage can be prevented.     

Occurrence of Ceratitis capitata Wied. (Diptera: Tephritidae) on papaya fruits in Minas Gerais State, Brazil

The objective of this work was to register the infestation of C. capitata on papaya fruits in Minas Gerais State. Papaya fruits were collected, in a commercial orchard, in Jaíba, north of the State of Minas Gerais. C. capitata was the only specie collected (794 individuals). Doryctobracon areolatus (Szépligeti) was collected parasitizing C. capitata larvae/pupae. The level of infestation was of 7,7 pupae/kg of fruit or 1,4 pupae/fruit, in average. C. capitata is registered for the first time on papaya fruits in the State of Minas Gerais.     

Studies on an overwintering population of the mushroom phorid Megaselia halterata (Diptera: Phoridae) parasitized by Howardula husseyi (Nematoda: Allantonematidae)

An overwintering population of the mushroom phorid fly Megaselia halterata parasitized by Howardula husseyi was studied in an attempt to explain the winter decline in incidence of parasitism that has been observed in flies from mushroom farms. Fly larvae from eggs hatching in November developed into pupae in December and flies emerged in May. No selective mortality of parasitized specimens of larvae, pupae, or flies was observed. Dead parasites were found in only 10% of parasitized flies. The incidence of parasitism in the emerging flies (50%) was five times that of their parental generation and although parasitism significantly delayed fly emergence the delay was only 2–3 days. There was no evidence of winter decline in parasitism; instead there was strong evidence that parasitism enhanced phorid survival through the winter.     

Effects of gamma-irradiation on midgut proteolytic activity of the mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), is a key pest of citrus in Spain because of significant yield losses and to quarantine restrictions. Biologically based control methods, such as the Sterile Insect Technique (SIT), which relies on the sterilization by irradiation of large numbers of insects, is gaining an increasing role in the control of medfly in Mediterranean areas. However, gamma-irradiation might damage the midgut epithelium cells, causing a lowering of nutritive assimilation that can negatively affect adult performance. Irradiation effects on digestive physiology are well established for a number of insect pests, but there is no information on medfly. Our aim was to determine the effects of gamma-irradiation on C. capitata digestive protease activity. Both larvae and adults were found to use a similar proteolytic system based on aspartyl-, trypsin-, chymotrypsin-, amino peptidase-, and carboxypeptidase A- and B-like activities. Pupae of the Vienna-7 (tsl) strain were irradiated at 70 or 140 Gy, two days before emergence, and the adults fed during 5 days on sugar-protein (4:1) diets. Protease activity was measured in midgut extracts and compared with males non-irradiated reared in the same conditions. The results showed that the irradiation doses tested had no effect on the digestive proteolytic activities of medfly adults. Moreover, the longevity of irradiated medflies at the highest dose (140 Gy) was similar to that of controls.     

Superparasitism in laboratory rearing of Spalangia cameroni (Hymenoptera: Pteromalidae), a parasitoid of medfly (Diptera: Tephritidae)

The frequency of superparasitism and its effects on the quality of laboratory-reared Spalangia cameroni (Hymenoptera: Pteromalidae) parasitoids were investigated under laboratory conditions. Numerous variables were measured, such as the number of 'ovip holes' per host as a measure of superparasitism. Adult emergence and sex ratio, as well as female size, emergence ability from soil and longevity were also measured. Finally, an assessment was made of fertility and survival of adult parasitoids emerging from the medfly Ceratitis capitata (Diptera: Tephritidae) pupae with different levels of superparasitism. A high frequency and prevalence of superparasitism under laboratory rearing conditions was observed. The number of 'ovip holes' per host ranged from one to 17, with an average (±SD) of 2.8±3.4. Sex ratios became increasingly female-biased with increasing levels of superparasitism, although overall levels of wasp emergence (male, female) declined. Nevertheless, no relationship was discerned between female size and level of superparasitism. The 'emergence ability from the soil' was higher in those parasitoids that emerged from strongly superparasitized hosts, but not related to the type of substrate in which the host pupae were buried. The level of superparasitism did not have a significant effect on the longevity, fertility and survival of female parasitoids. Our results support the hypothesis that superparasitism in S. cameroni might be adaptive, since attributes such as 'emergence ability from the soil', longevity, fertility and survival were not affected by the level of superparasitism or the presumably detrimental effects derived from physical combats among conspecific larvae. Our findings are relevant to recommendations for rearing S. cameroni for biological control releases, as well as shedding light on superparasitism under both laboratory and field conditions.     

Parasitism by Coptera haywardi and Diachasmimorpha longicaudata on Anastrepha flies with different fruits under laboratory and field cage conditions

Larvae of Anastrepha ludens and A. serpentina that developed in mango and sapodilla fruits, respectively, were exposed to Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) and sequentially exposed as pupae to Coptera haywardi (Oglobin) (Hymenoptera: Diapriidae). Sequential exposure to both parasitoid species contributed to a decrease in fruit fly emergence due to higher levels of parasitism, which varied according to fruit type. In creole mango, D. longicaudata represented the highest percentage of parasitism. C. haywardi parasitism was greater in pupae from Ataulfo mangos and sapodilla, where the pulp size and volume may have acted as a refuge, allowing fly larvae to escape and leaving a greater number of unparasitised pupae available to C. haywardi. Similar results were obtained under field cage conditions, but the level of parasitism by C. haywardi was lower, suggesting that its effectiveness has some limitations under natural conditions. Our results suggest that both species can exert complementary parasitism, which represents an alternative worth to investigate under open field conditions.     

Survival and development of immature stages of the Mediterranean fruit fly (Diptera: Tephritidae) in citrus fruit

We studied, under laboratory conditions, the performance of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), immature stages in intact whole fruit of three sweet orange varieties, lemon, and bitter oranges. Both citrus variety and fruit part (flavedo, albedo, and pulp) had strong effects on larval performance, smaller effects on pupae, and no effects on eggs. Fruit peel was the most critical parameter for larval development and survival, drastically affecting larval survival (inducing very high mortality rates). Among fruit regions, survival of larvae placed in flavedo was zero for all varieties tested except for bitter orange (22.5% survival), whereas survival in albedo was very low (9.8-17.4%) for all varieties except for bitter orange (76%). Survival of pupae obtained from larvae placed in the above-mentioned fruit regions was high for all varieties tested (81.1-90.7%). Fruit pulp of all citrus fruit tested was favorable for larval development. The highest survival was observed on bitter oranges, but the shortest developmental times and heaviest pupae were obtained from orange cultivars. Pulp chemical properties, such as soluble solid contents, acidity, and pH had rather small effects on larval and pupal survival and developmental time (except for juice pH on larvae developmental duration), but they had significant effects on pupal weight.     

Seasonal population fluctuations of the diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae) on different cauliflower cultivars

The diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, it has been identified as a serious pest of the cauliflower fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported until now. According to many researchers, to solve the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. Despite this condition, it seems that the use of resistant cauliflower cultivars is an appropriate policy for integrated control of the pest in the field. In order to identify the most resistant cultivar in the field, eight cauliflower cultivars in a completely randomised design with five replicates were planted at the Shahed University research field (south of Tehran). Density of eggs, larvae and pupae of P. xylostella were measured every 10 days in these cultivars. The results showed that there is no significant difference between numbers of eggs per plant on different cultivars. But number of larvae and pupae per plant were significantly different among different cultivars. Smilla and Snow mystique cultivars had the highest number of larvae and pupae. On the other hand, Buris and Snow crown cultivars had the lowest number of pupae and Snow crown and SG cultivars had the lowest number of larvae per plant. According to the results, the Buris and Snow crown cultivars had the lowest infestation and had a kind of resistance to pest.     

Influence of mulberry cultivars Morus spp. on the production and quality of silkworm Bombyx mori L. (Lepidoptera: Bombycidae) cocoons

The success of sericiculture greatly depends on the availability of mulberry cultivars with agronomic characteristics that maximize the production and quality of silkworm, Bombyx mori L., cocoons. The effect of the cultivars Miura (standard) and Korin, and the hybrids SM 14, SM 63, SK 1, SK 4 and FM 86 was evaluated on silkworm development, and on cocoon production and quality, at the Instituto Agron?mico do Paraná, IAPAR, in Londrina, PR, Brazil (23 +/- 3 degrees C; 61 +/- 8% RH). The experiment was arranged in a randomized block design with four replicates. Larvae feeding either on 'SK 4' or on 'Korin' showed a higher weight compared to that of larvae feeding on 'Miura'. Cocoon weight (both sexes) and pupae weight (male) obtained with larvae fed on SK 4 were higher compared with that of insects that fed on Miura; there was no difference among the remaining treatments. Silk net weight was independent of the cultivar used. Cocoon shell weight was similar amongst insects raised on 'Miura' and on the other mulberry materials. The percentage of cocoon spinning was higher than 90% in all treatments, with the spinning concentrating in the first two days. The proportion of first grade cocoons varied from 80% (SK4) to 90%. The results obtained with the studied cultivars were either similar or superior to that of the standard cultivar Miura with emphasis to 'SK 4', thus showing the potential use of these cultivars in sericulture in the state of Paraná.     

外寄生性花绒寄甲的寄生选择及其发育表现

"选择-表现"假说认为,成虫应该选择有利于子代发育的高品质寄主,但在寄主选择中,除了寄主品质外,其他因素也可能影响寄主选择决策。寄主选择研究通常以成虫为对象,而对那些初龄幼虫选择寄主的寄生性昆虫很少关注。以1龄幼虫积极搜寻寄主的寄生性花绒寄甲为模式生物,采用双选试验设计,观察了花绒寄甲初孵幼虫在不同体重青杨天牛幼虫之间、在已被寄生与健康的黄粉虫蛹之间的寄生选择性;然后采用回归设计,观察了花绒寄甲寄生若干不同体重的青杨天牛幼虫后的发育表现。研究结果表明,花绒寄甲1龄幼虫对体型较大的青杨天牛幼虫的选择偏好显著大于对体型较小的寄主幼虫的选择,选择大体型幼虫的比值比是选择小体型幼虫的4.55倍;对已被寄生的寄主黄粉虫蛹的选择偏好显著大于对健康寄主蛹的选择,选择已被寄生寄主的比值比是选择健康寄主的12.57倍。寄生青杨天牛幼虫的花绒寄甲幼虫发育历期平均为11.49 d、蛹历期为26.67 d、幼虫发育至成虫的羽化率50%,这些发育表现与寄生时青杨天牛幼虫的体重没有显著关系。但刚羽化寄甲成虫体重与寄生时寄主的体重存在显著的正直线关系:寄生时的寄主体重每增大0.01 g,羽化出的寄甲成虫体重增大近0.08%;方差分析寄甲成虫体重在不同寄主体重水平之间的差异表明,从体型较大寄主中羽化的寄甲成虫体重显著大于从体型较小寄主中羽化的成虫。研究结果说明,花绒寄甲初孵幼虫在寄主选择决策时,在寄主体型大小与被寄生状态之间可能采取折衷对策,而且对体型大小不同的寄主选择与子代发育适合度表现存在一致性,从而支持"选择-表现"假说。     

Parasitism of Aganaspis daci against Ceratitis capitata under Mediterranean climate conditions

The effect of environmental factors is essential to the success of parasitoids as biological control agents, as it determines their foraging activity, development, and survival. The larval‐pupal parasitoid wasp Aganaspis daci (Weld) (Hymenoptera: Figitidae) is known to have a very low fertility (i.e., offspring production) in the field in certain Mediterranean areas, probably due to its inability to efficiently oviposit under such climatic conditions. In this study, the percentage of parasitism and induced mortality (mortality of host pupae attributed to parasitoids, from which adults do not emerge) caused by this wasp to the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), was assessed under field conditions across 1 year, using medfly‐infested apples and parasitoid‐confined release in a lemon orchard of southeastern Spain. As A. daci is known to have very few emergences in the field, fertility was assessed in the laboratory from parasitized pupae recovered from the field. We found average parasitism rates of 27% and high induced mortality rates of 66% under field conditions. Consequently, medfly population reduction (total mortality of C. capitata caused by A. daci, i.e., induced mortality + % parasitism) was, on average, 87%. Parasitism and induced mortality varied throughout the year, depending on the average temperature and relative humidity. The interaction of these factors resulted in the highest parasitism rates at low mean temperature and humidity values; likewise, the highest percentages of induced mortality were obtained with a combination of high mean temperature and low mean humidity values. In conclusion, A. daci may exert a strong impact on medfly populations, being a good candidate for inundative field releases for the management of C. capitata in the Mediterranean Basin.     

Comparison of the mitotic karyotypes of Ceratitis capitata, Ceratitis rosa, and Trirhithrum coffeae (Diptera: Tephritidae) by C-banding and FISH.

The sex chromosomes of the tephritid fruit fly Ceratitis capitata (Wiedemann) are heteromorphic. The male-determining region was located on the Y chromosome by deletion mapping using unbalanced offspring from several translocation strains. In addition, we showed that only 15% of the Y chromosome is required for male determination and male fertility. Based on this result, we expected to find Y-chromosomal length polymorphism in natural populations. Using fluorescence in situ hybridization with two repetitive DNA probes that label the Y chromosome, no obvious size differences were detected in seven wild-type strains and three mutant strains. As the medfly is probably of East African origin, we also analyzed two wild-type strains established recently from pupae sampled in Kenya. The Y chromosomes show a polymorphism in the hybridization pattern of a repetitive Y-specific medfly clone. However, the overall size of the Y chromosome is similar to that of the other strains. Besides C. capitata, the tephritid fruit flies Ceratitis (Pterandrus) rosa Karsch and Trirhithrum coffeae Bezzi also emerged from pupae sampled in Kenya. Their karyotype was analyzed by C-banding. Furthermore, the ribosomal genes were mapped to the sex chromosomes in these two species. Key words : Ceratitis capitata, Tephritidae, C-Banding, FISH, rDNA.     

A preliminary investigation of pre-dispersal seed predation by Acanthoscelides schrankiae Horn (Coleoptera: Bruchidae) in Mimosa bimucronata (DC.) Kuntze trees

This is the first record of Acanthoscelides schrankiae Horn. feeding in seeds of Mimosa bimucronata (DC.) Kuntze. We investigated the pattern of oviposition and seed exploitation by A. schrankiae, and the distribution of mature fruits and seed predation in the inflorescences. We also compared the percentage of predated seeds, the total dry weight of fruits and non-predated seeds, the percentage of aborted seeds, and the percentage of non-emergent insects, among different quadrants of the M. bimucronata canopy. To determine the occurring species, the emergence of bruchids and parasitoids was observed in the laboratory, resulting altogether, only in individuals of A. schrankiae and Horismenus sp. (Hymenoptera: Eulophidae) species, respectively. Mean number of fruits produced in the median region of inflorescence was significantly higher than in the inferior and superior regions, and the frequencies (observed and expected) of predated and non-predated seeds differed among the different regions of inflorescence. Females of A. schrankiae laid their eggs on fruits, and larvae, after emergence, perforated the exocarp to reach the seeds. Most fruits presented one to three eggs and only one bruchid larva was observed in each seed. The highest value of the rate "number of eggs/fruit" and the highest percentage of predated seeds were recorded in April. Dry weight of fruits (total) and seeds (non-predated), proportions of predated seeds, seed abortions, and non-emergent seed predators, were evenly distributed in the canopy.     

Combined use of the larvo‐pupal parasitoids Diachasmimorpha longicaudata and Aganaspis daci for biological control of the medfly

In biological control programmes, it is very common to employ multiple species to manage a single insect pest. However, the beneficial effects of natural enemies are not always additive because of several factors, including interspecific competition between these biocontrol agents. For this reason, in the present study we assessed several biological parameters (percentage parasitism, fertility, induced mortality and population reduction) of the parasitoids Diachasmimorpha longicaudata and Aganaspis daci when used together against the medfly Ceratitis capitata under laboratory and greenhouse conditions. Our results showed that, under laboratory conditions, fertility and percentage parasitism corresponded to a different functional response for each species (D. longicaudata: type II; A. daci: type III), whilst under greenhouse conditions, and unlike what occurs with single releases, both parasitoids showed a type III functional response; this is the only response which may lead to direct density dependence when host densities are low. Our results also revealed that when both species acted together, they produced a very high total percentage parasitism compared to that reported for single releases under both laboratory (64–76%) and greenhouse (21–51%) conditions. The parasitism was also higher for A. daci except when medfly larvae were provided in an artificial diet. Furthermore, host mortality induced by the two parasitoids acting together was very high, especially at low‐host densities; medfly population was almost completely reduced under greenhouse conditions. In summary, the data reported here supports the combined use of these species in biological control programmes against the medfly and highlights the importance of several factors, such as climatic conditions and host density, when planning their field releases.     

Determination of host status of citrus fruits against the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae)

Abstract  The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) is a pest of citrus in parts of Western Australia. Three citrus cultivars: Valencia oranges, Eureka lemons and Imperial mandarins, as well as non-citrus control fruits, were examined for attractiveness and suitability to Medfly in the field and in the laboratory using choice and no-choice experiments. Oranges were more susceptible to Medfly than mandarins and lemons. Punctures in the skin had a significant impact on the degree of infestation in both citrus and non-citrus control fruit. Artificial infestation and larval survivorship were used to investigate the suitability of each cultivar to Medfly under laboratory conditions. Oranges and mandarins were suitable for the development of Medfly, but lemons were a poor host. When each cultivar was in season, field cage trials demonstrated that infestation occurred in oranges and mandarins but not in lemons.     

Biology of Cuterebra lepusculi Townsend (Diptera: Cuterebridae) in cottontail rabbits in Idaho

Cuterebra lepusculi Townsend parasitize cottontail rabbits (Sylvilagus nuttallii) in southern Idaho. Peak parasitism was 69% in mid-September. Mean development time in the host was 27 days. The species is univoltine in Idaho. Partially developed larvae were transferred from freshly killed to living hosts and the resulting larvae matured normally. Developing pupae were cooled or warmed to retard or speed development and synchronize adult emergence.     

Abiotic factors affecting Diachasmimorpha longicaudata (Hymenoptera: Braconidae) activity as a natural enemy of Ceratitis capitata (Diptera: Tephritidae) under semi‐natural conditions in the Mediterranean region

The larval–pupal endoparasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) is currently the most commonly employed biological control agent against Tephritid fruit flies in the Americas. However, this parasitoid remains largely ignored and is not used in many regions, including the Mediterranean Basin. In this study, the potential of D. longicaudata as a biocontrol agent against the Mediterranean fruit fly (medfly) Ceratitis capitata (Diptera: Tephritidae) was addressed in an area of eastern Spain (the Valencian community). The parasitic activity of parasitoids and the effects of climatic conditions were evaluated throughout a 1‐year period in field‐cage experiments in which parasitoids were confined with apples artificially infested with medfly larvae. The following parameters were calculated and related statistically to several environmental conditions: the parasitism rate, the induced mortality and progeny sex ratio. The results show that D. longicaudata is able to parasitize medfly larvae throughout the year under semi‐natural conditions. Important fluctuations in the parasitism rate (from almost zero to 42%) and the induced mortality (from 6% to 80%) were partially influenced by climatic conditions. The parasitism rate increased with mean temperature and decreased with mean relative humidity, while the induced mortality decreased with minimum relative humidity. The optimal climatic conditions for the activity of the parasitoid were a mean temperature of 16–24°C combined with a relative humidity of 45%–60%. Overall, these results suggest that reduction in the medfly population due to D. longicaudata activity is feasible and provide information about the optimal time period for parasitoid release in the field. In conclusion, D. longicaudata has a significant potential to control C. capitata in the Mediterranean region.     

Comparative Effectiveness of Three Release Rates for a Pteromalid Parasitoid (Hymenoptera) of House Flies (Diptera) in Beef Cattle Feedlots

Muscidifurax zaraptor Kogan and Legner (Hymenoptera: Pteromalidae) was released at three rates in nine beef cattle feedlots in eastern Nebraska to measure dosage response. Dosage response was measured by the percentage parasitism of sentinel house fly pupae. Releases were made from a single location near the center of the pen at three feedlots, from two locations within the pen at three feedlots, and from four corners of the pen at three feedlots. One-time releases initiated held propagation of M. zaraptor using freeze-killed house fly pupae as hosts. Three treatment rates, averaging 4480, 20,300, and 37,100 parasitoids, were released weekly over a 15-week period with each of the three release methods receiving a low, medium, or high treatment rate. All nine release sites produced significantly higher levels of parasitoid emergence and sentinel host mortality than sentinel hosts at two control facilities. The three sites receiving the high treatment rate averaged 38% host mortality, compared with 26% for the medium treatment rate and 17% for the low treatment rate. The two control sites averaged 2% host mortality. No significant differences could be detected in the number of release stations except at the four-station method using the low treatment rate. High temperatures during at least two of the weekly periods were detrimental to the released parasitoids.