Performance of Psyttalia humilis (Hymenoptera: Braconidae) reared from irradiated host on olive fruit fly (Diptera: Tephritidae) in California

The parasitoid Psyttalia humilis (Silvestri) was reared on Mediterranean fruit fly, Ceratitis capitata (Wiedemann), third instars irradiated at 0-70 Gy at the USDA, APHIS, PPQ, Moscamed biological control laboratory in San Miguel Petapa, Guatemala, and shipped to the USDA, ARS, Parlier, CA. Irradiation dose did not affect the parasitoid's offspring sex ratio (53-62% females), percentage of unemerged adults (12-34%), number of progeny produced per female (1.4-1.8), and parasitism (19-24%). Host irradiation dose had no significant effect on the forewing length of female P. humilis and its parasitism on olive fruit fly, Bactrocera oleae (Rossi) and offspring sex ratio, but dissection of 1-wk-old female parasitoids reared from hosts irradiated with 70 Gy had a significantly lower number of mature eggs than females from nonirradiated hosts. Longevity of P. humilis adults decreased with increased temperature from 15 to 35°C, regardless of food provisions, gender, and host irradiation dose. Females survived 37-49 d at 15°C with water and food, and only 1-2 d at 35°C without food, whereas males lived shorter than females at all temperatures and food combinations tested. Adult P. humilis reared from fertile C. capitata and aspirated for dispensing in cups lived significantly longer after shipment than those specimens chilled and dispensed by weight. At 21 and 32°C, 50% of parasitoids departed release cages after 180 and 30 min, respectively, but none departed at 12°C. Thirteen shipments of P. humilis (2,980-21,922 parasitoids per shipment) were received between September and December 2009, and seven shipments (7,502-22,560 parasitoids per shipment) were received between October and December 2010 from San Miguel Petapa, Guatemala. Daily number of olive fruit fly adult and percentage female trap captures ranged <1-19 and 8-58% in 2009, and <1-11 and 0-42% in 2010, respectively. The number of parasitoids released ranged 848-12,257 in 2009 and 3,675-11,154 in 2010. Percentage parasitism of olive fruit fly third instars at all locations ranged 0-9% in 2009 and 0-36% in 2010.     

Quarantine strategies for olive fruit fly (Diptera: Tephritidae): low-temperature storage, brine, and host relations

A dose-response relationship was not observed in olive fruit fly, Bactrocera oleae (Gmelin), larvae exposed to acetic acid concentrations (0-2.5%) used in commercial brine solutions to cure olives. Immersion in a 1% acetic acid brine solution impeded emergence of the immature stages. A 1-wk exposure of olives infested with olive fruit fly larvae to low-temperature storage as a postharvest treatment at 0-1 degree C resulted in 8% survival of the population, and exposures of 2 through 5 wk further reduced pupal and adult emergence to <1.0%. One- to 2-wk exposures at 2-3 degrees C resulted in a significant decrease in survival from 20 to 3%, respectively, and longer durations of 3-5 wk reduced survival to <1.0%. Mean daily fruit pulp temperatures in olives in the top, middle, and bottom of plastic bins stored at 2-3 degrees C decreased by 5-8 degrees C from the first to the second day. Lowest temperatures were observed in the top, and highest temperatures were observed in the middle layer of fruit, which attained a mean temperature of 3.8 degrees C on day 5. Laboratory choice tests showed that olive fruit fly oviposited at a higher rate in late season Mission olives that were green than in fruit that were in the red blush maturity stage in tests with 1- and 3-4-d exposure periods, and an increase in duration of exposure was related to an increase in the total number of ovipositional sites. Higher percentages of olive fruit fly third instars, pupae, and adults were reared from green fruit than from fruit in the red blush stage after a 1-d exposure to oviposition. Manzanillo olives were more attractive for oviposition by olive fruit fly than Mission olives, and significantly more third instars, pupae, and adults developed in Manzanillo fruit than in Mission fruit in the red blush stage. These differences were related to the better quality and higher flesh content of the Manzanillo versus Mission olives used in the tests.     

Psyttalia ponerophaga (Hymenoptera: Braconidae) as a potential biological control agent of olive fruit fly Bactrocera oleae (Diptera: Tephritidae) in California

The olive fruit fly, Bactrocera oleae (Rossi), is a newly invasive, significant threat to California's olive industry. As part of a classical biological control programme, Psyttalia ponerophaga (Silvestri) was imported to California from Pakistan and evaluated in quarantine. Biological parameters that would improve rearing and field-release protocols and permit comparisons to other olive fruit fly biological control agents were measured. Potential barriers to the successful establishment of P. ponerophaga, including the geographic origins of parasitoid and pest populations and constraints imposed by fruit size, were also evaluated as part of this investigation. Under insectary conditions, all larval stages except neonates were acceptable hosts. Provided a choice of host ages, the parasitoids' host-searching and oviposition preferences were a positive function of host age, with most offspring reared from hosts attacked as third instars. Immature developmental time was a negative function of tested temperatures, ranging from 25.5 to 12.4 days at 22 and 30 degrees C, respectively. Evaluation of adult longevity, at constant temperatures ranging from 15 to 34 degrees C, showed that P. ponerophaga had a broad tolerance of temperature, living from 3 to 34 days at 34 and 15 degrees C, respectively. Lifetime fecundity was 18.7 +/- 2.8 adult offspring per female, with most eggs deposited within 12 days after adult eclosion. Olive size affected parasitoid performance, with lower parasitism levels on hosts feeding in larger olives. The implications of these findings are discussed with respect to field manipulation and selection of parasitoid species for olive fruit fly biological control in California and worldwide.     

Olive fruit fly (Diptera: Tephritidae) in California: longevity, oviposition, and development in canning olives in the laboratory and greenhouse

The biology of olive fruit fly, Bactrocera oleae (Rossi), was studied in the laboratory, greenhouse, and in canning olives, Olea europaea L., in relation to California regional climates. Adults survived in laboratory tests at constant temperatures and relative humidities of 5 degrees C and 83%; 15 degrees C and 59%; 25 degrees C and 30%; and 35 degrees C and 29% for 15, 6, 3, and 2 d without provisions of food and water and for 37, 63, 25, and 4 d with provisions, respectively. In a divided greenhouse, adults survived for 8-11 d in the warm side (36 degrees C and 31% RH daytime); and in the cool side (26 degrees C and 63% RH daytime) 10 d without provisions and 203 d with provisions. A significantly greater number of adults survived in the cool side than the warm side, and with provisions than without. First and last eggs were oviposited in olive fruit when females were 6 and 90 d old, respectively. The highest number of eggs was 55 per day in 10 olive fruit oviposited by 10 28 d-old females, with maximum egg production by 13-37 d-old females. A significantly greater number of ovipositional sites occurred in all sizes of immature green fruit when exposed to adults in cages for 5 d than 2 d. Adults emerged from fruit with a height of > or = 1.0 cm or a volume of > or = 0.2 cm3. More than seven adults per 15 fruit emerged from field infested fruit with a height of 1.1 cm and volume of 0.1 cm3. Larval length was significantly different among the first, second, and third instars and ranged from 0.7 to 1.6, 2.4-4.3, and 4.8-5.6 mm at 14 degrees C; 0.8-1.1, 1.9-2.9, and 3.9-4.4 mm at 21 degrees C, and 0.7-1.3, 2.4-2.9, and 4.4-4.8 mm at 26 degrees C, respectively. Survival of pupae to the adult stage was significantly lower at 26 degrees C than 14 degrees C or 21 degrees C. The period of adult emergence began at 38, 14, and 11 d over a period of 8, 5, and 1 d at 14, 21, and 26 degrees C, respectively. Findings were related to the occurrence and control of California olive fruit fly infestations.     

Bioecology of Stenoma catenifer (Lepidoptera: Elachistidae) and associated larval parasitoids reared from Hass avocados in Guatemala

A 10-wk study of the avocado seed-feeding moth Stenoma catenifer Walsingham (Lepidoptera: Elachistidae), was conducted in a commercial 'Hass' avocado (Persea americana Miller [Lauraceae]) orchard in Guatemala. Up to 45% of fruit in the orchard were damaged by larval S. catenifer. Larval-to-adult survivorship for 1,881 S. catenifer larvae in Hass fruit was 37%, and adult sex ratio was 51% female. Four species of larval parasitoid were reared from field-collected S. catenifer larvae. The most common parasitoid reared was a gregarious Apanteles sp., which parasitized 53% of larvae and produced on average eight to nine cocoons per host. Apanteles sp. sex ratio was 47% female and 87% of parasitoids emerged successfully from cocoons. Apanteles sp. longevity was approximately equal to 1.5 d in the absence of food, and when provisioned with honey, parasitoids survived for 5-7 d. The mean number of cocoons produced by Apanteles sp. per host, and larval parasitism rates were not significantly affected by the number of S. catenifer larvae inhabiting seeds. Oviposition studies conducted with S. catenifer in the laboratory indicated that this moth lays significantly more eggs on the branch to which the fruit pedicel is attached than on avocado fruit. When given a choice between Hass and non-Hass avocados, S. catenifer lays up to 2.69 times more eggs on Hass.     

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

The 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.     

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

Fopius caudatus (Szépligeti) 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.     

The Distributions of Parasitoids (Hymenoptera) of Anastrepha Fruit Flies (Diptera: Tephritidae) along an Altitudinal Gradient in Veracruz, Mexico

In the state of Veracruz, Mexico, fruits from 38 sites at various altitudes were collected monthly over a period of 2 years, and the tephritid fruit flies of the genus Anastrepha and associated parasitoids that emerged from these fruits were identified and counted. Of the 26 species of fruits that contained Anastrepha larvae, 18 species also contained a total of 10 species of Anastrepha parasitoids. These consisted of 4 native and 1 exotic species of opiine braconid larval–pupal parasitoids, 2 native species of eucoilid larval–pupal parasitoids, 1 exotic species of eulophid larval–pupal parasitoid, 1 exotic species of pteromalid pupal parasitoid, and 1 native species of diapriid pupal parasitoid. Overall parasitism (including flies from fruit species that bore no parasitoids) was 6% and was greatest, 16%, at 600–800 m in altitude. The relative contributions of individual parasitoid species to overall parasitism were frequently influenced by both the altitude (and correlated changes in temperature and precipitation) and the species of plant in which the Anastrepha larvae were found. This was particularly the case among the more abundant and widespread Braconidae. To distinguish the role of altitude from that of the distributions of the host plants, these braconids were examined in 4 individual species of fruit that grew over a broad range of altitudes. In guava (Psidium guajava L.) and “jobo” (Spondias mombin L.) the parasitoid Doryctobracon areolatus (Szepligeti) was relatively more common at low altitudes. Its congener, Doryctobracon crawfordi (Viereck), was relatively more abundant at high altitudes in sour orange (Citrus aurantium L.). Utetes anastrephae (Viereck) became relatively more common at higher altitudes in S. mombin, whereas Diachasmimorpha longicaudata (Ashmead) tended to become relatively rare at the highest altitudes in C. aurantium, but increased at high altitudes in P. guajava compared to other braconids. Different altitudinal patterns of abundance in different fruits suggests the importance of both biotic and abiotic factors in parasitoid distributions. We discuss the effect of an expanding agricultural frontier on parasitoid abundance and relate our findings to the design of a fruit fly biological control program that tailors mass releases to parasitoid climate preferences.     

A compound produced by fruigivorous Tephritidae (Diptera) larvae promotes oviposition behavior by the biological control agent Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Tephritid fruit fly parasitoids use fruit-derived chemical cues and the vibrations that result from larval movements to locate hosts sequestered inside fruit. However, compounds produced by the larvae themselves have not been previously described nor their significance to parasitoid foraging determined. We collected the volatiles from four species of tropical and subtropical Tephritidae: Anastrepha suspensa (Loew), Bactrocera dorsalis Hendel, Bactrocera cucurbitae Coquillett, and Ceratitis capitata (Wiedemann), representing two subfamilies (Dacinae and Trypetinae). Para-ethylacetophenone, an analog of a known tephritid parasitoid attractant, was a major constituent of all four, and was not associated with larvae of another acalypterate fly, Drosophila melanogaster Meigen, or with the calypterate Musca domestica L. It also was present in volatiles from whole, A. suspensa infested fruits of Eugenia uniflora (L.). Para-ethylacetophenone was not necessarily produced as a direct consequence of fruit consumption because it also was detected from larvae that developed in two artificial diets and in spent diets subsequent to larval development. Sensillae on both the antennae and ovipositor of the opiine braconid fruit fly parasitoid, Diachasmimorpha longicaudata (Ashmead) responded to the para-ethylacetophenone in larval volatiles and as a synthetic. Although a potential cue to foraging parasitoids, para-ethylacetophenone showed no long range (>1m) attractiveness to the adult female parasitoid, but did stimulate ovipositor-insertion and oviposition into both a natural (fruit) and an artificial (parafilm) substrate. Thus it may prove useful in colonizing and mass-rearing opine fruit fly parasitoids.     

Biological Control of Anastrepha spp. (Diptera: Tephritidae) in Mango Orchards through Augmentative Releases of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae)

Diachasmimorpha longicaudata (Ashmead) parasitoids were released by air on a weekly basis over 1600 ha of commercial mango orchards, backyard orchards, and patches of native vegetation, at a density of ca. 940 parasitoids/ha. Releases were made during 2 consecutive years, beginning at flower onset and lasting until the end of the production cycle. Two areas, 7 km apart, were compared. In one area parasitoids were released, whereas the other area was used as a control. During the 2nd year treatments were reversed. Fruit was sampled in commercial mango orchards and in backyard orchards to assess levels of parasitism in fruit fly larvae. Highly significant differences in percentage parasitism were found in release and control zones in backyard orchards. Furthermore, trapping results indicated that D. longicaudata releases were associated with ca. 2.7-fold suppression of Anastrepha spp. populations in backyard orchards. Results suggest that suppression might be affected by environmental conditions and by the parasitoid:fly ratio achieved. Anastrepha obliqua McQuart populations were suppressed more effectively by use of parasitoids than those of Anastrepha ludens Loew, perhaps due to the type of host fruits used by each species. Augmentative parasitoid releases in marginal areas surrounding commercial orchards (backyard orchards, wild vegetation) can substantially suppress fly populations. Through this approach, the number of flies that later move into commercial orchards can be significantly reduced. Such a strategy, when combined with sound orchard management schemes, can allow growers to produce clean fruit without the need to resort to the widespread use of insecticides.     

Incidence of the introduced parasitoids Cotesia kazak and Microplitis croceipes (Hymenoptera: Braconidae) from Helicoverpa armigera (Lepidoptera: Noctuidae) in tomatoes,sweet corn,and lucerne in New Zealand

Two parasitoids,Cotesia kazak (Telenga) and Microplitis croceipes (Cresson) have been successfully introduced into New Zealand to improve control of Helicoverpa armigera (Hübner), tomato fruitworm. C. kazak has spread throughout the North Island, but M. croceipes is restricted largely to its release areas in crops in the Gisborne and Hawke’s Bay regions in the East Coast of the North Island and in pine plantations in the central North Island. Rates of mortality of H. armigera from parasitism were studied in processing tomato crops where these parasitoids are a key component of an integrated pest management programme, and in sweet corn, lucerne and soybeans. C. kazak was the dominant parasitoid in tomatoes and soybeans. It emerged from small H. armigera larvae and usually killed the host before it caused major damage to fruit. M. croceipes emerged from larger host larvae than C. kazak. Death rates from parasitism of H. armigera larvae in tomatoes increased from less than 1% caused by native parasitoids prior to parasitoid introductions, to 25–45% in 1988 and 70–80% in 1996 following the establishment of both introduced parasitoids. M. croceipes was the most common parasitoid in lucerne and total mortality from all parasitoids was similar to that in tomatoes. Low rates of parasitism by C. kazak in sweet corn were attributed to the reduced penetration of the adult parasitoid into sweet corn fields and to the protection afforded by sweet corn when H. armigera larvae burrowed into corn cobs. The implementation of an IPM programme based partly on the effectiveness of these parasitoids has contributed to a decrease in insecticide applications to processing tomatoes.     

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.     

闭弯尾姬蜂与菜蛾盘绒茧蜂寄生菜蛾幼虫时的种间竞争

在室内25℃下,以菜蛾3龄初幼虫作寄主,研究了菜蛾盘绒茧蜂Cotesia plutellae和半闭弯尾姬蜂Diadegma semiclausum的种间竞争。当寄主供2种蜂同时产卵寄生时,2种蜂各自的寄生率与其单独寄生时无显著差异,合计寄生率比一种蜂单独存在时有所提高,但差异不显著。2种蜂均能产卵寄生已被另一种蜂寄生了的寄主幼虫。当寄主被2种蜂寄生的间隔时间很短（少于10 h）时,所育出的蜂绝大部分（80%以上）为绒茧蜂;当寄主先被绒茧蜂寄生,并饲养2天以上再供弯尾姬蜂寄生时,所育出的全为绒茧蜂;当寄主先被弯尾姬蜂寄生,并饲养2天以上再供绒茧蜂寄生时,寄主幼虫绝大部分不能存活,只有少部分能育出寄生蜂,且多为弯尾姬蜂。当2种蜂的幼虫存在于同一寄主体内时,2种蜂的发育均受到另一种蜂的抑制;绒茧蜂1龄幼虫具有物理攻击能力,能将弯尾姬蜂卵或幼虫致死。这些结果表明,菜蛾盘绒茧蜂与半闭弯尾姬蜂在同一寄主中发育时,前者具有明显的竞争优势。     

Interactions Between Augmentatively Released Diachasmimorpha longicaudata (Hymenoptera: Braconidae) and a Complex of Opiine Parasitoids in a Commercial Guava Orchard

A study was conducted to determine the eVect of augmentatively releasing mass-reared Diachasmimorpha longicaudata (Ashmead) on a complex of four co-existing parasitoid species which attack the oriental fruit fly, Bactrocera dorsalis (Hendel). The species belonging to this complex are the egg-pupal parasitoid, Biosteres arisanus (Sonan) and the larval-pupal parasitoids, Biosteres vandenboschi (Fullaway), D. longicaudata and Psyttalia incisi (Silvestri). The study site was a 160-ha commercial orchard of common guava, Psidium guajava L. (cv. Beaumont) located on Kauai island. One year before the release of D. longicaudata, B. arisanus was the dominant parasitoid, accounting for 91.1% of the parasitoids recovered. Despite releases of large numbers of D. longicaudata (600000-800 000 parasitized puparia/ week), B. arisanus continued to account for 90% of all parasitoids recovered from the oriental fruit fly. The larval parasitoid P. incisi may have been reduced as a result of D. longicaudata releases. D. longicaudata was significantly more abundant in over-ripe and rotting fruits compared with freshly fallen fruits. However, no increase in the overall percentage parasitism was observed in any fruit ripeness category. B. arisanus was eY cient at colonizing hosts when fruit fly densities and fruit abundance were relatively low in the orchard. The implications for future augmentative release programmes with D. longicaudata are discussed.     

Crop domestication relaxes both top-down and bottom-up effects on a specialist herbivore

Domestication of crop plants selects for numerous traits that often distinguish them dramatically from their wild progenitors. In some cases, these modifications lead to increased herbivory, by enhancing their attractiveness to herbivorous insects or reducing the efficiency of natural enemies, or both. This study investigated the effects of fruit enlargement on the olive (Olea europaea L.), the specialist olive fruit fly, Bactrocera oleae (Rossi), and its specialized larval parasitoids. Wild olive fruit are small (<2 mm pulp thickness) and the larval parasitoids associated with B. oleae have short ovipositors (<3 mm), while cultivated fruit are larger (4–8 mm pulp thickness). Female flies allocate more offspring to large than to small fruit within or across different-sized commercial cultivars, without reducing the fitness of their offspring. Fly larvae move deeper into the olive pulp with their increasing age and fruit size. In contrast, the specialist larval parasitoid, Psyttalia lounsburyi (Silvestri), more effectively parasitizes hosts in smaller than larger fruit. The inverse relationship between the performance of the fly and its co-evolved parasitoids on fruit of increasing sizes indicates that olive cultivation favors the success of the fly by providing a better food resource and more enemy-free space. These findings offer some explanation for the failure of the decades-old classical biological efforts to manage B. oleae using specialized larval parasitoids in the Mediterranean Basin and provide further evidence that crop domestication can alter host–parasitoid interactions.     

X-ray doses to safely release the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) reared on Anastrepha fraterculus larvae (Diptera: Tephritidae)

Diachasmimorpha longicaudata is a koinobiont larval parasitoid that is currently used to control fruit flies of the genera Anastrepha, Ceratitis and Bactrocera. In the rearing process, a fraction of the host larvae that are exposed to parasitoids escape from parasitism and develop into viable and fertile flies. This creates the need to eliminate emerging flies before the parasitoids are shipped for release, increasing costs due to additional handling steps. Exposure of fly eggs or larvae to gamma-irradiation before they are parasitised has been used to reproductively sterilise hosts, or even inhibit their emergence. Our aim was to determine whether X-ray radiation applied to Anastrepha fraterculus third instar larvae before they are exposed to parasitoids, inhibits fly emergence in non-parasitised larvae without affecting the performance of the parasitoids that emerge from parasitised larvae. Three X-ray doses: 6250.2 R, 8333.6 R and 10417 R (equivalent to 60, 80 and 100 Gy, respectively) and one γ-ray dose (100 Gy) were tested. Fly emergence decreased with increasing doses of radiation, showing null values for the higher X-ray dose and the dose of 100 Gy. Irradiation showed either no impact or a positive effect on parasitism rate and fecundity. Sex rate was biased towards females in almost every dose. We conclude that the two types of radiation evaluated here were equally effective in suppressing fly emergence with no detrimental effects on the biological quality of the produced parasitoids. X-rays offer an alternative method of irradiation than the conventional radiation source, i.e. γ-rays. These results represent a significant improvement in the development of a biological control programme against A. fraterculus.     

Parasitism on medfly by Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) in different guava cultivars

The parasitism efficiency of the Braconidae wasp, Diachasmimorpha longicaudata (Ashmead), was checked on four guava cultivars (Paluma, Sassaoca, Pedro Sato and Kumagai) infested with larvae of medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Five blocks of eight fruits, each with two fruits of each cultivar, were put inside C. capitata adult cages, during 2h for oviposition, and a week later, when the larvae inside guavas were developed, the fruits were exposed to parasitoids for 24h. The mean fruit weight, larvae mortality, number of pupae, percentage of medfly and parasitoid emergence were evaluated. There was not statistical difference among cultivars to weight, larvae mortality, number of pupae e emergence of medfly. The percentage of parasitism was higher in Pedro Sato cultivar (19.8%) compared with Kumagai cultivar (2.9%), but it was statistically similar to the other cultivars.     

Predation potential of the earwig Euborellia annulipes on fruit fly larvae and trophic interactions with the parasitoid Diachasmimorpha longicaudata

The earwig Euborellia annulipes (Lucas) (Dermaptera: Anisolabididae), a generalist predator, has been observed in fruits infested with fruit fly larvae, which are frequently parasitized by parasitoid wasps. Neither the capacity of earwigs to predate on fruit flies nor intraguild interactions between earwigs and fruit fly parasitoids have been investigated. Here, we studied in laboratory conditions the predation on the fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) by the earwig E. annulipes, and whether parasitism of fruit fly larvae by the parasitoid wasp Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) influences predation by the earwig. We evaluated the predation capacity, functional response and prey preference of E. annulipes for parasitized and non-parasitized fruit fly larvae in choice and no-choice tests. We found that earwigs prey on second- and third-instar larvae and pupae of C. capitata and consumed larger numbers of second-instar larvae, followed by third-instar larvae and pupae. Females prey on larger numbers of fruit flies than did males, regardless of the prey developmental stage, but both sexes exhibited a type II functional response. Interestingly, males killed but did not consume fruit fly larvae more than did females. In no-choice tests, earwig females consumed equal numbers of parasitized and non-parasitized fruit fly larvae. However, in choice tests, the females avoided feeding on parasitized larvae. Subsequent tests with hexane-washed parasitized and non-parasitized larvae showed that putative chemical markings left on fruit flies by parasitoids did not drive the earwig preference towards non-parasitized larvae. These findings suggest that E. annulipes is a potential biological control agent for C. capitata, and that, because the earwig avoids consuming larvae parasitized by D. longicaudata, a combination of the two natural enemies could have an additive effect on pest mortality.     

Acceptance and suitability of different host stages of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and seven other tephritid fruit fly species to Tetrastichus giffardii Silvestri (Hymenoptera: Eulophidae)

Tetrastichus giffardii Silvestri is a gregarious eulophid endoparasitoid of several tephritid fruit fly species. Host stage suitability was studied using nine age groups of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), namely, eggs less than 24 h and between 24 and 48 h old, and 1- to 7-day-old larvae. Life table studies for T. giffardii using C. capitata as host were done at 26 ± 5 °C and 55–60% RH. Egg load in relation to age of the female parasitoid was also assessed as was the effect of host deprivation on adult longevity. Host acceptance and suitability were examined with respect to eight species of tephritids. Potential hosts so tested were five Ceratitis species, the Medfly, C. capitata, the mango fruit fly, Ceratitis cosyra (Walker), the Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), and Ceratitis anonae Graham; two Bactrocera species, the melon fruit fly, Bactrocera cucurbitae (Coquillett) and the newly invasive Bactrocera invadens Drew, Tsuruta, and White; and one Dacus species, the lesser pumpkin fly, Dacus ciliatus Loew. No parasitoids were obtained from eggs while all larval stages were suitable though at varying degrees. Parasitism and number of progeny was related to host age in a curvilinear manner with maxima at 4- to 5-day-old larvae. By contrast, development time decreased with age of host larvae while sex ratio was not affected. The intrinsic rate of increase was 0.17 ± 0.01; gross and net reproductive rates were 64.9 ± 4.3 and 44.9 ± 3.8, respectively. Non-ovipositing females lived significantly longer than ovipositing ones. The females accepted all host species tested, but only C. capitata, D. ciliatus and, to a much lesser extent, C. cosyra were suitable. In the remaining host species, most eggs were encapsulated. In C. capitata and D. ciliatus, percent parasitism was similar, but number of progeny was lower and the sex ratio, as the proportion of females, was higher when the parasitoid was reared on D. ciliatus. Progeny per puparium were also similar for the two hosts. In the light of these results it can be concluded that T. giffardii has a narrow host range, but it attacks and successfully develops in larvae representing a wide range of ages.     

Interspecific competition between Diadegma semiclausum Hellen (Hym., Ichneumonidae) and Cotesia plutellae (Kurdjumov) (Hym., Braconidae) in parasitizing Plutella xylostella (L.) (Lep., Plutellidea)

Abstract:  Interspecific competition between Diadegma semiclausum and Cotesia plutellae was investigated at 25°C in the laboratory, by exposing the third instar larvae of the diamondback moth, Plutella xylostella to both species together, either species alone or by exposing the host larvae already parasitized by one species, at different intervals, to the other. When host larvae were exposed simultaneously to two species in one arena, parasitism rates of the host by each species were not reduced by the presence of the other species; joint parasitism rate by two species was not significantly higher than that by either parasitoid alone. Both parasitoids could lay eggs into the host larvae which had previously been parasitized by the other species, leading to the occurrence of multiparasitized hosts. When host larvae were parasitized first by D. semiclausum and then being followed within 1–2 h by exposing to C. plutellae , or vice versa, ensuing parasitoid cocoons from the multiparasitized host larvae were nearly all C. plutellae . When host larvae were parasitized initially by C. plutellae and then being followed by D. semiclausum two or more days later, all parasitoids ensued from the multiparasitized hosts were C. plutellae . In contrast, when host larvae were parasitized initially by D. semiclausum and then being followed by C. plutellae two or more days later, most host larvae could not survive to prepupae and most of the ensuing parasitoid adults from the surviving hosts were D. semiclausum . Dissections of host larvae at various time intervals after parasitization by the two parasitoids showed that development of both parasitoids in multiparasitized hosts were somewhat arrested, and that the first instar larvae of C. plutellae could initiate a physical attack on the larvae of D. semiclausum and remove the latter.