Effect of tomato fruit cultivar and ripening stage on Bactrocera tryoni (Froggatt) egg and larval survival

In studies of frugivorous tephritids, determining when offspring (i.e. egg and three larval instars) mortality occurs within the fruit can greatly improve the mechanistic understanding of the fly/host interaction. Previous research has demonstrated that the Queensland fruit fly, Bactrocera tryoni, has differential offspring performance in two tomato cultivars Cherry and Roma, but when juvenile mortality was occurring was not determined. We examined B. tryoni egg and larval survival in three different ripening stages (immature-green (IG), colour-break (CB) and fully-ripe (FR)) of Cherry and Roma tomato cultivars through destructive fruit sampling at 72 and 120 hr for eggs, and 48 (1st instar), 96 (2nd instar) and 120 hr (3rd instar) after fruit inoculation with neonates for larvae. Cultivar and ripening stage had no significant effect on egg survival, nor larval survival at 48 hr: the overall percentage of egg survival was at least 80% across all treatments, while 1st-instar larval was less than 52% across all treatments. In immature-green tomatoes of both varieties, nearly all mortality occurred during the first and second instars, but at 96 and 120 hr, there were significant interaction effects between cultivar and ripening stage on larval survival. In both colour-break Cherry and Roma tomatoes, there was significant larval mortality between 96 and 120 hr. However, in fully-ripe Cherry, no further significant larval mortality happened after 48 hr, while in fully-ripe Roma significant larval mortality occurred between the first and second larval instars but not thereafter. The difference in timing of larval mortality with ripening stage provides indirect evidence of active fruit defence which is strongest in immature-green fruit, less in colour-break fruit and absent in fully-ripe fruit.     

Influence of fruit traits on oviposition preference and offspring performance of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) on three tomato (Lycopersicon lycopersicum) cultivars

Abstract  In Queensland, three tomato ( Lycopersicon lycopersicum ) cultivars, Grosse Lisse, Roma and Cherry, are infested by Queensland fruit fly, Bactrocera tryoni (Froggatt). In this study, we examined if there was a correlation between oviposition preference and offspring performance of B. tryoni among the three tomato cultivars. We also investigated host plant traits that may explain any variation in preference and performance. Choice and no-choice experiments were carried out under laboratory conditions. A positive correlation between oviposition preference and offspring performance of B. tryoni was observed in the three tomato cultivars. Grosse Lisse and Roma cultivars were highly preferred by B. tryoni over Cherry cultivar. Performance (measured as proportion of eggs developing to the pupal stage) was significantly higher in Grosse Lisse and Roma cultivars than in Cherry cultivar. The pericarp toughness of Cherry cultivar appears responsible for its low rate of infestation, while the presence of 2-butanol and 1,4-butanediamine in Roma and Grosse Lisse, respectively, may partly be responsible for the high oviposition preference shown by B. tryoni towards these cultivars.     

The mating system of the true fruit fly Bactrocera tryoni and its sister species,Bactrocera neohumeralis

The frugivorous “true” fruit fly, Bactrocera tryoni (Queensland fruit fly), is presumed to have a nonresourced‐based lek mating system. This is largely untested, and contrary data exists to suggest Bactrocera tryoni may have a resource‐based mating system focused on fruiting host plants. We tested the mating system of Bactrocera tryoni, and its close sibling Bactrocera neohumeralis, in large field cages using laboratory reared flies. We used observational experiments that allowed us to determine if: (i) mating pairs were aggregated or nonaggregated; (ii) mating system was resource or nonresource based; (iii) flies utilized possible landmarks (tall trees over short) as mate‐rendezvous sites; and (iv) males called females from male‐dominated leks. We recorded nearly 250 Bactrocera tryoni mating pairs across all experiments, revealing that: (i) mating pairs were aggregated; (ii) mating nearly always occurred in tall trees over short; (iii) mating was nonresource based; and (iv) that males and females arrived at the mate‐rendezvous site together with no evidence that males preceded females. Bactrocera neohumeralis copulations were much more infrequent (only 30 mating pairs in total), but for those pairs there was a similar preference for tall trees and no evidence of a resource‐based mating system. Some aspects of Bactrocera tryoni mating behavior align with theoretical expectations of a lekking system, but others do not. Until evidence for unequivocal female choice can be provided (as predicted under a true lek), the mating system of Bactrocera tryoni is best described as a nonresource based, aggregation system for which we also have evidence that land‐marking may be involved.     

Oviposition responses of Queensland fruit fly (Bactrocera tryoni) to mineral oil deposits on tomato fruit

Behavioural responses of wild and laboratory‐culture females of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), to mineral oil deposits on tomato fruit dipped in aqueous oil emulsions were assessed in a no‐choice test and three choice tests. The oils were two commercial products used to manage plant pests and diseases, Ampol D‐C‐Tron NR and SK EnSpray 99, one distillation fraction of the base oil of the former, and four distillation fractions of the base oil of the latter. The initial and final boiling points of the fractions were equivalent to those of n‐alkanes with chain lengths of C20–22 (Ampol), and C21–C23, C22–23.5, C22–24, and C22–24.5 (SK). For both fly types in the no‐choice test, numbers of punctures and eggs per fruit declined strongly as concentrations of the nC20–22 Ampol fraction in emulsions rose from 0.25 to 2% (vol/vol). Fly type affected the extent of responses but there was no significant interaction for fly type*oil concentration. Responses of laboratory‐culture females in the choice tests also declined as concentrations of SK and the four fractions of its base oil in emulsions rose from 0 to 0.25%. The SK nC22–24 and nC22–24.5 fractions had least impact. Responses of laboratory‐culture flies to 0.5% emulsions of the nC20–22 Ampol fraction and the nC21–23 SK fraction in choice tests were not significantly different. Likewise, responses of laboratory‐culture flies to 0.5% emulsions of the two commercial products were not significantly different. Emulsifier type did not affect numbers of punctures or eggs per fruit in choice responses of laboratory‐culture flies to 0.5% emulsions of the Ampol nC20–22 fraction or 0.5% emulsions of the SK nC21–23 fraction. If the equivalence of no‐choice and choice responses in the laboratory were to hold in the field, then unsprayed ‘sacrificial’ plants would not be necessary and oil emulsions could be used as cover sprays.     

Resting sites,edge effects and dispersion of a polyphagous Bactrocera fruit fly within crops of different architecture

The spot or strip application of poisoned protein bait is a lure‐and‐kill technique used for the management of fruit flies. Knowledge of where flies occur in the crop environment is an important part of maximizing the efficacy of this tool. Bactrocera tryoni is a polyphagous pest of horticulture for which very little is known about its distribution within crops. With particular reference to edge effects, we monitored the abundance of B. tryoni in two crops of different architecture; strawberry and apple. In strawberries, we found more flies on the crop edge early in the fruiting season, which lessened gradually and eventually disappeared as the season progressed. In apple orchards, no such edge effect was observed and flies were found equally throughout the orchard. We postulated these differences may be due to differences in crop height (high vs. short) and/or crop canopy architecture (opened and branched in apple, dense and closed in strawberry). In a field cage trial, we tested these predictions using artificial plants of different height and canopy condition. Height and canopy structure type had no significant effects on fly oviposition and protein feeding, but the ‘apple’ type canopy significantly influenced resting. We thus postulate that there was an edge effect in strawberry because the crop was not providing resting sites and flies were doing so in vegetation around the field margins. The finding that B. tryoni shows different resting site preferences based on plant architecture offers the potential for strategic manipulation of the fly through specific border or inter‐row plantings.     

Preference and performance of Diachasmimorpha kraussii (Fullaway) (Hymenoptera: Braconidae) on five commercial fruit species

Diachasmimorpha kraussii is a polyphagous endoparasitoid of dacine fruit flies. The fruit fly hosts of D. krausii, in turn, attack a wide range of fruits and vegetables. The role that fruits play in host selection behaviour of D. kraussii has not been previously investigated. This study examines fruit preference of D. kraussii through a laboratory choice‐test trial and field fruit sampling. In the laboratory trial, oviposition preference and offspring performance measures (sex ratio, developmental time, body length, hind tibial length) of D. kraussii were investigated with respect to five fruit species [Psidium guajava L. (guava), Prunis persica L. (peach), Malus domestica Borkh. (apple), Pyrus communis L. (pear) and Citrus sinensis L. (orange)], and two fruit fly species (Bactrocera jarvisi and B. tryoni). Diachasmimorpha kraussii responded to infested fruit of all fruit types in both choice and no‐choice tests, but showed stronger preference for guava and peach in the choice tests irrespective of the species of fly larvae within the fruit. The wasp did not respond to uninfested fruit. The offspring performance measures differed in a non‐consistent fashion between the fruit types, but generally wasp offspring performed better in guava, peach and orange. The offspring sex ratio, except for one fruit/fly combination (B. jarvisi in apple), was always female biased. The combined results suggest that of the five fruits tested, guava and peach are the best fruit substrates for D. krausii. Field sampling indicated a non‐random use of available, fruit fly infested fruit by D. kraussii. Fruit fly maggots within two fruit species, Plachonia careya and Terminalia cattappa, had disproportionately higher levels of D. krausii parasitism than would be expected based on the proportion of different infested fruit species sampled, or levels of fruit fly infestation within those fruit.     

Laboratory evaluation of interspecific mating between Zeugodacus fruit flies and Bactrocera dorsalis

The increasing number of tephritid pest invasions worldwide highlights the importance of interspecific interactions among tephritid pests. The melon fly [Zeugodacus cucurbitae (Coquillett)], the pumpkin fruit fly [Zeugodacus tau (Walker)], and the oriental fruit fly [Bactrocera dorsalis (Hendel)] (all Diptera: Tephritidae) are neotropical fruit flies with overlapping distributions. Their interactions during mating hours have rarely been observed in nature due to their nocturnal behavior. Here, laboratory studies were conducted under no-choice and choice conditions to quantify interspecific mating. The interactions during mating hours resulted in interspecific mating, which reduced conspecific mating success and interrupted mating activity patterns. Successful interspecific mating pairs of Z. cucurbitae and Z. tau were recorded in no-choice and choice tests. Interspecific mating between male Z. cucurbitae and female Z. tau significantly reduced conspecific mating in Z. tau. Observations of the diel mating activity patterns showed that male Z. cucurbitae initiated calling behaviors earlier than Z. tau males, giving Z. cucurbitae more chances to court Z. tau. Though males of neither Zeugodacus species formed mating pairs with B. dorsalis, Zeugodacus males reduced conspecific mating in B. dorsalis in the choice trials. Thus, interspecific interactions among Z. cucurbitae, Z. tau, and B. dorsalis affected conspecific mating; interrupted conspecific mating activity patterns were recorded in all three species. This information could be used to improve management practices.     

The effects of thermal acclimation on immature mortality in the Queensland fruit fly Bactrocera tryoni and the light brown apple moth Epiphyas postvittana at a lethal temperature

Mortality data for non-acclimated and acclimated 3rd instar larvae and mid-term eggs of Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) were obtained after immersing in hot water at 46 °C. Acclimation consisted of holding the larvae and eggs at 35 °C for 20 and 11 h respectively just prior to heat-treatment. The median lethal time (LT50) for acclimated larvae was found to be 6.9 min compared to 2.5 min for non-acclimated larvae. LT99.999 for acclimated larvae was 20.9 min compared to 8.7 min for non-acclimated larvae. LT50 for acclimated eggs was 5.0 min compared to 2.4 min for non-acclimated eggs. LT99.999 for acclimated eggs was 26.0 min compared to 6.6 min for non-acclimated eggs. For 3rd instar larvae, most acclimation effect on mortality had occurred by 8 h. A notable residual response was present 20 h after acclimation had occurred, reducing mortality at 46 °C for 4.5 min by roughly 25%. Mortality data at 46 °C were also obtained for non-acclimated and acclimated late instar larvae of Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). With this species, LT50 for acclimated larvae was 2.5 min compared to 1.1 min for non-acclimated larvae. LT99.999 for acclimated larvae was 9.5 min compared to 4.6 min for non-acclimated larvae.     

Relationships between temperature, development and survival of different life stages of the tomato fruit fly, Neoceratitis cyanescens

The development and survival of female Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) from egg to complete ovarian maturation were studied in the laboratory at five different constant temperatures: 15, 20, 25, 30, and 35 °C. The aim of this study was to get information on the influence of temperature on pre-mature stages, as a prerequisite to optimise rearing procedures and to understand temporal and geographical patterns of fruit fly occurrence. The developmental rate of the different life stages increased linearly with increasing temperatures up to 30 °C. The fastest development of pre-mature stages was recorded at 30 °C (22±1 days) and the slowest at 15 °C (98±3 days). The day-degrees requirements (K) to complete total development were 432.6 day-degrees. Lower temperature thresholds were 11.4, 11.9, 10.0, and 11.1 °C for egg, larval, pupal stages and ovarian maturation, respectively. The number of adults obtained from an initial batch of 100 eggs reached a maximum (64) at 25 °C. At 35 °C, no adults emerged. Larval developmental time was significantly shorter in green tomato fruits than in potato tubers at 15, 20, and 25 °C. Mortality rate of larvae was higher in green tomato fruits than in potato tubers at 25 and 30 °C.     

Dietary wheat germ oil influences gene expression in larvae and eggs of the oriental fruit fly

Changes in animal nutrition, particularly essential dietary components, alter global gene expression patterns. Our goal is to identify molecular markers that serve as early indicators of the quality of insect culture media. Markers of deficient culture media will increase the efficiency of developing optimal systems for mass rearing beneficial insects and some pest species because decisions on culture media quality can be made without waiting through one or several life cycles. The objective of our current study is to discover molecular markers of essential dietary lipid deficiency in the oriental fruit fly, Bactrocera dorsalis. We reared groups of fruit flies separately on media either devoid of or supplemented with wheat germ oil (WGO) and analyzed gene expression in third instar larvae and F(1) eggs using 2D electrophoresis. Gel densitometry revealed significant changes in expression levels of genes encoding eight proteins in larvae and 22 proteins in eggs. We identified these proteins by using mass spectrometry (MALDI TOF/TOF) and bioinformatic analyses of the protein sequences. Among these, we identified one gene encoding the receptor of activated C Kinase 1 (RACK1) that increased in expression by 6.8-fold in eggs from adults that were reared as larvae on media supplemented with WGO. RACK1 is an essential component of at least three intracellular signal transduction pathways, making it a good molecular marker candidate of lipid deficiency in fruit flies and possibly many other insect species.     

Bactrocera dorsalis preference for and performance on two mango varieties at three stages of ripeness

Most tropical fruit flies only lay into mature fruit, but a small number can also oviposit into unripe fruit. Little is known about the link between adult oviposition preference and offspring performance in such situations. In this study, we examine the influence of different ripening stages of two mango, Mangifera indica L. (Anacardiaceae), varieties on the preference and performance of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a fly known to be able to develop in unripe fruit . A series of laboratory-based choice and no-choice oviposition experiments and larval growth trials were carried out. The results demonstrated a general preference by B. dorsalis for mango variety Oakrong over variety Namdorkmai, but in most cases the single largest dependent variable influencing results was fruit ripening stage. Ripe and fully-ripe mangoes were most preferred for oviposition by B. dorsalis . In contrast, unripe mango was infrequently used by ovipositing females, particularly in choice trials. Consistent with the results of oviposition preference, ripe and fully-ripe mangoes were also best for offspring survival, with a higher percentage of larval survival to pupation and shorter development times in comparison to unripe mango. Changes in total soluble solids and pericarp toughness correlated with changing host use across the ripening stages. Regardless of the mango variety or ripeness stage, B. dorsalis had difficulty penetrating the pericarp of all fruits offered in experiments. Larval survival was also often poor in all experiments. We discuss the possibility that there may be differences in the ability of laboratory and wild flies to penetrate fruit for oviposition, or that in the field flies more regularly utilize natural fruit wounds as oviposition sites.     

Effects of sucrose concentrations and fly age on feeding responses and survival of female and male western cherry fruit flies, Rhagoletis indifferens

Abstract. The effects of single meals of different sucrose concentrations on feeding responses and survival of 8–24-h-old, 1–2-, 10–12- and 31–36-day-old female and male western cherry fruit flies, Rhagoletis indifferens Curran, were determined. Feeding time and food consumption response patterns in both sexes within age groups were curvilinear. Feeding times increased as sucrose concentrations increased, and were longest when the sucrose concentration was 100% (dry). Consumption of dilute wet sucrose was low, whereas consumption of concentrated wet sucrose was high. However, consumption of dry, 100% sucrose was also low. One to 2-day-old flies of both sexes that had not previously fed consumed more sucrose foods than unfed 8–24-h-old flies and 10–12- and 31–36-day-old flies that had been starved for 16–24 h. Females consumed more than males, but they consumed the same amount as males per mg bodyweight. When fed single 20% and 60% sucrose meals, 1–2-day-old flies survived longer compared to flies in all other age groups, with 31–36-day-old flies surviving shortest. Despite age-related differences in survival, in general, no sex differences in survival were seen in flies fed sucrose within any age groups, or in flies fed sucrose-yeast, cherry juice and honeydew foods. The results suggest that sugar-feeding behaviours and the energy invested in sugar 'seeking' by both sexes of R. indifferens should be the same throughout life.     

Field parasitism levels of Ceratitis capitata larvae (Diptera: Tephritidae) by Aganaspis daci on different host fruit species in the coastal region of Tartous,Syria

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), is a key pest of fruit trees in Syria and is attacked by the larval-pupal parasitoid, Aganaspis daci (Weld) (Hymenoptera: Figitidae). The seasonal population dynamics and distribution of A. daci were studied in surveys of orchards [Citrus reticulatum (clementine), Citrus sinensis (maourdi blood orange), Citrus paradise (grapefruit), C. sinensis (sweet orange), Eriobotrya japonica (loquat), Prunus persica (peach), Prunus domestica (plum), Malus domestica (apple), Figus carica (fig) and Psidium guajava (guava)] at eight locations along the coastal region of Syria, between November 2013 and November 2014. A total of 69.4?kg of infested fruits were sampled, yielding 4274 puparia. From these, 3173 emerged as C. capitata adults, 351 as hymenopteran parasitoids and 750 did not eclose. The parasitoids were identified as A. daci (Hymenoptera: Figitidae) and Psyttalia sp. (Szépligeti) (Hymenoptera: Braconidae). The predominant species was A. daci comprising 348 (99.1%) of the total number of parasitoids collected. Populations of A. daci were present from May 2014 to September 2014, and numbers increased with increasing temperature to peak at 32.05% and 34.01% parasitism in June and August 2014, respectively. Parasitoids were only retrieved from larvae reared from loquat, grapefruit, peach and guava with parasitism levels of 1.68%, 30.76%, 18.28% and 16.15%, respectively. These results are important because they suggest that populations of A. daci have potential to be used for biological control in integrated pest management programmes for C. capitata in the coastal region of Syria.     

Oviposition response and development of the egg-pupal parasitoid Fopius arisanus on Bactrocera oleae, a tephritid fruit fly pest of olive in the Mediterranean basin

To date, information is wanting with regard to the use of new exotic parasitoids against olive fruit fly, Bactrocera (=Dacus) oleae (Gmelin) (Diptera: Tephritidae), a serious pest of olives Olea europaea L., in the Mediterranean basin. We investigated the oviposition response and developmental biology on B. oleae of Fopius (=Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae), an egg-pupal parasitoid of tephritid fruit flies, never tested before as a potential parasitoid of this host. Our results showed that olive fruits infested with B. oleae eggs exerted a relevant attraction to gravid F. arisanus and represented a stimulus for oviposition. Nevertheless they were not as attractive to female parasitoids as the Mediterranean fruit fly, Ceratitis capitata Wiedemann (Diptera: Tephritidae), eggs infested papaya fruits (Carica papaya L.). In our experimental conditions, F. arisanus completed development in B. oleae within 33 ± 1.7 days (males) and 35 ± 1.6 (females). Increases in host egg to female parasitoid ratios of 1:1, 5:1, 10:1 and 20:1 corresponded with decreases in the percentage of B. oleae parasitisation and host killing but corresponded also with increases in absolute parasitisation. Our findings are discussed in light of possibilities of utilising F. arisanus for biological control of olive fruit fly.