Host plants used by phytophagous insects can have significant consequences on demography parameters, overall lifetime fitness and their subsequent population dynamics. Here, we conduct a comparative ...demographic study between the specialist Zeugodacus cucumis (French) and generalist Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) to determine whether the host plants used by these fly species play any role in their overall lifetime fitness and explains current host use patterns. These two fly species are pests within the north‐eastern region of Australia and we further aimed to use complete life‐history data to determine the population parameters and models that would help identify the sensitive life‐history stage that could be targeted for effective field management. Eggs collected from laboratory‐reared flies were inoculated into organically grown fruits of both the primary and alternate host plant cultivars of both fly species. The proportion surviving each life stage from egg through to adult and fecundity were monitored for all cohorts from the different plant cultivars. Complete stage‐base life‐tables for cohorts of each fly species developing from each fruit cultivar were constructed, and the key demographic parameters and population models were analysed using PopTools matrix model programme. Our results showed that the host used by each fly species had significant consequences on fly demographic parameters and hence their overall lifetime fitness. The generalist B. tryoni was able to compensate for the fitness loss experienced at the pre‐adult stage by having adults with higher fecundity, but this was not the case for the specialist Z. cucumis. Stage‐base population models revealed that the population growth rate of both species was highly sensitive at the adult reproductive stage, indicating that manipulating probability of survival at this life stage would effectively manage populations of these pest species. This study provides the empirical evidence of undertaking complete life history demography studies of phytophagous insects to accurately understand their lifetime fitness consequences of using a certain host, their observed host use patterns, and overall population dynamics. We suggest that any efforts to manage dacine fruit fly pest population should consider life‐history consequences of host use.
Here, we conduct a comparative demographic study between the specialist Zeugodacus cucumis (French) and generalist Bactrocera tryoni (Froggatt) to determine whether the host plants used by these fly species play any role in their overall lifetime fitness and explain current host use patterns. This study provides the empirical evidence of undertaking complete life history demography studies of phytophagous insects to accurately understand their lifetime fitness consequences of using a certain host, their observed host use patterns, and overall population dynamics. We suggest that any efforts to manage dacine fruit fly pest population should consider life‐history consequences of host use.
Queensland fruit fly (Qfly), Bactrocera tryoni (Froggatt), is a major quarantine pest of fresh horticultural commodity along the eastern coastal region of Australia and restricts market access of its ...host commodity. Consequently, various post‐harvest disinfestation treatments are used to facilitate trade and one such treatment for Qfly is ‘cold disinfestation’. Our study evaluated the effect of cold storage as a post‐harvest disinfestation treatment for Qfly on ‘gold3’ kiwifruit (Actinidia chinensis var. gold3‐sungold), a cultivar grown in New Zealand. Qfly is not present in New Zealand but due to its close proximity to Australia, New Zealand's trading partners have shown concern that Qfly presents a biosecurity risk to their own industry. Our study specifically aimed to demonstrate how this risk would be addressed. Experiment 1 investigated developmental rate of the individual life stages of Qfly in ‘gold3’ kiwifruit under optimal Qfly development conditions of 26 ± 1°C and 65 ± 5% rh, while experiment 2 focused on determination of the most cold tolerant life stage of Qfly in ‘gold3’ kiwifruits. Experiment 3 was a large‐scale confirmatory trial undertaken using the most cold tolerant life stage. The results revealed that Qfly successfully developed in ‘gold3’ kiwifruit and that the most‐cold tolerant Qfly life stage was the 1st instar. Our study further demonstrated that storage of ‘gold3’ kiwifruit at 2.5°C (fruit temperature) for a period of ≥12 days resulted in zero Qfly survival. The large‐scale verification trial treated 61,412 first instar and confirmed that storage of ‘gold3’ kiwifruit at 2.5°C for a 14‐day period resulted in 99.9951% mortality of first instar at the 95% confidence level, hence demonstrating a probit 8.7 level of efficacy. A 14‐day cold storage period was used in this confirmatory trial to ensure additional quarantine security. We recommend that if there was any Qfly infestation on ‘gold3’ kiwifruit, a post‐harvest quarantine treatment of cold storage at 2.5°C (fruit temperature) for a 14‐day period must be used to disinfest Qfly from ‘gold3’ kiwifruit.
1. The extent to which plant-herbivore feeding interactions are specialized is key to understand the processes maintaining the diversity of both tropical forest plants and their insect herbivores. ...However, studies documenting the full complexity of tropical plant-herbivore food webs are lacking. 2. We describe a complex, species-rich plant-herbivore food web for lowland rain forest in Papua New Guinea, resolving 6818 feeding links between 224 plant species and 1490 herbivore species drawn from 11 distinct feeding guilds. By standardizing sampling intensity and the phylogenetic diversity of focal plants, we are able to make the first rigorous and unbiased comparisons of specificity patterns across feeding guilds. 3. Specificity was highly variable among guilds, spanning almost the full range of theoretically possible values from extreme trophic generalization to monophagy. 4. We identify guilds of herbivores that are most likely to influence the composition of tropical forest vegetation through density-dependent herbivory or apparent competition. 5. We calculate that 251 herbivore species (48 of them unique) are associated with each rain forest tree species in our study site so that the ~200 tree species coexisting in the lowland rain forest community are involved in ~50 000 trophic interactions with ~9600 herbivore species of insects. This is the first estimate of total herbivore and interaction number in a rain forest plant-herbivore food web. 6. A comprehensive classification of insect herbivores into 24 guilds is proposed, providing a framework for comparative analyses across ecosystems and geographical regions.
Sterile insect technique is an effective tool to manage a range of pest insects, including the true fruit flies (Diptera: Tephritidae). As part of the process, pupae are dispatched from a ...mass‐rearing facility for several hundred km to a rearing out centre typically located near the release sites. Transportation of Queensland fruit fly (Qfly), Bactrocera tryoni (Froggatt), pupae from mass production facilities to field release sites is known to negatively affect fly quality. To determine which quality parameters are affected, we assessed adult emergence, flight ability, and rate of fliers between irradiated and non‐irradiated flies that were or were not transported long distance. Pupal weight was not affected by irradiation or transport. We found that transportation and irradiation of pupae resulted in a decrease in percentage fly emergence, flight ability, and fliers. Transportation and irradiation both resulted in 8% reduction in emergence of flies. Additionally, we found that transportation resulted in an increase in the rate of deformity by 65% and irradiation could increase deformity by 75%. Compounding these losses, both transportation and irradiation resulted in the decline of number of fliers by approximately 23% each.
Sterile insect technique involves the release of irradiated male insects, rendering them infertile, resulting in non‐viable offspring. The insects are mass‐reared and then transported to distant release sites. Both irradiation and transport of Queensland fruit fly (Qfly) pupae, Bactrocera tryoni (Diptera: Tephritidae), resulted in a decrease of most quality parameters in adult flies. More research is required to understand what part of transport causes the damage, to improve this technique to combat economically important pests.
The preference-performance and phylogenetic conservatism hypotheses have been postulated to explain the mechanisms driving host-use patterns of phytophagous insects. The preference-performance ...hypothesis predicts that insects will use plants that provide higher offspring fitness, while the phylogenetic conservatism hypothesis predicts that insects will use phylogenetically closely related plants over more distantly related plants. Although some studies have supported these two hypotheses, others have not. Simultaneous tests of the two hypotheses on more than one species are lacking, and this limits comparative interpretation of previous studies. We undertook a comparative investigation to determine whether preference-performance and/or the phylogenetic conservatism hypothesis can explain host-use patterns of two phytophagous insects, the fruit flies
Bactrocera cucumis
and
B. tryoni
. Within a nested, plant phylogenetic framework, oviposition preference and offspring performance of the two fruit fly species were tested on fruits of plant species from across different plant families, from within a family and across cultivars within a species. The results show that
both
the preference-performance and the phylogenetic conservatism hypotheses can, depending on the host plant taxonomic level, explain host usage patterns in
B. cucumis
, while neither theory explained the host patterns seen in
B. tryoni
. In the light of increasing recognition of the complexity of host plant–herbivore relationships, and of ongoing studies which as often as not fail to find support for these theories as those that do, we discuss the limited value of either theory as a basis for future research.
The males of many Bactrocera species (Diptera: Tephritidae) respond strongly and positively to a small number of plant-derived chemicals (=male lures). Males that have imbibed the lures commonly have ...a mating advantage over unfed males, but no female benefits have been demonstrated for females mating with lure-fed males. It has been hypothesized that the strong lure response is a case of runaway selection, where males receive direct benefits and females receive indirect benefits via ‘sexy sons’, or a case of sensory bias where females have a lower threshold response to lures. To test these hypotheses we studied the effects of lure feeding on male mating, remating and longevity; while for females that had mated with lure-fed males we recorded mating refractoriness, fecundity, egg viability and longevity. We used Bactrocera tryoni as our test animal and as lures the naturally occurring zingerone and chemically related, but synthetic chemical cuelure. Feeding on lures provided direct male benefits in greater mating success and increased multiple mating. For the first time, we recorded direct female effects: increased fecundity and reduced remating receptivity. Egg viability did not differ in females mated with lure-fed or unfed males. The life span of males and females exposed to lures was reduced. These results reveal direct, current-generation fitness benefits for both males and females, although the male benefits appear greater. We discuss that while lure response is indeed likely to be a sexual selection trait, there is no need to invoke runaway selection to explain its evolution.
► We studied lure effects on the mating behaviour and physiology of Bactrocera tryoni. ► Lure-fed males had high propensity to mate in no-choice and choice conditions. ► Females mated to lure-fed had higher fecundity and showed reduced remating. ► Longevity of lure-fed males and females mated to them was shorter than unfed rivals. ► Male lures are involved in sexual selection in Bactrocera tryoni.
Sugar flotation procedures have been used for many years to separate insects from soil and other substrates. In this study we investigated whether brown sugar flotation (BSF) could be used for ...detecting eggs and larvae of Bactrocera tryoni (Froggatt) and Ceratitis capitata (Wiedemann) in cherries. Our first study involved both species and combined BSF with either manually or mechanically crushed fruit to quantify the egg and larval detection ability of BSF in conjunction with these sample preparation methods. A second set of experiments (using B. tryoni only) focused on determining the sensitivity of BSF for detecting fruit fly infestation and determining the proportions of different life stages recoverable. This was done by varying oviposition periods to generate fruits with different infestation levels. Our final experiments were used to develop an optimized cherry fruit sampling regime for detecting B. tryoni using BSF. Wet sieving/maceration of the fruit residue and incubation of the macerated fruit sample to allow further insect development were used to determine the number of eggs and larvae in each test sample that were not detected using BSF. Our results show that BSF is more effective when combined with mechanical (rather than manual) fruit crushing. BSF is highly sensitive, detecting at least one B. tryoni second instar from all the samples tested down to a pest density of 1–5 larvae in one fruit within a 35-fruit sample. BSF was less sensitive for egg detection, however when 6 or more eggs were present within a sample of 35 fruits, the probability of detecting at least one egg was ≥85%. Samples of 35 or 42 cherries provided a higher probability of detecting B. tryoni than larger samples when 1–5 eggs or larvae were present in total. BSF is an effective tool for detecting the presence of fruit fly eggs and particularly larvae in cherries and should be considered for incorporation into the current market access protocol for minimizing fruit fly risk in Australian cherry exports.
•Brown sugar flotation procedure is an effective tool for detecting fruit fly in cherry.•Mechanical fruit crushing technique exposes more fruit fly for detection than manual crushing.•Current cherry market access protocol should incorporate the brown sugar flotation procedure.
Poisoned protein baits comprise a recognized method for controlling tephritid fruit flies in the form of a ‘lure‐and‐kill’ technique. However, little is known about how a fly's internal protein and ...carbohydrate levels (i.e. nutritional status) might influence the efficacy of this control. In the present study, the relationships between the internal levels of protein (as measured by total body nitrogen) and carbohydrate (as measured by total body carbon) of the fruit fly Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) are investigated, as well as its foraging behaviours in response to protein, fruit and cue‐lure (a male‐specific attractant) baits. Small cage behavioural experiments are conducted using flies from cultures of different nutritional status and wild flies sampled from the field during the fruiting cycle of a guava crop. For female flies, increasing total body nitrogen is correlated with decreased protein foraging and increased oviposition activity; increasing total body carbon levels generate the same behavioural changes except that the oviposition response is not significant. For males, there are no significant correlations between changes in total body nitrogen and total body carbon and protein or cue‐lure foraging. For wild flies from the guava orchard, almost all of them are sexually mature when entering the crop and, over the entire season, total body nitrogen and total body carbon levels are such that protein hunger is unlikely for most flies. The results infer strongly that the requirements of wild, sexually mature flies for protein are minimal and that flies can readily gain sufficient nutrients from wild sources for their physiological needs. The results offer a mechanistic explanation for the poor response of male and mature female fruit flies to protein bait spray.
Frugivorous dacine fruit flies were studied in a lowland tropical rain forest in Papua New Guinea to determine their host specificity, abundance, and the number of species attacking various plant ...species. Plant species hosted 0–3 fruit fly species at median (1–3 quartile) densities of 1 (0–17) fruit flies per 100 fruits. Fruit flies were mostly specialized to a single plant family (83% species) and within each family to a single genus (88% species), while most of the species (66%) were able to feed on >1 congeneric plant species. Only 30 from the 53 studied plant species were colonized by fruit flies. The plant–fruit fly food web, including these 30 plant species and the total of 29 fruit fly species feeding on them, was divided into 14 compartments, each including 1–8 plant species hosting mutually disjunct assemblages of fruit flies. This structure minimizes indirect interactions among plant species via shared herbivores. The local species pool was estimated at 152±32 (±SE) fruit fly species. Forty per cent of all taxonomically described species known from Papua New Guinea were reared or trapped in our study area. Such a high proportion indicates low beta-diversity of fruit flies. Steiner traps were highly efficient in sampling the lure-responsive fruit fly species as they re-collected 84% of all species trapped in the same area 5 y before. Fruit fly monitoring by these traps is a cheap, simple and efficient method for the study of spatial and temporal changes in rain-forest communities.
Fruit flies require protein for reproductive development and actively feed upon protein sources in the field. Liquid protein baits mixed with insecticide are used routinely to manage pest fruit ...flies, such as Bactrocera tryoni (Froggatt). However, there are still some gaps in the underpinning science required to improve the efficacy of bait spray technology. The spatial and temporal foraging behaviour of B. tryoni in response to protein was investigated in the field. A series of linked trials using either wild flies in the open field or laboratory‐reared flies in field cages and a netted orchard were undertaken using nectarines and guavas. Key questions investigated were the fly's response to protein relative to: height of protein within the canopy, fruiting status of the tree, time of day, season and size of the experimental arena. Canopy height had a significant response on B. tryoni foraging, with more flies foraging on protein in the mid to upper canopy. Fruiting status also had a significant effect on foraging, with most flies responding to protein when applied to fruiting hosts. B. tryoni demonstrated a repeatable diurnal response pattern to protein, with the peak response being between 12:00–16:00 h. Season showed significant but unpredictable effects on fruit fly response to protein in the subtropical environment where the work was undertaken. Relative humidity, but not temperature or rainfall, was positively correlated with protein response. The number of B. tryoni responding to protein decreased dramatically as the spatial scale increased from field cage through to the open field. Based on these results, it is recommend that, to be most effective, protein bait sprays should be applied to the mid to upper canopies of fruiting hosts. Overall, the results show that the protein used, an industry standard, has very low attractancy to B. tryoni and that further work is urgently needed to develop more volatile protein baits.
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