Non-infested Fruits Research Articles

Preference of hypothenemus hampei for coffee fruits according to state of maturation and infestation

The coffee berry borer Hypothenemus hampei (Ferrari) remains the most important coffee pest worldwide. Coffee fruits emit a mixture of volatiles, which function as insect attractants. Y-tube olfactometry tests allowed us to determine insect response to coffee fruits in different developmental stages: green, underripe, mature-ripe and overripe. The ripe fruits showed the highest levels of insect attraction, up to 30% more than the other stages. Additionally, insect attraction to fruits previously infested with H. hampei for 3 and 24 h vs. noninfested fruits was tested. The infested and noninfested ripe fruits showed the same levels of attraction. The overripe and green fruits infested for 3 h showed 12% greater insect attraction. The green fruits infested for 24 h showed 20% more attraction. When evaluating insect attraction to the methanol:ethanol alcohol mixture vs. the fruits, the alcohols showed greater insect attraction than all developmental stages except the ripe fruits. The understanding of H. hampei behavioral characteristics and preferences for coffee fruits in different developmental and infestation stages will allow the design of better insect control strategies.

New Proposed Dose of Irradiation to Control Fruit Flies (Diptera:Tephritidae) and its Influence to Super Red Pittaya (Hylocereus costaricensis) Quality

As one of the important pests, fruit flies derived from Tephritidae family have caused the worst consequences in losing the economic value of fresh horticultural commodity including on the dragon fruits. As a prospective quarantine treatment, gamma irradiation has been thrived to eliminate totally the appearance of those adults’ flies with less impact on the fruit quality degradation. In this study, a series of irradiation dosages were examined to both the third instar larvae (subsequently from Bactrocera papayae, B. cucurbitae and B. carambolae) infesting fruits and the non-infested ones afterwards at 0, 50, 100, 150, 200, 250, 300, 350 and 400 Gy. For a number of the infested fruits, a series of observations were persisted in at room temperature (27±1°C) until two weeks of the post-treatment period. Whereas the non-infested fruits were stored at 11±1°C for 17 days of the storage. Results showed that B. papayae required the highest recommended dosages (the effective dose = 248.4 Gy; the minimum dose = 225.1 Gy; the maximum dose = 279.6 Gy) for achieving LD0.99 rather than the other tested spesies. There were also no significant differences among each of the non-infested fruits in terms of altering of the observed physical attributes. This result has become a distinct indication that a higher dose value than the generic one is mostly recommended both for phytosanitary irradiation and stabilization of fruit quality.

Early infestation volatile biomarkers of fruit fly Bactrocera dorsalis (Hendel) ovipositional activity in mango (Mangifera indica L.)

Infestation of agricultural commodities by insect pests results in significant economic, import and export, food safety, and invasive insect introduction issues for growers, consumers, and inspectors. The Oriental fruit fly (Bactrocera dorsalis) is considered a highly invasive insect pest with populations reported in more than 60 countries, with prevalent distributions in Asia and Africa. B. dorsalis is phytophagous with a host range encompassing hundreds of fruits and vegetables. Damage to the fruit or vegetable is inflicted through oviposition and subsequent larval feeding resulting in spoilage. Early detection of insect pest infestations is a critical component for ensuring food safety as well as controlling introduction and spread of invasive insects. However, detection of ovipositional activity and early larval development is visually difficult, thus rapid and non-destructive detection often relies on odors associated with infestation. We investigated the odors of mangoes (Mangifera indica L.) infested with B. dorsalis and compared the volatile profiles of infested mangoes to non-infested and mechanically damaged mangoes 24 h post-infestation. GC-MS and multivariate analyses provided the identification of eleven compounds unique to infested mangoes compared to mechanically damaged or non-infested fruit. Results indicated compositional and quantitative differentiation of volatile profiles among treatments for detection of infested fruit at quality checks or points of commerce.

Aversive responses of Queensland fruit flies towards larval-infested fruits are modified by fruit quality and prior experience

For frugivorous fruit flies, the decision whether to accept or reject a host fruit for oviposition is influenced by a variety of fruit quality factors. Additionally, ovipositing flies may be influenced by the presence of eggs or larvae already within the host fruit. Species of the genus Bactrocera have been shown to avoid ovipositing into larval-infested fruits. However, the observed oviposition aversion in Bactrocera is variable, with some studies showing that deterrence to infested fruits may not always occur, but what may influence such variation is unknown. Using the polyphagous fruit fly Bactrocera tryoni (Froggatt), we tested if the quality of host fruit for offspring survival was a factor in influencing a female fly’s decision whether to oviposit or not into larval-infested fruits. In both small cages and field cages, ovipositing B. tryoni did not discriminate between infested and non-infested high-quality fruits. However, when given a choice between poor-quality infested and non-infested fruits, significantly more flies selected and oviposited in non-infested fruits. For example, B. tryoni did not discriminate between infested and non-infested guava (a fruit in which there is high offspring survival), but more flies selected and oviposited on non-infested than on infested green apples (a fruit in which there is poor offspring survival). Small cage experiments also showed that prior oviposition experience on a larval-infested host negated the previously observed aversive response for that particular infested host fruit. The results are discussed in the light of a long recognised, but often ignored fact that herbivore host choice is about the sum of both the positive and negative cues received from the host.

Some Physiological Observations on Date Palm Fruits during its infestation by the date palm dust mite, Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae)

The current study aimed to survey the phytophagous tetranychid mite, Oligonychus afrasiaticus (McGregor) Tetranychidae in different regions of Egypt. Also, the effect of O. afrasiaticus infestation on the different components of date palm fruits was determined after one month of filed infestation. The results showed that the O. afrasiaticus appeared infested the date palm fruits in New -Valley, Giza, and Marsa Matruh Governorates only and disappeared from the other tested locations of Egypt. It was observed from the study that O. afrasiaticus infested Barhi Variety (Fresh) with a rare number in Sharq El-Ewinate region (New –Valley) only. On the other hand, Siwi variety (Semi-dry) infested with O. afrasiaticus on date palm fruits in Baharia Oasis (Giza Governorate), Siwa Oasis region (Marsa Matruh), El-Kharga Oasis and Dakhla Oasis region (New -Valley ). However, it was noticed that Samani and Zaghloul (Fresh varieties) did not infest with O. afrasiaticus during this study. The current study indicated that the protein contents were decreased when the fruits exposed to the infestation by O. afrasiaticus where it was recorded 18.6 mg/gm of fruits in infested fruits compared to 26.37 mg/gm in non-infested fruits. The highest level of carbohydrate content was (445.0 mg/gm) in non-infested date palm fruits. While the lowest carbohydrates level (308.0 mg/gm) was found when the date fruits exposed to mite's infestation. The obtained data showed that the nitrogen content of infested date palm fruits was 3.33 ug/gm of fruits but the recorded level of nitrogen in non-infested fruits was 4.37 ug/gm of fruits.The lowest content of phosphorus (3.1 µg/gm) was observed with infested fruits compared with 7.43µg/gm in the case of non-infested fruits. There were slight differences in potassium contents(7.16 and 7.83 µg/gm ) between infested and non-infested date fruits respectively,.The biochemical data revealed that the level of calcium contents was slightly differed (16.4 and 16.67 µg/gm) in date palm fruits infested and non-infested with mite individuals of O. afrasiaticus, respectively.

Evaluation of d-Limonene and β-Ocimene as Attractants of Aphytis melinus (Hymenoptera: Aphelinidae), a Parasitoid of Aonidiella aurantii (Hemiptera: Diaspididae) on Citrus spp.

The volatile organic compounds (VOCs) released from herbivore-infested plants can be used as chemical signals by parasitoids during host location. In this research, we investigated the VOC chemical signals for the parasitoid Aphytis melinus to discriminate between Aonidiella aurantii (California red scale)-infested fruit and non-infested fruit on three different citrus species. First, we identified the chemical stimuli emanating from non-infested and A. aurantii-infested citrus fruits via solid phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) analyses and identified 34 volatile organic compounds (VOCs). The GC-MS analysis showed qualitative and quantitative differences between VOCs emitted from non-infested and infested citrus fruit. Two VOCs, d-limonene and β-ocimene, were significantly increased in all infested fruit, regardless of the fruit species. The response of the female adult A. melinus to olfactory cues associated with A. aurantii infested fruit was evaluated using a Y-tube olfactometer. In two-choice behavioural assays, A. melinus females preferred infested citrus cues over non-infested fruit. Females showed positive chemotaxis toward these VOCs in all tested combinations involving two dosages of synthetic compounds, d-limonene and β-ocimene, except for d-limonene at a dosage of 10 μL/mL. The application of these VOCs may help to enhance the effectiveness of bio-control programs and parasitoid mass-rearing techniques.

Trichopria drosophilae parasitizes Drosophila suzukii in seven common non-crop fruits

The invasive vinegar fly Drosophila suzukii not only infests and damages numerous fruit crops but also develops in many wild fruit species in semi-natural habitats. Biological control in these refuges could reduce D. suzukii populations and minimize their dispersal into fruit crops. We investigated parasitization of D. suzukii by the pupal parasitoid Trichopria drosophilae in seven common wild fruit species. Development and nutrient content of D. suzukii differed among the fruit species. Nevertheless, T. drosophilae significantly reduced D. suzukii numbers in all fruits. The development of T. drosophilae was affected by both the fruit species and the quality of the pupal host (size, nutrient content). In olfactometer assays, parasitoid females preferred infested fruits to an empty control and to most non-infested fruits, but spent an equal amount of time on the walking arena above the infested and non-infested fruits of Rhamnus cathartica and Viscum album. Our results show that T. drosophilae can utilize D. suzukii hosts from a variety of wild fruit species and therefore has the potential to be used as a control agent of D. suzukii in semi-natural habitats.

Temporal distribution, seed damage and notes on the natural history of Acanthoscelides quadridentatus and Acanthoscelides winderi (Coleoptera: Chrysomelidae: Bruchinae) on their host plant, Mimosa setosa var. paludosa (Fabaceae: Mimosoideae), in the Brazilian Cerrado

ABSTRACTThe seed beetles, Acanthoscelides quadridentatus and Acanthoscelides winderi are here recorded for the first time feeding on seeds of Mimosa setosa var. paludosa in the Brazilian Cerrado. Our main aims were to describe the temporal distribution, seed damage, and notes on the natural history of these two species on their host plant. We hypothesised that: (a) healthy seeds from infested fruits would have worse germination rate than healthy seeds from noninfested fruits, and (b) females of seed beetles would lay more eggs on large fruits. We made field observations and an experimental field study with the presence of seed beetles versus their exclusion on plants. Results revealed that seed beetles are synchronised with fruiting, with a temporal partitioning in occurrence. Attacked seeds did not germinate, whereas healthy seeds from infested fruits had worse germination rate than healthy seeds from noninfested fruits. Females of seed beetles laid more eggs on large fruits. These results suggest that seed beetles avoid competition through a temporal partitioning curcial for their coexistence, and select large fruits to oviposit as these fruits probably provide more food resource for their offspring. Furthermore, plants might perceive seed beetles’ damage and then reduce resource allocation on infested fruits.

Effect of fruit and host fly species on the associative learning by Fopius arisanus.

Parasitoids, released in augmentative biological control programmes, which display a rapid host-location capacity, have a higher likelihood of successfully controlling target pest species. By learning to associate sensory cues to a suitable oviposition site, might parasitoids used as biological control agents, locate hosts more rapidly, and perhaps increase the efficacity of e.g. Tephritidae fruit fly management. We studied associative learning of Fopius arisanus (Hymenoptera: Braconidae) and tested its range of learning in natural and conditional hosts and host fruits, i.e. Bactrocera dorsalis, Zeugodacus cucurbitae, Ceratitis capitata and Ceratitis cosyra (Diptera: Tephritidae) and on fruits (papaya, tomato, banana). Naïve female F. arisanus were compared with experienced wasps, which had been offered infested and non-infested fruit, and been allowed to oviposit. Preferences for olfactory cues from infested fruits were thereafter assessed in a two-choice olfactometer. Naïve and trained parasitoids preference differed in general and non-responders to infested fruits were higher among naïve parasitoids. The trained wasps preferred the fruit infested in the training more than the control fruit, for all combination, except when C. cosyra infested the fruits, hence avoidance behavioural response was observed towards the odour of the infested fruit. Fopius arisanus was capable of behaviourally respond to the learned information, e.g. associative odour learning was achieved, yet limited depending on interaction level, fruit fly and fruit combination. To create F. arisanus preference of an associated odour, it might hence be needed to ensure oviposition in perceived suitable host and host fruit, for the parasitoid learning to become favourable in a biological control setup.

Dynamics of soluble sugars and secondary metabolites in fruit of Juglans australis attacked by Anastrepha fraterculus and Ceratitis capitata (Diptera: Tephritidae)

The development and fitness of phytophagous insects are tightly linked to the nutritional quality of their host plants and many studies have examined the influence of primary and secondary metabolites of plants and their effects on the development of insects. Herbivore tactics to modify plant metabolic pathways to lower host toxicity need to be better understood as they are critical to a better understanding of herbivore–host plant relationships. To contribute to this end, in this study we analyzed temporal patterns of glucose, sucrose, fructose, and total soluble sugar contents, as well as tannins, phenols, and flavonoids in the mesocarp of fruit of native walnut (Juglans australis), uninfested and infested by Anastrepha fraterculus and Ceratitis capitata (sometimes simultaneously in a single fruit). Both fly species are polyphagous tephritids whose larvae feed on a wide variety of hosts. We observed a high correlation between infestation and adult emergence of these two insects which was positive in the case of sugar content and negative in the case of toxic secondary metabolites in fruit. At particular ripening stages, infested fruit contained higher levels of sugars and lower levels of phenols and tannins than non-infested fruit. We discuss the possibility that A. fraterculus and C. capitata, each with different egg-laying strategies, may modify metabolical pathways in the fruit for their own benefit through larval activity with the help of bacteria in their gut. Alternatively, the patterns observed may be simple side effects of larval feeding and associated growth of opportunistic microorganisms.

Detection of Mediterranean Fruit Fly Larvae Ceratitis capitata (Diptera: Tephritidae) in Different Types of Fruit by HS-SPME GC-MS Method

Timely detection of Mediterranean fruit fly (Medfly) is very important so that eradication action can be taken on time. The larvae stage of this insect is the most dangerous stage as it is within the pulp of the fruit, making it hard to detect by visual inspection. In most countries at ports of entry the inspector check a small sample of fruit by visual inspection or by cutting the produce and searching for fungus and pests. This paper will investigate a quick, reliable and sensitive method to determine the presence of fruit flies. Our research focuses on developing the technology for detecting hidden infestations by using the Head Space-Soild Phase Micro Extraction (HS-SPME) method coupled with Gas Chromatography-Mass Spectrocopy (GC-MS) technique. Five different types of fruit were infested with an early stage of Medfly Ceratitis capitata Wiedemann (Diptera: Tephidae). We investigated to detect the differences in volatile organic compounds (VOC’s) between infested and non- infested fruits by using HS-SPME with (GC-MS). The results indicated that for few chemicals no significant differences between infested and non-infested fruit can be seen, especially in the fruits with first instar. However, in case of third instar larvae infested fruits significant differences in the chemicals can be seen as compare to non infested fruits and other instar infestations. These chemicals include ethyl (Z)-2 butenoate, 2-heptanone, anisole, β-cis-ocimene, 1,3,7-nonatriene,4,8-dimethy-,ethyl octyate, isoamyl caproate and 1β,4βh,10βh- guaia-5,11-diene, in apple. Ethyl (Z)-2-butenoate, (+)-2-bornanone, (-)-trans- isopiperitenol, methyl caprate, caryophyllene and farnesene in orange. Butanoic acid, 3-methyl-,2-methylbutul acetate, sabinene, β-myrcene, octanoic acid, methyl ester, dihydrocarvone, (-)-trans-isopiperitenol and ethyl laurate in mandarin. Butyl 2-methylbutanoate, terpinen-4-ol, P-menth-8-en-2-one, E-,(3E,7E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and dodecanoic acid, ethyl ester in lemon. Decane, 3-methyl-, p-menth-1,4(8)-diene, 1-undecene and α-cubebene in avocado. Thus, the VOC’s method could provide a possible tool for detecting tephritid larvae and this method could be adopted by industries importing and exporting fruit.

Anastrephaegg deposition induces volatiles in fruits that attract the parasitoidFopius arisanus

Fopius arisanus is a solitary egg-pupal endoparasitoid that attacks several species of tephritid fruit flies, particularly Bactrocera spp. This species, indigenous from the Indo-Australian region, was introduced into Mexico for biological control purposes. From the standpoint of the 'new associations' concept this parasitoid has been evaluated against fruit flies in the Anastrepha complex. We investigated the specificity of F. arisanus responses to fruits infested with two species of Anastrepha. We examined whether fruit volatiles attractive to this parasitoid are induced as a result of fruit fly oviposition. We also investigated whether F. arisanus females are able to discriminate between the oviposition-induced volatiles from host eggs parasitised by conspecifics and volatiles from unparasitised eggs. All experiments were performed in a wind tunnel. Results showed that mango fruits infested with A. ludens eggs (2-3 days after egg deposition) were significantly more attractive to naïve F. arisanus females compared with non-infested fruits or fruits infested with larvae. In addition, guava fruits harbouring A. striata eggs were significantly more attractive to the parasitoid than non-infested fruits or fruits infested with larvae. Thus, the parasitoid was attracted to fruits with eggs, but fruit and fly species did not influence the parasitoid attraction. We also found that F. arisanus females were more attracted to fruits exposed to fertile A. ludens females (i.e. fruits with eggs inside) compared with fruits exposed to sterile females (i.e. fruits with no eggs inside) or fruits with mechanical damage. Parasitoid females were not attracted to A. ludens eggs. The results suggest that the presence of eggs induces volatiles that attract parasitoids. Finally, we found that F. arisanus was able to discriminate between fruits with unparasitised eggs vs. eggs parasitised by conspecifics, indicating that host discrimination could be mediated by olfactory cues.

Response of the fruit fly parasitoid Diachasmimorpha longicaudata to host and host‐habitat volatile cues

AbstractChemical information is crucial to insect parasitoids for successful host location. Here, we evaluated the innate response of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), a fruit fly larval parasitoid, to cues from host and host habitat (i.e., fruit infested with host larvae). We first assessed the preference of female parasitoids between oranges infested with Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) and non‐infested fruit. Females were highly attracted towards infested oranges on the basis of volatile chemical cues. After this initial experiment, we aimed at revealing the potential sources of volatile cues present in an infested fruit. To this end, we considered five potential sources: (1) punctured fruit; (2) fly feeding, frass, or host‐marking pheromone deposited on the orange surface; (3) larval activity inside the fruit; (4) the larvae themselves; and (5) fungi associated with infestation of oranges. Habitat cues associated with host activity and those produced by rotten oranges or oranges colonized by fungi were highly attractive for female wasps, whereas odours associated with the activity of the adults on the surface of the fruit, and those released by the fruit after being damaged (as happens during fruit fly egg‐laying) were not used as cues by female parasitoids. Once the female had landed on the fruit, direct cues associated with larval activity became important although some indirect signals (e.g., products derived from larval activity inside the fruit) also increased host searching activity. Our findings indicate that naïve D. longicaudata uses chemical cues during host habitat searching and that these cues are produced both by the habitat and by the host larvae.

Digestibility of palm seeds and bruchids larvae by Neotropical rodents

AbstractVertebrates show different tendencies in regard to their preference for seeds or fruits infested by insects compared to non-infested ones. Behaviour may include rejection of one type, preferential consumption of one type or no differentiation among them. When comparing infested versus non-infested fruits, most studies have focused on energy content and nutritional components of the food items; but the energy input provided to the consumer is a better measure for the comparison of the value of each type of food. In this study, I calculated the energy assimilated by rodents for the seeds of the palm Attalea butyracea contained in non-infested endocarps and from bruchid beetle larvae contained in infested endocarps. Using the energy assimilation and time of handling by rodents for both types of endocarps, I quantitatively demonstrated that both infested and non-infested endocarps produce a similar energy input. This finding is consistent with the previous hypothesis that there is a trade-off between the energy content and the time required to extract the insect larvae compared with the seeds in endocarps of Attalea butyracea.

Gas chromatography for detection of citrus infestation by fruit fly larvae (Diptera: Tephritidae)

Tephritid fruit flies are serious economic pests worldwide. As larvae, they feed and develop within the pulp of host fruits, making infestation difficult to detect by visual inspection. At U.S. ports of entry, incoming produce shipments are checked for infestation by manually cutting open a small sample of fruit and searching for tephritid larvae. Consequently, there is a need for more sensitive, high-throughput screening methods. This study evaluated gas chromatography (GC) as a potential technology for improved detection of hidden infestation. Grapefruits ( Citrus × paradisi Macfad.) infested with immature stages of the Caribbean fruit fly Anastrepha suspensa (Loew) (Diptera: Tephritidae) were examined to determine if infested fruit emitted a chemical profile distinct from that of non-infested fruit. Peaks identified by GC analysis were grouped into three classes. Chemicals detected in similar quantities in all samples, or slightly elevated in infested samples, were regarded as non-diagnostic background volatiles. Chemicals highly elevated after oviposition, during the last instar exit stage, and in experimentally-pierced fruit were interpreted to be indicators of citrus peel injury, and included d-limonene and β-ocimene. Chemicals elevated exclusively in the larval infestation stages were considered indicators of feeding damage and potentially diagnostic of infestation, and included hexyl butanoate and an unidentified compound. The peaks associated with injury and feeding were also detectable with a portable ultra-fast GC analyzer that required less than 80 s per sample. Further studies will investigate the potential application of these results for development of a rapid, non-destructive screening method for detection of tephritid infestation.

Bottom-up and top-down effects in a pre-dispersal seed predation system: are non-predated seeds damaged?

Seed predators that severely affect seed germination rates are well known for many plant species. Here, we hypothesised that due to differences in resource allocation within fruits, seed predation can negatively affect non-predated seeds in infested fruits when predation occurs during fruit maturation (a ‘top-down’ effect). We addressed this question using a system of bruchid beetles on Mimosa trees and we also investigated whether seed quality (nitrogen concentration) affects beetle body mass, which would have implications for adult fitness (‘bottom-up’ effect). To assess spatial variation, bottom-up and top-down effects were investigated in two plant populations. Nitrogen concentration was significantly higher in seeds from non-infested fruits than from infested fruits. This supports the hypothesis that resource allocation may differ between seeds from infested and non-infested fruits. Germination experiments showed that seeds from non-infested fruits germinated better than non-predated seeds from infested fruits. It was also confirmed that seed quality affected bruchid body mass. There was also evidence that more resources were taken from well-developed seeds. These results showed that seed predation can damage non-predated seeds.

Relationship Among Phenolic Contents, Seed Predation, and Physical Seed Traits in Mimosa bimucronata Plants

Phenolic contents were compared between Mimosa bimucronata seeds from infested and non-infested fruits to assess induced defense response. By measuring leg length of the bruchid beetle Acanthoscelides schrankiae, we verified whether phenolic contents affected bruchid body size. In addition, the relationship between physical seed traits and phenolic contents was examined. Results showed that seeds from infested fruits had significantly greater phenolic contents than seeds from non-infested fruits, which suggested induced defense. Body size variation in A. schrankiae was marginally nonsignificant according to phenolic contents among plants (negative trend), indicating that phenols may interfere directly with bruchid performance. Seeds that were more irregularly shaped had significantly greater phenolic contents than those that were more uniform. Therefore, the most perfectly spherical seeds may be more vulnerable to seed predation, and our results suggest that the production of phenolic compounds was increased in infested fruits, which in turn may affect A. schrankiae development.

Benefits and costs to pollinating, seed-eating insects: the effect of flower size and fruit abortion on larval performance

Plant-pollinator interactions are well-known examples of mutualism, but are not free of antagonism. Antagonistic interactions and defenses or counter-defenses are expected particularly in nursery pollination. In these systems, adult insects, while pollinating, lay their eggs in flowers, and juveniles consume the seeds from one or several fruits, thereby substantially reducing plant fitness. The outcome of such interactions will depend, for the plant, on the balance between pollination versus seed predation and for the larvae on the balance between the food and shelter provided versus the costs imposed by plant defenses, e.g., through abortion of infested fruits. Here, we examine the costs and benefits to the larvae in the nursery-pollination system Silene latifolia/Hadena bicruris. Using selection lines that varied in flower size (large- vs. small-flowered plants), we investigated the effects of variation in flower and fruit size and of a potential defense, fruit abortion, on larval performance. In this system, infested fruits are significantly more likely to be aborted than non-infested fruits; however, it is unclear whether fruit abortion is effective as a defense. Larger flowers gave rise to larger fruits with more seeds, and larvae that were heavier at emergence. Fruit abortion was frequently observed (ca. 40% of the infested fruits). From aborted fruits, larvae emerged earlier and were substantially lighter than larvae emerging from non-aborted fruits. The lower mass at emergence of larvae from aborted fruits indicates that abortion is a resistance mechanism. Assuming that lower larval mass implies fewer resources invested in the frugivore, these results also suggest that abortion is likely to benefit the plant as a defense mechanism, by limiting both resources invested in attacked fruits, as well as the risk of secondary attack. This suggests that selective fruit abortion may contribute to the stability of mutualism also in this non-obligate system.

Effects of the seed predator Acanthoscelides schrankiae on viability of its host plant Mimosa bimucronata

Seeds of Mimosa bimucronata are heavily infested (pre-dispersal predation) by the bruchid beetle Acanthoscelides schrankiae in Brazil. In this study, firstly we set up experiments to assess seed germination under seven and six different light and temperature regimes, respectively, and then we evaluated the ability of seeds to germinate after predation. We tested the hypothesis that the non-predated seeds from infested fruits may respond differently when set for germination than those seeds of non-infested fruits. We also hypothesized that predation may increase the production of unviable seeds. Seeds under 18 hours of light presented the highest percentage of germination, and the alternating temperature 20-30 degrees C was considered as optimum for germination (abnormal seedlings were not considered as a successful germination). Germination of seeds from non-infested fruits was significantly higher than germination of non-predated seeds from infested fruits, and predation also caused a significant increase in the proportion of dead seeds. Our results also show a positive correlation between proportions of unviable seeds and predated seeds. These results demonstrated that seeds of M. bimucronata are strongly affected by predation because predated seeds did not germinate and non-predated seeds had their viability reduced when located in infested fruits, supporting our hypothesis.

EVALUATION OF COLD TREATMENT AGAINST MEDITERRANEAN FRUIT FLY IN ´TAROCCO´ ORANGES

Citrus intended for export to some overseas markets requires post-harvest treatment to eliminate the presence of insect pests that are of quarantine significance. Several importing countries allow fresh citrus from competing regions if it has undergone cold treatment. Cold treatment involves storage of fruits at low temperature for specified periods to ensure their freedom from insects. This paper addresses the effectiveness of cold treatment against Medfly (Ceratitis capitata Wiedemann) infestation in 'Tarocco' oranges. In large scale disinfestations tests a static trial with simulation of transport was simultaneously carried out using a set of three different full equipped van containers with bottom air delivery system under a 14 day 1.5°C cold treatment schedule. The containers were loaded with cartons of 'Tarocco' oranges from a grove located in a typical blood orange production area. Infested fruits, containing the most tolerant Medfly stage (third instar), were packaged and stuffed inside containers, randomly distributed on three different levels and among boxes containing non-infested fruits. At the end of cold treatment all infested fruits were removed and dissected to determine the number of survivors and dead larvae, then the temperature was set at 15°C to simulate shelf-life. After 1 week shelf-life, fruits were inspected for visible blemishes and decay. In order to evaluate the effect of cold treatment on the fruit quality, initially (just before loading into the container) and after cold treatment plus 1 week shelf-life, physicochemical and sensory parameters were determined. Experiments provided 100% larval mortality. Very low incidence of fruits with light chilling injury was found. Cold-treated 'Tarocco' oranges had good appearance, no substantial quality differences and did not exhibit excessive level of decay.