Lack of toxicity to adults of the Mexican fruit fly (Diptera: Tephritidae) of beta-exotoxin in Bacillus thuringiensis endotoxin preparations

beta-Exotoxin (thuringiensin) was found in high titers in centrifugation supernatants and acetone/lactose powders produced from centrifugation pellets of strains Guat 1 and HD 2 of Bacillus thuringiensis (Berliner). Diets containing powders of either strain were toxic, diets containing Guat 1 supernatant were not toxic, diets containing HD 2 supernatant were slightly toxic, and diets containing powders or supernatants from uninoculated culturing medium spiked with beta-exotoxin were not toxic. Most mortality occurred within 3 d when flies fed on powders but not until 6-7 d when flies fed on HD 2 supernatant. These results indicated that the primary toxic principals of the powders were endotoxins/spores and that beta-exotoxin alone was not toxic to adult flies at the concentrations found in the supernatants or powders.     

Generic ionizing radiation quarantine treatments against fruit flies (Diptera: Tephritidae) proposed

Tephritid fruit flies comprise the most important group of quarantined pests of fresh produce. Most quarantine treatments of fresh agricultural commodities are directed against these pests, and considerable effort in detection, trapping, and population control is expended worldwide to prevent these pests from invading new territories. Ionizing radiation has been studied for 70 yr for its possible use as a quarantine treatment against fruit flies, but has only been applied commercially on a limited basis since 1995. The treatment has great potential and will probably be used extensively in the future as it is tolerated by more species of fruits than any other major treatment. The U.S. Department Agriculture, Animal and Plant Health Inspection Service only recently proposed allowing irradiation for fresh agricultural imports from other countries, and other countries are studying proposals to do likewise. In 1991, the International Consultative Group on Food Irradiation recommended a generic dose against all tephritid fruit flies of 150 Gy. This article examines the literature dealing with irradiation quarantine treatments against fruit flies and recommends minimum absorbed doses of 70 Gy for Anastrepha spp., 101 Gy for Bactrocera jarvisi and B. tryoni, and 150 Gy for all Tephritidae except when fruits have been stored in hypoxic atmospheres.     

Field evaluation of a phototoxic dye, phloxine B, against three species of fruit flies (Diptera: Tephritidae).

The xanthene dye phloxine B (D&C Red #28) bait was sprayed against fruit flies in mango orchards in 1996 and 1997. The flies used for testing were Mexican fruit fly, Anastrepha ludens (Loew), West Indian fruit fly, Anastrepha obliqua (Macquart), and Mediterranean fruit fly, Ceratitis capitata (Wiedeman). Results of the experiments indicate that the toxic efficacy of phloxine B against these fruit flies is as good as that of malathion-bait sprays. Results also indicate that type of protein used with phloxine B can dramatically influence its efficacy. Hydrolyzed proteins of corn origin, Mazoferm 802 and Nutriplus, and one from microbial origin, Coltec yeast broth, were best. Phloxine B-bait applications as complete coverage or alternate swaths reduced fly populations as well as 19.5 or 9.8% (AI) malathion-Captor 300. Applications of phloxine B bait at concentrations of 0.12% phloxine B reduced populations as well as those applied at 0.48% (AI). The fruit fly parasitoid Diachasmimorpha longicaudata was adversely affected when exposed to phloxine B-Nutriplus bait but not when exposed to the other proteins.     

Toxicity of spinosad in protein bait to three economically important tephritid fruit fly species (Diptera: Tephritidae) and their parasitoids (Hymenoptera: Braconidae)

The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60-3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosadthan females (4.2 [3.8-4.6] mg/liter). Male (5.5 [4.7-6.6] mg/liter) andfemale (4.3 [3.7-4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1-3.6] mg/liter) and male (3.1 [2.9-3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations > or =500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.     

The response of two Bactrocera species (Diptera: Tephritidae) to fruit volatiles

Bactrocera dorsalis and B. correcta are serious pests of agricultural fruit crops. Both species are widely distributed in tropical and subtropical countries, especially in Asia. For integrated management of both Bactrocera species, understanding their olfactory behavior is vital for designing reliable control strategies. In this study, the response of female B. dorsalis and B. correcta adults to three main volatile components of fruits was evaluated using the Y-tube olfactometer. Our results showed that at higher concentrations all volatile components, except α-humulene and its combination with β-caryophyllene, attracted significantly more B. dorsalis than the untreated arm. For B. correcta, all the volatile components attracted significantly more females in the treated arm than the untreated arm. However, at 5% and 1% concentration, all the volatile components had similar attraction for B. dorsalis females. In the case of female B. correcta, the percentage of attraction was similar for all the individual volatile chemicals and their respective mixtures at 10% concentration. While, at 5% and 1% concentrations, the percentage of attraction was significantly higher for a mixture of β-caryophyllene and α-humulene than that of individual volatile components and all possible mixture of two and three volatile components. Based on the olfactometer results, this study concluded that 3-carene and the mixture of β-caryophyllene and α-humulene are strong attractants for female flies of B. dorsalis and B. correcta, respectively. This study might be helpful for the bait application against the female adults of B. dorsalis and B. correcta in farms and orchards.     

Efficacy of wax matrix bait stations for Mediterranean fruit flies (Diptera: Tephritidae)

Tests were conducted that evaluated efficacy of wax matrix bait stations for Ceratitis capitata (Wiedemann) adults in Guatemala. Bait stations were exposed to outdoor conditions to determine effect of weathering on longevity as indicated by bait station age. Results of laboratory tests found that bait stations with spinosad and ammonium acetate remained effective for at least 31 d compared with pesticide-free controls, although there was some loss of efficacy over time. Percentage mortality for bait station strips with 2% spinosad and 1% ammonium acetate decreased from 100 +/- 0.0% on day 0 to 70 +/- 7.1% after 31 d. Ammonia concentration had little effect on percentage mortality although there was some indication that ammonia concentration affected number of flies observed on the bait stations. Bait station strips (one per cage) were more effective than controls for 6-8 wk when tests were conducted in field cages (3 m diameter x 2 m), but only 2-3 wk when tests were conducted in large (2.5 m high and 6.0 m wide and 7.5 m long) field cages. Longevity was restored when multiple bait stations (3, 6, or 12) were deployed per cage. Bait stations containing methomyl were used for field tests of efficacy for wild flies. Dipped lure bait stations, which were made by coating two edges of commercial ammonium acetate and trimethylamine lures, killed six times more flies than corn cob bait stations dipped into a Nulure/malathion solution. They also killed more flies than pesticide-free controls for 8 wk.     

Biological attributes of three introduced parasitoids as natural enemies of fruit flies,genus Anastrepha (Diptera: Tephritidae)

The biological attributes of three introduced species of parasitoids which attack the fruit fly Anastrepha ludens were evaluated. Larvae and eggs of A. ludens were exposed to larval parasitoids Diachasmimorpha longicaudata and D. tryoni and the egg parasitoid Fopius arisanus. Parasitoid longevity and fecundity were determined using larvae and eggs of A. ludens. Likewise, the parasitism rates of these parasitoid species in infested host fruits were recorded. The intrinsic rate of increase for F. arisanus was 0.1019 followed by D. tryoni with a rate of 0.1641 and D. longicaudata with the highest rate of 0.2233. Although F. arisanus females had the highest levels of fecundity, only 50% of them remained alive until reproductive age. These results in combination with the longer generation time (in comparison with D. longicaudata and D. tryoni), can be considered as the most important factors explaining F. arisanus reduced rate of increase. However, we note that oviposition activity caused egg mortality which reduced Anastrepha egg hatch by ca. 20%. This result suggests that F. arisanus has a high potential as a natural enemy of A. ludens, in accordance with our research efforts to develop a new F. arisanus strain specialized for development in Anastrepha eggs. The results show that D. tryoni is not a good candidate for biological control of Anastrepha. Meanwhile, D. longicaudata continues to be the most important exotic parasitoid for suppression of Anastrepha fruit fly populations.     

Effects of energetic reserves on behavioral patterns of Mediterranean fruit flies (Diptera: Tephritidae)

The objective of this study was to associate levels of nutritional reserves (specifically lipids, sugars, and glycogen) in individual Mediterranean fruit flies, Ceratitis capitata (Diptera: Tephritidae), with observed patterns of behavior in the field. We collected females (n=255) and males (n=181) from the field, recording the time of collection and the activity they were engaged in when collected. Subsequently, we employed colorimetric biochemical techniques to determine the precise amounts of lipids, sugars, and glycogen in each individual. Lipid and sugar levels in males varied significantly according to the time of collection and the type of activity. Lipid and sugar levels in females did not vary in this manner. Sugar levels in both males and females were highest during the evening, when most feeding occurs. Males that engaged in sexual signaling in leks during the mid-afternoon had relatively low sugar and high lipid levels. Males engaged in the alternative mating tactic of fruit guarding had relatively high sugar and low lipid contents. Glycogen levels in males were high in the mornings, and a decline in glycogen content was associated with participation in leks; however, female glycogen levels did not vary significantly with time of day or activity. Our results provide quantitative evidence for the role nutrient reserves play in driving patterns of male reproductive behavior, yet suggest that factors other than sugar and lipid reserves constrain female behavior. Received: 8 April 1997 / Accepted: 23 June 1997     

Recapture of sterile Mediterranean fruit flies (Diptera: Tephritidae) in California's Preventative Release Program

In southern California, the sterile insect technique has been used since 1994 to prevent establishment of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This method involves the continual mass release of sterile flies, which suppress or eliminate any introduced wild fly populations. In addition, Jackson traps baited with trimedlure are deployed throughout the preventative release region for the dual purpose of detecting wild flies and monitoring released sterile flies. Sterile fly recapture data for a 3-yr period was compared with climate and to host plant (in which traps were placed). Precipitation was negatively correlated; and temperature and relative humidity were positively correlated with fly recapture levels. The highest numbers of flies were recaptured during trapping periods associated with intermediate relative humidity and temperature, and low precipitation. Flies were recaptured throughout the entire year, in traps that had been frequently relocated to host plants with fruit. This finding suggests that these flies were capable of locating acceptable fruit in a variety of abiotic conditions. However, these data do not necessarily suggest that measurements unimportant in explaining sterile fly recapture are not of value in determining other outcomes important to the goals of sterile release programs, such as reducing the likelihood of establishment of an introduced wild Mediterranean fruit fly population. Future research might build on these results in developing more precise models useful in predicting recapture of sterile flies.     

Electronic traps for detection and population monitoring of adult fruit flies (Diptera: Tephritidae)

During the last decades, the economic importance of tephritid fruit flies (FF) has increased worldwide because of recurrent invasions and expansions into new areas, and reduced control capabilities of current control systems. Efficient monitoring systems, thus, are required to provide fast information to act promptly. With this aim in mind, we developed two electronic trap (e‐trap) versions for adult FF: one with specific volatiles for male and female adult Ceratitis capitata, and the second, based on the attraction of adult FF to yellow colour, targeting Dacus ciliatus, Rhagoletis cerasi and Bactrocera oleae. In the case of B. oleae, the female pheromone and ammonium bicarbonate were added as synergists. In the two versions, attracted FF were retained in the trap on glued surfaces. Real‐time images of the surfaces were automatically taken and transmitted to a server. We tested the two e‐trap versions in insect‐proof cages, where flies were released and recaptured, and in commercial orchards throughout the Mediterranean: C. capitata in peach orchards in Italy; R. cerasi in cherry orchards in Greece; B. oleae in olive orchards in Spain and in Greece; and D. ciliatus in melons in plastic tunnels in Israel. The e‐trap showed excellent abilities to transmit real‐time images of trapped FF and a high specificity for trapping different FF species. The ability of the entomologist to correctly classify FF from images in the office was >88%. In addition, average number of flies/trap in e‐trap grids did not differ from numbers reported on grids of conventional traps that were operating simultaneously. The e‐traps developed and tested in this study provide the basis for the real‐time monitoring of FF were no olfactory attractants are available, and for the surveillance of alien FF incursions where generic, but not specific, olfactory attractants exists.     

Ant cues affect the oviposition behaviour of fruit flies (Diptera: Tephritidae) in Africa

Abstract. Although most studies on fruit fly oviposition behaviour focus on horizontal interactions with competitors and cues from host plants, vertical interactions with predators are poorly documented. The present study provides direct evidence indicating that the oviposition behaviour of the two main mango fruit fly species, Ceratitis cosyra (Walker) and Bactrocera invadens Drew‐Tsurata & White, is affected by secretions of the dominant arboreal ant Oecophylla longinoda (Latreille). When offered ant‐exposed and unexposed mangoes in the absence of the ants, both fly species are reluctant to land on ant‐exposed fruits and, when having landed, often take off quickly and fail to oviposit. The number of puparia collected from unexposed mangoes is approximately eight‐fold higher than from ant‐exposed ones. The results obtained from laboratory experiments and field observations confirm that adult fruit flies are more affected through repellence by ant cues than by direct predation. The use of cues by fruit flies in predator avoidance has implications for evolutionary ecology, behavioural ecology and chemical ecology.     

Ecological studies of Eastern Australian fruit flies (Diptera: Tephritidae) in their endemic habitat

Fortnightly fruit fly captures for a 2-year period at Cooloola (south-east Queensland) contained 11 species. Three species, viz., D. tryoni, D. neohumeralis and D. endiandrae predominated. The peak trap catches of 7 species corresponded with the peak fruiting times of their major hosts. There was no direct relationship between temperature and rainfall and the variations in population numbers. The host plants of some species do not grow in the Cooloola area and there is evidence that large numbers of flies migrate into the region from other breeding areas up to 100 km away. Pockets of tropical rainforest such as Cooloola could be important adult fruit fly feeding areas even in the absence of larval host plants.     

Irradiation of mangoes as a postharvest quarantine treatment for fruit flies (Diptera: Tephritidae)

Mangoes infested with third instar larvae were irradiated using Co-60 gamma rays and a dose interval of 2-250 Gy to assess the irradiation dose required to prevent adult emergence of the Mexican fruit fly (Anastrepha ludens), the West Indies fruit fly (A. obliqua), the sapote fruit fly (A. serpentina), and the Mediterranean fruit fly (Ceratitis capitata). Doses of 76.9, 87.3, 91.4 and 112.7 Gy, were estimated to inhibit 99.9968% (probit 9) of adult emergence forA. obliqua, A. serpentina, A. ludens, and C. capitata, respectively. Using mangoes infested with a total of 100,000 larvae of each species, the results obtained in the laboratory were confirmed using a dose of 100 Gy for the Anastrepha species and 150 Gy for C. capitata. No adult emergence was observed for any of the four species compared with approximately 80% emergence in the controls. A dose of 150 Gy is recommended as a generic quarantine treatment against potential infestation of these species in exported mangoes. A minor decrease in the ascorbic acid content was the only adverse effects observed in irradiated mangoes.     

Toxicity of gallic acid to melon fruit fly,Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae)

Melon fruit fly, Bactrocera cucurbitae (Coquillett) is an important pest of cucurbits and other vegetable crops. It is not only a serious pest of cucurbit crops but sometimes also attacks non-host plants. In an endeavour to explore secondary metabolites as important and safe means of pest management, we investigated the effects of gallic acid, a phenolic compound, on the growth and development of melon fruit fly, B. cucurbitae. Larval survival and emergence were severely affected by gallic acid treatment. Both decreased in a concentration dependent manner with increase in concentration. Gallic acid-treated larvae took longer duration to pupate and reach the adult stage as compared to control larvae. Inhibitory effects of gallic acid were also observed on larval weight, pupal weight, mean relative growth rate and food assimilated which decreased with treatment. The ability of gallic acid to disrupt the development of B. cucurbitae suggests that the phenolic compound might have caused oxidative stress in the body of the insect.     

Chilled packing systems for fruit flies (Diptera: Tephritidae) in the sterile insect technique

We evaluated three packing systems (PARC boxes, "GT" screen towers and "MX" screen towers) for the emergence and sexual maturation of sterile fruit flies, at three adult fly densities (1, 1.2 and 1.3 fly/cm2) and three food types. At the lowest density, results showed no significant differences in the longevity and flight ability of adult Anastrepha ludens (Loew) and Anastrepha obliqua Macquart among the three packing systems. Higher densities resulted in a decrease in these parameters. In the evaluation of the three food types, no significant differences were found either on longevity or flight ability of A. ludens. However, the greatest longevity for both sexes A. obliqua was obtained with commercial powdered Mb? and the mix of sugar, protein and corn starch on paper (SPCP) food types. The highest value for flight ability in A. obliqua males was obtained with powdered Mb? and SPCP food types, and for females with Mb? powdered food. Our data indicated that GT and MX screen tower packing systems are an alternative to the PARC boxes, since they were suitable for adult fly sexual maturation without any harm to their longevity or flight ability. The tested foods were equivalent in both fruit fly species, with the exception of the agar type for A. obliqua, which yielded the lowest biological parameters evaluated. Our results contribute to the application of new methods for the packing and release of sterile flies in large-scale programs.     

Prior experience affects the visual ability ofRhagoletis pomonella flies (Diptera: Tephritidae) to find host fruit

Females of the apple maggot fly,Rhagoletis pomonella, were allowed for 3 days to alight upon and oviposit in green or red 18- to 20-mm hawthorn host fruit (Crategus mollis) or green or red 45- to 55-mm apple host fruit (Malus pumila) hung from branches of potted host trees in field enclosures. Subsequently, when females were released individually on potted host trees harboring fruit of one of these types, their ability to find fruit of unfamiliar size proved unaffected by prior experience with fruit but their ability to find fruit of unfamiliar color was significantly affected. Specifically, females exposed to red hawthorns or red apples were less able to find green hawthorns or green apples than were females experienced with either of the latter fruit types. Fruit odor was found to have no effect on female ability to find familiar compared with unfamiliar green fruit. In contrast, a difference in size (or surface chemistry) between familiar and unfamiliar fruit but not a difference in fruit color had a significant negative influence on the propensity of alighting females to bore into unfamiliar fruit. Three bouts of experience with alighting upon and ovipositing into fruit over a period of about 1 h had no detectable effect on female ability to find unfamiliar fruit but did reduce propensity to bore into unfamiliar fruit. Our findings are discussed in relation to insect ability to learn visual and chemical stimuli of resources and insect propensity to form host races. We also discuss the potential impact of our findings on nonpesticidal, behavioral methods of managingR. pomonella in commercial apple orchards.