Effectiveness of GF-120 fruit fly bait spray applied to border area plants for control of melon flies (Diptera: Tephritidae)

In a field study in Hawaii, color-marked protein-deprived and protein-fed female melon flies, Bactrocera cucurbitae Coquillett, were released within canopies of unsprayed sorghum plants (a nonhost of melon flies) outside of a border area of unsprayed or bait-sprayed sorghum plants or open space that surrounded cucumbers, a favored host of melon flies. Application of bait spray to sorghum or sugarcane surrounding host plants of melon flies is a common practice for melon fly control in Hawaii. GF-120 Fruit Fly Bait spray proved very effective in preventing protein-deprived females from alighting on cucumbers (23% of released females were observed dead on bait-sprayed sorghum; 0% were observed alive on cucumbers), but proved less effective in suppressing protein-fed females (14% of released females were observed dead on bait-sprayed sorghum; 11% were observed alive on cucumbers). No females were found dead on unsprayed sorghum. Compared with open space surrounding cucumbers, the presence of unsprayed sorghum as surrounding border area neither significantly enhanced nor significantly inhibited the ability of either type of female with respect to finding cucumbers. Greenhouse cage assays revealed that compared with droplets of water, droplets of GF-120 Fruit Fly Bait spray were highly attractive to protein-deprived females within 1 h of bait spray application to sorghum, but lost about half of their attractiveness within 5 h and all of it within 24 h under the dry greenhouse conditions used for maintaining baited-sprayed sorghum plants in these assays. Laboratory cup assays showed that bait spray droplets remained highly toxic to protein-deprived females 24 h after application, but lost nearly half of their toxicity within 4 d under laboratory exposure and nearly all of it after approximately 8 mm of rainfall. Combined findings suggest that application of GF-120 Fruit Fly Bait spray to nonhost plants for melon fly control either be made often enough to overcome loss of attractiveness of bait spray droplets to females or that bait spray be applied to nonhost plants that are themselves attractive to the females.     

Effects of GF-120 fruit fly bait concentrations on attraction, feeding, mortality, and control of Rhagoletis indifferens (Diptera: Tephritidae)

Effects of different concentrations of GF-120 NF Naturalyte Fruit Fly Bait on attraction and feeding responses, mortality, and control of the western cherry fruit fly, Rhagoletis indifferens Curran, were determined. In the laboratory, flies that had been exposed to sugar and yeast extract and then deprived of all food for 16-20 h were attracted to 40.0% GF-120, but not to 0.6 and 4.8% GF-120 (vol:vol). Nonstarved flies were not attracted to any concentration. Flies in the field were not attracted to 55.6% GF-120 on cherry leaves, and few flies fed on the bait. In the laboratory, males fed for shorter durations on and ingested lower amounts of 0.6% than 4.8 or 40.0% GF-120, but females fed equally on all concentrations. Spinosad in GF-120 was highly toxic to flies. Lethal concentrations50 (LC50 values) of spinosad for starved flies at 1-4 d were 1.5-0.7 ppm. When gravid flies were exposed to cherries treated with 0.6, 4.8, and 40.0% GF-120, mortality was greater at each higher concentration, but none prevented oviposition. Field spray tests comparing 0.6, 4.8, and 40.0% GF-120 in 225 ml of spray per cherry tree resulted in 79-94% lower larval infestations than in controls, but no differences were seen among the concentrations. Evidence from this study indicates that fresh 40.0% GF-120 was attractive in the laboratory but that flies were not attracted to fresh GF-120 from far distances within trees, suggesting that suppression of populations is caused in large part by flies finding the bait through normal movement over large areas.     

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.     

Behavioral responses of Rhagoletis cingulata (Diptera: Tephritidae) to GF-120 insecticidal bait enhanced with ammonium acetate

GF-120 is a baited formulation of the insecticide spinosad containing 1% ammonium acetate, developed for control of economically important fruit flies. The response of feral cherry fruit flies, Rhagoletis cingulata Loew, to GF-120 augmented with 0, 5, or 10% ammonium acetate was evaluated under orchard conditions. Significantly more flies were observed within 30 cm of bait droplets with 10% ammonium acetate added compared with standard bait or to a water control. These fly visits to GF-120 enhanced with 10 or 5% ammonium acetate lasted an average of 263.2 +/- 85.2 and 337.6 +/- 72.6 s, respectively, compared with 50.3 +/- 36.4 s for standard GF-120. Droplets containing additional ammonium acetate also were contacted by more flies, and more flies fed upon these droplets than on GF-120 or the water control. Furthermore, the duration of feeding on GF-120 bait enhanced with either level of additional ammonium acetate was significantly greater compared with standard GF-120 or water. Feeding events lasted between 61.5 +/- 30.7 and 73.4 +/- 21.0 s on enhanced GF-120 compared with 6.8 +/- 5.7 s on standard GF-120. Collectively, these results indicate that the interaction of feral R. cingulata with GF-120 droplets and the toxicant spinosad can be increased by addition of ammonium acetate.     

Lethal and sublethal effects of spinosad-based GF-120 bait on the tephritid parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Experiments were performed to determine the likely compatibility of spinosad-based GF-120 applications and mass-releases of the braconid parasitoid Diachasmimorpha longicaudata (Ashmead) for control of tephritid fruit flies. Severe effects on D. longicaudata survival and reproduction in the laboratory contrasted with mild effects in semi-field studies. Topical application and contact with dried residues on plastic surfaces in the laboratory generally resulted in high mortality of wasps and significantly reduced survival times compared to controls. Survival times of both sexes were more severely affected when exposure to dried residues on mango leaves compared to wasps that were offered GF-120 mixed with honey. Brief (24 h) exposure to GF-120 in honey or dried residues on mango leaves did not affect total progeny production by wasps, whereas continuous exposure over a 10 d period resulted in reductions in female survival, progeny production and net fecundity (∑L_xM_x) compared to honey-fed controls. During the rainy season, wasp survival times in field cages with young mango trees that had been sprayed with GF-120 or treated with GF-120 mixed with honey were only reduced by 1 or 2 days, respectively, compared to average 10.1 d survival of honey-fed controls. During the dry season, wasp mortality was not significantly affected by exposure to GF-120 residues on mango leaves that had been subjected to natural weathering in the field, compared to controls. Our results suggest that applications of GF-120 are unlikely to adversely influence the effectiveness of mass-releases of D. longicaudata. This prediction requires validation from comparative field studies on parasitoid populations in treated and untreated areas.     

Feeding and foraging of wild and sterile Mediterranean fruit flies (Diptera: Tephritidae) in the presence of spinosad bait

The sterile insect technique (SIT) is used to control wild Mediterranean fruit fly introductions in California and Florida in the U.S. In the past, bait sprays containing malathion proved invaluable in treating new outbreaks or large populations before the use of SIT. Recently, a spinosad protein bait spray, GF-120, has been developed as a possible alternative to malathion, the standard insecticide in protein bait sprays. In this study, protein-deficient and protein-fed Vienna-7 (sterile, mass-reared, "male-only" strain) flies and wild males and females were evaluated to determine the effectiveness of the GF-120 protein bait containing spinosad with respect to bait attraction, feeding, and toxicology. There were no effects of diet or fly type on feeding duration in small laboratory cages. Wild flies, however, registered more feeding events than Vienna-7 males. Flies that fed longer on fresh bait died faster. Protein-deficient flies were more active and found the bait more often than protein-fed flies. Data suggest that adding protein to the diet of SIT flies may decrease their response to baits, therefore, reduce mortality, and thus, allow the concurrent use of SIT and bait sprays in a management or eradication program.     

Effectiveness of protein baits on melon fly and oriental fruit fly (Diptera: Tephritidae): attraction and feeding

Attraction and feeding responses of oriental fruit fly, Bactrocera dorsalis (Hendel), and melon fly, Bactrocera cucurbitae (Coquillett), were determined for different protein baits. In separate choice attraction assays for each species, significantly more flies arrived at stations with bait than water, but no differences existed among baits of GF-120 Fruit Fly Bait, GF-120 NF Naturalyte Fruit Fly Bait, Provesta 621 autolyzed yeast extract, and Mazoferm E802. In comparison with B. dorsalis, B. cucurbitae had 2.8 times more responders and a 4.8 times better discrimination between baits and water. In a second attraction assay with only B. dorsalis, volume of bait was negatively correlated to numbers of flies alighting on the bait. Feeding assays for both species demonstrated that time spent feeding and duration on a leaf were both significantly affected by bait type. B. dorsalis fed the longest on Provesta 621, with significantly less feeding on the other baits, and with all baits resulting in more feeding than water. The longest feeding times for B. cucurbitae resulted with Mazoferm E802 and Provesta 621, and all baits except GF-120 NF resulted in eliciting a significantly longer feeding duration than water. In separate toxicology assays for each species, significantly higher mortality resulted from bait formulations containing spinosad compared with blank baits, but no differences existed between GF-120 and GF-120 NF formulations. The differences are discussed between the two Bactrocera species primarily in regard to bait preference, extent of response, and previous work on laboratory flies.     

Increased food intake after starvation enhances sleep in Drosophila melanogaster

Feeding and sleep are highly conserved,interconnected behaviors essential for survival.Starvation has been shown to potently suppress sleep across species;however,whether satiety promotes sleep is still unclear.Here we use the fruit fly,Drosophila melanogaster,as a model organism to address the interaction between feeding and sleep.We first monitored the sleep of flies that had been starved for 24 h and found that sleep amount increased in the first 4 h after flies were given food.Increased sleep after starvation was due to an increase in sleep bout number and average sleep bout length.Mutants of translin or adipokinetic hormone,which fail to suppress sleep during starvation,still exhibited a sleep increase after starvation,suggesting that sleep increase after starvation is not a consequence of sleep loss during starvation.We also found that feeding activity and food consumption were higher in the first 10-30 min after starvation.Restricting food consumption in starved flies to 30 min was sufficient to increase sleep for 1 h.Although flies ingested a comparable amount of food at differing sucrose concentrations,sleep increase after starvation on a lower sucrose concentration was undetectable.Taken together,our results suggest that increased food intake after starvation enhances sleep and reveals a novel relationship between feeding and sleep.     

Physiology of feeding preference patterns of female black blowflies (Phormia regina Meigen)

Summary The relative effectiveness of 0. 1 M sucrose and 10% yeast extract in eliciting feeding by femalePhormia regina has been shown to be related to the fly's carbohydrate reserve levels. Females that have had ad lib. access to 0.1 M sucrose (S flies, standard condition) take larger drinks of 10% yeast than 0.1 M sucrose starting at three days of age, indicating that 10% is the more effective feeding stimulus. Females that have had ad lib. access to 0.1 M sucrose and 10% yeast (S/Y flies, standard condition) always drink more 0.1 M sucrose than 10% yeast (Fig. 1). S/Y (standard condition) flies appear to respond to the yeast as if it were dilute carbohydrate: the volumes of 0.1 M sucrose and 10% yeast that they drink fluctuate in parallel. S (standard condition) flies respond to the yeast differently: starting day 3, their drink volumes of 10% yeast increase as drink volumes of 0.1 M sucrose decrease.The elevation of the volume of 0.1 M sucrose drunk by flies whose carbohydrate reserve levels have been depleted by diet, starvation or flight (Figs. 2–4) supports the hypothesis that some physiological state or process related to carbohydrate metabolism regulates the fly's responsiveness to yeast extract. Possible mechanism by which the fly translates carbohydrate reserve level into feeding preference are discussed. Available evidence points to a CNS phenomenon, probably involving the stomatogastric nervous system. The pattern of the selective feeding cycle of femalePhormia can be explained in terms of the accumulation and utilization of carbohydrate reserves.This work was supported by a Spencer Foundation Predoctoral Fellowship from Princeton University and by NSF Grant number BNS 76-02172 to Dr. Vincent G. Dethier. I am grateful to the Departments of Zoology and Entomology of the University of Massachusetts, Amherst, for the use of their facilities. Many thanks to Drs. V.G. Dethier, Elizabeth Bowdan and David Falk for critical discussion and assistance.     

Potential for pre-release diet supplements to increase the sexual performance and longevity of male Queensland fruit flies

1 Recent studies have shown that continuous access to a protein source (yeast hydrolysate) can greatly enhance the sexual performance of male Queensland fruit flies ( Bactrocera tryoni ; 'Q-flies'). However, in Sterile Insect Technique programmes used to eradicate or suppress wild populations, mass-reared Q-flies are typically fed only sucrose and water for up to 2 days before release.
2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies.
3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males.
4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein-deprived males. Females were also less likely to remate if their first mate had been large.
5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access.
6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations.     

Ingestion of spinosad bait GF-120 and resulting impact on adult Chrysoperla carnea (Neuroptera: Chrysopidae)

The spinosad bait spray GF-120 Naturalyte F® (Dow AgroSciences LLC, Indianapolis, IN, USA) is widely used in commercial olives in California. Because of concern about its non-target effects on beneficial insects, we studied its impact on feeding behavior, mortality, and reproductive parameters of adult green lacewings, Chrysoperla carnea (Stephens), under laboratory conditions. Male and female feeding rate and quantity, and subsequent mortality, were compared over a 5-day period following a 24-h exposure to honey, GF-120, or the bait component (without spinosad) in two-choice and no-choice assays. All treatments were ingested equally when offered alone. Spinosad did not impart repellency or preference to GF-120 relative to the bait. Honey was preferred in choice tests with GF-120 or bait. Significant mortality occurred when GF-120 was offered alone, but was not significant when it was offered in choice with honey or bait. In a separate assay of female longevity and reproduction, mortality rate as a function of time was similar in all treatments, except for some significantly earlier mortality due to GF-120 compared with honey. GF-120 ingestion significantly reduced fecundity compared with bait during the first week after treatment. Egg hatch was not significantly affected. The preference of adult C. carnea for food should ameliorate the potential negative effect of GF-120 on adult C. carnea mortality in the field. The laboratory study finds that GF-120 is a potentially safer choice for C. carnea than an aqueous suspension of spinosad, and provides no new evidence for definitive risk to field populations.     

Efficacy of soil application of Metarhizium anisopliae and the use of GF-120 spinosad bait spray for suppression of Bactrocera invadens (Diptera: Tephritidae) in mango orchards

Field trials were conducted for two seasons in mango orchards at Nthagaiya, Kenya, to evaluate the efficacy of soil inoculation with Metarhizium anisopliae (Hypocreales: Clavicipitaceae) and GF-120 spinosad bait sprays, applied either alone or in combination, for suppression of the invasive fruit fly, Bactrocera invadens (Diptera: Tephritidae). During the 2006/2007 season, average post-treatment samples showed that B. invadens catches from the control orchards were four times higher than the number of flies captured in the plots receiving M. anisopliae+GF-120. Fruit infestation was 16, 45, 30 and 60% in the M. anisopliae+GF-120, M. anisopliae alone, GF-120 alone and control orchards, respectively. In the 2007/2008 season, average B. invadens post-treatment samples in the control orchards were seven times higher than the treatment with M. anisopliae+GF-120; and fruit infestation was 11, 38, 28, and 52% in the orchards assigned to M. anisopliae+GF-120, M. anisopliae alone, GF-120 alone and control treatments, respectively. Enumeration of conidial densities from soil samples on agar plates showed initial densities of 1.1–2.1×10⁵ colony forming units (cfu)/g of dry weight of soil but decreased to 1.0–1.4×10³ cfu/g at the end of the experimental period. Exposure of laboratory-reared pupariating larvae to soil samples taken from fungus-treated fields showed significant reduction in B. invadens adult emergence (25–36%) compared with the control (80–82%). Our results suggest that the combined use of soil application of M. anisopliae and GF-120 spinosad bait spray is an effective IPM strategy for field suppression of B. invadens on mango.     

A comparative assessment of the response of three fruit fly species (Diptera: Tephritidae) to a spinosad-based bait: effect of ammonium acetate, female age, and protein hunger

Ammonia-releasing substances are known to play an important role in fruit fly (Diptera: Tephritidae) attraction to food sources, and this information has been exploited for the development of effective synthetic food-based lures and insecticidal baits. In field studies conducted in Hawaii, we examined the behavioural response of wild female oriental fruit fly (Bactrocera dorsalis (Hendel)), melon fly (B. cucurbitae (Coquillett)), and Mediterranean fruit fly (Ceratitis capitata (Wiedemann)) to spinosad-based GF-120 NF Naturalyte Fruit Fly Bait(?) formulated to contain either 0, 1 or 2% ammonium acetate. Use of visually-attractive yellow bait stations for bait application in the field allowed for proper comparisons among bait formulations. Field cage tests were also conducted to investigate, using a comparative behavioural approach, the effects of female age and protein starvation on the subsequent response of F1 generation B. cucurbitae and B. dorsalis to the same three bait formulations that were evaluated in the field. Our field results indicate a significant positive effect of the presence, regardless of amount, of AA in GF-120 for B. dorsalis and B. cucurbitae. For C. capitata, there was a significant positive linear relationship between the relative amounts of AA in bait and female response. GF-120 with no AA was significantly more attractive to female C. capitata, but not to female B. dorsalis or B. cucurbitae, than the control treatment. Our field cage results indicate that the effects of varying amounts of AA present in GF-120 can be modulated by the physiological stage of the female flies and that the response of female B. cucurbitae to GF-120 was consistently greater than that of B. dorsalis over the various ages and levels of protein starvation regimes evaluated. Results are discussed in light of their applications for effective fruit fly suppression.     

Protection of fruit against infestation by apple maggot and blueberry maggot (Diptera: Tephritidae) using compounds containing spinosad

Two insecticide formulations containing the naturalyte insecticide spinosad, GF-120 Fruit Fly Bait and SpinTor 2 SC, were compared for control of apple maggot, Rhagoletis pomonella (Walsh), and blueberry maggot, Rhagoletis mendax Curran. In 2002 and 2003, larval infestation in blueberries and apples was significantly lower in plots treated with GF-120 (spinosad bait) or SpinTor than in untreated control plots. Fruit fly infestation in apples was reduced by 67% in 2002 after weekly application of GF-120 for 6 wk. Six weeks of GF-120 treatment reduced infestation in blueberries by 85% in 2002 and 98% in 2003. Plots treated weekly with the bait component of GF-120 for 6 wk had significantly higher infestation of blueberry maggot larvae compared with untreated plots in 2002. Observations of wild R. mendax flies revealed that similar numbers of flies landed on blueberry foliage treated with spinosad bait, the bait component alone, or water droplets. However, flies on spinosad bait and bait treated plants spent significantly more time within 5 cm of the treatment droplets compared with control (water) droplets. Overall, the results demonstrate a high degree of efficacy of baited spinosad formulations against these key pests of temperate fruit and suggest that GF-120 is an arrestant for foraging flies.     

Visual and olfactory cue interaction in resource-location by the blowfly, Lucilia sericata

Abstract. The interactions between olfactory and visual cues in the landing responses of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) were examined in a laboratory wind tunnel. The odour of liver and sodium sulphide solution released at 1 L/min, resulted in a greater number of landings, closer to, but downwind of, the central odour release point, than when odour was absent. Three-day-old protein-deprived females landed in greater numbers than protein-fed female flies of the same age; no difference existed between 6-day-old protein-fed or protein-deprived females. Six-day-old, protein-fed flies landed closer to the odour source than did 3-day-old, protein-fed flies. In the presence of odour, flies landed closer to the central release point when it was accompanied by a visual cue. No such effect of the visual cue was evident in the absence of odour. When a plain white sticky-surface (25 × 25 cm) was paired with an identical white surface plus odour, approximately equal numbers of flies landed when the surfaces were placed together; increasingly higher numbers of flies landed on the surface with the odour cue when the distance between the surfaces was increased. When a white surface with a visual cue was presented with the plain white surface plus odour, more flies landed on the white surface with the visual cue than on the plain white surface with odour when they were close together. However, as these two surfaces were moved apart, flies landed increasingly more on the surface with the odour than the surface with the visual cue. The results show that while odour cues may enhance the induction of landing by female L. sericata , visual cues are important when selecting a final landing site.     

A cost-benefit analysis of feeding in female tsetse

Abstract. Three models for feeding in female tsetse are considered. Model I: there is a prolonged non-feeding phase after each meal followed by feeding at a constant rate, with a constant probability of dying as a consequence of feeding. Model II: the feeding rate increases linearly after each meal. Model III: the feeding rate increases exponentially after each meal. In Models II and III the feeding hazard is a linear function of the probability of feeding. Production of viable female offspring is estimated under each model, making allowance for losses of adults due to starvation and to background and feeding mortality, losses of pupae due to predation and parasitization, and losses of young flies if their mothers take insufficient blood during pregnancy. Under Model I, if females require three meals to produce viable pupae in 9 days, then for a non-decreasing population with a background mortality of 1%/day, and 25% pupal losses due to predation and parasitism, the feeding risk must be ≤5%/feed. At this maximum level the non-feeding phase should be 2–2.5 days for optimal productivity, with a mean feeding interval of 60–72 h. If the background mortality is 2%/day, feeding losses cannot exceed 1%/feed for a non-decreasing population. If four or five meals are required for the production of fully viable pupae, the optimal values of the non-feeding phase and mean feeding interval tend towards 1 and 2 days respectively. Under Models II and HI the mean feeding interval is 50–60 h for optimal productivity (with variances 3 times as large as for Model I), in good agreement with estimates from recent models for feeding and digestion. Field evidence suggests that feeding tsetse take greater risks as their fat levels dwindle. This should result in feeding (and feeding mortality) rates which increase during the feeding phase - as assumed in Models II and III but not in Model I. These models allow greater flexibility than Model I, because flies can feed early in the hunger cycle, at low probability, as long as the feeding risk is also low.     

Effect of the natural pesticide spinosad (GF-120 formulation) on the foraging behavior of Plebeia moureana (Hymenoptera: Apidae)

In this study we evaluated the effects of the biorational pesticide, Spinosad (GF-120 formulation), on foraging behavior in the stingless bee Plebeia moureana (Ayala). Several foragers were individually trained to collect an unscented 1.0 M sucrose solution (31% sucrose wt:wt) from a blue plate in one arm of a Y-tube maze. The other arm offered plain water on a yellow plate. After 20-30 visits to the setup, the sucrose solution was exchanged for a sucrose solution mixed with one of five concentrations of GF-120 and 30 consecutive choices of each bee were recorded. Interestingly, the foragers collected the sucrose solution with GF-120 at all concentrations. Our results show that: 1) the GF-120 formulation, when applied at the recommended concentration and mixed with food, does not discourage engaged foragers and, 2) foraging behavior over time is not significantly impaired by the continuous collection of GF-120.     

The effects of different cycles of starvation and re‐feeding on growth and body composition in rainbow trout (Oncorhynchus mykiss,Walbaum, 1792)

This study was designed to investigate the effects of starvation and re‐feeding cycles on the growth performance and body chemical composition of Oncorhynchus mykiss juveniles. A total of 360 juveniles with initial mean weights (IW) of 8.46 ± 0.07 g (n = 360) were stocked into 400‐L tanks in triplicate for each group, with 30 juveniles per tanks. The control group received regular feed, as is the common practice. The three other groups were periodically starved: 1 day starvation followed by 6 days re‐feeding (S1), 2 days starvation followed by 5 days re‐feeding (S2) and 3 days starvation followed by 4 days re‐feeding (S3). The experiment lasted for 10 weeks, over the course of which the water flow rate was 4 L min^?1 and the water quality parameters determined as: temperature 14.4 ± 1.1°C, oxygen 8.2 ± 0.4 mg L^?1 and pH 7.5 ± 0.2. At the end of the study, S1 had the best growth performance (final weight, specific growth rate, average daily growth) of all test groups (P < 0.05). The lowest daily feed intake (DFI) and growth performance parameters were observed in S3 (P < 0.05), while protein efficiency ratio (PER), net protein utilization (NPU) and lipid efficiency ratio (LER) were higher in the S3 fish group than in the other groups (P < 0.05). Whole body protein and lipid contents were highest in S1 fish. The hepatosomatic index (HSI) and viscerosomatic index (VSI) were significantly different among groups (P < 0.05). Feed conversion ratio (FCR) was significantly lower in starvation groups S1, S2 and S3 than in the control (P < 0.05). Compensation coefficient (CC) values were higher than 1 in all starvation groups. The concluding indicate that rainbow trout exposed to 1 and 2 days of starvation in week cycles could achieve over compensation compared to the control. Additionally, partial growth compensation and improved feed utilization could be achieved in a starvation group within 3 days in a week, by beginning with the juvenile size over a 10‐week experimental period.     

Mechanical transmission of Trypanosoma evansi and T. congolense by Stomoxys niger and S. taeniatus in a laboratory mouse model

Abstract .Mechanical transmission of Trypanosoma evansi (South American origin) and T. congolense of Kilifi DNA type (Kenyan origin) was studied in laboratory mice using the African stable flies Stomoxys niger niger and S. taeniatus . Altogether, 355 flies were interrupted after feeding on infected blood and then transferred immediately to an uninfected mouse to complete feeding. Microscopy and subinoculation of triturated flies into uninfected mice demonstrated the survival of T. congolense in Stomoxys for up to 210 min and T. evansi for up to 480 min. Parasites survived for much longer periods in the digestive tract than inside or on the mouthparts. Trypanosoma congolense was transmitted only by S. n. niger , and only at low rates of 3, 8 and 10% using flies of different feeding histories: fed on blood the previous day, freshly caught, and teneral. Trypanosoma evansi was transmitted by both Stomoxys species at higher rates: S. taeniatus range 13–18%; S. n. niger range 17–35%. The highest transmission rate occurred with the combination of teneral S. n. niger and T. evansi.     

Effects of aging and dilution on attraction and toxicity of GF-120 fruit fly bait spray for melon fly control in Hawaii

Attractiveness and toxicity of GF-120 Fruit Fly Bait (Dow AgroScience Indianapolis, IN) to melon flies, Bactrocera cucurbitae Coquillett, were examined to assess the effects of concentration and aging. We tested dilutions of 20, 40, and 80 ppm (AI) (spinosad) against water controls. The 80 and 40 ppm treatments were significantly more attractive than the 20 ppm and control treatments. Attraction was compared between baits aged for 2 and 24 h, fresh bait and water controls. Age had significant effects on both attractiveness and toxicity of GF-120. Baits aged for 2 h were 11 times less attractive to female melon flies than fresh bait. Mortality rates were reduced by 50% when GF-120 was subjected to rain. Our results suggest the need for frequent applications of GF-120 to obtain maximum benefits, particularly in wet tropical climates.