Species diversity of the orchard fruit fly complex and the biorational management of the mango fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)
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Date
2008
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College of Horticulture, Vellanikkara
Abstract
The mango fruit fly, Bactrocera dorsalis (Hendel), is one of the serious pest of orchard systems, causing severe economic damage in fruit crops. Because of the enigmatic behavioural adaptations of the fruit fly species in different host fruits, the conventional pest management practices often provide unsatisfactory results. More over, the use of chemical interventions result in the usual set backs of insecticide resistance, pest resurgence, destruction of natural enemies and pollinators, pesticide residue in the harvested produce and related environmental and health hazards. Hence, there is an impetus for research and development on sustainable and eco friendly fruit fly management technology in orchard crop systems. In this context, the study on “Species diversity of the orchard fruit fly complex, and the biorational management of the mango fruit fly, Bactrocera dorsalis (Hendel) (Diptera : Tephritidae)” was carried out in the Department of Agricultural Entomology, College of Horticulture at Vellanikkara and farmers field during 2005-07. Investigations were undertaken to study the population dynamics of orchard fruit fly complex in different host fruits and to correlate its seasonal occurrence with the weather parameters, to evaluate the different types of lure material for fruit fly monitoring and management by various lure application techniques, to evaluate the emergence pattern, location of alightment on host trees, optimum height of trapping and distribution of fruit fly, to evaluate different food lures under cage experimentation and finally, to evolve an eco-friendly and biorational pest management strategy against B. dorsalis in mango orchards. The population of orchard fruit flies responding to methyl eugenol was monitored at weekly intervals from August 2005 to July 2006 at three locations in the KAU orchards in Vellanikkara and Mannuthy campuses and found that the highest peak of population was observed during the second week of March and the lowest during the third week of December. As different orchard fruits are serving as hosts for the B. dorsalis complex such as sapota, lovi lovi, citrus, fig, guava, carambola and jack, their population attained several peaks as and when different fruits were available in plenty in their respective fruiting seasons. Correlations between fruit fly catch (in mango) in ME traps and the weather parameters at Vellanikkara revealed that the maximum and minimum temperatures showed a significant positive correlation with the fruit fly population. Among other host fruits, rainfall showed a positive correlation with the fruit fly population in sapota. In Lovi lovi, maximum and minimum temperatures as well as relative humidity showed a positive correlation with the fruit fly population. In jack maximum and minimum temperatures increased the catch of fruit fly numbers. In guava, fig and carambola, all the weather parameters showed a non significant correlation with fly population. The population of mango fruit flies and other species responding to methyl eugenol traps were monitored at monthly intervals from August 2005 to July 2006 at Vellanikkara. Four species of fruit flies viz., B. dorsalis, B. caryeae, B. correcta and B. zonata were identified and the average monthly catches were 1436.41, 77.83, 27.25, 19.33 flies/trap respectively. The species diversity index worked out revealed that the mango fruit fly, B. dorsalis is the most dominant species as compared to the other three species. Sex ratio studies revealed that B. dorsalis population in ripe mango, bread fruit, rose apple and fig was more rather male biased with 1:0.99, 1:0.89, 1:0.97, 1:0.94 respectively, while, there was a slight female dominance (1:1.06) in guava. The optimum height for the ME bottle traps for fruit fly monitoring and management in mango was determined to be at two metre above the ground level during both rainy and non rainy periods in mango. The optimum height for the lure swab treatment on mango and bread fruit trees was found to be again at two metre height with more number of entrapped flies while, in sapota, it was only at 1.5 metre height. Among the four directions of attractional and behavioural orientations to the lure swabs, the western and southern sides of the tree trunks were having the higher number of fly catches as got stuck. The emergence rate of mango fruit flies from the soil was recorded to be higher from the middle zone at a distance of 2-3 meters radial distance from the tree base. The peak time of adult fly emergence from the soil litter was found to be between 6 am to 10 am. The time of attraction in the Spathiphyllum plants acting as a trap plant for fruit fly attraction to its spadix was found to be between 7 to 8 am. The studies on the behavioral alightment and hiding place of the adult flies on the mango tree revealed that they prefer to colonize on the under side of the leaves in the lower canopy during the season. The flies were also observed to frequent more on the proximal end of the maturing fruits especially borne in the lower branches of the tree canopy. The fruit fly attraction to different food lures when tested under cage experimentation proved that the flies were attracted more towards the fruit macerates of banana varieties viz., Poovan and Robusta and also to other host fruits namely Prior variety of mango followed by rose apple. The maximum response of fruit flies to ME traps as evidenced by the male catch was determined between 4-6 pm and 6-8 am under shaded tree canopy during the mango season. The studies on the population levels of mango fruit fly in ten different locations from Thrissur (Kerala) to Sadayanpallam (Tamil Nadu) over a distance of 75 km with the ME traps revealed that the trend of population increase from flowering to harvest across the region was almost similar and there was no probability of any suspected migration. Among mango varieties observed, the Prior and Alphonso were found to be having the maximum fruit fly infestation. Neelam, Moovandan and Chandrakaran were the least susceptible ones. Among the other host fruits, rose apple and guava had recorded higher infestations as high as 100 per cent and 30 per cent respectively. The results on the sticky trap experiments in mango and sapota orchard revealed that a vertically hanging yellow poly pack board of size 30 x 20 cm was having the maximum number of entrapped fruit flies. The newer application technique with sticky lure swabs on the tree trunks with gelatin based formulations in combination with ME and ME- banana macerate proved efficient in both trapping the adult flies and consequent reduction in fruit damage. Three field experiments undertaken to evaluate the efficacy of selected biorational techniques against mango fruit fly in variety Prior and Alphonso in the College orchard at Vellanikkara, revealed that the methyl eugenol bottle trap and methyl eugeonl + banana lure swab formulation on the tree trunk recorded the lowest fruit damage as compared to other treatments. Post harvest loss by the latent damage incited by the already oviposited eggs on the pre ripened fruit before harvest could be successfully prevented by the hot brine (0.5%) dip treatment of the fruits at 55°C for 15 minutes which afforded 100 per cent protection by the fly maggots during post harvest storage. Studies on the natural enemies of B. dorsalis complex in mango, resulted in the identification of one larval pupal parasitoid namely Biosteres arisanus (Sonan), which was having only 2.76 per cent natural parasitism on the maggots with in the fruits as evidenced by the ecloded adult parasitoid under the laboratory conditions. The mango fruit fly, Bactrocera dorsalis (Hendel), is one of the serious pest of orchard systems, causing severe economic damage in fruit crops. Because of the enigmatic behavioural adaptations of the fruit fly species in different host fruits, the conventional pest management practices often provide unsatisfactory results. More over, the use of chemical interventions result in the usual set backs of insecticide resistance, pest resurgence, destruction of natural enemies and pollinators, pesticide residue in the harvested produce and related environmental and health hazards. Hence, there is an impetus for research and development on sustainable and eco friendly fruit fly management technology in orchard crop systems. In this context, the study on “Species diversity of the orchard fruit fly complex, and the biorational management of the mango fruit fly, Bactrocera dorsalis (Hendel) (Diptera : Tephritidae)” was carried out in the Department of Agricultural Entomology, College of Horticulture at Vellanikkara and farmers field during 2005-07. Investigations were undertaken to study the population dynamics of orchard fruit fly complex in different host fruits and to correlate its seasonal occurrence with the weather parameters, to evaluate the different types of lure material for fruit fly monitoring and management by various lure application techniques, to evaluate the emergence pattern, location of alightment on host trees, optimum height of trapping and distribution of fruit fly, to evaluate different food lures under cage experimentation and finally, to evolve an eco-friendly and biorational pest management strategy against B. dorsalis in mango orchards. The population of orchard fruit flies responding to methyl eugenol was monitored at weekly intervals from August 2005 to July 2006 at three locations in the KAU orchards in Vellanikkara and Mannuthy campuses and found that the highest peak of population was observed during the second week of March and the lowest during the third week of December. As different orchard fruits are serving as hosts for the B. dorsalis complex such as sapota, lovi lovi, citrus, fig, guava, carambola and jack, their population attained several peaks as and when different fruits were available in plenty in their respective fruiting seasons. Correlations between fruit fly catch (in mango) in ME traps and the weather parameters at Vellanikkara revealed that the maximum and minimum temperatures showed a significant positive correlation with the fruit fly population. Among other host fruits, rainfall showed a positive correlation with the fruit fly population in sapota. In Lovi lovi, maximum and minimum temperatures as well as relative humidity showed a positive correlation with the fruit fly population. In jack maximum and minimum temperatures increased the catch of fruit fly numbers. In guava, fig and carambola, all the weather parameters showed a non significant correlation with fly population. The population of mango fruit flies and other species responding to methyl eugenol traps were monitored at monthly intervals from August 2005 to July 2006 at Vellanikkara. Four species of fruit flies viz., B. dorsalis, B. caryeae, B. correcta and B. zonata were identified and the average monthly catches were 1436.41, 77.83, 27.25, 19.33 flies/trap respectively. The species diversity index worked out revealed that the mango fruit fly, B. dorsalis is the most dominant species as compared to the other three species. Sex ratio studies revealed that B. dorsalis population in ripe mango, bread fruit, rose apple and fig was more rather male biased with 1:0.99, 1:0.89, 1:0.97, 1:0.94 respectively, while, there was a slight female dominance (1:1.06) in guava. The optimum height for the ME bottle traps for fruit fly monitoring and management in mango was determined to be at two metre above the ground level during both rainy and non rainy periods in mango. The optimum height for the lure swab treatment on mango and bread fruit trees was found to be again at two metre height with more number of entrapped flies while, in sapota, it was only at 1.5 metre height. Among the four directions of attractional and behavioural orientations to the lure swabs, the western and southern sides of the tree trunks were having the higher number of fly catches as got stuck. The emergence rate of mango fruit flies from the soil was recorded to be higher from the middle zone at a distance of 2-3 meters radial distance from the tree base. The peak time of adult fly emergence from the soil litter was found to be between 6 am to 10 am. The time of attraction in the Spathiphyllum plants acting as a trap plant for fruit fly attraction to its spadix was found to be between 7 to 8 am. The studies on the behavioral alightment and hiding place of the adult flies on the mango tree revealed that they prefer to colonize on the under side of the leaves in the lower canopy during the season. The flies were also observed to frequent more on the proximal end of the maturing fruits especially borne in the lower branches of the tree canopy. The fruit fly attraction to different food lures when tested under cage experimentation proved that the flies were attracted more towards the fruit macerates of banana varieties viz., Poovan and Robusta and also to other host fruits namely Prior variety of mango followed by rose apple. The maximum response of fruit flies to ME traps as evidenced by the male catch was determined between 4-6 pm and 6-8 am under shaded tree canopy during the mango season. The studies on the population levels of mango fruit fly in ten different locations from Thrissur (Kerala) to Sadayanpallam (Tamil Nadu) over a distance of 75 km with the ME traps revealed that the trend of population increase from flowering to harvest across the region was almost similar and there was no probability of any suspected migration. Among mango varieties observed, the Prior and Alphonso were found to be having the maximum fruit fly infestation. Neelam, Moovandan and Chandrakaran were the least susceptible ones. Among the other host fruits, rose apple and guava had recorded higher infestations as high as 100 per cent and 30 per cent respectively. The results on the sticky trap experiments in mango and sapota orchard revealed that a vertically hanging yellow poly pack board of size 30 x 20 cm was having the maximum number of entrapped fruit flies. The newer application technique with sticky lure swabs on the tree trunks with gelatin based formulations in combination with ME and ME- banana macerate proved efficient in both trapping the adult flies and consequent reduction in fruit damage. Three field experiments undertaken to evaluate the efficacy of selected biorational techniques against mango fruit fly in variety Prior and Alphonso in the College orchard at Vellanikkara, revealed that the methyl eugenol bottle trap and methyl eugeonl + banana lure swab formulation on the tree trunk recorded the lowest fruit damage as compared to other treatments. Post harvest loss by the latent damage incited by the already oviposited eggs on the pre ripened fruit before harvest could be successfully prevented by the hot brine (0.5%) dip treatment of the fruits at 55°C for 15 minutes which afforded 100 per cent protection by the fly maggots during post harvest storage. Studies on the natural enemies of B. dorsalis complex in mango, resulted in the identification of one larval pupal parasitoid namely Biosteres arisanus (Sonan), which was having only 2.76 per cent natural parasitism on the maggots with in the fruits as evidenced by the ecloded adult parasitoid under the laboratory conditions.
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