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Open Access
Population dynamics and management of aphids in vegetable ecosystem
(Department of Agricultural Entomology, College of Agriculture, Vellayani, 2009) Thamilvel, D; KAU; Hebsy, Bai
Eight species of aphids viz., A. gossypii, A. craccivora, A. spiraecola, A. fabae, A. nerii, H. setariae, M. persicae and L. erysimi were recorded from 32 vegetables in a survey conducted in the four taluks of Thiruvananthapuram district of Kerala. Occurrence of A. gossypii on C. grandis, M. oleifera and P. tetragonolobus; A. craccivora on C. gladiata, P. tetragonolobus and S. grandiflora ; A. spiraecola on A. tricolor, C. sativus, C. tetragonoloba, M. oleifera, M. charantia, M. koeingii, P. tetragonolobus and S. androgynus ; M. persicae on A. tricolor and R. sativu; A. nerii on C. annuum and C. frutescens was recorded for the first time from the State and H. setariae on A. tricolor and A. dubius from South India. One hundred and twenty two other plants were identified as host plants of the different aphids. A. gossypii was the dominant species noted, closely followed by A. craccivora, and A. spiraecola. Maximum species of aphids were recorded on amaranthus followed by winged bean. Among the vegetables surveyed, chilli and coccinia were highly susceptible to A. gossypii and winged bean and cowpea to A. craccivora. Mosaic disease incidence was noted in 10 vegetables. Predators were the predominant group of natural enemies associated with the aphids with the coccinellids constituting the major predatory fauna. Twenty species of coccinellids were recorded from different species of aphids on various host plants of which 13 species were new records from Kerala. M. sexmaculatus was the dominant species followed by C. transversalis, S. latemaculatus and C. septempunctata, Four species of syrphids were recorded of which I. scutellaris was predominant. P. yerburiensis and D. aegrota were recorded for the first time from Kerala. Leucopis sp. was the only Chamaemyiid species recorded from the vegetable fields. The chrysopids, C. carneae and A. octopunctata and the hemerobiid, Micromus sp. were the Neuropteran predators of the aphids recorded of which Micromus sp. was dominant. A. octopunctata was recorded for the first time from Kerala. Eleven species of spiders were observed in the vegetable fields among which, O. javanus, T.mandibulata, O. quadridentatus, O. shweta and Phidippus sp. were the frequently encountered species. Aphidius sp. was the most dominant parasitoid in the vegetable ecosystem. Aphelinus sp. and D. rapae were the other parasitoids recorded. Seven species of ants were observed attending the aphids. Studies on the population fluctuation of A. gossypii in chilli and A. craccivora in winged bean during a cropping season indicated that high population was seen during November and December. Correlation studies revealed a significant and positive correlation between the population of both the aphids with the insect predators, spiders and parasitoids. None of the climatic parameters had any significant influence on the aphid population. Excepting, maximum temperature which had a positive influence, all the other weather parameters viz., minimum temperature, relative humidity, rainfall and wind velocity had a negative influence on the population of the predators and parasitoids. Among the botanicals screened in the laboratory, only neem oil- garlic emulsion 2% and NeemAzal T/S 4 ml/l recorded more than 50 per cent mortality of A. gossypii and A. craccivora. Among the insecticides, the neonicotinoids viz., acetamiprid 0.002% imidacloprid, 0.003%, and dimethoate 0.05% proved superior to all other treatments. Dimethoate 0.05% was highly toxic to the coccinellids, syrphids and a hemerobiid (Micromus sp.) predator under laboratory condition. Between the two neonicotinods, acetamiprid 0.002% registered higher mortality than imidacloprid 0.003% whereas NeemAzal T/S 4 ml/l and neem oil + garlic emulsion 2% were safe to the predators. Foliar application of dimethoate 0.05%, acetamiprid 0.002% and imidacloprid 0.003% gave good control of A. gossypii, A. biguttula biguttula, S. dorsalis and A. dispersus in chilli and A. craccivora, A. dispersus, R. pedestris and M. vitrata in winged bean. NeemAzal T/S 4ml/l and neem oil garlic emulsion 2% too checked the population of the pests appreciably. Dimethoate 0.05% was highly toxic to the predators and parasitoids followed by acetamiprid 0.002% both in the chilli and winged bean fields. Comparatively, imidacloprid 0.003% was less toxic. The botanicals were safer to the natural enemies. Dimethoate 0.05% was highly toxic to soil fauna and flora whereas acetamiprid and imidacloprid were less toxic while NeemAzal T/S 4ml/l and neem oil + garlic emulsion 2% were non toxic. In both the trials, significantly higher yield was obtained from all the treatments. However, no significant difference was noted in the yields obtained from acetamiprid 0.002%, imidacloprid 0.003% and dimethoate 0.05% treated plots. Residues of imidacloprid were detected in chilli and winged bean fruits five days after spraying. While on the tenth day after spraying, residues of acetamiprid, and dimethoate were detected in chilli fruits, only residue of acetamiprid was recorded from winged bean pods. Imidacloprid was below detectable level (BDL). Residues of all the three insecticides were below detectable level when estimated fifteen days after spraying. Based on the results of the study, early detection of aphids on weeds and other host through regular monitoring, proper weed and ant management, conservation of the beneficials, application of neem oil + garlic emulsion 2% or NeemAzal T/S 4ml/l during the early stage of infestation and use of imidacloprid 0.003% when needed are suggested for aphid management in vegetables.
Open Access
Species diversity of the orchard fruit fly complex and the biorational management of the mango fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)
(College of Horticulture, Vellanikkara, 2008) Thiyagarajan, P; KAU; Jim, Thomas
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.
Open Access
Biopotency of Indian privet, Vitex negundo Linn. (Verbenaceae) against Spodoptera litura fab. (Lepidoptera: Noctuidae) and Henosepilachna vigintioctopunctata Fab. Ccoleoptera: Coccinellidae)
(College of Horticulture, Vellanikkara, 2009) Deepthy, K B; KAU; Sheela, M K
The present investigations on “Biopotency of Indian privet, Vitex negundo Linn. (Verbenaceae) against Spodoptera litura Fab. (Lepidoptera: Noctuidae) and Henosepilachna vigintioctopunctata (Coleoptera: Noctuidae) were carried out in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2005-2008. The objectives of this study were to screen the different parts (leaf, shoot and flower) of V. negundo for its biological efficiency with different solvent extracts against S. litura and H. vigintioctopunctata and to test the V. negundo extracts for their biological responses as with ovipositional deterrency, ovicidal action, antifeedancy, morphogenic effects and reproductive inhibition against the test insects. Experiments were also conducted to assess the potency of V. negundo extracts in combination with different entomopathogens. Screening experiments revealed that among the different parts viz., leaves, shoots and flowers of V. negundo, leaves showed significant bio response against S. litura and H. vigintioctopunctata. Methanol and hexane extract of leaves of V. negundo at six per cent resulted in maximum mortality of S. litura and H. vigintioctopunctata. V. negundo extracts with methanol (6%) indicated significant ovipositional deterrency with 94.02 and 100 per cent reduction in egg laying of S. litura and H. vigintioctopunctata respectively. Methanol extract (6%) proved as an efficient ovicidal agent against S. litura. Against H. vigintioctopunctata acetone aqueous extracts showed pronounced ovicidal action at lower concentration of four per cent resulting in cent percent reduction in hatching. Studies on growth and developmental effects of V. negundo extracts revealed that methanol and acetone extracts resulted in maximum reduction in pupal weight and pupation of S. litura. Delay in moulting of S. litura was observed in different treatments with V. negundo. S. litura reared in treated castor leaves and semi synthetic diet recorded maximum larval duration (19 and 26 days respectively) with acetone (6%) while water extract resulted in greater duration of 17.67 days in banana fed larvae. V. negundo cause no antifeedant action against S. litura and H. vigintioctopunctata. Food consumption and utilization studies on S. litura and H. vigintioctopunctata revealed that V. negundo extracts caused a drastic decline in growth parameters like, Efficiency of Conversion of Ingested Food (ECI) and Efficiency of Conversion of Digested Food (ECD), larval growth and Relative Growth Rate (RGR) thus indicating the inhibitory action of V. negundo on the growth of test insects. All the solvent extracts (except aqueous extract) reduced ECI and ECD against both S. litura and H. vigintioctopunctata proving the potency of V. negundo as an efficient growth inhibitor. Acetone extract (6%) resulted in maximum reduction in RCR of S. litura and H. vigintioctopunctata. Hexane, acetone and methanol extracts caused highest growth inhibition in H. vigintioctopunctata. Correlation studies revealed that there is a highly significant positive correlation of ECI and ECD with RGR both in S. litura and H. vigintioctopunctata. Solvent extracts of V. negundo were found to induce pupal and adult malformations in S. litura and H. vigintioctopunctata. Hexane and methanol extracts caused highest pupal and adult malformations in S. litura larvae. All the solvent extracts (6%) caused significant reduction in longevity and fecundity of both S. litura and H. vigintioctopunctata. Methanol extract was proved to be the most toxic (least LD50 value) against S. litura and against H. vigintioctopunctata, hexane extract showed maximum toxicity. Compatibility studies revealed that methanol extract inhibited growth of both Metarhizium anisopliae and Beauveria bassiana. Combination treatment of methanol extract with M. anisopliae resulted in reduction in mortality of S. litura leading to antagonistic interaction. Combination studies conducted with Bacillus thuringiensis and Nuclear Polyhedrosis Virus (NPV) resulted in enhanced mortality and reduction in Median Lethal Time (LT50). The results of the present study thus indicate the multiple modes of action of V. negundo against insect pests and hence there is good scope of its utilization as an efficient component in Integrated Pest Management (IPM) programmes against S. litura and H. vigintioctopunctata.

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