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    Bioefficacy of Tagetes minuta L. against Teranychus truncatus ehara (Prostigmata: Tetranychidae) and Aphis craccivora koch (Hemiptera: Aphididae)
    (Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2023-03-25) Ashish, V V.; Haseena, Bhaskar
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    Toxicity of insecticides to cheilomenes sexmaculata fabricius (coleoptera:coccinellidae)
    (Department of Agricultural Entomology, College of Agriculture, Vellanikkara, 2021) Pavithrakumar, K; Smitha, M S
    Biocontrol represents a sustainable and economically feasible way of pest management. However, under high herbivore pressure, bioagents alone are often unable to provide quick reduction of pest population, calling for insecticide based interventions. Chemical control, though designed to cause rapid mortality of target pests also adversely impact the natural enemies, leading to reduction in their growth, survival and reproduction. Hence it becomes imperative to evaluate the effects of insecticides on efficient natural biocontrol agents, to select safe insecticides and use them harmoniously. The six spotted zigzag lady beetle, Cheilomenes sexmaculata (Coleoptera: Coccinellidae), is an efficient natural enemy of aphid species in various crops due to its voracious feeding habit and density responsiveness. It is very common in cowpea and plays a major regulatory role against the cowpea aphid, Aphis craccivora. However, biocontrol by C. sexmaculata is often destabilized by the indiscriminate use of insecticides. Selection of insecticides safe to C. sexmaculata requires knowledge on direct and indirect effects of insecticides on the growth and development of the predator. Hence five insecticides and a botanical that are recommended in cowpea for pest management were evaluated for their toxicity to C. sexmaculata in the laboratory as well as their impact on field efficacy of the predator. Assessment of direct lethal impact, by exposing the life stages of the predator to field doses of insecticides, revealed the highly toxic nature of dimethoate and thiamethoxam to grub, pupa and adult stages of C. sexmaculata, leading to 100.00 per cent mortality. Exposure to dimethoate caused complete mortality of eggs while thiamethoxam was harmless to eggs with only 22.50 per cent mortality. Neem oil emulsion (3%) was found harmful to the non-feeding egg and pupal stages by completely inhibiting hatching and adult eclosion. In grub and adult stage, neem oil caused a mortality of 32.5 and 50 per cent respectively. Flubendiamide and spinosad were relatively harmless to all stages, inducing 22.50 and 15.00 per cent mortality in eggs, less than 10 per cent mortality to grubs and pupae, and 12.5 per cent mortality to adults of C. sexmaculata. Exposure of first instar grubs to sub lethal doses of insecticides also revealed adverse effects on development and reproduction of the predator. While exposure todimethoate led to complete mortality of grubs, exposure to thiamethoxam and neem oil prolonged the development period by two days and reduced the oviposition period by eight and five days, respectively. Adult longevity also was reduced by 4-8 days, after exposure to these insecticides. The fecundity was also reduced to 1637.13±92.10 and 1727.13±51.75 eggs/female respectively in thiamethoxam and neem oil as compared to 2151.88±27.31 in control. In both thiamethoxam and neem oil treatments, fertility was reduced by 15.00 per cent of 1868±26.50 offsprings/female recorded in control. Flubendiamide had no influence on the development period but reduced the oviposition period by seven days and male and female longevity by four and eight days respectively. There was a reduction in fecundity and fertility by 27.00 and 14.00 per cent respectively as well. Spinosad had no significant influence on developmental period of immatures but reduced the fecundity to 1917.00±89.43 eggs/female. Evaluation of insecticides in cowpea field demonstrated the effectiveness of dimethoate and thiamethoxam in managing aphids with drastic reduction in population till 15 th day with 3.20 and 1.80 aphids/10cm twig compared to 33.88 aphids in control 15 days after spray. The plots treated with flubendiamide, neem oil emulsion and spinosad recorded 17.90, 17.35 and 17.00 aphids/10cm twig respectively at 15 DAS and were inferior to dimethoate and thiamethoxam in aphid management. However, there was a gradual increase in the predator population after third day of spray from 1.05, 1.25 and 1.20 numbers/plant to 1.90, 2.00 and 1.90 numbers/plant at 15 DAS in flubendiamide, neem oil emulsion and spinosad treatments respectively compared to control (1.55 and 2.15 numbers/plant). This indicates the safety of these insecticides to predator in field. Whereas, no predator population was observed in dimethoate and thiamethoxam treatments till 15 DAS. The study provides a measure of safety of insecticides in an IPM programme with C. sexmaculata, a promising bioagent against the key pest, A. craccivora in cowpea. The results point out the deleterious effect of dimethoate and thiamethoxam to C. sexmaculata. Botanical, neem oil is harmless to grubs but harmful to other life stages of the predator and also adversely affects growth and reproduction at sublethal doses. Flubendiamide, though harmless at field doses, alters the reproductive parameters at sublethal level. Spinosad, with only minimal reduction in fecundity, is harmless to C. sexmaculata.
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    Insecticide mixtures for the management of pest complex in cowpea
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2018) Banka Kanda Kishore Reddy; Ambily Paul
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    Eco-friendly management of major pests of yard long bean, vigna unguiculata subsp. sesquipedalis (L.) Verdcourt.
    (Department of Agricultural Entomology, College of Agriculture, Padannakkad, 2017) Vineetha, V; KAU; Ramesha, B
    The study entitled ′′Eco-friendly management of major pests of yard long bean, Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt′′ was carried out in the Instructional farm of College of Agriculture, Padannakkad, Kasaragod during two seasons viz., kharif (May to August) and rabi (September to December) in the year 2016. The vegetable cowpea variety ‘Lola’ released by KAU was selected for the study. The study was undertaken with an intention to find out the efficacy of different microbial agents, neem based and biorational insecticides. The experimental design was RBD with 9 treatments and three replications. The treatments included; T1- Beauveria bassiana (liquid formulation @ 107 spores/ml of water), T2- Metarhizium anisopliae (liquid formulation @ 107 spores/ml of water), T3- Lecanicillium lecanii (liquid formulation @ 107 spores/ml of water), T4- Bt formulation 2× 108 cfu/ml @ 1 ml/l of water, T5- Neem based insecticide (Azadirachtin 1 per cent @ 5 ml/l of water), T6- Neem oil emulsion 5 per cent (50 ml/l of water), T7- Spinosad 45 SC @ 0.4 ml/l of water, T8- Malathion 50 EC @ 2ml/l of water (standard check), T9- Absolute control. All the treatments were imposed at fortnightly intervals just after the initial attack of pest was seen and observations were recorded at weekly intervals corresponding to standard weeks. The data were subjected to square root transformation and analyzed using ANOVA. After three consecutive sprays of Spinosad 45 SC @ 0.4 ml/l of water at fortnightly intervals there was complete reduction of pod borer larvae during kharif and rabi season. The percentage of flowers and pods infested by pod borer larvae were also reduced completely and no infestation was noticed after three consecutive sprays of Spinosad during both seasons. Thus it was found that Spinosad 45 SC was effective in reducing the number of pod borers, percentage of flowers infested and percentage of pods infested. During kharif season, Beauveria bassiana was found to be the most effective treatment in reducing the nymphs and adults of pod bugs with minimum number of 0.56 bugs per plant followed by 0.63 bugs in T5 compared to T9 with 7.46 bugs per plant after three consecutive sprays. During rabi season, Azadirachtin 1 per cent showed no incidence of pod bugs after three sprays and Neem oil 5 per cent consistently reduced number of bugs to zero on 15 days after third spray whereas T9 exhibited maximum number of 4.26 bugs/plant. The effect of Beauveria bassiana was lowered during rabi season. It might be due to the inability of Beauveria spores to germinate and cause infection during that season because of inadequate humidity. Azadirachtin 1 per cent incessantly lowered the per cent of pods infested by pod bugs to zero even after two sprays during both seasons and leaf miner attacked leaves was also found minimum in plot treated with Azadirachtin 1 per cent (0.63 leaves/plant) compared to T9 (7.12 leaves/plant). The aphid population on shoots and per cent of aphid infestation on shoots were found to be zero after three consecutive sprays of Lecanicillium lecanii at fortnightly intervals during kharif season. Lecanicillium lecanii also lowered the aphid population on pods and caused exorbitant reduction in the percentage of infested pods during both seasons after three sprays. Though pod length is an inheriting character, maximum length of 42.30cm and 48.40cm was shown by T7 during kharif and rabi seasons respectively. During both seasons viz., kharif and rabi, the total and marketable yield was high in T7 with highest benefit – cost ratio of 1.50 and 2.26 respectively.
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    Insecticide resisitance in cowpea aphid, Aphis craccivora (koch) and its management
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 2018) Jangam Hampaiah; Ambily Paul
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    Biology and predatory potential of rhynocoris marginatus (FAB.) (hemiptera: reduviidae) on insect pests of cowpea
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2018) Femi Mohasina, M; Smitha, M S
    Insect pests form major threat to cowpea cultivation often causing a yield loss of 30 – 60 per cent. Even though insecticides are the most popular tools for pest management in cowpea their application throughout the crop period is not economically, socially and ecologically advisable. Biological control methods could be an option to reduce the insecticide load on the crop that is often constrained by lack of natural enemies that can effectively control several pests at a time. Members of the predatory family Reduviidae are gaining increased attention due to their broad host range as well as high density responsiveness. Rhynocoris marginatus belonging to the subfamily Harpactorinae of the family Reduviidae (Order: Hemiptera) has been found promising in managing a wide range of insect pests in various legume crop ecosystems. This predator reportedly has preference to lepidopteran caterpillars followed by nymphs and adults of hemipterans, two major insect groups regularly occurring in cowpea. In this context, the work on “Biology and predatory potential of Rhynocoris marginatus (Fab.) (Hemiptera: Reduviidae) on insect pests of cowpea” was carried out in the Department of Agricultural Entomology, College of Horticulture, Vellanikkara. The project aimed to study the biology and predatory potential of R. marginatus on leaf eating caterpillar of cowpea, Spodoptera litura (Fab.); to evaluate the predatory potential of R. marginatus on Aphis craccivora (Koch) and S. litura under caged condition and to study the field efficiency of R. marginatus against insect pests of cowpea. The egg stage recorded an average incubation period of 6.80 ± 0.91 days. It took 32.90 ± 1.81 days to complete nymphal development in five instars. Adult female lived longer than male. The preoviposition period was 14 ± 1.30 days and during the oviposition period of 66.13 ± 6.27 days, it laid 8.60 ± 0.97 batches of egg mass with mean fecundity of 377.20 ± 45.52 eggs. The predatory potential of second, third, fourth and fifth nymphal instars and adult were studied on third instar larvae of S. litura at prey densities, 2, 4, 6, 8 and 10 prey/ predator. Predation had strong correlation with the prey density and stage of the predator. When the number of prey killed by the predator was plotted against the prey density a Holling’s type II functional response curve was obtained. The predatory potential was also assessed against cowpea aphid, A. craccivora and leaf eating caterpillar, S. litura on caged cowpea plants. The third instar nymph of R. marginatus was released on cowpea plants in cages artificially infested with aphid and compared with control. Aphid population in predator released cages were significantly less than that in control. The predator was able to kill all the released third instar larvae of S. litura completely within four days. Field evaluation was carried out by releasing the predator at 30, 50 and 70 days after sowing of the crop. The release of the predator significantly reduced the aphid population on cowpea. The infestation by pod borer Maruca vitrata (Fab.) and pod bug, Riptortus pedestris (Fab.) were negligible. However, the number of pods damaged by pod bug was comparatively less in predator released field. At the same time, the predator had no impact on the population of coccinellid predators in the field.
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    Evaluation of the effect of mineral nutrition in the management of major pests of cowpea
    (Department of Agricultural Entomology, College of Agriculture, padannakkad, 2017) Vishnu Priya, T A; Sreekumar, K M