Effectiveness of some bioinsecticides against bean weevil (Acanthoscelides obtectus Say) in field conditions

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1 Vegetable Growing ORIGINAL SCIENTIFIC PAPER Effectiveness of some bioinsecticides against bean weevil (Acanthoscelides obtectus Say) in field conditions Vinelina Yankova Maritsa Vegetable Crops Research Institute, 32 Brezovsko shosse Str., Plovdiv 4003, Bulgaria, Abstract During the period at Maritsa Vegetable Crops Research Institute, Plovdiv, trials for limiting the invasion of Acanthoscelides obtectus Say in the field as biological activity of five bioproducts were studied. The effectiveness was recorded on the basis of the index of infestation on seeds after harvesting beans in single, twofold and threefold treatment at an interval of 7 days. Laboratory trials were carried out for establishment the insecticidal effect of products included in the study against bean weevil adults. High toxicity against bean weevil in laboratory conditions were established in product Lirosect 2 EC 0.12% (88.00%). In field conditions the highest effectiven ess was determined in threefold treatment by phytopesticides NeemAzal T/S 0.3% % and Pyrethrum 0.05% %. Key words: Acanthoscelides obtectus, effectiveness, bioinsecticides, common bean, field Introduction The common bean is crop in which pests are found in all phenophases of crop development as well as in and seed storage. Dangerous pest in the common bean, which causes serious damage to the seed is bean weevil (Acanthoscelides obtectus Say) (Coleoptera: Bruchidae). The attack was in the field in the beginning of seed ripening. As a result of damages on the seed caused by larvae their nutrition and taste quality is worsen (Staneva, 1995; Ospina et al., 1981). The laying of A. obtectus in the field is confined in a very short period before harvesting of the crop. This relatively short period of time is appropriate for conducting of plant-protection practices in the field (Schmale et al., 2002). Experiments to control adults for establishing the various insecticides efficacy under controlled conditions was conducted (Cindea, 1987). In recent years the use of bioproducts is an alternative possibility to control pests in modern ecological technologies. Avermectins are natural products produced by microbiological synthesis of soil microorganism Streptomyces avermitilis. This bioinsecticides are wide spectrum and have stomach and contact action. Many plant extracts have phytopesticides properties. These properties are due to the natural chemical compounds - alkaloids, esters, glycosides, etc being part of plant composition. Neale (1997) refers the plant extracts to the group of biopesticides. Some medicinal plants that have repelent, atractant or deterent action against bean weevil were examined (Ignatowicz and Gersz, 1997). At present, prepared plant-based biopesticides with good insecticide qualities are produced (Adis et al., 1997). Their successful use requires to have a knowledge about their action mechanism and effectiveness. The purpose of this study was to establish the efficacy of some bioinsecticides and possibilities for control on bean weevil (Acanthoscelides obtectus Say) under field conditions. Material and Methods The study was conducted during the period in Maritsa Vegetable Crops Research Institute, Plovdiv. 614

2 Povrdarstvo Laboratory experiment: Pot experiments under laboratory condition by the plunge method for determination toxicity of including insecticides against bean weevil adults were conducted. Bean leaves with working solution were treated. Treatments: Decis 2.5 EC 0.04% (a. i. deltamethrin) (standard) Bayer CropScience; Lirosekt 2 EC 0.12% (a. i. avermectin) strain synthesis of Streptomyces avermitilis Biovet Peshtera; Pyrethrum 0.05% (a. i. pyrethrin) extract of Chrysanthemum cinerariaefolium:asteraceae - Andermatt Biocontrol; Pyros 0.08% (a. i. pyrethrin), also based on an extract of C. cinerariaefolium - Serbios; Rotena 0.3% (a. i. rothenon), extract of Derris elliptica: Leguminosae - Serbios; NeemAzal T/S 0.3% (a. i. azadirachtin), extract of Azadirachta indica:meliaceae - Trifolio M. Each treatment is in two replications when adults were put in plastic boxes with an isolator , respectively or total of 2x50 individuals for variant. Mortality of testing individual is recorded 24 h after treatment. Untreated bean leaves were used as control. Effectiveness (%) of laboratory testing products to adults of bean weevil based on recorded mortality is calculated using the formula of Abbott (1925). Field experiments: Field vegetation experiments under natural pest population density in bean variety Oreol were conducted. Single, twofold and threefold treatment with insecticides in laboratory studies at an interval of 7 days are done. Consumption of working solution was 1000 l/ha. First treatment was conducted at the beginning of pods ripening. Density of 2 adults per 100 strokes with entomological bag was established. Untreated plants were used as control. Index of attack on seeds is determined 50 days after harvesting beans by the formula of McKinney (1923). A hundred pods in complete ripeness were tested in single, twofold and threefold treatment. Effectiveness is calculated using a modified formula by Abbott, based on the index of attack. Results and discussion The bean weevil starts to lay eggs on bean pods in the beginning of pods ripening. This short period is very important because it is determining moment for the rate of infestation on the bean seeds and the economical damage size. The effectiveness in application of different insecticides against bean weevil depends on their action towards the adults in definite degree. Results from the pod experiment performed in laboratory conditions, demonstrate that the bioinsecticide Lirosect 2 EC 0.12% % shows the strongest toxic effect which is better than that recorded in the standard Decis 2.5 EC 0.04% %. Comparatively lower toxicity is recorded in the phytopesticides: Pyrethrum 0.05% %, NeemAzal T/S 0.3% %, Rotena 0.3% % and Pyros 0.08% % (Table 1). Comparatively high efficacy was established in the conducted laboratory trials of the product Lirosect 2 EC 0.12% % that is higher than the recorded in the standard Decis 2.5 EC 0.04% % (Figure 1). Table 1. Toxicity of some bioinsecticides towards the bean weevil (Acanthoscelides obtectus Say) in laboratory conditions Treatment Mortality, % (concentration) average Control (untreated) Decis 2.5 EC 0.04% (standard) Lirosect 2 EC 0.12% NeemAzal T/S 0.3% Pyrethrum 0.05% Pyros 0.08% Rotena 0.3% hrvatski i 5. međunarodni simpozij agronoma 615

3 effectiveness, % effectiveness, % Vegetable Growing 100,00 90,00 80,00 70,00 60,00 50,00 40,00 30,00 20,00 10,00 0,00 Decis 2.5 EC 0,04% (standard) Lirosect 2 EC 0,12% Neem Azal T/S 0,3% Pyrethrum 0,05% Pyros 0,08% average Rotena 0,3% Figure 1. Effectiveness of some bioinsecticides against bean weevil (Acanthoscelides obtectus Say) (laboratory experiment) The synthetic pyrethroid Decis 2.5 EC 0.04%, included as a standard shows good effectiveness and as a result of that a decrease in the index of infestation and percentage damaged seeds is observed (Table 2). A satisfying effectiveness is recorded in this product at twofold treatment and high one in threefold application 79.42% and 86.68%, respectively (Figure 2). 100,00 90,00 80,00 70,00 60,00 50,00 40,00 30,00 20,00 10,00 0,00 Decis EC 0,04% (standard) Lirosect 2 EC 0,12% Neem Azal T/S 0,3% Pyrethrum 0,05% Pyros 0,08% Rotena 0,3% II treatment I treatment III treatment Figure 2. Effectiveness of some bioinsecticides against bean weevil (Acanthoscelides obtectus Say) in field conditions The results of application in Lirosect 2 EC 0.12% show that action of this bioinsecticide is not satisfactory with respect to the degree of damage in single and twofold treatment. The situation is the same in the recorded effectiveness where the values are comparatively low 46.74% and 69.77%, respectively in single and twofold treatment. The values of these three characters are good in threefold treatment of the sowing low percentage of the damaged seeds (3.51%), low index of infestation (2.01%) and comparatively high effectiveness (82.39%) (Table 2). 616

4 Povrdarstvo Table 2. Damages on common bean seeds variety Oreol by bean weevil (Acanthoscelides obtectus Say) in different number of treatments with insecticides in the field Treatment Number of treatment Damages on seeds Percentage of infested seeds Index of infestation, % averag averag e e Control (untreated) Lirosect 2 EC 0.12% Lirosect 2 EC 0.12% Lirosect 2 EC 0.12% NeemAzal T/S 0.3% NeemAzal T/S 0.3% NeemAzal T/S 0.3% Pyrethrum 0.05% Pyrethrum 0.05% Pyrethrum 0.05% Pyros 0.08% Pyros 0.08% Pyros 0.08% Rotena 0.3% Rotena 0.3% Rotena 0.3% The analysis of these results gives a reason for comparisons. The products NeemAzal T/S 0.3% and Pyrethrum 0.05% are with high effectiveness 87.72% and 85.64%, respectively in threefold spraying among the phytopesticides. In treatment with NeemAzal T/S applied twofold and threefold the efficacy is in close values 83.08% and 87.72%. The percentage of the damaged seeds is also low 5.17% and 4.19%. The effectiveness recorded in the products Pyros 0.05% and Rotena 0.3% in threefold spraying is comparatively lower 81.04% and 79.50%, respectively than that recorded in the standard Decis 2.5 EC 0.04% (81.22%). However higher effectiveness in twofold spraying with these two phythopesticides compared to that of the standard is observed. Phytopesticides NeemAzal T/S 0.3% and Pyrethrum 0.05% as well as the bioinsecticide Lirosect 2 EC 0.12% demonstrate good results in threefold application. The effectiveness recorded in twofold and threefold spraying with these products is higher than that in application of the standard Decis 2.5 EC 0.04 %. The above mentioned bioinsecticides could be use in plant protecting systems for control on bean weevil in field conditions. Conclusions The product Lirosect 2 EC 0.12% (88.00%) demonstrates high toxicity on adults from bean weevil in laboratory conditions. The phytopesticides NeemAzal T/S 0.3% (87.72%) and Pyrethrum 0.05% (85.64%) demonstrate the highest effectiveness in threefold treatment in field conditions. Acknowledgement This article was published thanks to the participation in Human Resources Development Operational Programme financed by the ESF under grant BG051PO001/07/3.3-02/ hrvatski i 5. međunarodni simpozij agronoma 617

5 Vegetable Growing References Abbott, W. S. (1925). A method of computing the effectiveness of an insecticide. Journal of Economic Entomology 18: Adis J. A., Paarmann W., da Fonesca C. R.V., Rafael J. A. (1997). Knockdown efficiency of natural pyrethrum and survival rate of living arthropods obtained by canopy fogging in central Amazonia, London, UK. Cindea E. (1987). Toxicity of some pesticides for the adults of Acanthoscelides obtectus Say. Analele Institutului de Cercetari pentru Legumicultura si Floricultura, vol. 8: Vidra,Romania. Ignatowicz S., and Gersz M. (1997). Extracts of medical herbs as repellents and attractamts for the dry bean weevil, Acanthoscelides obtectus Say (Coleoptera:Bruchidae). Polsk. Pismo Ent., 66(1-2): McKinney, H. H. (1923). A new system of grading plant diseases. Journal of Agricultural Research 26: Neale M. C. (1997). Biopesticides harmonization of registration requirements within EU Directive 91/44 an industry view. Bull. OEPP/EPPO Bull., vol. 27(1): Ospina H. F., van Schoonhoven A., Cardona M. C., Garsia J. E. (1981). Principales insectos que atacan el grano de frijol almacenado y su control. UNDP/CIAT 75/084, 2a. Edicion, 33. Cali, Colombia. Schmale I., Wäckers F. L., Cardona C., Dorn S. (2002). Field infestation of Phaseolus vulgaris by Acanthoscelides obtectus (Coleoptera:Bruchidae), parasitoid abundance, and cosequences for storage pest control. Environm. Ent. 31 (5): Staneva E. (1995). Protect the bean of the bean weevil. Agriculture, 1: