The effects of treatments against Bactrocera oleae
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| The effects of treatments against Bactrocera oleae (Gmelin) on the entomo-fauna of the olive ecosystem
Nino Iannotta*, Tiziana Belfiore**, Pietro Brandmayr**, Stefano Scalercio* *C.R.A. Institute for Olive Growing - 87036 Rende, Cosenza, ITALY **Department of Ecology, University of Calabria - 87036 Rende, Cosenza, ITALY Abstract: Only a limited number of studies have examined the efficacy and environmental effects of treatments against Bactrocera oleae in organic production of olives, especially in terms of the insect community present in these ecosystems. Herein, we compared the effects of a conventional insecticide (dimethoate) with a plant protection system allowed by organic legislation (mass trapping plus rotenone), and an untreated, control field against B. oleae. The experiments were performed in the Calabria region in Italy (on the Ionic side of Cosenza), in a grove (Mirto-Crosia) with extensive active insect infestation. In two conventionally treated fields with a surface area of 2 hectares each, two treatments were performed (in August and September) utilizing dimethoate (150 g in 100 liters water). In another 2 hectare area, mass-trapping devices (attract and kill) were installed and treatment with rotenone (Rotena 300 g in 100 l water) was performed in September. The entomo-fauna present in the different areas was evaluated by insect capture utilizing cromotropic traps. The integrated protection system (mass-trapping plus rotenone treatment) led to a reduction in the total number of insects in comparison to the traditional method (dimethoate treatment). It proves the negative effect of organic system on the olive ecosystem entomo-fauna. Key words: Bactrocera oleae, organic farming, entomo-fauna, olive agroecosystem, diversity. Introduction During recent years, more ecologically friendly olive growing techniques have become relatively widespread and are used in both integrated and organic farming methods. These cultivation methods are guided by regulations that list the active ingredients and describe how they should be applied. The regulations for organic farming techniques are instituted by experimental evaluation of efficacy, although only a few studies have examined their environmental impact, with particular reference to the entomo-fauna in olive groves. It is well-known that, especially in southern regions, olive fruit fly (Bactrocera oleae) is a key phytophagous insect that massively infest olive groves and provoke heavy damage. Thus, appropriate control measures are essential. In the present report, we evaluated the impact of treatment against B. oleae on several groups of arthropod fauna present in olive groves carried out with conventional pesticides (dimethoate) for integrated cultivation compared to mass-trapping and rotenone, which is allowed in organic farming. Materials and Methods The analyses were carried in an olive field in the Calabria in southern Italy where infestation by olive fruit flies is particularly extensive (Mirto-Crosia in Cosenza) due to climatic conditions that are particularly favorable for its development. Two fields treated by conventional methods, each with a surface area of 2 hectares, differed in their varietal composition (A, several cultivars; B, single cultivar); two treatments using dimethoate (150 gm in 100 liters water) were made in August and September. In another field (C) with the same surface area, biological traps for mass-trapping were installed (150 per hectare; Agrisense attract and kill model). In this case, rotenone treatment (300 g Rotena in 100 l water) was performed in September. Evaluation of entomo-fauna in the different areas was carried out by capture using cromotropic traps. The taxonomic groups examined were among those most frequently encountered in these groves and included Neuroptera, Diptera Syrphidae, Coleoptera Coccinellidae, Lepidoptera, and Mecoptera Panorpidae. The results are presented as the mean of the number of individuals captured in traps per unit of time exposed (activity density; Brandmayr and Brunello Zanitti, 1982). The meteorological conditions of the fields were also monitored using electronic equipment. Results The data are summarized in Figure 1. From these results, it is evident that the mass-trapping device is less efficient compared to the other two conventional treatment groups. Nonetheless, no differences were observed regarding the number of macrotaxa present. Table 1 detailed the data relevant to the five macrotaxa found, from which it can be deduced that mass-trapping led to a smaller number of Lepidoptera, Neuroptera, Diptera, and Coleoptera; only Mecoptera showed a greater number of individuals. Almost all the species of Lepidotteri were present at a lower frequency in area C, and the Shannon index, a measure of diversity, was also lower in the same area. 
Figure 1. Overall biomass observed in the three treatment areas. Table 1. Abundance of selected macrotaxa within surveyed sites reported as density of activity (DA), DA = (individuals / n° of pitfall traps) x (10 / days of traps exposure).
Discussion Our results demonstrate that mass-trapping integrated with rotenone leads to a more efficient reduction in the number of insects present compared to treatment with dimethoate. In particular, from the taxonomic groups the number of Lepidoptera captured was lower in the mass-trapping field (Table 2). A similar trend was observed regarding the number of Coccinellidae, Syrphidae, and Neuroptera. Only the number of Mecoptera Panorpidae was higher in field C. In conclusion, mass-trapping combined with rotenone for control of olive fruit flies in organic farming provokes negative effects on the entomo-fauna in olive groves. The negative effects of mass-trapping were even greater with respect to conventional pesticide treatments. Table 2. Species of Lepidoptera present at the three treatment areas.
References Bagnoli, B. 2000: Indagini sull’impatto di dispositivi per la cattura massale di adulti di Bactrocera oleae sull’entomofauna utile dell’oliveto. Prog. Reg. A.R.S.I.A. Firenze. Brandmayr, P. & Brunello Zanitti, C. 1982: Le comunità a Coleotteri Carabidi di alcuni Querco-Carpineti della bassa pianura del Friuli. Quaderni sulla “Struttura delle Zoocenosi Terrestri”. 4. I boschi della Pianura Padano-Veneta: 69-124. Castro Rodas, N. 2004: Individuazione di bioindicatori entomologici nell’agroecosistema oliveto. Tesi di Perfezionamento. Scuola Superiore S. Anna, Classe di Scienze sperimentali settore di Agraria. Castro Rodas, N. & Petacchi, R. 2002: Risultati preliminari sull’individuazione di bioindicatori entomologici nell’agroecosistema oliveto. Atti XIX Congresso Italiano di Entomologia, Catania, 10-15 giugno 2002: 267-272. Iannotta, N. 2003: La difesa fitosanitaria ed i parassiti. In: AA.VV., OLEA, Trattato di olivicoltura, pp. 391- 407. Petacchi, R., & Minocci, A. 1993: Analisi sulla composizione dell’entomofauna dell’oliveto e sull’impatto provocato da diverse strategie di lotta antidacica. Atti Convegno su “Tecniche,norme e qualità in olivicoltura”, Potenza, 15-17 dicembre 1993: 509-525. Pimentel, D.A., Stachoww, U., Takacs, D.A., Brubaker, H.W., Dumas, A.R., Meaney, J.J., O’Neil, J.A.S., Onsi, D.E. & Corsilius, D.B. 1992: Conserving biological diversity in agricultural and forestry systems. Bioscience 42: 354-364. Ricketts, T.H., Daily, G.C. & Ehrlich, P.R. 2002: Does butterfly diversity predict moth diversity? Testing a popular indicator taxon at local scales. Biological Conservation 103: 361-370. |