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| Author(s): |
Angelina Maria Marcomini
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2009-10-09 |
| Examining board members: |
José Djair Vendramim;
Moacir Rossi Forim;
Fábio Mazzonetto
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| Advisor: | José Djair Vendramim |
| Abstract | |
Neem extracts were nanoformulated with several types of nanoparticles and polymers in a tentative to reduce the biodegradation of neem active compounds and improve their residual effect. These nanoformulations were tested against Spodoptera frugiperda and their efficacy compared to a commercial product. The polymers poly(-caprolactone) (PCL), poly(- hidroxibutirate) (PHB) and poly(methyl methacrylate) (PMMA) were used in the quantities 0.25, 0.50 and 0.75g and two sorts of nanoparticles (capsules and spheres). Tween®80 and poly(vinyl alcohol) (PVA) were utilized as surfactants. The nanoformulations were produced as aqueous suspension and powder and further diluted before application. These nanoformulations were sprayed on artificial diet offered to second instars of S. frugiperda, and on corn plants which had their leaves offered to first instars. The efficacy of the different formulations was tested by assessing larval mortality and weight 10 days after treatment. When applied to artificial diets, reduced larval weight was observed, but four of them caused 40 to 46% mortality when applied on corn plants. The four most effective nanoformulations were further tested to evaluate their effects on S. frugiperda larval feeding preference and their residual effect. Three bioassays were set up using corn leaves treated with these, wich were offered to larvae at days 1, 3 and 7 after spraying (DAS), having the larval mortality and weight assessed 10 days after larval exposure. Simultaneously, choice tests for larval feeding preference (treatment x control) were carried out using corn leaf discs 1, 3 and 7 DAS. Feeding preference was evaluated by using a preference index calculated after the assessment of the leaf area fed by the larva 24h after exposure. The residual effect of the neem nanoformulations was lower than the commercial product evaluated. Only one nanoformulation and Organic Neem® were feeding deterrents to S. frugiperda, but only in the first day after the treatment. Although the nanoformulations caused larval mortality and weight reduction, their efficacy was not any better than that of the commercial product tested. (AU) | |