L. R. D. Faroni

Efficacy of ozone as a fungicidal and detoxifying agent of aflatoxins in peanuts

BACKGROUND Peanut contamination by fungi is a concern of processors and consumers owing to the association of these micro-organisms with quality deterioration and aflatoxin production. In this study the fungicidal and detoxifying effects of ozone on aflatoxins in peanuts was investigated. Peanut kernels were ozonated at concentrations of 13 and 21 mg L⁻¹ for periods of 0, 24, 48, 72 and 96 h. RESULTS Ozone was effective in controlling total fungi and potentially aflatoxigenic species in peanuts, with a reduction in colony-forming units per gram greater than 3 log cycles at the concentration of 21 mg L⁻¹ after 96 h of exposure. A reduction in the percentage of peanuts with internal fungal populations was also observed, particularly after exposure to ozone at 21 mg L⁻¹. A reduction in the concentrations of total aflatoxins and aflatoxin B1 of approximately 30 and 25% respectively was observed for kernels exposed to ozone at 21 mg L⁻¹ for 96 h. CONCLUSION It was concluded that ozone is an important alternative for peanut detoxification because it is effective in controlling potentially aflatoxigenic fungi and also acts in the reduction of aflatoxin levels in kernels.

Potential of Acarophenax lacunatus (Prostigmata: Acarophenacidae) as a biological control agent of Rhyzopertha dominica (Coleoptera: Bostrichidae)

A recent report of the parasitic mite species Acarophenax lacunatus (Cross and Krantz) (Prostigmata: Acarophenacidae) attacking populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) led to the present investigation. Maximum female size and average number of progeny per female mite were assessed at eight different temperatures (ranging from 20 to 41°C) and 60% r.h. using R. dominica as the host. The ability of the mite species to suppress eggs, first instar larvae, and adults of R. dominica was assessed at 30°C and 60% r.h. The largest female sizes of the mite and progeny numbers were obtained around 30°C (259 μm and 17 offspring/female respectively) with minimum values obtained at the most extreme temperatures used in this study. Mite densities of at least four individuals per 500 ml jar containing 50 adults of R. dominica, resulted in almost complete suppression of eggs, first instar larvae, and adults of the host species after 45 days. This same range of mite densities led to reductions of wheat weight losses of 15 and 25% after 45 and 60 days after infestation respectively. Acarophenax lacunatus shows good potential as a biological control agent of R. dominica.

Resistance of stored-product insects to phosphine

The objectives of this work were to assess phosphine resistance in insect populations (Tribolium castaneum, Rhyzopertha dominica, Sitophilus zeamais and Oryzaephilus surinamensis) from different regions of Brazil and to verify if the prevailing mechanism of phosphine resistance in these populations involves reduced respiration rates. Sixteen populations of T. castaneum, 15 of R. dominica, 27 of S. zeamais and eight of O. surinamensis were collected from 36 locations over seven Brazilian states. Each population was tested for resistance to phosphine, based on the response of adults to discriminating concentrations, according to FAO standard method. For each insect species, the production of carbon dioxide of the most resistant and of the most susceptible populations was inversely related to their phosphine resistance. The screening tests identified possible phosphine resistant populations. R. dominica and O. surinamensis were less susceptible to phosphine than the other two species. The populations with lower respiration rate showed a lower mortality at discriminating concentration, possibly related to a phosphine resistance mechanism. Phosphine resistance occurs in stored-product insects, in different regions of Brazil, and the resistance mechanism involves reduced respiration rate. Index terms: Oryzaephilus surinamensis, Rhyzopertha dominica, Sitophilus zeamais, Tribolium castaneum, fumigant resistance, respiration rate.Os objetivos deste trabalho foram avaliar a resistencia a fosfina, em populacoes de insetos ( Tribolium castaneum , Rhyzopertha dominica , Sitophilus zeamais e Oryzaephilus surinamensis ), de diferentes regioes do Brasil, e verificar se o mecanismo predominante de resistencia a fosfina, nessas populacoes, envolve a reducao das taxas respiratorias. Dezesseis populacoes de T. castaneum , 15 de R. dominica , 27 de S. zeamais e oito de O. surinamensis foram coletadas em 36 locais de sete estados brasileiros. Cada populacao foi testada quanto a resistencia a fosfina, com base na resposta dos adultos a concentracao discriminante, de acordo com o metodo padrao da FAO. Para cada especie de insetos, as producoes de dioxido de carbono da populacao mais resistente e a da mais suscetivel foram inversamente relacionadas a resistencia a fosfina. Os testes de deteccao identificaram possiveis populacoes resistentes a fosfina. R. dominica e O. surinamensis foram menos suscetiveis a fosfina do que as outras duas especies. As populacoes com menor taxa respiratoria apresentaram menor mortalidade a concentracao discriminante, o que esta possivelmente relacionado ao mecanismo de resistencia a fosfina. A resistencia a fosfina ocorre em insetos de produtos armazenados, em diferentes regioes do Brasil, e o mecanismo de resistencia envolve a reducao da taxa respiratoria.

Avaliação da qualidade tecnológica do feijão durante o armazenamento

No presente trabalho, conduziram-se os estudos para avaliar a qualidade tecnologica dos graos de feijao, durante quatro meses de armazenamento, em condicoes ambientais e na presenca do inseto-praga Acanthocelides obtectus. Foram utilizados graos de feijao com teor de agua de aproximadamente 18 (%b.s.). Para infestacao do produto, foram colocados 20 insetos adultos em cada pote de vidro, que foi fechado com uma tampa telada. As analises tecnologicas foram realizadas no produto com e sem o inseto-praga, no inicio do experimento e a cada 28 dias, totalizando 112 dias de armazenagem. O teste de coccao foi realizado com aparelho de Mattson utilizando-se amostras previamente imersas por 12 horas. Para a determinacao da absorcao de agua, as amostras foram submetidas a imersao em agua destilada, durante um periodo de 12 horas, em diferentes temperaturas (20, 30, 40 e 50 °C). Com base nos resultados obtidos, pode-se concluir que a presenca do inseto-praga causa a deterioracao intensa dos graos de feijao, resultando na reducao da sua qualidade tecnologica. A temperatura de embebicao aumenta a absorcao de agua dos graos de feijao, sendo intensificada pela presenca do inseto-praga ao longo do periodo de armazenamento.

Eficácia biológica de bifentrina aplicado em milho armazenado sob diferentes temperaturas

Considering the high temperatures in the granary ships alongwith the transporting mat, the objective of this paper was to evaluate the influence of the temperature at the moment of spraying on the biological effectiveness of the bifenthrin. For the purpose the insecticide was sprayed on maize grains inside a climatic chamber maintained at the temperatures of 25, 30, 35, 40, 45 and 50 oC with relative humidity around 55%. After the spraying and every fifteen days up to 90 days, analyses of the biological effectiveness were made by using insects of the Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). A decreasing tendency of the biological effectiveness of the bifenthrin was observed with the increase of the air temperature at the moment of spraying and with the increased time of maize storage, resulting in a smaller mortality of the insect-pest.

Postharvest quality of ozonized "nanicão" cv. bananas

This study was done to analyze the physic-chemical, microbiological and sensory qualities of the banana, after being either dry or wet treatment with ozone. For dry processing, the fruits were directly fumigated with ozone for 30 min. The wet treatment included the ozonization of water for 20 min followed by immersion of the fruit in the ozonized water for 10 min. In both treatments, the utilized gas concentration and flow were 0.36 mg L-1 and 1.5 L min-1, respectively. The quality of the fruits was evaluated at the beginning of storage and after 3; 6; 9 and 12 days. The variables analyzed were: fresh mater loss, total titratable acidity, total soluble solids, pH, pulp/peel ratio, color index of the peel, rot severity, microbiological analysis (total fungi and yeast count) and sensorial analysis. In general, the fruits immersed in the ozonized water presented better quality, in reference to both the physico-chemical and microbiological parameters, as well as have good sensory acceptance among those tested. It could therefore be concluded that treatment with ozonized water is a new alternative for the postharvest handling of bananas.

Potential of Tyrophagus putrescentiae (Schrank) (Astigmata: Acaridae) for the Biological Control of Lasioderma serricorne (F.) (Coleoptera: Anobiidae)

This work investigated the potential of Tyrophagus putrescentiae (Schrank) (Astigmata: Acaridae) to control Lasioderma serricorne (F.) (Coleoptera: Anobiidae) in the laboratory. L. serricorne is the most destructive insect pest ever found on stored tobacco. The experimental delineation had 33 arenas being each experimental unit with 11 arenas of experiments with eggs, larva of L. serricorne with the density of T. putrescentiae maintained constant, where from 11 of these arenas, eight were for the analysis of predation and three to evaluate the natural mortality of the insect. The highest predation rate was found during the larval stage with, approximately, 54, 68 and 78% mortality of L. serricorne from the fourth until the sixty day of predation. These results indicated that it was possible to use the predatory mite T. putrescentiae in pest management programs of L. serricorne in the storage units of tobacco.

Nível de dano econômico de Sitophilus zeamais (M.) em trigo armazenado

Calcular o nivel de dano economico (NDE) para o principal inseto-praga Sitophilus zeamais (Motschulsky, 1895) do trigo armazenado, foi o objetivo deste trabalho. Para o calculo do NDE relacionaram-se o grau de infestacao e as perdas qualitativa e quantitativa dos graos, depois de tres meses de armazenamento. Utilizaram-se potes de vidro transparente de 2,5 L, com 1,5 kg de graos de trigo tipo durum, da safra de setembro/97, com teor de umidade de 12,5%. Os potes foram infestados com densidades populacionais de 0, 2, 10, 20, 30, 50, 100, 200 e 300 insetos da especie S. zeamais, em tres repeticoes, e entao armazenados por um periodo de 90 d, em câmaras tipo BOD, com temperatura de 27 oC e 65 ± 5% de umidade relativa. Logo depois do periodo de armazenamento tomava-se a temperatura da massa de graos e, em seguida, contava-se o numero de insetos adultos vivos e mortos. Os graos foram analisados quanto a perda de peso e a perda de qualidade (peso hectolitrico e teor de umidade). Tanto a massa final quanto o peso hectolitrico (PH) para cada nivel de infestacao, foram corrigidos para o teor de umidade inicial dos graos. Utilizando-se os dados do valor de mercado do grao de trigo importado e nacional, do custo de controle para fumigacao e do valor obtido pela inclinacao das curvas de regressao entre perda de peso (g) e PH (g 250 mL-1) em relacao a infestacao final de S. zeamais, calculou-se o NDE. Com base na reducao do peso da massa de graos, no peso hectolitrico e no valor de mercado do trigo, encontrou-se um NDE de 0,18 inseto kg-1 de grao.

Desenvolvimento do método de extração sólido-líquido com partição em baixa temperatura para determinação de inseticidas em grãos de milho ozonizados

The objective of this study was to optimize and validate a solid-liquid extraction method with low-temperature partitioning (SLE/LTP) for the analysis of pesticides. This method was coupled with gas chromatography (GC/ECD) and used to evaluate the degradation of bifenthrin and pirimiphos-methyl in maize grains on exposure to ozone. The optimized SLE/LTP-GC/ECD method is simple, effective and consumes low quantities of the solvent. It can be routinely used for the determination of bifenthrin and pirimiphos-methyl in maize samples. The use of this method of analysis determined that the levels of the insecticides in maize grains were reduced on exposure of the grains to the ozone gas. The observed reduction in the levels of insecticide was directly proportional to the increase in the concentration of the ozone gas.

Ozone treatment for pesticide removal from carrots: Optimization by response surface methodology

The present study aimed to optimize ozone (O3) treatments, as gas and dissolved in water, to remove difenoconazole and linuron in carrots. We employed a central composite design to study three variables governing the efficacy of treatments: O3 concentration, temperature and treatment time. The temperature did not influence the efficacy of treatments. The removal percentage of pesticides increases with increases in ozone concentration and the time of treatment. O3 application promoted the removal of more than 80% of pesticides when the roots were exposed for approximately 120min at 5 and 10mgL-1, respectively, in treatments with O3 as gas and dissolved in water. After storage, pesticide removal was higher than 98% for difenoconazole and 95% for linuron. The degradation products from the pesticides resulting from treatment were monitored, but none were found. This is the first report demonstrating the removal of difenoconazole and linuron from carrots by ozone.