Eliana Alcantra

Efeito de indutores da resistência e cultivares de algodão no comportamento de Aphis gossypii

Aimed to evaluate the effect of silicon, acibenzolar-S-methyl (ASM) and cultivars of cotton plant on the behavior of A. gossypii. Were conducted non-preference trials with apterous aphid and with winged aphid, both with nine treatments arranged in a factorial scheme 3 (inductors: Silicon ASM and Control) x 3 (cultivars BRS Verde, BRS Rubi and Safira), with thirteen replications. The treatments were distributed in a factorial scheme 3 (cv. BRS Verde, BRS Safira and BRS Rubi) x 3 (silicon, ASM and control) with thirteen replicates. Silicic acid at the dosage equivalent to 3 t ha -1 and 0.2% ASM were tested. For the test with apterous aphid, after 14 days from the application of the inducers, leaf sections of each treatment were placed into Petri dishes forming an arena where 24 adults aphid were released. The number of adults and nymphs of the aphid was evaluated after 24; 48 and 72 hours after release. For the second test, after 14 days from the application of the inducers, winged aphids were released randomly on the plants grown in an acclimatized chamber. After 24; 48 and 72 hours from the release, the number of winged adults and of nymphs present on the plants was evaluated. From the results, the both cv. Verde and Rubi were less infested in relation to Safira and the application of silicon did not affect the preference of A. gossypii. However the product ASM proved viable and could contribute to the reduction of the colonization of the plants by aphids.

Aspectos biológicos e capacidade predatória de Ceraeochrysa cubana (Hagen, 1861) (Neuroptera: Chrysopidae) alimentada com Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) em diferentes temperaturas

Avaliou-se alguns aspectos biologicos e a capacidade predatoria em tres temperaturas de larvas de Ceraeochrysa cubana (Hagen) alimentadas com ninfas de terceiro e quarto instares de Aphis gossypii Glover. Os experimentos foram conduzidos em câmaras climaticas a 22; 25 e 28±1oC, 70±10% de UR e fotofase de 12 horas. O delineamento experimental foi inteiramente casualizado com tres tratamentos (temperaturas), com 40 repeticoes. Verificou-se reducao no tempo de vida das larvas nos tres instares, das fases de pre-pupa e pupa em funcao do aumento da temperatura. As maiores viabilidades foram obtidas a 22oC. Para larvas de primeiro instar nao houve diferenca significativa no consumo medio diario nas tres temperaturas. Para larvas de segundo e terceiro instares houve maior consumo diario de pulgoes na maior temperatura. O numero medio total de afideos consumido por larvas de primeiro e segundo instares nao diferiu em funcao do aumento da temperatura. Para larvas de terceiro instar o maior consumo total foi observado a 22oC, e o menor a 25oC. Na menor temperatura observou-se maior consumo medio total na fase larval.

Effect of silicon and acibenzolar-s-methyl on colored cotton plants infested or not with Aphis gossypii Glover (Hemiptera, Aphididae)

Effect of silicon and acibenzolar-s-methyl on colored cotton plants infested or not with Aphis gossypii Glover (Hemiptera, Aphididae). The aphid Aphis gossypii is an insect pest that causes damage mainly at the beginning of the cotton plant development. The effect of resistance inductors silicon and acibenzolar-s-methyl (ASM) on the development of colored cotton plants were researched in the presence and absence of A. gossypii. Three colored cotton cultivars were sown in pots and individually infested with 25 apterous aphids, 13 days after the application of the inductors. Fifteen days after plant emergence, the silicon was applied at a dosage equivalent to 3 t/ha and acibenzolar-s-methyl in 0.2% solution of the product BION 500®. After 21 days of infestation the following parameters were evaluated: plant height, stem diameter, dry matter of aerial part and root, and total number of aphids replaced. It was verified that the plant height was reduced in the presence of aphids and all variables were negatively affected by the application of ASM. However, silicon did not affect plant development.