Resistência de genótipos de algodoeiro a Sclerotinia sclerotiorum pelos métodos straw test e imersão em ácido oxálico

The objective of this work was to evaluate the efficiency of the straw and oxalic acid tests to identify resistance levels of white and colored cotton (Gossypium hirsutum) genotypes to white mold (Sclerotinia sclerotiorum). Ten genotypes were evaluated: five with colored fiber, four with white fiber, and a white-fiber susceptible genotype. The genotypes MAB-1 with white fiber and MAC-2 with colored fiber were the most resistant to white mold, according to the immersion in oxalic acid and straw tests, respectively. These genotypes can be recommended as resistance sources for breeding programs. Both assessed tests are complementary to each other; however, the straw test is more efficient in evaluating the resistance of cotton genotypes to white mold.O objetivo deste trabalho foi avaliar a eficácia dos métodos “straw test” e imersão em ácido oxálico na identificação dos níveis de resistência do algodoeiro (Gossypium hirsutum) branco e colorido ao mofo-branco (Sclerotinia sclerotiorum). Foram avaliados dez genótipos: cinco de fibra colorida, quatro de fibra branca e um genótipo suscetível de fibra branca. Os genótipos MAB-1 de fibra branca e MAC-2 de fibra colorida foram os mais resistentes ao mofo-branco de acordo com os métodos imersão em ácido oxálico e straw test, respectivamente. Esses genótipos podem ser indicados como fontes de resistência para programas de melhoramento. Ambos os métodos analisados são complementares entre si; no entanto, o straw test é mais eficiente na avaliação da resistência dos genótipos de algodão ao mofo-branco

Effect of Brachiaria Grass on Vegetative Development of Teak

ABSTRACT Invasive plants are a limiting factor for the establishment of planted teak (Tectona grandis L.f.) forests, especially because most of them are planted on Urochloa decumbens Stapf degraded pastures. This study evaluated initial teak development applying different control alternatives for U. decumbens . Treatments were no weed control (T1), continuous control of U. decumbens (T2), U. decumbens control after six months of competition (T3), and 60 cm control of U. decumbens around the seedlings (T4). The experiment was established in a pasture, containing U. decumbens, in May 2012. The experimental design was randomized blocks, with four treatments and four replications. Twenty two months after transplanting the seedlings, all treatments in which seedlings had to compete with any weed competition had their growth compromised. Complete control of Urochloa was the best treatment for teak growth

Occurrence of Scaptocoris castanea Perty (Hemiptera: Cydnidae) damaging Azadirachta indica (Meliaceae) seedings in Brazil

Neem (Azadirachta indica) seedlings were found infested by the brown burrower bug, Scaptocoris castanea Perty, in December 2009, in the county of Tupaciguara, Minas Gerais state. Symptoms observed varied from leaf yellowing and stem drying, reduction in root size and number to plant death. This is the irst report of S. castanea attacking neem plants

Occurrence of Scaptocoris castanea Perty (Hemiptera: Cydnidae) damaging Azadirachta indica (Meliaceae) seedings in Brazil

Neem (Azadirachta indica) seedlings were found infested by the brown burrower bug, Scaptocoris castanea Perty, in December 2009, in the county of Tupaciguara, Minas Gerais state. Symptoms observed varied from leaf yellowing and stem drying, reduction in root size and number to plant death. This is the irst report of S. castanea attacking neem plants

Germination and mycelial growth of Bipolaris euphorbiae Muchovej & Carvalho as influenced by herbicides and surfactants

Bipolaris euphorbiae Muchovej & Carvalho é um forte candidato para o controle de Euphorbia heterophylla L. (amendoim bravo). Este fungo pode ser aplicado em combinação com herbicidas para controlar um maior espectro de espécies daninhas. Para tanto, experimentos laboratoriais foram realizados para verificar a possibilidade da utilização de mistura de tanque de esporos de B. euphorbiae e herbicidas ou surfatantes recomendados para a cultura da soja. Crescimento micelial e germinação de conídios foram avaliados em meio BDA acrescido dos herbicidas, nas concentrações recomendadas dos produtos comerciais, oxasulfuron (80 g/ha), glifosato (4 L/ha), bentazon (1.5 L/ha), fomesafen (1 L/ha), chlorimuron-ethyl (80 g/ha), lactofen (1 L/ha) e imazetaphyr (1 L/ha) e dos surfatantes Energic (2 ml/L), Aterbane (2,5 ml/L), Silwet L-77Ag (1 ml/L), Herbitensil (2 ml/L) e Natur L'óleo (10 ml/L). Diluições dos herbicidas de 50% e 25% foram avaliadas com um consumo de calda equivalente a 300 L/ha. Os surfatantes foram somente utilizados nas concentrações recomendadas. O crescimento micelial não foi afetado por bentazon e fomesafen e apenas levemente por oxasulfuron. Porém, glifosato, chlorimuron-ethyl, lactofen, Energic, Herbitensil, Silwet, e Aterbane o reduziram drasticamente. A redução observada com imazetaphyr foi intermediária e Natur L' óleo promoveu o crescimento micelial. Na presença dos surfatantes, observou-se que todos permitiram uma porcentagem de germinação equivalente àquela alcançada na presença de água. Energic e Herbitensil causaram um retardamento expressivo. Com Herbitensil, o processo germinativo iniciou somente aos 120 minutos. Com herbicidas, foi observado que somente na presença de glifosato e imazetaphyr a germinação dos conídios não seguiu a tendência observada com água, como ocorreu com os outros produtos testados.Bipolaris euphorbiae Muchovej & Carvalho can be combined with herbicide in order to control a large spectrum of weed species, being a strong candidate for the biocontrol of Euphorbia heterophylla L. (milk weed). The fungus release can be combined with herbicide in order to control a broader spectrum of weed species. Thus, laboratory experiments were set up to study the feasibility of using tank mixes of B. euphorbiae spores with herbicides or surfactants recommended for soybean. Mycelial growth and conidia germination were evaluated in PDA medium enriched with the herbicides oxasulfuron (80 g/ha), glyphosate (4 L/ha), bentazon (1.5 L/ha), fomesafen (1 L/ha), chlorimuron-ethyl (80 g/ha), lactofen (1 L/ha) and imazetaphyr (1 L/ha), and the surfactants Energic (2 ml/L), Aterbane (2.5 ml/L), Silwet L-77Ag (1 ml/L), Herbitensil (2 ml/L) and Natur L'óleo (10 ml/L). Dilution of the herbicides at 50% and 25% were evaluated based on solution consumption of 300 L/ha. The surfactants were evaluated only in the recommended concentrations. Mycelial growth was not affected by bentazon and fomesafen and slightly by oxasulfuron. However, glyphosate and the surfactants Energic, Herbitensil and Aterbane strongly reduced its growth. The reduction observed on imazetaphyr enriched medium was intermediate and the Natur L'óleo promoted mycelial growth. All of the surfactants allowed B. euphorbiae conidia germination equivalent to that reached in the presence of water. Energic and Herbitensil caused an expressive retardation on spore germination. The germinative process only began after 120 minutes in the presence of Herbitensil. In relation to the herbicides, it was observed that only in the presence of glyphosate and imazetaphyr the conidia germination did not follow the trend of the treatment with water