New concepts in phytopathometry continue to emerge,

A abundância e o potencial inseticida de Derris amazonica e a necessidade de controle de Cerotoma arcuatus Olivier (Coleoptera: Chrysomelidae) na cultura do feijão-caupi (Vigna unguiculata L. Walp) estimularam a realização desta pesquisa, que objetivou avaliar a ação inseticida do extrato de D. amazonica a adultos de C. arcuatus em condições de laboratório. Os bioensaios testaram as vias de intoxicação por ingestão de folhas contaminadas, contato com superfície contaminada e aplicação tópica, com delineamento experimental inteiramente casualizado, com quatro repetições. Insecticide action of the extract of Derris amazonica Killip for Cerotoma arcuatus Olivier (Coleoptera: Chrysomelidae) ABSTRACTThe abundance and insecticidal potential of Derris amazonica in addition to need of controlling Cerotoma arcuatus for bean crop stimulated this research. The objective of this work was to evaluate insecticide action of the extract of D. amazonica to adults of C. arcuatus in laboratory conditions. The bioassays were carried out using three distend methodologies: leaf intake, contact in treated surface (filter paper) and topical application. A completed randomized experimental design was used with four replications. Mortality values and leaf consumption of the insects were subjected to regression analyses, being the Probit analyses used to determine of the i.e., LC 50 , LT 50 and LD 50 . The extract of D. amazonica containing 3.7% of rotenone was toxic to adults C. arcuatus when exposed to treated leaves (LC 50 = 15.14 µl.mL ). In all bioassays the adults mortality was higher than 80% with lower median lethal times obtained with 5% (v.v -1 ) concentrations of the extract. Leaf consumption by adults C. arcuatus was inversely proportional to the concentration of the extract when exposed by leaf intake or topical application, also being observed inhibition of feeding individuals. The extract of D. amazonica is toxic to C. arcuatus and inhibits the feeding of insects from the concentration of 1% (v v -1 ).

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The capacity of Fusarium oxysporum f. sp. phaseoli to multiply in the roots of 12 non-host plant species was determined with the objective of selecting potential candidates for crop rotation and/or green manuring in infested bean ®elds. The plants were inoculated at the seedling stage by a benomyl-resistant mutant of the pathogen using the root-dip technique and transplanted to natural soil. The number of colony forming units/g dry root tissue (CFU/g) was determined at the full bloom stage. Quantitatively, the root colonization diered greatly among the plant species. The roots and lower stem of Dolichos lablab, Phaseolus lunatus, Mucuna aterrima, Canavalia ensiforme and Vigna unguiculata were the most compatible with the pathogen and those of Sorghum bicolor, Crotalaria juncea, Oryza sativa and Zea mays were least compatible. No disease symptoms developed on any plant species. Chlamydospore germination in the rhizosphere also diered signi®cantly among the plant species. There was no correlation between percentage chlamydospore germination in the rhizosphere and extent of root colonization. Most plant species recommended for green manuring in bean ®elds allowed extensive root and stem colonization by F. o. f. sp. phaseoli and were considered as reservoir hosts. All three of the gramineous species tested and C. juncea were classed as non-reservoir host, because the pathogen did not colonize the stem and its multiplication in the roots was very low. These plant species appear to be good candidates for long-term ®eld evaluation to determine their usefulness in an integrated management of Fusarium bean-wilt.

a incidência de murcha bacteriana causada por Ralstonia solanacearum foi registrada em 25 municípios do estado do Amazonas. A bactéria foi encontrada nas seguintes espécies vegetais: Capsicum annuum, C. chinense, C. frutescens, Cucumis sativus, Heliconia sp., Lycopersicon esculentum, Melanthera discoidea, Moringa oleifera, Musa sp., Solanum melongena, S. gilo, e S. nigrum. Em tomateiros (Lycopersicon esculentum), a murcha bacteriana estava presente em todos os plantios. Em bananeiras (Musa spp.), a incidência do Moko foi menor nas várzeas dos rios Madeira e Negro do que nas dos rios Solimões e Amazonas. Caracterizaram-se 320 isolados de R. solanacearum, obtidos no levantamento, com relação a raça e a biovar. A biovar 1 predominou em todos os hospedeiros, com exceção de C. annuum e C. chinense, onde estirpes da biovar 3 foram maioria. Apenas 7,8% das estirpes foram da biovar N2. A sensibilidade de 56 estirpes da raça 1 a 23 bacteriocinas foi avaliada. As estirpes da biovar 3 apresentaram uma menor variabilidade, na sensibilidade a bacteriocinas do que as estirpes das biovares 1 e N2. Palavras-chave aadicionais: Ralstonia solanacearum, Pseudomonas solanacearum, Burkholderia solanacearum, bacteriocinas. ABSTRACT Bacterial wilt in Amazonas State, BrazilA survey for bacterial wilt caused by Ralstonia solanacearum was conducted in 25 counties in the state of Amazonas during the years 1998 and 2000. Ralstonia solanacearum was found in the following species: Capsicum annuum, C. chinense, C. frutescens, Cucumis sativus, Heliconia sp., Lycopersicon esculentum, Melanthera discoidea, Moringa oleifera, Musa sp., Solanum melongena, S. gilo, and S. nigrum. In tomatoes (Lycopersicon esculentum), bacterial wilt was present in all fields. In banana (Musa spp.), the incidence of Moko disease was lower in the flooded areas of the Madeira and Negro Rivers than in the Solimões and Amazonas Rivers. In this survey the race and biovar of 320 R. solanacearum isolates was determined. The biovar 1 strains predominate in almost all hosts. In C. annuum and C. chinense, however, biovar 3 was more common. Only 7.8% of the strains were biovar N2. Fifty-six race 1 strains originating from different hosts and counties were evaluated with regard to sensitivity to 23 bacteriocins. Strains from biovars 1 and N2 showed more variability regarding bacteriocin sensitivity than biovar 3 strains.

The capacity of Fusarium oxysporum f. sp. phaseoli to multiply in the roots of 12 non-host plant species was determined with the objective of selecting potential candidates for crop rotation and/or green manuring in infested bean ®elds. The plants were inoculated at the seedling stage by a benomyl-resistant mutant of the pathogen using the root-dip technique and transplanted to natural soil. The number of colony forming units/g dry root tissue (CFU/g) was determined at the full bloom stage. Quantitatively, the root colonization diered greatly among the plant species. The roots and lower stem of Dolichos lablab, Phaseolus lunatus, Mucuna aterrima, Canavalia ensiforme and Vigna unguiculata were the most compatible with the pathogen and those of Sorghum bicolor, Crotalaria juncea, Oryza sativa and Zea mays were least compatible. No disease symptoms developed on any plant species. Chlamydospore germination in the rhizosphere also diered signi®cantly among the plant species. There was no correlation between percentage chlamydospore germination in the rhizosphere and extent of root colonization. Most plant species recommended for green manuring in bean ®elds allowed extensive root and stem colonization by F. o. f. sp. phaseoli and were considered as reservoir hosts. All three of the gramineous species tested and C. juncea were classed as non-reservoir host, because the pathogen did not colonize the stem and its multiplication in the roots was very low. These plant species appear to be good candidates for long-term ®eld evaluation to determine their usefulness in an integrated management of Fusarium bean-wilt.

RESUMO O cultivo do cubiu (Solanum sessiliflorum Dunal), no Amazonas, é limitado pela alta incidência da doença podridão-de-escleródio (Sclerotium rolfsii Sacc.) e a incorporação de material vegetal ao substrato de cultivo altera a microflora presente. O trabalho objetivou avaliar o potencial de controle da podridão-de-escleródio em cubiu por meio de incorporação, ao substrato de cultivo, de biomassa fresca triturada de quatro espécies de fabáceas: Erythrina fusca Loureiro e Senna reticulata (Wild.) Irwin & Barneby, nativas da Amazônia, e Desmodium heterocarpon (L.) DC. subsp. ovalifolium (Prain) Ohashi e Gliricidia sepium (Jacq.) Walp., exóticas. O substrato foi infestado com 10 g de arroz colonizado com S. rolfsii .L-1 de substrato e incorporadas 40 g da biomassa das fabáceas.L-1 de substrato em vasos com volume de 8 L nos quais foram cultivadas mudas de cubiu em viveiro. O experimento foi em DIC com três repetições e sete tratamentos (quatro espécies de fabáceas e três testemunhas, sem a incorporação de biomassa). Em uma das testemunhas não houve infestação do substrato e em duas, o substrato foi infestado, sendo que em uma, as plantas foram pulverizadas com fungicida. Outro experimento foi realizado avaliando-se o efeito de doses de G. sepium incorporadas ao substrato. O experimento foi em DIC com três repetições e seis tratamentos (40, 80, 120 e 160 g de G. sepium.L-1 de substrato e duas testemunhas sem incorporação de G. sepium sendo que em uma das testemunhas, as plantas foram tratadas com fungicida). Em ambos os experimentos foi avaliada a incidência da doença e a densidade do inóculo no substrato. No primeiro experimento, os dados da área abaixo da curva de progresso da doença foram submetidos à ANOVA e as médias comparadas pelo teste Tukey. No segundo experimento os dados foram submetidos à análise de regressão entre os níveis de biomassa incorporada no substrato. No primeiro experimento a incorporação da biomassa não diferiu do fungicida na redução da incidência da podridão-de-escleródio e na supressão da densidade do patógeno. No segundo experimento, a redução da incidência da podridão-de-escleródio foi proporcional da biomassa de G. sepium, apresentando 100% de controle com a incorporação de 139 g de G. sepium.L-1 de substrato. A adição de 142 g de biomassa reduziu a população de S. rolfsii no substrato em 20%.

Coleus barbatus: a new Ralstonia solanacearum host Coleus barbatus commonly known as "false boldo" belongs to the family of the Laminaceae and has cardiotonic and analgesic properties. Plants of C. barbatus developing wilt symptoms were observed in a domestic garden located in Manaus, AM, Brazil. A vascular pathogen was isolated and identified as Ralstonia solanacearum, biovar N2, race 1. The inoculation of healthy C. barbatus plants produced the symptoms observed in