Luiz Eduardo Bassay Blum

Effect of organic amendments on sclerotial germination, mycelial growth, and Sclerotium rolfsii-induced diseases

A adicao ao solo de residuos orgânicos e uma opcao para o manejo de doencas causadas por patogenos de solo. Benzaldeido e residuos moidos de pueraria (Pueraria lobata), mucuna (Mucuna deeringiana) e casca de Pinus (Pinus elliottii e P. taeda) podem reduzir certas doencas propagadas pelo solo. Este estudo avaliou os efeitos do benzaldeido e de pos-secos de pueraria, mucuna e casca de Pinus sp. como residuos de solo na germinacao e formacao de esclerocios, no crescimento micelial de Sclerotium rolfsii, na sobrevivencia de plantas, na incidencia de doenca e na atividade enzimatica do solo. Concentracoes mais altas de benzaldeido (0,4 ml kg-1 de solo) e mucuna (100 g kg-1) inibiram o crescimento micelial e a germinacao de esclerocios. Todavia, concentracoes mais baixas de benzaldeido (0,1 g kg-1), pueraria (25 g kg-1), e casca de Pinus sp. (25 g kg-1) estimularam o crescimento micelial e a germinacao de esclerocios. Pueraria (25-100 g kg-1) e mucuna (25-100 g kg-1) inibiram a formacao de esclerocios. Contudo, benzaldeido a 0,2 e 0,4 ml kg-1 estimulou a formacao de esclerocios. Pueraria (50 e 100 g kg-1) e casca de Pinus sp. (50 g kg-1) favoreceram a colonizacao dos esclerocios por Trichoderma sp. O numero de plantas de soja (Glycine max) foi maior e o numero de plantas doentes foi mais baixo em solos com pueraria (50 e 100 g kg-1), mucuna (50 e 100 g kg-1) e casca de Pinus sp. (50 g kg-1) do que em solos sem estes residuos. A severidade de doenca em tomateiro (Lycopersicon esculentum) foi baixa em solo com pueraria ou mucuna (30 e 35 g kg-1) e casca de Pinus sp. (35 g kg-1). Pos-secos de pueraria, mucuna ou casca de Pinus sp. incorporados ao solo podem reduzir a doenca devido a reducao do inoculo do patogeno.

Padrões de liberação de urediniósporos e desenvolvimento da ferrugem do jambeiro

Patterns of urediniospores release and development of rose apple rust Abstract†n†This research was conducted to evaluate some epidemiological features of the rose apple (Syzygium jambos) rust (Puccinia psidii Winter) under field conditions at the Universidade de BrasIlia, BrasIlia, DF, Brazil, from March 29 through December 31, 1988. Data for the amount of airborne urediniospores were collected in ten plants, using a Burkardis seven-day volumetric spore trap set between two rose apple trees. Most of the airborne urediniospores were collected between June 23 and July 6, from 10†a.m. to 1†p.m. The†major quantity of S.†jambos affected shoots occurred between April 28 and July 20. There was a positive correlation between the amount of trapped urediniospores and infected young shoots. A†negative correlation was shown between temperature (12h) and number of airborne urediniospores. The number of days with relative humidity (RH)†‡80% was positively corre- lated to the amount of deformed shoots. Also, the amount of urediniospores and infected young shoots were positively correlated to the number of days with night (24h) temperature £20 o C or night RH‡80%. These data show that this disease was favored by low temperatures (£20 o C), high night RH†(‡80%) and high levels of airborne urediniospores.

Thidiazuron effects on shoot growth, return bloom, fruit set and nutrition of apples

Abstract – Apple ( Malus domestica Borkh.) trees, cultivars Gala and Fuji, were sprayed at full bloomwith thidiazuron (TDZ) at doses of 0, 5, 10, or 20 g ha -1 of a.i. in order to evaluate its effects on plantgrowth and development, return bloom, fruit set, nutrition, and fruit yield. Fruit set increased withTDZ dose in ‘Gala’ but not in ‘Fuji’. TDZ did not affect fruit yield in any cultivar. In ‘Gala’, the returnbloom was reduced in about 50% at TDZ doses of 10 or 20 g ha -1 . TDZ increased shoot growth in bothcultivars. In leaves, TDZ decreased the concentration of Ca and Mg in ‘Gala’ and of Mg in ‘Fuji’, butdid not affect the chlorophyll content, leaf area, length, width, and dry mass per cm 2 regardless ofcultivar. In fruits, the effect of TDZ varied according to the portion evaluated. Highest doses of TDZdecreased the concentration of Ca and K in ‘Gala’ and of K in ‘Fuji’ in the entire fruits (flesh + skin); inthe skin, highest doses of TDZ reduced the levels of N, Ca, and Mg in both cultivars, in addition to thelevel of K in ‘Fuji’.Index terms:

Avaliação do efeito de fosfitos na redução da varíola (Asperisporium caricae) do mamoeiro (Carica papaya)

The control of black spot of papaya is necessary, therefore, the objective of this study was to evaluate the effect of foliar applications of phosphites (K, Ca, Mg and Cu) on papaya black spot. Two phosphites and the fungicide Fosetyl-Al were tested on a field trial with papaya plants naturally infected by the pathogen. Ten phosphites and the fungicide Fosetyl-Al were tested in a greenhouse trial, also with plants naturally infected by A. caricae. In both, field and greenhouse trials, the phosphite treatments reduced black spot severity.

Control of Post-harvest Anthracnose Infection in Guava (Psidium guajava) Fruits with Phosphites, Calcium Chloride, Acetyl Salicylic Acid, Hot Water, and 1-MCP

The control of anthracnose (Colletotrichum simmondsii) during the post-harvest stage in guava fruits (Psidium guajava L.) was performed by the application of phosphites [phosphite-K (40% P2O5 and 30% K2O) and phosphite-Ca (10.7% P2O5, 3.89% Ca, and 0.5% B)] including the Carbendazim as reference, calcium chloride (CaCl2), acetyl salicylic acid (ASA), hot water (HW), and 1-methylcyclopropene (1-MCP). These treatments were applied individually or in combination each other with two or three compounds. The evaluated parameters were diameter of anthracnose lesion (DL), number of lesions (NL), and fruit quality (fresh weight loss, pH, total soluble solids, and titrable acidity]. The fruits were disinfested, inoculated, and maintained in an incubator containing fluorescent lights at 75 µmol·m-2·s-1 (25°C, 12h photoperiod) for 5 days and were then analyzed. The results showed that the DL and the NL were reduced following treatments, and that the HW (47°C for 20 min) was the strongest and the 1-MCP treatment was the least effective. The physico-chemical characteristics of fruits were affected by some treatments without compromising fruit quality. The combination of treatments was also able to alleviate the anthracnose effect on fruits compared to individual treatments and the control without affect the fruit quality. The combinations which included the HW treatment showed the best performance to control this disease, particularly when combined with the 1-MCP and phosphite.

Powders of kudzu, velvetbean, and pine bark added to soil increase microbial population and reduce Southern blight of soybean

Southern blight (Sclerotium rolfsii) of soybean (Glycine max) is an important disease throughout the world. Some soil amendments can reduce disease levels by improving soil microbial activity. The main goals of this study were to investigate the effects of soil amendments such as dried powders of kudzu (Pueraria lobata), velvetbean (Mucuna deeringiana), and pine bark (Pinus taeda), on soil microbial population and disease caused by S. rolfsii on soybean. Pine bark, velvetbean (mucuna) and kudzu (25 g kg-1) added to soil were effective in reducing disease incidence [non-amended (NA) ~ 39%; amended (A) ~ 2 to 11%)]. Bacillus megaterium was the bacteria most frequently isolated in soils with velvetbean or kudzu (NA ~ log 5.7 CFU g-1 of dried soil; A ~ log 6.2). Soils with velvetbean and kudzu stimulated increase in population of Enterobacter aerogenes (NA ~ log 3; A ~ log 5.1-5.8). Pseudomonas putida population was higher in A than in NA (NA ~ log 4; A ~ log 5.5), and was negatively correlated (r = -0.83, P = 1%) to disease incidence. Soil amended with kudzu and pine bark stimulated increases in populations of Trichoderma koningii (NA ~ log 1.6; A ~ log 2.9) and Penicillium citreonigrum (NA ~ log 1.3; A ~ log 2.6), respectively. Penicillium herquei soil population increased with addition of kudzu (NA ~ log 1.2; A, ~ log 2.5). These microorganisms are antagonists of soil-borne pathogens. Powders of velvetbean, kudzu, and pine bark can increase antagonistic population in soil and reduce disease.

Desfolha, população de plantas e precocidade do milho afetam a incidência e a severidade de podridões de colmo

The relationship between source and sink interferes on maize (Zea mays) stalk rot occurrence. This study was conducted in Lages, SC, Brazil, to evaluate the effect of defoliation, plant population, and hybrids on the intensity (incidence or severity) of maize stalk rots. The experiment was set in a randomized complete block design (three replications) with a split-split-plot arrangement. The hybrids P32R21 (very early), Premium (early) and C333B (late) were tested without defoliation and with 50% defoliation on ear formation stage at plant populations of 25,000, 50,000, 75,000, and 100,000 plants ha-1. The incidence and severity of Colletotrichum graminicola, Diplodia maydis and Fusarium moniliforme stalk rots were evaluated. The hybrid P32R21 was the most affected by stalk rots. Defoliation enhanced rots on P32R21 and Premium. Enhancements in plant population increased stalk rots intensity on intact plants but decreased rot occurrence when hybrids were defoliated.

Reduction of incidence and severity of Septoria lycopersici leaf spot of tomato with bacteria and yeasts

A mancha foliar causada pelo fungo Septoria lycopersici e uma doenca no tomateiro (Lycopersicon esculentum), controlada basicamente pela aplicacao de fungicidas. Uma das alternativas ao controle quimico dessa enfermidade e a utilizacao de bacterias e leveduras antagonistas. Este estudo foi conduzido de 1994 a 1995 em Auburn, Alabama, EUA. O patogeno e um dos antagonistas foram isolados do filoplano de plantas de tomateiro infectadas pela doenca em questao. Sete antagonistas (um isolado de bacteria e seis de leveduras) foram testados em uma serie de sete experimentos conduzidos em casa de vegetacao. Os experimentos foram conduzidos em um delineamento completamente casualizado com quatro a oito tratamentos e seis repeticoes. Em todos os experimentos, os antagonistas (1-3 ´ 108 unidades formadoras de colonia ml-1) foram inoculados 48h antes da inoculacao com o patogeno (1-2 ´ 105 conidios ml-1), sob condicoes de nebulosidade intermitente. Entre os antagonistas testados, destacaram-se o isolado de levedura Y236 (Cryptococcus laurentii) e o isolado bacteriano BTL (Pseudomonas putida). Ambos os isolados reduziram significativamente (P £ 0.05) a incidencia e a severidade da doenca na maioria dos experimentos.

Papaya (Carica papaya) foot rot (Phytophthora palmivora) reduction due to phosphites

Papaya (Carica papaya) foot rot (Phytophthora palmivora) reduction due to phosphites This study showed that two weekly sprays of phosphite [A (40 % P2O5 + 20 % K2O, 150 mL commercial product. hL-1), B (40 % P2O5 + 20 % K2O, 250 mL), C (10 % P2O5 + 6 % Ca, 400 mL), D (20 % P2O5 + 20 % K2O, 200 mL), E (40 % P2O5 + 6 % Mg, 150 mL), F (30 % P2O5 + 20 % K2O, 175 mL), G (20 % P2O5 + 20 % K2O, 200 mL) ] for three consecutive weeks before pathogen inoculation reduced disease severity. A podridao do pe, causada por Phytophthora palmivora Butler, e uma das principais doencas mamoeiro (Carica papaya L.). Os fosfitos constituem uma alternativa para o controle de Phytophthora em plantas, pois inibem o patogeno ou induzem na hospedeira a producao de substâncias e compostos que agem no processo de defesa contra a infeccao. A determinacao de metodos eficientes de controle da doenca menos agressivos ao ambiente e necessaria. Neste estudo objetivou-se determinar o efeito de aplicacoes de fosfitos sobre a severidade da doenca. Os testes foram realizados em casa de vegetacao com plantas de ‘Tailândia Roxao’ (2 meses de idade). O patogeno (PP-24) foi multiplicado em meio seletivo (200 ml suco de tomate temperado ‘Superbom’, 18 g agar, 3 g CaCO3, 800 mL agua destilada, 10 mg pimaricina, 250 mg ampicilina, 10 mg rifampicina, 30 mg rosa de bengala). Os tratamentos aplicados estao apresentados na tabela 1. Os produtos foram aplicados nas folhas via pulverizacao (pulverizador manual – 500 mL) ate o ponto de escorrimento. A inoculacao do patogeno ocorreu 48 h apos a ultima pulverizacao, inserindo-se palitos colonizados pelo fungo na base do caule das plantas. Seguiu-se um delineamento em blocos ao acaso (9 tratamentos; 4 repeticoes de 5 plantas). A severidade da doenca foi avaliada diariamente utilizando-se a seguinte escala: (0) sem sintomas; (1) ate 50% de murcha; (2) de 51 a 100% de murcha; (3) – planta morta. Os dados foram submetidos a analise de variância com repeticao de medidas, e, as medias comparadas pelo teste de Tukey (P < 5 %). Com uma aplicacao semanal (Tabela 1), somente o tratamento com o fosfito C (10 % P2O5 + 6 % Ca – 400 mL.hL -1) diferiu significativamente da testemunha. Ja, com duas aplicacoes semanais, todos os tratamentos com fosfito diferiram da testemunha, sendo que, neste caso, o tratamento com fosfito B (40 % P2O5 + 20 % K2O 150 mL.hL-1), foi o que mais reduziu a doenca.

Fungicidas e mistura de fungicidas no controle do oídio da soja

Two experiments were performed in Londrina, PR, Brazil to evaluate the efficacy of fungicides on the control of soybean (Glycine max) powdery mildew (Microsphaera diffusa). One application of the different commercial products was made on soybean cv. EMBRAPA 48 growth stage R4. The best fungicides to control powdery mildew were tebuconazole-1 and tebuconazole-2, carbendazin-1 and carbendazin-2. Test 1 - tebuconazole-2 (150 g a.i. / ha), prochloraz + propiconazole (225 + 62.5), propiconazole + carbendazin-1 (50 + 175), and tebuconazole-1 + propiconazole (75 + 62.5); Test 2 - carbendazin-1 (250), carbendazin-2 (250), and tebuconazole-2 (100).