Severity Of Black Spot Research Articles

Reação de genótipos de mamoeiro à varíola e à podridão-do-pé

Genótipos de mamoeiro (Carica papaya) ('NT Red', 'Golden', 'Baixinho de St. Amália', 'Sunrise Solo', 'Cross Paris', 'Tailândia Verde', 'Tailândia Roxo', 'Tailândia Roxão', 'Sekati' e 'Tainung-1') foram avaliados quanto à reação à varíola (Asperisporium caricae) e à podridão-do-pé (Phytophthora palmivora). O estudo foi conduzido em uma área com plantas naturalmente infectadas com ambos os patógenos e sob telado utilizando solo naturalmente infestado com P. palmivora. A severidade de varíola foi avaliada usando-se uma escala, de 1 (0-3% da superfície coberta por lesões) a 6 (>de 50% da superfície coberta por lesões). As avaliações foram feitas entre março e abril / 2003 e entre outubro 2003 e fevereiro 2004. A podridão-do-pé foi avaliada, no campo, por incidência em cada cultivar nos mesmos períodos. Nos experimentos sob telado a severidade da doença por P. palmivora foi avaliada em cada planta utilizando-se a seguinte escala: 0- sem sintomas; 1- até 50% de murcha; 2- de 51 a 100% de murcha; 3- morta. Quanto à varíola, verificou-se que plantas de 'Sekati' (grupo Formosa) apresentaram os menores valores médios finais de severidade da doença na folhagem (2,0) enquanto que, 'Golden' (3,1) e'NT Red' (3,7) apresentaram os maiores. Nos frutos, 'Tailândia Roxão' (1,6), 'Tailândia Verde' (1,7) e 'Sekati' (1,7) apresentaram os menores valores de varíola, enquanto que, 'Tailândia Roxo' (2,3), 'Cross Paris' (2,5), e 'Sunrise Solo' (3,1) apresentaram os maiores. Quanto à podridão do pé, 'Tailândia Roxão' (grupo Formosa) apresentou a menor quantidade de doença, enquanto que, 'Golden', 'Sunrise Solo e 'NT Red' apresentaram os maiores valores.

Levantamento da intensidade da alternariose e da podridão negra em cultivos orgânicos de brássicas em Pernambuco e Santa Catarina

O objetivo deste trabalho foi avaliar a intensidade da alternariose, causada por Alternaria brassicicola e/ou Alternaria brassicae, e da podridão negra, causada por Xanthomonas campestris pv. campestris, em cultivos orgânicos de brássicas em Pernambuco e Santa Catarina. Os levantamentos foram realizados no período de novembro de 2001 a fevereiro de 2002, num total de 103 cultivos orgânicos de várias espécies de brássicas. Foram registradas elevadas prevalências das doenças nos estados, com exceção em couve-chinesa em Santa Catarina. A prevalência da alternariose foi 100% nos cultivos de brócolis em Pernambuco, bem como em couve-flor nos dois estados, enquanto a podridão negra atingiu esse nível nos cultivos de brócolis e couve-flor em Santa Catarina. Na média das diferentes espécies de brássicas, as doenças foram mais prevalentes em Pernambuco que Santa Catarina. Entretanto, as médias de severidade de cada doença no conjunto das brássicas não foram diferentes entre os estados, embora as condições climáticas tenham sido nitidamente distintas. A severidade da alternariose variou entre as espécies de brássicas somente em Pernambuco, com a menor severidade registrada em couve-manteiga. Em relação à podridão negra, apenas em Santa Catarina houve diferença na severidade entre as brássicas, sendo registrados os menores níveis em couve-chinesa. Não foram constatadas correlações significativas entre os níveis de severidade da alternariose e da podridão negra, bem como da severidade destas com o número total de plantas e a idade das plantas nos cultivos.

Management of Blackspot on Three Rose Cultivars Using Antitranspirants in Combination with Chlorothalonil

Abstract The efficacy of reducing fungicide use, by combining chlorothalonil with film-forming antitranspirant products and lengthening intervals between applications, was evaluated for control of blackspot of rose. Antitranspirants included three highly refined pine oil (pinolene) products (Nu Film 17, Vapor Gard, and Wilt Pruf) and two latex products (Stressguard and Transfilm), each of which were applied in combination with chlorothalonil fungicide. Antitranspirant solutions were applied at 2- or 3-week intervals, depending on recommended use of the antitranspirant. Blackspot severity, based on proportion of symptomatic foliage, did not differ among treatments in either year of the study. In both study years, defoliation was lower on plants treated weekly with the fungicide alone, with Stressguard (applied at 0.25% in combination with chlorothalonil every 2 weeks), or with Vapor Gard (applied at 2% in solution with chlorothalonil every 3 weeks) compared to nontreated plants. Overall, the above fungicide and antitranspirant solutions reduced season-long fungicide use by 40-69%, without a decrease in disease control, compared to the weekly chlorothalonil treatment. Plant vigor and/or growth, however, was lower with the antitranspirant treatments compared to chlorothalonil alone.

Pea yield decline syndrome in South Australia: the role of diseases and the impact of agronomic practices

Sixty commercial pea crops were surveyed in 1995 to determine the causes of declining yields. Blackspot (Mycosphaerella pinodes and Phoma medicaginis var. pinodella) and downy mildew (Peronospora viciae) were prevalent in most crops and were identified as probable major contributors to the syndrome. Short rotation intervals (<5 years) between pea crops in paddocks were correlated with increased levels of blackspot and lower grain yields. Early sowing dates were correlated with increased levels of blackspot. A detailed survey of blackspot development was conducted in 5 commercial paddocks in 1996. The relative importance of sowing time and rotation varied between regions and seasons. The impact of a range of herbicides and the micronutrients manganese and zinc on blackspot, caused by the M. pinodes component of the blackspot complex, was investigated in a field trial during 1996. The herbicides diuron, metribuzin, and fluazifop significantly increased blackspot crown lesions compared with the nil treatment. There was a significant interaction between blackspot severity, herbicides, and the micronutrients manganese and zinc. Manganese concentration in pea plants was negatively correlated with the severity of blackspot crown lesions and positively correlated with severity of downy mildew.

“Black Spot,” a Physiological Disorder of Seed Development in Watermelon

Production of watermelons for seed consumption is popular in many regions of the world. In the Mediterranean area, large white seeds are preferred. Six breeding lines were selected for investigating the nature of black spot, an undesirable feature reducing the commercial value of the seeds. Black spot is expressed as blackened areas of the seed coat, mostly near the margin in mild cases, but extending over much of the seed coat in severe cases. Sowing date had a significant effect on expression of black spot. Seeds that developed in early summer (June) had low frequency and severity of black spot expression, whereas seeds that developed later in the summer (July–August) had markedly increased expression. Large differences were also observed among the breeding lines. There was a significant negative correlation between severity of black spot and seed weight, suggesting that black spot is a stress-related phenomenon.

Management of Blackspot of Rose in the Landscape in Alabama

Two application schedules for chlorothalonil, a solution of sodium bicarbonate and horticultural oil, and an untreated control, were assessed for effectiveness in the control of blackspot of rose during 1992 and 1993 in Alabama using a variety of ground covers. Weekly applications of chlorothalonil were superior to applications following 0.63 cm of rain for both years. Sodium bicarbonate solution reduced disease when inoculum levels were low, i.e., after initial establishment of rose beds, but were ineffective in the subsequent year when inoculum levels were higher. In 1992, less blackspot developed on plants with oat straw or pine straw ground covers than on those with landscape mat or bare soil. In 1993, lowest disease severity was observed on plants with oat straw ground cover. When disease levels were high, severity of blackspot was inversely correlated to flower production on each of three varieties

Influence of ethylene on black spot of potato tubers

Sound, hand harvested, whole potatoes were exposed to continuous flowing atmosphere containing air, air with 3 or 5% CO2, and air with concentrations of 0.5, 1.0, and 10ppm C2H4 for periods of 1 to 11 days at 20°C. At 1-day intervals, potatoes were bruised and black spot development assessed. Development of black spot in potatoes exposed to C2H4 was equal to or less than in potatoes at harvest. The severity remained low during 3-day exposure to 1 ppm C2H4 and after transfer to 4 days in air, then increased. Severity of black spot increased in potatoes exposed to air, with intermediate response from exposure to air with CO2. With an increase in sprouting, differences in black spot among treatments diminished. Less black spot developed in immature than in mature potatoes.