Incidence Of Eyespot Research Articles

밀 잎집눈무늬병의 발생에 파종량이 미치는 영향과 방제 약제 선발

본 연구는 국내 육성 밀 3품종을 이용하여 파종량과 밀잎집눈무늬병의 발생정도를 조사하고, 이 식물병을 효과적으로 방제하기 위한 약제를 선발하기 하기 위하여 수행되었다. 파종량이 기준량의 2배로 증가할 때 발병률이 약 13% 증가하였다. 그러나 감수성인 조품밀만이 2배량 파종시에 발병률이 높아지는 유의적인 차이를 보였다. 잎집눈무늬병의 방제 약제 선발을 위해 배지상에서 약제별 효과를 검정한 결과, Triazole 계통인 Hexaconazole EC과 Tebuconazole EC는 균사생장을 효과적으로 억제하였다. 하지만 strobilurin 계통의 Pyraclostrobin EC과 Trifloxystrobin SC는 균사 억제 효과가 약하였다. 식물체에 직접 처리하여 약효를 검정한 결과, in vivo 활성과 in vitro 활성은 유사하게 나타났고 예방효과가 치료효과보다 높은 것으로 나타났다. 즉, Hexaconazole EC와 Tebuconazole EC의 예방효과는 각각 64%와 73%였고, 치료효과는 각각 45%와 39%였다. 본 연구결과는 Hexaconazole EC와 Tebuconazole EC가 밀에 발생하는 입짚눈무늬병의 방제제로 이용될 수 있다는 것을 나타낸다. This study was conducted to examine the effects of the seeding rate on the disease incidence of sharp eyespot(Rhizoctonia cerealis) on three different varieties and to select effective chemicals to control the disease. When the seeds were sown twice as many as the recommendation, the disease incidence increased by approximately 13%. However, the susceptible variety 'Jopummil' alone showed the significantly enhanced disease incidence at a two-fold seeding rate. Two chemicals such as Hexaconazole EC and Tebuconazole EC highly inhibited the fungal growth on agar medium. However, two strobilurin fungicides such as Pyraclostrobin EC and Trifloxystrobin SC were relatively weak. The fungicides tested displayed the similar in vivo antifungal activities as in vitro activities. Hexaconazole EC and Tebuconazole EC showed the strongest both protective and curative activities and the protective activities of the chemicals were generally higher than the curative activities. Hexaconazole EC and Tebuconazole EC controlled the disease by 64% and 73%, respectively, and the two chemicals reduced the disease by 45% and 39%, respectively, when they were applied one day after pathogen inoculation. These results indicate that both Hexaconazole EC and Tebuconazole EC could be used to control sharp eyespot on wheat.

Relationship between Incidence of Brown Eye Spot of Coffee Cherries and the Chemical Composition of Coffee Beans

AbstractTo study the chemical composition of coffee beans from coffee cherries infected by brown eye spot, two experiments were conducted with coffee cherries from Catuaí Amarelo and Acaiá Cerrado farms, in the full physiological maturity stage. The coffee cherries were harvested manually, and 20 litres of cherries without visible symptoms of brown eye spot (healthy coffee cherries) and 20 l of cherries with visible symptoms of the disease (diseased coffee cherries) were individually separated. After separation, the cherries were mixed in five different proportions to form the treatments: 0, 25, 50, 75 and 100% of diseased coffee cherries to 100, 75, 50, 25 and 0% of healthy coffee cherries. The experimental design was performed in randomized blocks, with each 8 l of coffee cherries being considered an experimental unit. After drying (humidity 12%), the chemical characteristics were analysed. Polyphenols, potassium leachate and electrical conductivity had a linear increase with the rising of the proportion of diseased coffee cherries. Total sugars, soluble solids and pH decreased linearly with the rising of the proportion of diseased coffee cherries.

Potential of essential oils for the control of brown eye spot in coffee plants

The objectives of this work were to assess the in vitro effect of essential oils extracted from cinnamon, citronella, lemon grass, India clove, tea tree, thyme, neem and eucalyptus on the conidia germination and on mycelial growth of Cercospora coffeicola, and their efficacy to control the brown eye spot in coffee seedlings (cultivars Catucaí 2SL, Catuaí IAC 62 and Mundo Novo 379/19) in a greenhouse, as well as their effects on the initial germination and infection events by scanning electron microscopy. All essential oils promoted the inhibition of conidia germination with increasing concentrations. India clove, cinnamon, neem, thyme and lemon grass oils inhibited the mycelial growth of C. coffeicola. The cinnamon and citronella oils were the most promising for brown eye spot control in all cultivars. In scanning electron microscopy, the cinnamon and citronella oils reduced germination and mycelial development of C. coffeicola in vivo, eight and 16 hours after inoculation, promoting, in some cases, the leakage of the cellular content. Essential oils of cinnamon and citronella reduced the incidence and severity of brown eye spot, in addition to presenting direct toxicity to the pathogen.

Effect of different soil tillage and organic fertilizers on winter triticale and spring barley stem base diseases

Multi-factor crop management field experiments were conducted in Vezaiciai, in southwestern Lithuania, from 2004 to 2006 to assess the influence of tillage and organic fertilizer management on stem base disease development. The treatments included 4-year crop rotations of continuous grass, winter triticale, winter oilseed rape and spring barley in combination with three tillage systems (shallow (8–10 cm) non-ploughing tillage, shallow (10–12 cm) tillage and deep (20–25 cm) ploughing). Eyespot prevailed both in winter triticale and spring barley crops. Winter triticale was more susceptible than spring barley. Shallow tillage decreased eyespot incidence and severity relative to deep tillage. Crop residue management exerted a weak but statistically significant effect on the disease development on triticale; in general, slightly higher numbers of affected stems were recorded in triticale plots where the straw from the previous crop had been removed prior to planting. However, complete straw removal from plots significantly decreased eyespot severity in comparison with crop residue or manure management treatments in spring barley. The highest number of affected triticale and barley plants was found in shallow (10–12 cm) tillage plots. The effects of residue management on minimising eyespot severity can be expected only after a delay of a few years.

Development of Oculimacula yallundae and O. acuformis (eyespot) lesions on stems of winter wheat in relation to thermal time in the UK

Relationships between development of eyespot, caused by Oculimacula yallundae (OY) or O. acuformis (OA) on stems of winter wheat (cv. Avalon), and thermal time (°C days after sowing) were investigated in field experiments in 1985/86, 1986/87 and 1987/88 (two experiments). In all experiments, the incidence and severity of stem eyespot (uninoculated plots, OY‐ and OA‐inoculated plots) were linearly related to accumulated thermal time after sowing. There were ca. 600–800°C days from the time of the first sample when eyespot lesions were recorded on stems to the time when maximum eyespot incidence or severity was recorded. Relationships between stem eyespot incidence or severity and thermal time differed between seasons, with more severe eyespot in 1986/87 and 1987/88 than 1985/86. Both the severity and volume of stem lesions were initially greater in OY‐inoculated plots than OA‐inoculated plots in spring but differences were less by harvest in all seasons. The percentage of plants with stems colonized by OY or OA over all plots (including uninoculated) showed a consistent pattern in 1986/87 and 1987/88 (two experiments), with the percentage colonized by OY greater initially and the percentage colonized by OA gradually increasing with time towards harvest.

Water and Temperature Parameters Associated with Winter Wheat Diseases Caused by Soilborne Pathogens.

Wheat in eastern Oregon is produced mostly as a 2-year rotation of winter wheat and summer fallow. Maximum agronomic yield potential is expected with early September planting dates but actual yields are generally highest for plantings made in mid-October. Field experiments with sequential planting dates from early September to December were performed over 4 years. Associations among yield, disease incidence, and 19 moisture and temperature parameters were evaluated. Incidence of Cephalosporium stripe, crown rot, eyespot, and take-all decreased as planting was delayed. Crown rot and eyespot were negatively correlated more significantly and more frequently with temperature than moisture parameters, and take-all was more associated with moisture than temperature. Rhizoctonia root rot was unrelated to planting date and climatic parameters. Crown rot was identified most frequently (4 of 5 tests) as an important contributor to yield suppression but yield was most closely associated (R2 > 0.96) with effects from a single disease in only two of five location-year tests. Yield was most related to combinations of diseases in three of five tests, complicating development of disease modules for wheat growth-simulation models.

Modeling spatial variability and pattern of rust and brown eye spot in coffee agroecosystem

The advent of Precision Agriculture has made possible the analysis of complex spatial patterns of plant disease epidemiology considering statements of integrated disease management. The objective of this work was to use geostatistics, statistics and geographical information systems to characterize the structure and magnitude of spatial dependency of rust (Hemileia vastatrix) and brown eye spot (Cercospora coffeicola) incidence and severity in coffee agroecosystem cultivated with Catuai Vermelho IAC-99 (Coffea arabica L.). Evaluations of incidence and severity of rust and brown eye spot were accomplished at 67 georeferenced points arranged in 6.6202 ha of coffee crop, in the years of 2005, 2006 and 2007. Exponential models of covariance enabled the characterization of the magnitude and structure of rust and brown eye spot spatial variability in the evaluated dates. Ordinary block kriging presented satisfactory performance to map rust and brown eye spot outbreaks based on kriging error coefficients. Kriged maps enabled the visualization of intensity of rust and brown eye spot in each evaluation date. Assessments of incidence and severity presented highly statistical correlation based on linear regression models, also confirmed by the spatial variability of kriging maps. Kriging maps of rust and brown eye spot enabled to observe that intensity of disease was dispersed in foci patterns along the coffee plantation, indicating that the current strategy of disease control based in total area may be replaced by site specific disease management, with less environmental impact and sustainability of coffee crop, according to statements of integrated disease management and precision agriculture.

Adubação orgânica, nutrição e progresso de cercosporiose e ferrugem-do-cafeeiro

O objetivo deste trabalho foi avaliar o efeito de fontes nutricionais orgânicas, no progresso da cercosporiose e da ferrugem-do-cafeeiro, entre novembro/2003 e novembro/2005. Utilizou-se o delineamento de blocos ao acaso, com quatro repetições e seis tratamentos: palha de café + chorume suíno (PC+CS); torta de mamona + crotalária (TM+Cr); palha de café (PC); esterco bovino + crotalária (EB+Cr); palha de café + torta de mamona (PC+TM); e composto orgânico, torta de mamona, chorume suíno e crotalária (testemunha). A maior área abaixo da curva de progresso da incidência da cercosporiose e da ferrugem foi registrada no tratamento PC (respectivamente 62 e 38% superiores à testemunha). O maior progresso das doenças coincidiu com a elevação no teor de K e redução nos teores de Ca foliares no tratamento PC, comparado às demais fontes de adubação, e resultou em maior desfolha e menor produtividade. Os tratamentos PC+TM e PC+CS reduziram a incidência da cercosporiose em 38% e da ferrugem em 31 e 21%, respectivamente, e aumentou o teor de Ca foliar ao final da fase de granação do cafeeiro, em comparação ao tratamento PC. O equilíbrio nutricional desses cafeeiros conferiu-lhes maior resistência e reduziu o efeito da bienalidade nas safras 2003/2004 e 2004/2005.

Progresso da cercosporiose (Cercospora coffeicola Berkeley & Cooke) em cafeeiros sob cultivos orgânico e convencional

Avaliou-se o progresso da cercosporiose em cafeeiros sob sistemas de produção orgânico e convencional no município de Santo Antônio do Amparo, MG, entre novembro/2003 e novembro/2005. As lavouras, que são vizinhas, encontravam-se sob condições similares de clima, solo e relevo e eram formadas por cafeeiros cv. Acaiá MG-474-19, de dez anos. A doença foi mais intensa no sistema de produção convencional, cuja média de dois anos consecutivos de avaliações demonstrou área abaixo da curva de progresso da cercosporiose maior (3,905) do que o orgânico (2,529). Isso ficou demonstrado também pela incidência máxima nas folhas, equivalente a 28% em 2004 e 29% em 2005, enquanto no sistema orgânico foi de 9% e 12%, respectivamente. Nos frutos, a incidência foi de 18,2% em 2004 e 22% em 2005, enquanto no orgânico foi de 11,5% e 15%, respectivamente. A maior suscetibilidade dos cafeeiros à cercosporiose no sistema convencional coincidiu com menores teores de cálcio e magnésio foliares nas fases de granação e maturação dos frutos comparados ao orgânico, conseqüência da maior carga pendente que resultou em uma produtividade superior em 26,8 sc/ha ao orgânico em 2004 (alta carga pendente). Em 2005 a produtividade foi estatisticamente semelhante em ambos os sistemas. Houve menor alternância entre a produtividade das duas safras consecutivas no sistema orgânico (34% menor em 2005) quando comparada à convencional (64% menor) sugerindo uma tendência de menor efeito da doença sobre a safra seguinte dos cafeeiros no sistema orgânico de produção, comparado ao convencional.

Efficiency of Calcium Silicate and Carbonate in Soybean Disease Control

ABSTRACT Silicon (Si) affects the susceptibility of plants to fungal attack. In plants with low Si accumulation, disease-control mechanisms involve the accumulation of phenolic compounds and Si. This study compared the effects of calcium silicate and carbonate doses on the control of soybean (Glycine max) diseases. A sandy soil was collected from Santa Vitória, Minas Gerais state, Brazil, of which 200 kg was placed in plastic drums in a protected, uncovered area. Calcium carbonate or silicate was applied superficially in amounts equivalent to 0, 1500, 3000, 6000, or 12,000 kg ha−1, and soybean was cultivated for 120 d. Leaf Si concentration and incidence of Cercospora sojina (Frog's eye spot), Peronospora manshurica (downy mildew), and Phakopsora pachyrhizi (Asian rust) were evaluated. Calcium carbonate did not reduce disease incidence; however, calcium silicate was effective in the reduction of downy mildew at 47 and 66 d after soybean seeding, and of frog's eye spot incidence at all dates evaluated. Asian rust was observed only at 79 d after seeding and calcium silicate was not effective in its reduction.

Factors associated with stem base and root diseases of New Zealand wheat and barley crops

The incidence of stem base and root diseases of cereals in New Zealand was measured over a 3-year period to determine their relationships with soil and crop management factors. Samples were collected from 142 New Zealand wheat and barley crops during the milky ripe stage of crop growth and the proportion of tillers affected by stem base and root diseases in each crop was assessed. Take-all (caused by Gaeumannomyces graminis), and sharp eyespot (caused by Rhizoctonia cerealis) were common, whereas crown rot (caused by Fusarium spp.) was present at only low levels and eyespot (caused by Tapesia spp.) was not recorded. Incidence of both take-all and sharp eyespot was greater in wheat crops (mean of 8.3 and 12.6% tillers infected, respectively) than in barley (1.7 and 4.4%). Previous crop was the main factor associated with take-all in wheat crops. Incidence was highest where wheat followed wheat (mean of 29.3% tillers infected), and higher after barley, grass or clover than after other break crops. Although take-all incidence was high in most successive wheat crops, incidence was low (<20%) in a substantial proportion. A 1-year break from wheat was almost as effective as a longer break in reducing take-all levels in a subsequent wheat crop. Sowing month was the factor most closely associated with sharp eyespot incidence in wheat. Crops sown in early autumn had the highest incidence, whereas crops sown in winter and spring had only low levels of sharp eyespot. Several Fusarium species were associated with crown rot in wheat and barley. Fusarium avenaceum, F. crookwellense and F. culmorum were present in all regions, but F. pseudograminearum, F. semitectum and Microdochium nivale were more limited in distribution.

Development ofOculimacula yallundaeandO. acuformis(eyespot) on leaf sheaths of winter wheat in the UK in relation to thermal time

In a controlled environment (15/10°C) (day/night) container experiment on winter wheat (cv. Avalon), eyespot incidence (percentage of plants affected) and number of leaf sheaths penetrated after 6 weeks increased with inoculum concentration (102−106conidia mL−1) ofOculimacula yallundae(OY) orOculimacula acuformis(OA), but there was no difference between the two species. In an outdoor container experiment, seedlings inoculated with OY 2 weeks after sowing had a greater incidence of eyespot than those inoculated with OA, when assessed 7 weeks after inoculation. Seedlings inoculated with OA at 10 or 20 weeks after sowing developed more severe eyespot by maturity than those inoculated with OY. In an experiment at 15/10°C with seedlings inoculated with OY + OA 2 weeks after sowing, more leaf sheaths were penetrated by OY (3·0 per plant) than OA (2·3 per plant) 6 weeks after inoculation. Field experiments with winter wheat consistently showed leaf sheath production, leaf sheath death, and number of leaf sheaths infected or penetrated by OA or OY were related linearly to thermal time (°C days) after sowing. Depending on cultivar, season and sample, a new leaf sheath was produced in 116–216°C days; a leaf sheath died in 221–350°C days; and infection of a new leaf sheath occurred in 129–389°C days. The mean number of living leaf sheaths infected differed between samples, cultivars and seasons for both OY and OA. Regression analysis of the 1985/86 data suggested that OY progressed more rapidly than OA through the leaf sheaths, and that both the pathogens progressed more rapidly than the rate of leaf sheath death, but more slowly than the rate at which leaf sheaths were produced. It also suggested that OA progressed more slowly than the rate at which leaf sheaths died in 1987/88, but OY did not.

Effects of fungicides on eyespot, caused predominantly by Oculimacula acuformis, and yield of early-drilled winter wheat

The effectiveness against eyespot of nine fungicide treatments, applied at GS 31, was evaluated in early-drilled winter wheat crops. Visual assessments of stem-base diseases were made before fungicide application and at GS 39/55 and 69/70 of cultivars Consort, Savannah and Claire. Competitive PCR was used to quantify Oculimacula acuformis, O. yallundae, Microdochium nivale, Fusarium spp. and Rhizoctonia cerealis. PCR results indicated that O. acuformis was the predominant pathogen causing eyespot in all three crops. Treatments containing cyprodinil were most successful in reducing disease index and DNA of O. acuformis across cultivars. Treatments containing prochloraz were less consistent in eyespot control, significantly reducing the DNA of O. acuformis only in one instance at GS 70 of cultivar Claire. None of the fungicide treatments had any significant effect on brown foot rot or sharp eyespot, or DNA of M. nivale or R. cerealis. The potential for O. acuformis to cause yield loss was indicated by significant negative relationships between yield and eyespot incidence or DNA of O. acuformis at GS 69/70 for each wheat crop. Relationships between DNA of O. acuformis and eyespot incidence or severity at each growth stage were weak but generally improved at the later growth stages of the crops when disease symptoms were easily distinguished. Both molecular methods and visual assessment failed to predict eyespot incidence or pathogen DNA late in season using incidence or DNA of O. acuformis at GS 31. PCR assays, however, accurately identified the stem base pathogens at early growth stages of the crops when the symptoms of their respective diseases were not readily diagnosed.

Incidência e severidade da cercosporiose do cafeeiro em função do suprimento de potássio e cálcio em solução nutritiva

O objetivo deste trabalho foi avaliar a incidência e a severidade da cercosporiose causada por Cercospora coffeicola em mudas de cafeeiro (Coffea arabica) cultivar Mundo Novo IAC 379-19, em função do suprimento de K e Ca em solução nutritiva. Instalou-se o experimento em DIC, com 16 tratamentos, três repetições e duas plantas por repetição. Utilizou-se esquema fatorial 4 x 4, com quatro doses de K (1, 3, 5 e 7 mmol/l) e quatro níveis de Ca (2, 4, 6 e 8 mmol/l). As mudas foram inoculadas semanalmente, durante 12 semanas, com suspensão de esporos de C. coffeicola na concentração de 15.000 conídios/ml. Foram realizadas sete avaliações quinzenais para a obtenção da área foliar total, número total de folhas e número total de lesões de cada planta. Após as avaliações determinou-se a porcentagem de área foliar lesionada e o peso da matéria seca total. A interação K x Ca influenciou a área abaixo da curva de progresso do total de lesões, do número total de folhas e a porcentagem de área foliar lesionada. As doses de K, isoladamente, influenciaram a matéria seca total, a área foliar total e a área abaixo da curva de progresso da incidência. As doses de Ca, isoladamente, influenciaram apenas a área foliar total e a área abaixo da curva de progresso da incidência.

The Incidence and Seventy of Eyespot on Winter Wheat Variety Hereward Grown as a Monocrop and as a Bicrop With White Clover

In a three-year field trial, the level of eyespot on cv. Hereward winter wheat was recorded from cereal monoerops and cereal-clover bicrops receiving standard farming practice and reduced levels of input. Disease incidence (for years one, two and three) and severity (years two and three only), increased with each season in all treatments. In the third wheat crop the area under the disease progress curve (AUDPC) for disease incidence (mean of all treatments) was 3.30 times higher than that measured for the first wheat crop. The average AUDPC for disease severity in year three was l.78 times greater than that for year two. In year three the eyespot incidence AUDPC for bicrops was 1.12 times greater than in monocrops. Disease severity AUDPC in year three was MS times greater in bicrops than in monocrops. For all treatments there was a significant correlation between AUDPC and the rate of disease increase. The results are discussed in terms of those factors that are likely to affect eyespot levels within bicrops, especially microclimate changes, spore production on crop residues, and spore dispersal by rain-splash.

Effect of NPK Fertiliser Combinations on the Incidence and Severity of Eyespot

The effect of NPK fertiliser combinations on the development of eyespot was studied both in the greenhouse and in the field. Low levels of nitrogen fertilisers (urea) were found to reduce the severity of eyespot on wheat in comparison to controls without fertilisers. The severity of eyespot, however, increased as the dosage of nitogen fertiliser was increased above 60 kg/ha. Combinations of urea and phosphorus increased severity of eyespot while combinations with potassium reduced severity. A “recommendation” was made for such application: 90 kgN/ha or 90 kgN: 30 kgP/ha: 30 kgK/ha.

Development of apothecia ofTapesia yallundae in contrasting populations selected by fungicides

Apothecia of the eyespot fungus,Tapesia yallundae, were found on 0–18% of straws in plots of wheat stubble in February–March 1994. The fungicides carbendazim, prochloraz or carbendazim plus prochloraz had been applied repeatedly to the same plots in each of the previous 9 years in which successive wheat crops had been grown. The factors most strongly correlated with the incidence of apothecia were the incidence and severity of eyespot in the preceding wheat crop and the frequency of carbendazim-resistant W-type fungus in populations recovered from that wheat crop. Plots treated with carbendazim, which had previously had more disease and more resistance to carbendazim in the pathogen population relative to untreated plots, therefore yielded most apothecia. Plots treated with prochloraz, which had selected for predominantly R-type fungus and decreased eyespot, yielded few apothecia. Single-ascospore isolates were all of the W-type and were more frequently carbendazim-sensitive than expected, except those from plots treated only with carbendazim. None showed decreased sensitivity to prochloraz. The implications of applying fungicides regularly for controlling eyespot on the capability of the eyespot fungus for genetic variation through sexual reproduction are discussed.

Modelling the frequency and severity of root and foot diseases in winter wheat monocultures

From 1986 to 1993, wheat crops from plots which had been cultivated with cereals for various lengths of time were assessed for the major foot and root diseases : eyespot (Pseudocercosporella herpotrichoides), take-all (Gaeumannomyces graminis) and sharp eyespot (Rhizoctonia cereals). For each disease, mean frequency and severity were modelled as a function of the number of years of continuous cereal cropping.Both take-all and eyespot increased during the first 3 to 5 years of monoculture before disease decline was observed. Decline was more important for take-all severity than frequency, whereas it was considerably stronger for eyespot frequency than severity. Take-all decline started sooner than eyespot decline. Model quality was highest for eyespot frequency and lowest for take-all frequency and severity.The incidence of sharp eyespot was too low to observe any influence of crop succession. We observed however an important year effect and a negative correlation with eyespot.

Evaluation of fungicides for control of eyespot disease and yield loss nationships in winter wheat

Following the discovery of resistance to benzimidazole fungicides in the cereal eyespot pathogen Pseudocercosporella herpotrichoides in the UK in 1981, and an initial in vitro screen to select the fungicides with greatest activity against the pathogen, 40 field experiments were carried out between 1983 and 1986 to evaluate alternative fungicides for control of eyespot. At the majority of experimental sites, benomyl‐resistant strains of the pathogen were present, and carbendazim did not control eyespot. Prochloraz was the most effective fungicide, reducing the eyespot index by 30–60%. There was no extra benefit from adding carbendazim to prochloraz. Flusilazole was almost as effective as prochloraz, but other fungicides had little or no effect. At sites with a high incidence of eyespot, prochloraz, with or without the addition of carbendazim, generally gave the largest yield increase. The mean yield increases each year were in the range 0·36–0·85 t/ha, and the greatest yield increase at any site was 2·27 t/ha. Most other fungicides increased yield, but carbendazim did not from 1984 to 1986. There were also yield increases at many sites with a low incidence of eyespot. Yield increases were associated with increases in thousand‐grain weight at the majority of sites, but in only a few instances were there associated increases in specific weight. Prochloraz application at GS30‐31 was cost effective at 71% of sites. At most sites, in regression of yield on eyespot, eyespot accounted for less than 25% of the variance in yield. The mean relationship between severe eyespot lesions and yield loss was such that each 1% increase in the percentage of tillers affected by severe eyespot was associated with a yield loss of 0·21 %. There was a significant positive correlation between eyespot at GS75 and GS30‐31, and between yield increase from prochloraz treatment (at GS30‐31) and eyespot at GS75, but not between yield increase and eyespot at GS30‐31. The ADAS threshold for fungicide application of 20% tillers affected at GS30‐31 was a reliable indicator of the cost‐effectiveness of treatment at 60% of sites.

Effects of rotation, stubble retention and cultivation on take-all and eyespot of wheat in northeastern Victoria, Australia

The effects of different rotations and methods of seed-bed preparation on take-all ( Gaeumannomyces graminis var. tritici) ( Ggt) and eyespot ( Tapesia yallundae; anomorph Pseudocercosporella herpotrichoides) of wheat ( Triticum aestivum) were investigated in 1984–1986 in a long-term field experiment (established in 1981), on a fine sandy-clay loam in northeastern Victoria. One treatment, representing the conventional practice, involved burning stubble from the preceding crop followed by four passes with a scarifier in the autumn before sowing wheat each year. Other treatments were direct drilled each year (sown without prior cultivation) and included two stubble treatments (retained or burnt) in either continuously cropped wheat or in lupin ( Lupinus angustifolius)-wheat rotations. High levels of take-all and eyespot developed in the continuously cropped wheat (up to 79% and 66% plants affected, respectively). On the other hand, the incidence of plants with either disease was very low or negligible in wheat that was preceded by lupins. In continuous wheat the incidence of plants with Ggt lesions were up to two times higher in the conventionally cultivated treatment (14% 74% and 79% plants affected in 1984, 1985 and 1986, respectively) than in direct drilled treatment (5%, 36% and 39% plants affected, respectively). Generally, the incidence of plants with Ggt lesions and the severity of root symptoms in direct drilled wheat did not differ significantly between the two stubble treatments. The incidence of eyespot in direct drilled wheat was exacerbated by the retention of wheat stubble on the uncultivated plots (3%, 46% and 66% plants affected in 1984, 1985, and 1986, respectively) but was reduced by burning the stubble (4%, 19% and 33% plants affected in 1984, 1985, 1986, respectively). However, cultivating soil after burning stubble resulted in more plants with eyespot (14%, 39% and 46% plants affected in 1984, 1985 and 1986, respectively) than did burning stubble alone, and in one year the incidence of affected plants in the cultivated treatment was as high as in wheat direct drilled into stubble. The incidence of eyespot was positively correlated ( r=0.85, 0.84 and 0.61 in 1984, 1985 and 1986, respectively) with the incidence of lodged tillers. The incidence of lodging was, generally, highest each year in wheat sown directly into wheat stubble and was reduced by burning wheat stubble or by cropping wheat after lupins. Wojnowicia graminis was frequently isolated, as was Tapesia yallundae, from eyespot lesions suggesting that perhaps not all symptoms of lodging in Victoria can be attributed to Tapesia yallundae.