Wheat Leaf Diseases Research Articles

The effects of soil tillage and crop rotation on the development of winter wheat leaf diseases

The effects of soil tillage and crop rotation on the development of winter wheat leaf diseases

Controle de doenças foliares em trigo com equipamentos de pulverização de baixo volume de aplicação

A utilização de equipamentos de pulverização com menor volume de aplicação no controle de doenças é uma tendência na agricultura. Portanto, este trabalho tem por objetivo determinar a eficiência de equipamentos com baixo volume de aplicação no controle de doenças foliares do trigo. O experimento foi conduzido em duas safras agrícolas e três cultivares no município de Santa Maria, RS. Os tratamentos constituíram-se de diferentes equipamentos de pulverização, sendo eles: pontas hidráulicas do tipo leque (XR 110015) e cone vazio sem indução de ar (TX-VK6), ambos com volume de aplicação de 120L ha-1, atomizadores rotativos de discos, utilizando baixo volume oleoso (BVO(r)), com volumes de aplicação de 24L ha-1 e 34L ha-1 e uma testemunha sem aplicação. As gotas geradas pelos equipamentos (densidade, diâmetro mediano volumétrico) foram avaliadas através da utilização de papéis hidrosensíveis. Também foram avaliadas a severidade da mancha amarela e da ferrugem da folha. A utilização de bicos hidráulicos com volume de aplicação de 120L ha-1 apresentaram as maiores eficiências no controle das doenças. O atomizador rotativo de discos com volume de aplicação de 34L ha-1 apresentou eficiência no controle das doenças semelhantes ao bico hidráulico. A densidade de gotas foi superior a 40 gotas cm-2 em todos os tratamentos, mesmo nos tratamentos com atomizadores rotativos de disco com baixo volume de aplicação. O controle das doenças não apresentou relação direta com a cobertura mensurada pelos cartões hidrosensíveis

Image Recognition of Wheat Leaf Disease based on Learning Vector Quantization Neural Network and Combination Feature Parameters

Image Recognition of Wheat Leaf Disease based on Learning Vector Quantization Neural Network and Combination Feature Parameters

Effect of foliar fertilizer and fungicidal protection against leaf spot diseases on winter wheat

Field experiments were carried out in the seasons 2000/2001 and 2001/2002 in Plant Protection Institute, Sooenicowice Branch to assess the influence of foliar fertilizers such as Ekolist PK 1, Ekolist Mg, Mikrosol Z and Urea on healthiness of winter wheat. Foliar fertilizers were mixed with fungicides. The fungicides were applied at full or half recommended doses. The effect of the disease on wheat leaves was evaluated three times in each vegetation season. Remaining green leaf area (GLA) of leaves was also determined. GLA of the leaves F-1 was not significantly different for each combination with different fertilization and different levels of chemical treatment. The application of foliar fertilizer only had no effect on green leaf area (GLA). The results indicate that foliar fertilization of all experimental plots improved leaf condition and therefore halted the development of wheat leaf diseases. The increases of 1000 grain mass and yield was high for each plot where a fertilizer and a full or half dose of a fungicide was applied. Foliar fertilizing with no chemical control had no proven effect on studied parameters.

Tan spot - the most harmful wheat leaf disease in Latvia

Tan spot (<i>Pyrenophora tritici</i>-<i>repentis</i>) is one of the most important wheat diseases in Latvia. Significant spreading of this disease was observed from 1998. Field experiments were carried out at the Research and Training Farm "Peterlauki" of the Latvia University of Agriculture, during 1998-2003. Development of diseases was observed on 14 winter wheat varieties, dynamics of development was investigated on 'Donskaja polukarlikovaja' and 'Stava'. Assessments of the disease severity were carried out on the upper three leaves each week from the start of stem elongation to full ripening. Tan spot was observed at the stage of stem elongation in 2003, and only after flowering in 1999. Increase of the disease severity was slow until stage of milk ripeness, and only in late stages of wheat development sharp increase of the disease was observed. Total rate of infection (through the session of vegetation) was very slow (0,01-0,19), but during ripening rate achieved 0,5-0,6. The main reason of so unequal development of the disease seems changes in amount of infection sources. Other possible reason of rapid increase of the disease development is the relationship between leaf age and susceptibility to the disease. Further research is necessary for better understanding of tan spot life cycle.

Characteristics of wheat leaf diseases development in Latvia

The field observations were carried out in 1999-2004 on 29 fields in Latvia. Incidence and severities of wheat leaf diseases were determined. Tan pot caused by <i>Drechslera tritici</i>-<i>repentis</i> and Septoria leaf blotch, induced by <i>Septoria tritici</i> were the most harmful diseases at the time of research (incidence 10-100% and 1-100%, respectively). Also the incidence of powdery mildew, caused by <i>Blomeria graminis</i> was high (4-100%), while that of rusts (<i>Puccinia tritici</i> and <i>P. striiformis</i>) was very low. Changes in disease epidemics were determined and showed the differences between the analyzed diseases.

RNA‐mediated gene silencing of ToxB in Pyrenophora tritici‐repentis

The fungus Pyrenophora tritici-repentis causes tan spot, a wheat leaf disease of worldwide importance. The pathogen produces three host-selective toxins, including Ptr ToxB, which causes chlorophyll degradation and foliar chlorosis on toxin-sensitive wheat genotypes. The ToxB gene, which codes for Ptr ToxB, was silenced in a wild-type race 5 isolate of the fungus thorough a sense- and antisense-mediated silencing mechanism. Toxin production by the silenced strains was evaluated in culture filtrates of the fungus via Western blotting analysis, and plant bioassays were conducted to test the virulence of the transformants in planta. The chlorosis-inducing ability of the silenced strains was correlated with the quantity of Ptr ToxB, and transformants in which toxin production was strongly decreased also caused very little disease on toxin-sensitive wheat genotypes. Cytological analysis of the infection process revealed that, in addition to a reduced capacity to induce chlorosis, the silenced strains with the greatest decrease in the levels of Ptr ToxB produced significantly fewer appressoria than the wild-type isolate, 12 and 24 h after inoculation onto wheat leaves. The results provide strong support for the suggestion that the amount of Ptr ToxB protein produced by fungal isolates plays a significant role in the quantitative variation in the virulence of P. tritici-repentis.

Research on Feature Extraction of Wheat Leaf Disease Image

In order to resolve the problem of not taking into account color, texture and shape features in crop disease intelligent recognition systems, feature extraction method based on three feature types was proposed. Two types of color spaces such as RGB and HIS were considered, and the transformation formula of the two color spaces was improved. Then ten color features were defined and extracted. Meanwhile sixteen texture features were defined and extracted based on gray level co-occurrence matrix. And thirteen shape features were defined and extracted based on invariant moment theory. Finally the feature dataset was received which was suitable for identifying four types of wheat leaf diseases. The results show that the system recognition rate is relatively high, and can meet the practical application requirements.

Multiple Classifier Combination For Recognition Of Wheat Leaf Diseases

Abstract Wheat industry is an important constituent of Northern China's overall agricultural economy. Proper disease detection using computer vision and pattern recognition has being investigated to minimize the loss, and fmally achieve intelligent healthy farming. This paper proposes a new strategy of Multi-Classifier System based on SVM (support vector machine) for pattern recognition of wheat leaf diseases for higher recognition accuracy. Diseased leaf samples with Powdery Mildew, Rust Puccinia Triticina, Leaf Blight, Puccinia Striifomus were collected in the field and images were captured before a uniform black background. Three feature sets including color feature set, shape feature set and texture feature set were created for classification analysis. The proposed combination strategy was based on stacked generalization and included two-level structure: base-level was a module of three kinds of SVM-based classifiers trained by three feature sets and meta-level was one module of SVM-based decision cla...

Comparison of Disease Occurrence and Green Leaf Area (GLA) of Winter Wheat Depending on the Forecrop and Differentiated Fungicidal Protection Used

Comparison of Disease Occurrence and Green Leaf Area (GLA) of Winter Wheat Depending on the Forecrop and Differentiated Fungicidal Protection UsedThe effect of the forecrop and differentiated chemical plant protection on the intensity of fungal leaf diseases of winter wheat were studied from 1999-2008. Five (I-V) separate experiments were conducted in Mazury (Szestno I,), Żuławy Wiślane (Lisewo II), and Powiśle (Wielgłowy III, IV and Radostowo V). The intensity of diseases varied. Powdery mildew (Blumeria graminis) was noted in relatively low or trace intensity. On the other hand, there was a large amount of necrotic leaf spot complexes caused byMycosphaerella graminicola, Stagonospora nodorum, Pyrenophora tritici-repentisandFusariumspp. In 2000, 2001 and 2003 brown rust (Puccinia recondita) was noted in high intensity. The applied treatments were very effective in reducing fungal disease on leaves. The surface of the upper leaves (Green leaf area - GLA) with no symptoms of infection and fungicide use were significantly higher than in the control. It was also found that the GLA of crops grown after oilseed rape was higher than the GLA of crops grown after wheat.

Canola–Wheat Intercrops for Improved Agronomic Performance and Integrated Pest Management

Intercropping can enhance yields and reduce pest infestations, but investigations of intercropping regimes using crop species common to the large‐scale monoculture production systems of western Canada have not examined these diverse elements. Intercrops of canola (Brassica napus L.) and wheat (Triticum aestivum L.) were established at three sites in Alberta, Canada in 2005 and 2006 to determine interactions between intercropping regimes and crop grain and biomass yield, crop quality characteristics, soil microbial community biomass and diversity, flea beetles (Phyllotreta spp., Coleoptera: Chrysomelidae), and wheat leaf diseases. The study also investigated effects on flea beetles and soil microbial communities of a canola seed treatment containing a neonicotinoid insecticide and fungicides. Crop yields were comparable between intercrops and monocultures of canola and wheat. Crop quality characteristics and flea beetle feeding damage to canola seedlings had variable responses to intercropping. Flea beetle feeding was reduced with the inclusion of the seed treatment by between 1 and 20% damaged leaf area, although only one site‐year had damage levels great enough to overcome plant compensatory abilities in untreated plots. The first true‐leaf stage of canola development experienced the greatest flea beetle damage. Proportions of pathogen‐infected wheat leaf tissue were up to 2.5 times greater in intercrops than wheat monocultures but tended to decrease as the proportion of canola in the intercrops increased. Soil microbial parameters were unaffected by factors investigated. Although intercrop yields approximated those of monocultures, additional benefits of canola–wheat intercrops determined in this study appear insufficient to recommend this system for widespread adoption.

Modelo de ponto crítico para estimar danos de doenças foliares do trigo em patossistema múltiplo

A critical-point model to estimate damage caused by wheat leaf diseases in a multiple pathosystem Wheat leaf diseases cause damage by reducing photosynthetic activity in leaves. The objective was to obtain damage model equations for a wheat multiple pathosystem, by examining the relation between grain yield and the incidence of leaf diseases at different plant growth stages. The experiments were carried in Lages and Sao Jose do Cerrito, SC, during the 2005/06 and 2006/07 crop seasons with cultivars Onix and BRS Louro. The gradient of disease incidence was obtained by the number of fungicide applications (one, two, and three) and three different fungicide rates: azoxystrobin+cyproconazol (40+16, 60+24 and 80+32 g of a.i. ha -1

Wheat Leaf Diseases and Possibilities of Computer Program Application for Disease Control

The main task of integrated plant protection is to reduce usage of pesticides and to address a request of farmers to cut down variable costs for winter wheat growing (including costs of fungicides). A new tool providing these requirements is a Decision support system based on PC program. Validation trials of PC-P Diseases were carried out in collaboration with Danish Institute of Agricultural Sciences in 1999-2002 in different regions in Latvia. Comparisons were made among standard treatments with full dose of Tango Super (epoxiconazole 84 g l-1, fenpropimorf 250 g l-1) in GS 51-55, split doses in GS 37-39 and GS 51-55 and treatment according to PC-P recommendation. Tan spot (Drechslera tritici-repentis), leaf blotch (Septoria tritici) and mildew (Blumeria graminis) were the most important diseases in this period. The results of trials showed that average doses of fungicide were decreased according to PC-P Diseases recommendations, treatment frequency index fluctuated from 0.2-1.02. Reduced doses of fungicides showed the same efficiency of diseases control as standard doses. Level of additional yield was similar in comparison with variants where standard doses were used.

‘Aquilla'—a premium quality facultative bread wheat (Triticum aestivum)

‘Aquilla’ is a premium quality bread wheat (Triticum aestivum) bred by the New Zealand Institute for Crop and Food Research. Given appropriate management it is suitable for sowing in New Zealand in Canterbury from May until October and in the southern North Island in spring, and produces similar yields to the current standard spring wheat ‘Kohika’. It is resistant or moderately resistant to most common wheat leaf diseases and pre‐harvest sprouting. It produces a bright white flour with consistently high farinograph water absorption (3–4% higher than other New Zealand premium bread wheat cultivars). It has very consistent baking quality, producing medium‐high test bake scores at moderate work inputs. The name ‘Aquilla’ was chosen to reflect its high water absorption values.

Ability of retained stubble to carry-over leaf diseases of wheat in rotation crops

Increasingly, wheat rotations on sand-plain soils in Western Australia are being managed with stubble retention practices for reasons of moisture and soil conservation. A major concern in stubble retention practices is an associated increase in risk from septoria nodorum blotch (Phaeosphaeria nodorum) and yellow spot (Pyrenophora tritici-repentis). These pathogens frequently occur together in the region and survive in crop surface residues. The amount of disease carry-over on stubble is an important determinant of the severity of leaf diseases during the entire crop season. To provide a rationale for wheat leaf disease management in stubble retention rotation systems the extent to which retained wheat stubble induces disease in rotated crops was investigated. The frequency with which wheat stubble, which had been retained through a 1-year rotation, induced significant disease in seedling wheat was low (14%) over the 4-year period of study. While disease carry-over from wheat stubble retention in rotations is possible, it appears to be uncommon. The small proportion (1–8%) of retained wheat stubble that remained after germination of the return wheat crop in typical Western Australian farming systems further indicates that in general retained wheat stubble is not a significant source of disease carry-over in rotation wheat crops in this environment.

Ozone Effects on Fungal Leaf Diseases of Wheat in Relation to Epidemiology

AbstractWheat plants at growth stages tillering, stem elongation, ear emergence and anthesis were exposed to 80, 160, 240 μg m−3 ozone for 5 days (7 h per day) and to charcoal‐filtered air. Post‐exposure inoculations with Septoria nodorum or Bipolaris sorokiniana revealed a faster growth of lesions on ozonated leaves. However, whereas maximum size of Septoria lesions was measured on leaves exposed to the highest concentration of O3, Bipolaris lesions developed best at 160 μg m−2 and were significantly reduced at 240 μg m−3 O3. These predisposing effects were largely independent of the four growth stages tested. The latent period of S. nodorum was inversely related to the lesion growth and particularly shortened by ozone at growth stages (GS) 37 and 55. The latent period of B. sorokiniana was most strongly shortened at GS 65 (anthesis). It is concluded that both diseases may be enhanced by ozone throughout the main growing season of wheat and that in particular S. nodorum epidemics may be accelerated by shortened latent periods at decisive stages of the early season.Zusammenfassung Ozonwirkung auf pilzliche Blattkrankheiten an Weizen in bezug zur Epidemiologie I. Nekrotrophe Pathogene Weizenpflanzen im Stadium Bestockung, Schossen, Ährenschieben und Blüte wurden mit 80, 160, 240 μg m−3 Ozon 5 Tage lang begast (7 Stunden täglich) bzw. aktivkohlegefilteiter Luft ausgesetzt. Nach anschließender Inokulation mit Septoria nodorum und Bipolaris sorokiniana, entstanden auf ozonbehandelten Blättern größere Läsionen. Während jedoch bei Septoria die größten Läsionen bei der höchsten Ozonkonzentration entstanden, war dies bei Bipolaris bei 160 μg m−3 der Fall, während sich bei 240 μg m−3 Ozon die Pilzläsionen deutlich schlechter entwickelten. Diese ozonbedingten Prädispositionseffekte konnten weitgehend in alien Entwicklungsstadien reproduziert werden. Die Latenzzeit von S. nodorum verhielt sich umgekehrt proportional zum Läsionenwachstum und war besonders stark bei EC 37 und EC 55 durch Ozon verkürzt. Bei B. sorokiniana war die Latenzzeit am stärksten bei EC 65 verkürzt. Es wird gefolgert, daß beide Krankheiten während der gesamten Hauptvegetationsperiode durch Ozon gefördert werden können, wobei der Epidemieaufbau insbesondere bei Septoria schon frühzeitig durch verkürzte Latenzzeiten beschleunigt werden kann.

The use of rainfall and accumulated mean temperature to indicate fungicide activity in the control of leaf diseases of winter wheat in the UK1

During 1988/1990, a series of 21 experiments was established in commercial crops of winter wheat. Chlorothalonil, fenpropimorph and propiconazole were chosen as protectant, eradicant or curative fungicides active against leaf diseases of winter wheat in the UK. To test their properties each one was applied once only to separate plots during a period of 7–8 consecutive weeks in May and June (GS 32–39). Disease progress was assessed weekly on adjacent unsprayed control and sprayed plots up to GS 85. Septoria tritici leaf blotch (Mycosphaerella graminicola) was the disease that occurred most frequently and severely across the 21 sites. Powdery mildew (Erysiphe graminis), brown rust (Puccinia recondita) and yellow rust (P. striiformis) occurred at fewer sites and were sufficiently severe to distinguish differences between the active ingredients at only two or three sites. Analysis of the disease progress curves for 75% control of each disease at one site only indicated that chlorothalonil possessed very good protectant but shorter‐term eradicant activity against M. graminicola and P. striiformis. Fenpropimorph exhibited only short‐term eradicant control of M. graminicola, but gave excellent protectant and eradicant control of E. graminis and P. striiformis; against P. recondita only eradicant activity was apparent. Propiconazole showed activity similar to that of fenpropimorph against P. recondita and excellent protectant and eradicant activity against M. graminicola and P. striiformis; against E. graminis, it gave good protectant and eradicant control. From disease progress curves, it was possible to calculate the period of protectant and eradicant activity in thermal time (accumulated degree days above zero) for each of the three active ingredients and to identify the most effective timing(s) for fungicide application in relation to rainfall or imputed infection.

Effects of open-top chamber fumigations with ozone on three fungal leaf diseases of wheat and the mycoflora of the phyllosphere

Spring wheat ( Triticum aestivum L. cv. Turbo) was exposed in open-top chambers to six different ozone levels (8-h daily means from 12·4 to 122 μg m −3), to non-filtered air and to chamberless field conditions for 31 days from seedling stage through ear emergence. Powdery mildew ( Erysiphe graminis DC. f.sp. tritici Marchal) which developed during the exposure period was significantly enhanced from 0·3/0·6% (two chamber replicates), 1·2/2·1%, 0·9/2·2% in charcoal-filtered air (CF) to 1·5/1·6%, 3·7/4·3%, 4·4/4·6% at the highest level of ozone, on the flag leaf, second and third leaf position, respectively. Post-exposure inoculation with Septoria nodorum Berk. led to increases of disease severity on the flag leaf from 40·9/43·6% in CF to 66·3/70·6% at the highest ozone concentration and on the ears from 15·7/16·5% to 26·3/26·6%. In the same comparison, severity of spot blotch following inoculation with Bipolaris sorokiniana (Sacc.) Shoem. (syn. Helminthosporium sativum Pamm., King et Bakke) was increased on the flag leaf from 3·6/8·9% to 12·3/23·4%. The three diseases examined correlated significantly with the ozone treatments in fumigated chambers. Disease severity was enhanced even on undamaged plant tissue (flag leaves). Infections of the two facultative pathogens on lower leaf positions started only in part from visible ozone lesions, mildew did not start from such lesions. No significant effects of ozone in the chambers on the saprobial colonization of the phyllosphere were detected, whereas there were marked differences in this respect between plants from the field and the chambers. At the highest ozone treatment, contents of chlorophyll a and carotenoids on the second leaf position declined significantly, which was associated with symptoms of premature senescence. Senescing effects of ozone are therefore assumed to be one major factor in predisposing wheat for necrotrophic leaf pathogens. Surprisingly, injurious and predisposing effects of ozone were completely absent in chambers supplied with non-filtered air containing ambient ozone at doses equivalent to those in CF + ozone chambers. Evidently, biological effects of ozone in pure air and in ambient air may differ markedly.

Forecasting Septoria nodorum on winter wheat in England and Wales

SUMMARYThe regional incidence of septoria (Septoria nodorum Berk), on winter wheat, as found in the National Winter Wheat Leaf Disease Survey for 1970–75, was related to weather variables and amounts of inoculum. The relation between disease shortly before harvest and days with rain through the growing season was explored by a correlation method and it was found that the closest association was with days with 1 mm or more of rain (wet days) in the period mid‐May to mid‐June, When explored in detail, the relation between infection and wet days showed both non‐linearity and asymmetrical scatter, A graphical technique was therefore used to develop simple forecast rules. These performed well when tested against data for 1976–78, although these years did not include a septoria epidemic.In addition to wet days, the influence of other weather variables was investigated by a multiple regression technique. Sunshine in May and June and temperatures in July were found to have a slight effect on septoria incidence, as did the previous year's infection (taken as a measure of inoculum) but the overall reduction of variance was slight. It is suggested that these additional variables, together with others not treatecl quantitatively, may best be used to decide the regional forecast in marginal cases, and to make it applicable to individual crops.Attempts to relate septoria at individual sites in northern England to wet days at nearby rainfall stations were not successful; nor did rainfall data from all these stations contribute to a better regional forecast of septoria than did a few stations chosen at random.