Possibilities for integrated control of winter oilseed rape diseases in Latvia

The sowing area of winter oilseed rape in Latvia has been rapidly increasing during the last 10 years, therefore oilseed rape diseases have become an important risk factor. The present paper reports 4‐year data (2008–2011) on different fungicide application systems (including forecasting systems) tested in field trials in Central Latvia. The development of stem canker (Leptosphaeria spp.) and white stem rot (Sclerotinia sclerotiorum) was evaluated depending on fungicide application schemes. Stem canker was found to be a widespread disease, and coexistence of both L. maculans and L. biglobosa was established in Latvia. There was no epidemic of white stem rot observed during the investigation period (incidence of disease was only 0.7–4.5%). Application of fungicides significantly (P < 0.05) decreased severity of stem canker. However, substantial differences between different treatments were not detected. Yield of oilseed rape fluctuated at about 4.5 tonnes ha^?1, and use of fungicides did not increase the yield. It was found that DaCom Plant Plus program had overestimated the risk of white stem rot in years with low disease pressure, whereas the Swedish model of forecasting, based on the risk‐point system, had produced acceptable forecasts.     

The incidence of honey bee pests and diseases in England and Wales

The Central Science Laboratory (CSL) National Bee Unit (NBU) has been responsible for maintaining the Integrated Bee Health Programme in England and Wales since the early 1990s. The role of the Bee Health Programme is to protect the honey bee, a major pollinator of agricultural and horticultural crops and wild flora, and to provide up-to-date technical support to beekeepers. The Bee Health Programme is funded in England by the Department for Environment, Food and Rural Affairs (Defra) and in Wales by the Welsh Assembly Government (WAG). The work includes inspection of honey bee colonies, disease and pest diagnosis, development of contingency plans for emerging threats, minimising the risk of introduction of potentially serious exotic pests and diseases through importation by import risk analysis and related extension work and consultancy services to both government and industry. There is also an underpinning programme of research and development.     

Changes in agronomic practices and incidence and severity of diseases in winter wheat in England and Wales between 1999 and 2019

In continuation of the annual national surveys of winter wheat, which began in 1970, samples from between 250 and 350 randomly selected wheat crops in England and Wales between 1999 to 2019 were visually assessed for disease symptoms during the milky ripe development stages (GS 73–75). Septoria tritici blotch was the most prevalent and severe foliar disease each year, although annual levels fluctuated considerably and there was no overall significant change over the two decades. Incidence of brown rust, yellow rust, take-all, and barley yellow dwarf virus also showed no significant overall change during the survey period, whereas glume blotch, powdery mildew, eyespot, and sharp eyespot all showed significant decline. Fusarium ear blight has significantly increased in both incidence and severity, causing a serious epidemic in 2012, when 96% of crops were affected. Tan spot has been the third most prevalent foliar disease since 2009 although severity is still very low. Regional disease levels were consistent over the two decades, providing reliable baselines to measure changes in seasonal disease severity. There were significant changes in agronomic practice with a rise to predominance of minimum tillage over the use of ploughing, decreases in overall disease susceptibility of cultivars grown, a major increase in the use of oilseed rape in the rotation and a long-term trend towards earlier sowing. Fungicide use increased considerably, with over 98% crops sprayed and an average of 3.5 applications made per crop each year since 2014. Implications of changes over the last 21 years are discussed.     

The occurrence of carbendazim resistance in Rhynchosporium secalis on winter barley in England and Wales in 1992 and 1993

In 1992, samples of Rhynchosporium secalis from 19 winter barley crops in England and Wales were examined for carbendazim resistance. Of the 120 isolates obtained, 14·2% were resistant to carbendazim. A larger survey was carried out in England and Wales in 1993 when samples from 74 crops were examined. On this occasion 16·6% of the 639 isolates obtained were resistant to carbendazim, and resistant isolates were detected in 46% of crops.     

Predicting the risk of weed infestation in winter oilseed rape crops

Chemical weed control before crop and weed emergence is a systematic practice in winter oilseed rape crops in France. It would be profitable both for farmers and the environment to predict the level of weed infestation early on in the growing season and to control weeds only when necessary using post‐emergence weed control. The objective of this paper was to develop and evaluate simple models to predict weed biomass in oilseed rape crops. The model input variables were related to weed population characteristics and farmers’ practices. The models can be used to classify oilseed rape plots into two categories: plots with a level of weed infestation above a threshold or those with level of weed infestation below a threshold. A data set including 3 years of experiments, conducted across several regions in France, was used to estimate the parameters and to evaluate the models. High values of sensitivity and specificity were obtained when weed biomass was predicted as a function of sowing date, type of soil tillage, soil mineral nitrogen, crop density, weed density at emergence, and main characteristics of the most abundant weed species. Model performance strongly decreased when input variables related to the weed population were not taken into account. The best models correctly classified 90% of the plots with high weed infestation and 64% of the plots with low weed infestation.     

湖北和安徽省油菜病毒病调查和病毒血清鉴定

2003年秋至2005年春2个油菜生长季分别到湖北和安徽2省12县市油菜产区进行病毒病发病情况调查,除局部地区和地块发病率达到20%～40%,多数大面积油菜发病率在0.1%以下。应用间接酶联免疫吸附法检测258份病害样品,TuMV占样品总数的90.7%,CMV占样品总数的8.9%,ORMV占样品总数的0.8%。     

Predicting light leaf spot (Pyrenopeziza brassicae) risk on winter oilseed rape (Brassica napus) in England and Wales, using survey, weather and crop information

Data from surveys of winter oilseed rape crops in England and Wales in growing seasons with harvests in 1987–99 were used to construct statistical models to predict, in autumn (October), the incidence of light leaf spot caused by Pyrenopeziza brassicae on winter oilseed rape crops the following spring (March/April), at both regional and individual crop scales. Regions (groups of counties) with similar seasonal patterns of incidence (percentage of plants affected) of light leaf spot were defined by using principal coordinates analysis on the survey data. At the regional scale, explanatory variables for the statistical models were regional weather (mean summer temperature and mean monthly winter rainfall) and survey data for regional light leaf spot incidence (percentage of plants with affected pods) in July of the previous season. At the crop scale, further explanatory variables were crop cultivar (light leaf spot resistance rating), sowing date (number of weeks before/after 1 September), autumn fungicide use and light leaf spot incidence in autumn. Risk of severe light leaf spot (> 25% plants affected) in a crop in spring was also predicted, and uncertainty in predictions was assessed. The models were validated using data from spring surveys of winter oilseed rape crops in England and Wales from 2000 to 2003, and reasons for uncertainty in predictions for individual crops are discussed.     

Occurrence and distribution of important weed species in German winter oilseed rape fields

Journal of Plant Diseases and Protection - Data on weed species currently found in winter oilseed rape, the extent of their occurrence and regional distinctions were collected in autumn 2005, 2006...     

Geostatistical analysis of the distribution of Leptosphaeria species causing phoma stem canker on winter oilseed rape (Brassica napus) in England

In June/July 2001, 2002, 2003 and 2006, regional variation in distribution of the pathogens Leptosphaeria maculans and L. biglobosa that are causally associated with phoma stem canker was surveyed on winter oilseed rape crops in England. In 2001–2003, when isolates from basal cankers were visually identified as L. maculans or L. biglobosa based on cultural morphological characteristics, 70% were L. maculans and 30% L. biglobosa . In 2001, 2002, 2003 and 2006, when amounts of DNA of each species in basal cankers were determined by quantitative PCR, the abundance of L. maculans DNA was greater than that of L. biglobosa DNA in 77% of samples. When regional differences in amounts of L. maculans and L. biglobosa DNA were mapped geostatistically, quantities of L. maculans DNA were greater in cankers from southern England and those of L. biglobosa DNA were greater in northern England. A comparison with geostatistically mapped predictions made using a weather-based model describing stages in development of phoma stem canker epidemics suggested that these differences in Leptosphaeria populations may have been a consequence of differences in temperature after onset of leaf spotting between northern and southern England. Both PCR and morphological evidence suggested that the abundance of L. maculans in England has increased since the last surveys in the 1980s. Implications of these surveys for control of phoma stem canker are discussed.     

A survey of the incidence of the Bromus species as weeds of winter cereals in England, Wales and parts of Scotland

In June 1989, a survey was made of 733 fields of winter cereals, 627 in England and Wales and 106 in Fife and the Lothian regions of Scotland. The occurrence of Bromus species was noted in three areas of each field: the uncropped field margin, the cropped headland and the field centre. Three arbitrarily defined infestation levels were recorded: severe, light and intermediate. The most common species recorded was Bromus sterilis L., which accounted for almost 87% of all sightings. Most of the other occurrences were almost equally distributed between B. hordeaceus L., and B. commutatus Schrad. Two other species were found, on one field each: B. diandrus Roth and B. × pseudothominii Hard. Surveyors were briefed to recognize B. secalinus L, but none was reported. The brome grasses were widespread throughout the surveyed regions. They were most common in the Lothians (81 % of surveyed fields) and in the South East (60%) and the South West (52%) of England and least common in the English West Midlands, Fife and Wales (17%, 15% and 4% of surveyed fields). Distribution was biased towards the uncropped margins and field headlands. In England and Wales, there were 146 fields where Bromus species occurred in the field margins only, 179 in margins and headlands only and 63 with infestations in all three areas. In contrast, there were only 26 fields where they were restricted to the cropped areas. A similar pattern occurred in Scotland. The correlations between incidence of the Bromus species and management practices were much weaker than had been anticipated. The standard advice for control is to plough rather than use non-inversion tillage systems, to delay sowing and to avoid long runs of winter cereals. The conclusion of this survey is that, although these practices may be reducing or preventing increase of these weeds, they are not effective at eliminating infestations. Incidence des espèces Bromus comme mauvaises herbes des céréales d'hiver en Angleterre, au Pays de Galles et dans certaines parties de I'Écosse En juin 1989 une enquête a été réalisée dans 733 champs de céréales d'hiver, 627 en Angleterre et au Pays de Galles, et 106 dans les régions d'Écosse Fife et Lothian. La présence d'espèces Bromus a été notée sur trois zones de chaque champ: la bordure non-cultivée ('field margin'), la bordure cultivée ('headland') et le centre du champ. Trois niveaux d'infestation arbitraires ont eAté notés: sévère, léger et moyen. Les espèces les plus communément rencontrées étaient Bromus sterilis L. qui représentait presque 87 % de l'ensemble des présences. Dans la plupart des autres relevés, B. hordeaceus L. et B. commutatus Schrad se distribuaient presque également. Deuxautres espèces ont été trouvées, chacune dans un champ: B. diandrus Roth et B. × pseudothominii Hard. On avait appris aux enquêteurs à reconnaître B. secalinus L. mais cette espèce n'a pas été rapportée. Les bromes se rencontraient sur tout le territoire des régions étudiées. Elles étaient les plus communes dans les Lothians (81 % des champs étudiés) ainsi que dans le Sud Est (60 %) et dans le Sud Ouest (52 %) de l'Angleterre; les moins communes dans les West Midlands, en Fife et au Pays de Galles (17, 15 et 4 % des champs examinés). Leur distribution était biaisée en faveur des bordures non-cultivées et des bordures cultivées. En Angleterre et au Pays de Galles, dans 146 champs les bromes ne se rencontraient que dans les bordures non-cultivées, dans 179 ils ne se rencontraient que dans les bordures cultivées et non-cultivées, et dans 63 ils se rencontraient dans les trois secteurs du champ. Inversement, il n'y avait que 26 champs oü ils ne se trouvaient que dans la partie cultivée. Une répartition semblable s'observait en Écosse. Les corrélations entre la présence de bromes et la conduite des cultures étaient plus faibles qu'anticipé. Le conseil habituel est de labourer plutôt que de pratiquer des façons culturales sans renversement de la terre, de retarder le semis et d'éviter les longues successions de céréales d'hiver. La conclusion de cette étude est que, bien que ces pratiques peuvent réduire ou prévenir la prolifération de ces mauvaises herbes, elles ne sont pas efficaces pour les éliminer en cas d'infestations. Verbreitung von Bromus spp. in Wintergetreide in England, Wales und Teilen Schottlands Im Juni 1989 wurde auf 733 Wintergetreidefeldern, 627 in England und Wales und 106 in Fife und in den Lothian-Gebieten in Schottland, das Auftreten von Bromus spp. aufgenommen, getrennt nach dem nichtkultivierten Feldrand, dem Vorgewende und dem Feldinnern. Die Befallsstärke wurde nach schwer, mittel und leicht unterschieden. Die häufigste Trespen-Art war Bromus sterilis L. mit fast 87 % aller Beobachtungen. Die übrigen Vorkommen waren zu fast gleichen Teilen Bromus hordeaceus L. und Bromus commutatus Schrad. Aufje l Feld wurde Bromus diandrus Roth und Bromus × pseudothominii Hard, gefunden. Trotz intensiver Suche wurde kein Bromus secalinus L. festgestellt. Die Trespen traten im Beobachtungsgebiet verb-reitet auf, am häufigsten in den Lothians (81 % der untersuchten Felder) und im Südosten (60 %) und Südwesten (52 %) Englands, am wenigsten in dem englischen West Midland, in Fife und Wales (17, 15 bzw. 4 %). Die Verteilung konzentrierte sich in England und Wales auf 146 Feldern auf die kulturfreien Feldränder, in 179 Fällen auf die Feldränder sowie die Vorgewende, und auf 63 Feldern waren alle 3 Bereiche mit Trespen verunkrautet; nur auf 26 Feldern waren die Arten auf das Feldinnere beschränkt. In Schottland wurde eine ähnliche Verteilung beobachtet. Zwischen der Bewirtschaftung und dem Auftreten der Bromus spp. bestand eine weit schwächere Korrelation als erwartet. Die generelle Bekämpfungsempfehlung ist Pflügen statt nichtwendender Bodenbearbeitung, spätes Säen und Vermeidung von Fruchtfolgen mit hohem Wintergetreideanteil. Aus den Untersuchungsergebnissen folgt, daß diese Bekämp-fungsmaßnahmen Trespen wohl zurückdrängen oder ihre Zunahme verhindern, aber nicht eliminieren können.     

Weed control in conventional and herbicide tolerant winter oilseed rape (Brassica napus) grown in rotations with winter cereals in the UK

Two winter oilseed rape (Brassica napus) cultivars, tolerant to glyphosate and glufosinate, were compared with a conventional cultivar at three sites over 4 years, in 3‐year crop rotations in the UK. The winter oilseed rape was grown in Years 1 and 4, with winter cereals, which received uniform herbicide treatments, in the intervening years. The second winter oilseed rape treatments were applied to randomised sub‐plots of the original plots. Weed densities were recorded in autumn and spring and weed biomass was measured in summer. At most sites, there was only one application of glufosinate or glyphosate, whereas two products were often used on the conventional variety. The timing of glyphosate and glufosinate application was, on average, 34 days later than that of the conventional broad‐leaved weed control treatments. Overall weed control, across all sites and years, was not statistically different between the conventional, glyphosate and glufosinate treatments. However, glyphosate achieved higher control of individual weed species more frequently than the other treatments. Glufosinate and the conventional treatments were similar in performance. The treatments in Year 1 sometimes affected weed populations in the subsequent cereal crops and, in rare instances, those in the rape in Year 4. Carry‐over effects were small after most treatments. In general, weed survival was greater in the oilseed rape crops, irrespective of the treatment, than it was in the intervening cereal crops.     

Changes in the glucosinolate content of oilseed rape plants following infection with turnip mosaic virus

Low and high glucosinolate cultivars of oilseed rape were analysed for variation in both individual and total glucosinolate content up to 27 days after inoculation with turnip mosaic virus. Both infected and control plants of the two cultivars differed in the concentration of aliphatic, aromatic and indole glucosinolates. The biggest differences in glucosinolate content between the cultivars were found in the aliphatic and aromatic glucosinolate groups. Infected plants of the high glucosinolate cultivar, Solida, possessed lower amounts of glucosinolates, than did healthy control plants. Similar results were obtained with a low glucosinolate cultivar, S1. No significant difference was found between the two cultivars in resistance to turnip mosaic virus, using qualitative and quantitative ELISA to determine virus content in their tissues.