Pflanzenkrankheiten und Schädlinge im ökologischen Ackerbau

Zusammenfassung Auf der ökologisch bewirtschafteten Versuchsfläche des Versuchbetriebes Sickte der Biologischen Bundesanstalt wurden in der Vegetationsperiode 2002/2003 Feldversuche zur Untersuchung des Auftretens von Krankheiten und Schädlingen im ökologischen Ackerbau durchgeführt. Durch Auswertung der Ackerschlagkarteien der ökologisch bewirtschafteten Fläche und einer angrenzenden konventionell bewirtschafteten Fläche war ein ökonomischer Vergleich beider Anbausysteme unter gleichen Boden- und Klimabedingungen möglich.Insgesamt war auf Grund der trockenen Witterung das Krankheitsauftreten gering. Im Winterweizen war nach Vorfrucht Kleegras im Vergleich zur Vorfrucht Raps ein höherer Befall mit Mehltau (Erysiphe graminis) und in geringerem Umfang auch höherer Braunrostbefall (Puccinia recondita) festzustellen. Septoria-Blattdürre (Septoria tritici) wies von den genannten Krankheiten die höchste Befallshäufigkeit auf und zeigte keine Abhängigkeit von der Vorfrucht. Die Erträge variierten von 35,3 dt/ha (Sorte Bussard nach Raps) bis 70,1 dt/ha (Sorte Magnus nach Kleegras). Der Mischanbau von Weizensorten zeigte einen schwächeren Befall mit Braunrost (P. recondita), aber keinen geringeren Septoria-Befall als der Anbau der Einzelsorten.In der Sommergerste traten nur Netzflecken (Drechslera teres) mit Befallshäufigkeiten zwischen 25 und 100% in Abhängigkeit von der Sorte auf. Die Erhöhung der Aussaatstärke von 150 auf 500 Körner/m² führte zu einer leicht erhöhten Bestandsdichte und einer Ertragszunahme von 53,1 auf 68,9 dt/ha, nicht aber zu einem verstärkten Befall mit D. teres.An 5 verschiedenen Erbsensorten waren signifikante Unterschiede im Ertrag, in der Lagerneigung und hinsichtlich der Fraßschäden durch den Erbsenwickler (Cydia nigricana) feststellbar.Eine erste ökonomische Auswertung des ökologischen Ackerbaus im Vergleich zum konventionellen Anbau zeigte Vorteile für den ökologischen Anbau. Gründe hierfür sind der durch die Trockenheit hervorgerufene geringe Ertragsabstand zwischen beiden Systemen sowie die hohen Erlöse aus dem ökologischen Kartoffelanbau.     

Zur Verbreitung und Bedeutung von Pilzkrankheiten in K?rnerfuttererbsen (Pisum sativum L.) in Deutschland

Monitoring of the pathogen spectrum in grain peas (Pisum sativum L.) was conducted in Germany between 2005 and 2007. The outcome of this study implies that the infections of pathogens depend on the annual weather condition and the geographic area.Ascochyta pinodes, which infects aerial plant organs, was the pathogen found most frequently (on average 61, 8%). Especially in years with moist weather conditions a more severe spreading of the pathogen could be observed. Similarly, the occurrence ofBotrytis cinerea depends on the weather conditions. In 2007 were optimal conditions for infections and consequentlyB. cinerea was found with a high frequency of about 70%. Regarding diseases on root and stem base, this study clearly shows that infection of less prominent Fusarium species, such asF. redolens andF. avenaceum was significantly higher compared toF. oxysporum andF. solani.     

Neue Erkenntnisse zur Ökologie und Überwachung wichtiger Schädlinge im Apfelanbau

A large-scale three-year study on apple orchards in Havelland uncovered key knowledge about the ecology and control of significant pests for 3 different varieties. Experiments included a range of different blocks and varieties and focussed on the apple blossom weevil (Anthonomus pomorum), the rose tortrix moth (Archips rosana), the reticulated tortrix moth (Adoxophyes reticulana) and the European red mite (Panonychus ulmi). The experiments were divided according to season, from budding through flowering and finally at harvest. Infestation by the apple blossom weevil depended on the timing of flowering for the variety. The “Breuhahn” variety was the most heavily infested. Later and more delayed flowering resulted in higher infestation rates. The attack by pests had a thinning effect with corresponding flower infestation rates. There was no effect on yield when flowering tendency was normal. The flower clusters and leaves of the early-harvest variety “James Grieve” was most heavily infested by the rose tortrix moth (Archips rosana). The extent of the damage from pests that attack leaves could be determined exactly using the drying method. The rose tortrix showed significant differences only in the number of leaves in infected and healthy plants. There were significant differences in leaf mass between untreated controls and fruit clusters infested by the reticulated tortrix (Adoxophyes reticulana) for all 3 varieties. The “James Grieve” variety was most heavily infested. The results of the experiments involving the European red mite (Panonychus ulmi) in healthy and infested leaves and leaf number revealed preferential infestation of the “Golden Delicious” and “James Grieve” varieties. Overall, the study provided key information for the prognosis and control of key pests in apple cultivation.     

Verändern pfluglose Bodenbearbeitung und Frühsaaten die Unkrautvegetation im Winterraps?

Between 2005 and 2007 a total of 1364 oilseed rape (OSR) fields in 12 federal states of Germany was surveyed. Investigations took place in late autumn and included the identification and counting of all weeds in unsprayed parts of rape fields. Results on the impact of tillage intensity and crop sowing date on the level of total weed infestation, weed species number and weed flora composition in OSR fields are shown and those species identified which are sensitive to the analysed factors. Neither tillage intensity nor crop sowing date affect the level of weed infestation in OSR fields. In contrast, species richness was enhanced by non-inversion tillage as well as by an early crop sowing. While there were statistically proofed differences in the weed species composition of ploughed and unploughed OSR fields due to canonical correspondence analysis, the crop sowing date only had minor effects on species composition. Nevertheless, a multitude of single weed species was affected by tillage intensity and sowing date showing significantly differing relative frequencies and/or densities in fields with inversion and non-inversion tillage as well as between early and late sown crop. Among others Centaurea cyanus, Anchusa arvensis, A. spica-venti and Elymus repens were more abundant and partly reached higher densities after ploughing, whereas non-inversion tillage mainly favoured Galium aparine, Geranium spp. and Sisymbrium spp.. Lots of weed species tended to have higher populations when OSR was sown before August 15^th, species significantly increased by early sowing date were e. g. Centaurea cyanus, Convolvulus arvensis, Euphorbia spp. and Anchusa arvensis. However, only V. arvensis reached significantly higher densities when OSR was sown after September 1^st.     

Sporenverteilung des Echten Mehltaus im Hopfen ausgehend von Infektionsherden und Abhängigkeit vom Vegetationsstadium

In order to assess the potential of infection of hop powdery mildew it is important to know the spore dissemination coming from different sources. Overwintering via cleitothecia is not provable in experiments. So wild hops, not correctly cleared cultural hops and non-cultivation hops are potential carriers of powdery mildew which is overwintering via mycel. In 2007 we found a source which has infected an area of about 30?ha cultural hops. By the observation of infections in these hop gardens we found that half of the amount of conidia is in a distance of 9,55?m away from the source. In a smaller dimension we counted the amount of conidia around one single plant in a commercial hop garden by a special spore trap. In the single plant the amount of spores is lower than outside, while it is decreasing in a higher distance from the single plant. Analysing the micro spore dissemination in a single plant there was a big diversity of the amount of spores because of the complex architecture of the hop plants. Further studies showed that the susceptibility of hop is much higher in May than later in the year. Thus, statistically a lower amount of conidia is needed for one complete infection. However, a lower amount of conidia can easily be transported for long distances by wind. As a result a source of powdery mildew in a long distance from the cultural hops is a serious danger for the commercial hop gardens early in the year. Later each source of conidia looses its influence nearly completely.     

Silikate im Pflanzenschutz: Elektrostatische Applikation und Abhängigkeit der Wirksamkeit von der Schichtdicke

Natural occurring amorphous silica is ubiquitous on the earth in soils and sediments. Both, natural derived silica and synthetically produced amorphous silica are used against stored product pests and parasites in animal houses. New formulations, active even under higher relative humidity's can be possible used against horticultural arthropod pests. Since many horticultural pests hide on the undersides of leaves and silica is a physical contact insecticide, an appropriate application method is needed. This paper reviews electrostatic application of natural derived amorphous silica to Brassica chinensis leaves. Due to the inherent high volume resistivity of silica powder, induction charging was ineffective for electrostatic powder coating. Corona charging involves a reliable current source, but typically is inefficient in charging the powder particles and creates a high density of free ions between the gun and grounded substrate as well as within the coating layer. These factors resulted in poor coating quality and inefficient particle deposition. The best leave coating was archived using tribo charging. Here we have been able to apply coatings with different thickness. While a silica coating of 25–50?μm in petri dish experiments resulted in a reduced mortality of the granary weevil, Sitophilus granarius (L.), there was no difference between mortality with coatings of 50–100?μm and 100–125?μm. Silica applications on B. chinensis leaves resulted within two hours in a 45% reduction of the CO₂-absorption. Absorption level stayed reduced over a period of seven days and was between 45 and 73% compared to the control. Even after removing silica dust using pressurized air CO₂-absorption was between 19 and 28% reduced. This might be the case because silica particles where so small that they could possible clog the stomata opening resulting in a reduced transpiration and photosynthesis rate.     

Entwicklung, Samenbildung und Biomasseproduktion ausgewählter Problemunkrautarten in Rapshalbzwerghybriden

Recently semi-dwarf oilseed rape varieties appeared in practical cropping. So far, only few studies about their properties in combination with weeds are available. Recently however an increasing number of weeds that are difficult to control are observed in oilseed rape. For the experiment Anchusa arvensis (L.) M.??Bieb., Sisymbrium officinale (L.) Scop. and a mixture of three different Geranium species were selected to study their development, seed and biomass production. Consequences for cropping on semi-dwarf oilseed rape cultivars were derived from the results. Three rape cultivars different in plant height were chosen for the experiments: the normal growing variety “Viking”, the semi-dwarf variety “PR45D01” and a full dwarf rape biotype for breeding purposes. In contrast oilseed rape with normal height, infestation of light-indigently and high growing weeds is more probable in semi-dwarf oilseed rape varieties. These weeds show increased biomass production and higher seed production per plant.     

Energie zum richtigen ERNTE-Zeit-Punkt bei Optimierung von Qualität, Ertrag, Produktsicherheit und Umweltverträglichkeit im Siliermaisanbau durch Dynamische ReifeAnalyse (DRA)

Maize production trials carried out in eastern middle of Germany from 1999 to 2009 were used for statistical analysis of the optimum date for silage maize ripeness. The knowledge about difference in ripeness between grain and residual plants at the harvest were used for exactly choice of cultivar under drought conditions for silage and energy maize: The Silage maize Ripeness Index (the ratio of dry matter content of maize grains to dry matter content of residual plants) is more suitable for the leading of plant development, the determination of harvest date and the choice of cultivar as the dry matter content of the whole plant. The analysis is cheaper as well as not so material and time-consuming with the better financially results in feed-, milk- and methane production in comparison to the dry matter content of the silage maize of different hybrid maize populations and environments. Basically, the harvest of silage maize to be carried out at the maximum possible ripeness index in all years, on every site, regardless of the variety to perform their silage maize ripeness number (SRZ), the heat sum and the calendar. The requirements for the varieties in the silo and energy maize are identical. The phenological ensilage optimum and yield maximum correspond with the physiological ripeness of silage maize and are close to the grain dry matter content of 63% and a ripeness index from 2.6 to 2.9 depending on quality and yield parameters. The maximum ripeness on the basis of SRI from greater than 2.9 at physiological ripeness grain to be exceeded. Only under these conditions it is possible to reach the optimal ripeness of 30–35% in the whole plant silage maize (22–24% dry matter in the stover). The wide ripeness ratio between grain and stover is multifunctional guarantor for the better plant health, for example with regard to the zearalenone and carotene content, the resource efficiency of fertilizer-N in accordance with the yield-related N denials and soil stocks in N as well as basic product safety and sustainability of the procedure of silage maize. The Silage maize Ripeness Index (SRI) is, for whole plant maize, better than the Silage maize Ripeness Number (SRZ) for the choice of a hybrid in Germany. The dry matter content of grain in relation with the dry matter of residual plants are better than dry matter content of the whole plant maize as ripeness indicator in the production of silage and energy maize at the harvesting time. SRI is also universal suitable for use as a standard in scientific trials and for better characteristic of cultivar types and environmental influence universally appropriate and multifunctional.     

Einfluss der biologischen Bewirtschaftung auf die Phytodiversität in der Diasporenbank und oberirdischen Vegetation biologisch bewirtschafteter Ackerflächen

The project deals with the evaluation whether the conversion to organic farming leads to an increase of weed diversity. Additionally to the analysis of the above ground vegetation and the soil seedbank on the small permanent plots a mapping of the surrounding vegetation was conducted in 2012. The number of weed species varies highly over the years, but the inventory of species differs only slightly from the one found on the surrounding fields. The number of seeds per m² is highly correlated with the number of above ground weeds species. The crop has shown the highest influence on both.     

Rückgang von Ackerunkräutern in Baden-Württemberg – ein Vergleich von vegetationskundlichen Erhebungen in den Jahren 1948/49, 1975–1978 und 2011 im Raum Mehrstetten – Empfehlungen für Landwirtschaft und Naturschutz

In the period from the beginning of grain cultivation in Central Europe until the middle of the last century, the number of arable weed species has steadily increased due to diverse and extensive cropping systems. Since 1950, crop production systems have been intensified, arable land has been used for development (construction), chemical and mechanical weed control has improved and many crops have disappeared. These factors all have contributed to a strong decrease of weed species diversity. Based on detailed vegetation assessments this pattern was confirmed in the Mehrstetten area (Reutlingen County). Sampling data from 2011 were compared to data available for the same sites from 1948/1949 and 1975–1978. In the period covered, weed diversity decreased from by 64 % (97 species). Abundance of weed species was significantly higher in the field margins as compared to the center of the fields. Vegetation data obtained in 2011 no longer allowed for the identification of plant species communities since no species distinctly characterizing certain communities were recorded. There was no shift in the Ellenberg, Zeigerwerte von Pflanzen in Mitteleuropa, 1991, indicator values. None of the 23 endangered species still present in 1948/49 was recorded in 2011. Based on survey results, we assume that decrease in weed species diversity was caused by intensive cropping practices associated with the use of mineral fertilizer and herbicides as well as other effective methods of weed control.     

Studien zur Bekämpfung von Phytophthora ramorum an Rhododendron im Rahmen der Entwicklung eines Behandlungskonzeptes für Park- und Gartenanlagen

In this study dealing with the development of management strategies for P. ramorum in Rhododendron stands several plant protection and fertilizer products were tested for their suitability to control this pathogen on Rhododendron. Tests were conducted on young potted plants and abscised leaves, using the following products: phosphite (Nutri-Phite^® PK), copper hydroxide (Cuprozin^® liquid), Bacillus subtilis (Serenade^®), a mycorrhizal preparation, and a product based on ‘effective microorganisms’ (EMa). Although transmission of the pathogen from infected to healthy plants was successfully inhibited by phosphite, Cu hydroxide and B. subtilis, subsequent tests showed that only phosphite and Cu hydroxide had a significant effect on disease development. All other preparations based on antagonistic or growth promoting microorganisms had no preventive or curative effect. While B. subtilis tended to increase disease symptoms, the remaining products caused a slight reduction of disease severity only. In contrast, phosphite and Cu hydroxide almost completely inhibited infection by P. ramorum. Therefore, in field situations, the use of the ecologically safe, systemic phosphite against P. ramorum in Rhododendron stands appears to be reasonable and advisable. Along with other supporting measures within the framework of a management strategy, this will allow to prevent or slow down further spread of the disease.     

Feldstudie zum Nachweis und zur Regulation von Weizenschädlingen und natürlichen Antagonisten

Wheat insect pests and the beneficial arthropod populations were assessed using sweep net across a large scale winter wheat field in Bad Lausick (Free State of Saxony, Germany) before and after insecticide applications. The insecticides used were Karate (pyrethroid), Biscaya (neonicotinoid) and NeemAzal T/S (botanical insecticide). The tested compounds were sprayed twice during the early season growth stage (Elongation- GS 32) and at the heading stage (GS 55), and their effects were evaluated on wheat insect pests. The side effects of these insecticides on associated natural enemies were also studied. Monitoring was conducted for 4 weeks after each treatment. Cereal aphids, thrips, leafhoppers, cereal leaf beetles, cereal bugs and also many natural enemies such as predators (lady beetles, lacewings, syrphids, dance flies and spiders) and parasitoids (parasitic wasps) were surveyed. The dose of these insecticides resulted in reductions of wheat insect and natural enemy populations and this reduction was corrected based on Abbott equation. The results showed that Karate is correlated with the highest percentage reduction (79.5 %) to wheat insect pests. Karate use also resulted in a percentage reduction to natural enemies (30–60 %). Biscaya and NeemAzal T/S is correlated with an equivalent mortality percents (50–65 %) to wheat insect pests and resulted in a smaller percentage reduction of natural enemies (10–40 %) compared to Karate. Thrips and cereal bugs were more affected than leafhoppers. Lacewings and dance flies were more susceptible; while spider, syrphids and parasitoid wasps were more tolerant. Compatibility between natural insecticides and natural enemies is highly required to keep the environment clean.     

Bewertung der Pflanzenschutzintensität landwirtschaftlicher Betriebe im Rahmen des Umweltsicherungssystems Landwirtschaft

Zusammenfassung Der Verband Deutscher Landwirtschaftlicher Untersuchungs- und Forschungsanstalten (VDLUFA) Bonn bietet unter der Bezeichnung USL bundesweit eine Umweltverträglichkeitsbewertung landwirtschaftlicher Betriebe an und vergibt das Zertifikat Betrieb der umweltverträglichen Landbewirtschaftung, sofern die dafür geltenden Bedingungen erfüllt sind. Zu den 17 Prüfkriterien gehört auch die Bewertung der betrieblichen Pflanzenschutzintensität. Diese wird seit ca. zwei Jahren über den so genannten Behandlungsindex ermittelt, der in den letzten Jahren auf die spezifischen Bedürfnisse von USL (belegbare Datenbasis zur Absicherung der Justiziabilität) zugeschnitten worden ist. Das Verfahren ist von 2001 bis 2003 in zahlreichen Landwirtschaftsbetrieben getestet worden, darunter auch im Umwelttestbetriebsnetz Thüringen (25 Betriebe, 31 Bewertungen). Die Ergebnisse zeigen, dass mit dieser Methode aussagefähige sowie reproduzierbare und justiziable Ergebnisse gewonnen werden können.     

Maiszünslerbekämpfung – Bekämpfung und neue Entwicklungen beim Trichogramma brassicae-Einsatz

The European corn borer Ostrinia nubilalis (Huebner) is a well-known and investigated pest of corn and sweet corn particularly in the southwest of Germany since a long time. Nevertheless the pest can still surprise scientists and farmers. The first occurrence of a bivoltine race of the European corn borer in South Badenia in the years 2006 and 2007 is remarkable. The European corn borer had to be controlled in the last year on an area of approx. 60.000 hectares in Germany. An important antagonist of this pest is the parasitoid Trichogramma brassicae Bezdenko (Hym., Trichogrammatidae), which is already used for over 30 years on a continuously rising acreage for the control of Ostrinia nubilalis. The biology of the pest and its parasitoid are recapitulated particularly with regard to the biological control. The flight activities of the European corn borer are supervised with light traps in Southwest Germany. The data were inserted into a central data base at the LTZ Augustenberg, office Stuttgart (at first in 2007). The data can be used by advisors and farmers. They determinate the optimal time for the introduction of Trichogramma brassicae and optimize the application of insecticides. The annual randomized monitoring of the Trichogramma quantities and partially also qualities by the former state institute for plant protection and nowadays the LTZ Augustenberg helped to supply the farmers with good Trichogramma material. The efficiencies of the Trichogramma introduction reach up to over 70%. With the insecticide STEWARD (active ingredient Indoxacarb) similar and partly better efficiencies can be obtained. With the necessity of controlling Diabrotica virgifera virgifera with insecticides problems for the use of Trichogramma can arise – this will be discussed.     

Beitrag zum Qualitäts- und Ertragspotenzial stress- und trockenheitstoleranter Sorten für Silo- und Energiemais bei optimaler Reife

Maize production trials carried out in eastern middle of Germany from 1999–2007 were used for statistical analysis of the optimum date for silage maize ripeness, quality and yield potential as well as choice of cultivar under drought conditions for silage and energy maize. The Silage maize Ripeness Index (the ratio of dry matter content of maize grains to dry matter content of stover) is more suitable for the determination of harvest date, yield maximum and silage maize quality as the dry matter content of the plant. The analysis is cheaper as well as not so material and time-consuming in comparison to the dry matter content of the silage maize of different hybrid maize populations and environments. Ensilage optimum and yield maximum correspond almost with the physiological ripeness of silage maize and are close to the grain dry matter content of 60 to 65%, to the dry matter content of stover under 24% and a ripeness index from 2,5 and higher. Only under these conditions it is possible to reach the optimal ripeness of 30 to 35% in the whole plant silage maize. In dependence on the Silage maize Ripeness Index (SRZ) parameters of silage and energy maize were created differential ripeness optimum, quality and yield potential. The aims of silage and energy maize are similar. The vitality of stover has a greater importance for energy maize. The Silage maize Ripeness Index (SRI) is, for whole plant maize, better than the Whole Plant Maize Ripeness Index (SRZ) for the choice of a hybrid in Germany. The dry matter content of grain in interaction with the dry matter of stover are better than dry matter content of the whole plant maize as ripeness indicator in the production of silage and energy maize for the harvesting time. SRI is also suitable for use as a standard in scientific trials and for better characteristic of cultivar types and environmental influence.     

Zur Bedeutung betrieblicher Faktoren für die Pflanzenschutzmittel-Intensität im Ackerbau

In Europe, farmers are encouraged to reduce pesticide use. Pesticide use intensity in arable farming depends on many factors. Numerous studies report a high variance in pesticide use between farms. The aim of the present study is to identify farm specific determinants for the intensity of pesticide use. We investigated which farm characteristics and pesticide management factors are related to lower or higher pesticide use intensity. Data on chemical plant protection measures of 30 farms in two districts of North East Germany were examined for five field crops from 2005 until 2014. In the present study we investigated the pesticide use intensities described as Standardized Treatment Index (STI) of ten representative farms. Yield data and information on the field-specific soil quality were available from these ten farms. We used multiple regressions to estimate the relationship between farm characteristics and pesticide use.     

Risikoabschätzung von Schadelementen (Schwermetallen) im System Boden/Pflanze

In rural areas, representing about 97% of the agricultural and horticultural area, the content of heavy metals in harvested products does not create a significant risk to consumers. In urban areas with about 3% of the horticultural area and on agricultural production fields with corresponding history, local contaminations may exceed the precautionary values for soils. For these areas, an estimation of possible risks is advisable and necessary. On the base of investigations of transfer of heavy metals (As, Cd, Cr, Co, Cu, Hg, Ni, Pb as well as Zn) via the path soil to plant “bio concentration factors” (BCF) have been determined for various horticultural crops (leaf-vegetable, shoot-vegetable, fruit-vegetable, root-vegetable, kitchen herbs and fruit). By use of these BCFs in combination with human toxicological values of the heavy metals (TDI), guiding values can be derived for tolerable soil contamination with the respective metals. These guiding values allow a simple risk assessment of the respective contaminated soils for cultivation and consumption of crops or crop products.