Aspekte des Pflanzenschutzes bei der Pflanzgutvorbereitung von ökologisch produzierten Kartoffeln

Presprouting of seed tubers is a measure that is often recommended for organic potato growing. In on-farm field experiments the effect of presprouting was evaluated with respect to virus infection, yield and weed infestation. The effect of presprouting on yield was largely dependent on the year and on the late blight severity. Weeds were not affected significantly by presprouting. In most experiments virus incidence was higher in presprouted potatoes. Presprouting also had a suppressive effect on undesired regrowth after haulm destruction

Entwicklung eines situationsbezogenen Konzeptes zur Regulation des Erbsenwicklers in Gemüse- und Körnererbsen

Das Ziel des Projektes war es, ein Konzept zur Risikobewertung des Erbsenwicklerbefalls in Anbauregionen von Gemüseerbsen zu entwickeln, in dem präventive Maßnahmen und eine bedarfsgerechte Option zur Direktbekämpfung integriert sind. Die Datenerfassung zur Beurteilung von Risikolagen erfolgte in Erbsenanbaugebieten in Hessen und Sachsen, beide mit Schwerpunkt auf ökologischen Landbau. Die Risikobewertung umfasste die Abschätzung der Schlaggefährdung durch den Erbsenwickler innerhalb der Anbaugebiete mittels zeitlich-räumlicher Analysen und die Berücksichtigung phänologischer Daten zum Erscheinen, Flugaktivität und Entwicklung des Erbsenwicklers in Abhängigkeit von Temperatur und Photoperiode. Basierend auf der Risikobewertung sollten Entscheidungen zum Einsatz ökologischer Regulierungsverfahren getroffen werden können, die in einem zweiten Projektteil bearbeitet wurden. Die Regulierung des Erbsenwicklers wurde in einem Parzellenversuch über die präventiven Maßnahmen Sortenwahl und Aussaatzeitpunkt und eine bedarfsgerechte Direktbekämpfung untersucht. Als Ergebnis konnten die wesentlichen Faktoren, die für eine Risikobewertung zum Erbsenwicklerbefall notwendig sind, definiert werden: a) ein zeitlich-räumlicher Zusammenhang zwischen den vorjährigen Erbsenflächen und dem Erbsenwicklerauftreten im Folgejahr b) ein Einfluss von Photoperiode und Temperatur auf die Entwicklung der Überwinterungsstadien von C. nigricana, sowie Erscheinen und Flugaktivität der adulten Erbsenwickler c) eine Steuerung der zeitlichen Koinzidenzvermeidung von empfindlichen Entwicklungsstadien der Erbsenpflanze und dem Erbsenwicklerauftreten durch Sortenwahl und Aussaatzeitpunkt. Der Einsatz einer Pyrethrin-Rapsöl Formulierung hat eine variable Wirkung in der Regulierung des Erbsenwicklers gezeigt. Der Befall konnte nur bei geringem Befallsdruck unterhalb der sehr niedrigen Schadtoleranzgrenze von 0,5% geschädigter Ernteerbsen gehalten werden; bei einer starken Schädlingsdichte konnte keine ausreichende Befallsreduktion erreicht werden

First test of a cryogenic scintillation module with a CaWO4 scintillator and a low-temperature photomultiplier down to 6 K

Future cryogenic experiments searching for rare events require reliable, efficient and robust techniques for the detection of photons at temperatures well below that to which low-temperature photomultipliers (PMT) were characterised. Motivated by this we investigated the feasibility of a low-temperature PMT for the detection of scintillation from crystalline scintillators at T = 6 K. The scintillation module was composed of a CaWO4 scintillator and a low-temperature PMT D745B from ET Enterprises. The PMT responsivity was studied at T=290, 77 and 6 K using gamma-quanta from 241Am (60 keV) and 57Co (122 and 136 keV) sources. We have shown that the low-temperature PMT retains its single photon counting ability even at cryogenic temperatures. At T = 6 K, the response of the PMT decreases to 51 +- 13 % and 27 +- 6 % when assessed in photon counting and pulse height mode, respectively. Due to the light yield increase of the CaWO4 scintillating crystal the overall responsivity of the scintillation modules CaWO4+PMT is 94 +- 15 % (photon counting) and 48 +- 8 % (pulse height) when cooling to T = 6 K. The dark count rate was found to be 20 s-1. The energy resolution of the module remains similar to that measured at room temperature using either detection mode. It is concluded that commercially available low-temperature PMT are well suited for detection of scintillation light at cryogenic temperatures

Potato Virus Y reduction by straw mulch in organic potatoes

Potato virus Y (PVY) is transmitted non-persistently by winged morphs of many aphid species and is a major problem in seed potato production. In order to evaluate the potential of straw mulch applications (4-5 t ha-1) and presprouting on PVY reduction, small scale organically managed field experiments were carried out in Northern Hessen, Germany, over 3 yr. In all years mulching significantly reduced aphid infestation on leaves as well as PVY incidence in tubers. For the effect of presprouting the temporal coincidence of two factors was crucial � crop emergence and aphid flight activity. Presprouting decreased PVY incidence when in the phase of early crop emergence aphid spring flight activity was low, but increased it, although not significantly, when prominent aphid flight peaks occurred in this critical period. Straw mulch was most effective when vector pressure was concentrated early in the year acting as a PVY protectant for young plants. In later growth stages its effect declined gradually with increasing ground coverage of the crop. Combined mulching and presprouting had a synergistic, complementary effect on reduction of PVY incidence. In an on-farm experiment in 2001 scaling up the area mulched stepwise from 100 m² to 900 m² consistently kept aphid infestation at reduced levels

Effects of straw mulch on yield, weed development, nitrate dynamics and soil erosion in organically grown potatoes

The application of straw mulch to organic seed potatoes (Solanum tuberosum L.) has been shown to reduce virus incidence. In order to determine the associated agronomic effects of straw mulch, applied at 2.5–5 t ha�1, on soil nitrate dynamics, weed development, tuber yield and soil erosion, 12 field experiments were evaluated. Experiments were conducted on organic farms over 3 years at two locations in a temperate climate (635–709 mm precipitation/year; 8.1 8C mean air temperature) on loamy silt soils. Tuber yield and tuber size distribution were not influenced significantly by mulching. However, the risk of undesirable post harvest N-leaching was significantly reduced due to the immobilization of nitrate–N after harvest at 6.8–7.0 kg N t-1 straw in two experiments (18–34 kg NO3–N ha�1). There was no consistent effect of straw mulch on number of weeds, weed cover and above ground biomass of weeds. The fact that yield and weed development were not significantly affected by straw mulch is mainly attributed to the relatively low amounts of straw applied. Soil erosion was reduced by >97% in a rain simulation experiment on a potato field of 8% slope with 20% crop cover. Soil loss was greatest (1606 g m-2) in the unmulched treatment, and 31, 42 and 26 g m-2 in treatments with chopped straw at 1.25, 2.5 and 5 t ha-1, respectively

Effect of sowing date and straw mulch on virus incidence and aphid infestation in organic faba-beans (Vicia faba L.)

The effect of sowing date on aphid infestation and the incidence of aphid-transmitted viruses were investigated in organically managed, small-scale field experiments with two faba bean cultivars over 3 years (2002–04). As an additional factor, strawmulchwas applied in 2 of the 3 years shortly before the start of vector activity in May. Virus incidence was determined using enzyme-linked immunosorbent assay and immunoelectron microscopy. Aphid flight activity was monitored using standard yellow water traps. Bean colonising aphids were assessed throughout the vegetation period by counting the number of plants infested with Acyrthosiphon pisum, Megoura viciae and Aphis fabae. Pea enation mosaic virus and bean yellow mosaic virus were the most abundant aphid-transmitted viruses, being detected in 22–54% and 9–69%, respectively, of the total number of virus-infected plants analysed per year. Further aphid-transmitted viruses found in faba bean were bean leaf roll virus, beet western yellows virus, clover yellow vein virus (in 2002) and soybean dwarf virus (in 2004). A. pisum was the predominant aphid species colonising faba bean plants. Early sowing compared with late sowing led to a significant reduction of the total virus incidence in faba bean in all 3 years. However, significantly decreased levels of A. pisum colonisation as a result of early sowing were observed only in 1 year and one cultivar. Irrespective of sowing date, straw mulching had no significant effects on virus incidence and aphid colonisation. Compared with late sowing, early sowing significantly increased bean yield in all 3 years and kernel weight in 2 years, whereas straw mulching had no effect on yield

Observation of atom - photon entanglement

10.1109/EQEC.2005.15674792005 European Quantum Electronics Conference, EQEC '052005313