Einfluss verschiedener Saattermine auf den Erbsenwicklerbefall (Cydia nigricana Fabr.) in ökologischen Gemüseerbsen

The pea moth (Cydia nigricana) has developed to the most serious pest in organic green peas in recent years. In 2003 about 20 % of the contracted acreage needed to be rejected by the processing industry, due to the very low tolerance levels requiring at least 99,5 % (w/w) non affected high quality peas. The present study investigated the influence of different sowing dates on the damage level in green peas. In a small scale field experiment arranged in a complete randomized block design with four replicates three common cultivars suitable for early, mid and late sowings, namely Avola, Gonzo, Trompet, respectively, were utilized. Each variety was sown at an early and a late date, resulting in six sowing dates at total, covering the entire sowing period from mid March to mid May. Subsamples of 3 x 1,5m2/plot were harvested by threshing and pea moth related infestation was assessed as the percentage of damaged peas. Crop phenology was recorded in weekly inspections. Flight activity of male moths was monitored twice a week by pheromone traps. As a result, only the early sowing dates revealed damage levels below the required threshold of 0,5 %. Green peas sown after mid of April where increasingly affected, approaching 3-6 % damaged peas. Damage was closely related to the coincidence in time of a) flowering and the onset of maturing pods with b) the phenology of monitored pea moths. The onset of flowering did not depend only on the sowing date but also on the respective pea cultivar. As registered C. nigricana-control options are lacking as present, the described strategy of coincidence avoidance in combination with fast maturing cultivars appears to be the most suitable contribution in reducing the risk of pea moth attack in organic green peas

Einfluss des Gemengepartners Leindotter (Camelina sativa L.) auf Beikrautbesatz, Schädlingsbefall und Ertrag in Körnererbsen

The effect of mixed cropping semi-leafless peas with linseed dodder (Camelina sativa (L.) Crtz.) on weed development and pest incidence was investigated in small plot experiments in Northern Hessen, Germany, over two years. Mixed cropping peas together with linseed dodder had a significant suppressive effect on weed-coverage, in average 62 % efficacy in 2003 and 54 % in 2004, compared to mono cropped peas. The infestation level of pea aphid (Acyrthosiphon pisum) and the damage incidence of pea moth (Cydia nigricana) in harvested peas, was neither significantly reduced nor enhanced. In both years mixed cropping peas gained a relative surplus in yield compared to peas grown as a sole crop. The results demonstrate the advantageous complementary use of environmental resources in grain peas by the companion crop C. sativa and its antagonistic effect towards weed development

Viruserkrankungen in Möhren - gegenwärtige Probleme und verfügbare Nachweismethoden

An apparently new virus disease of carrots (Daucus carota) has gained increasing importance in Germany. The complex of symptoms consisting of leaf reddening, plant stunting, hairy and rat tailed roots is thought to be caused by viral infections. Particularly the main carrot growing areas in Lower Saxony are adversely affected. In field surveys in 2003 about 30 % symptomatic plants were observed with average weight losses of about 30 %. In severe cases symptom-related yield reduction was estimated to be 17 % on-farm, which corresponded to a monetary loss of up to 600 €/ha. In 2004 up to 6 % of the plants displayed virus like symptoms. Varietal differences in susceptibility were observed. In general, late maturing varieties for processing showed more symptoms than early maturing fresh market varietes. However, this was not consistent in all cases. At present eight different carrot viruses have been isolated and partially characterized. Antisera to Carrot yellow leaf virus (CYLV, Closterovirus), Carrot thin leaf virus (CTLV, Potyvirus), Carrot red leaf virus (CtRLV, Luteovirus), and the Anthriscus strain of Parsnip yellow fleck virus (PYFV, Sequivirus) are now commercially available for serological analysis of carrot samples. Our provisional experimental data indicate that CtRLV is highly variable and the causal agents typically associated with the carrot motley dwarf (CMD) disease complex may differ in Germany from those reported in the literature. Further analyses of single and multiple infections with their corresponding symptoms under controlled conditions will be necessary to identify the relevant environmental conditions leading to economic losses