Zum Stand der Kenntnisse überProstephanus truncatus (Horn) (Col., Bostrichidae), einen gef?hrlichen Maissch?dling in Afrika

Es wird ein gedrängter Überblick über die Lebens- und Schadensweise sowie Möglichkeiten der Bekämpfung des BostrichidenProstephanus truncatus gegeben, der nach seiner Einschleppung aus Mittelamerika in Afrika zu einem gefürchteten Maisschädling werde. Besonders zahlreich vermehrt er sich in belieschten Maiskolben, eine in ländlichen Regionen der Tropen häufig praktizierte Lagerform. Neuere Untersuchungen deuten darauf hin, daß der Käfer die Kolben an der Pflanze schon vor der Einlagerung befällt.Die Verluste in Maislägern mitP. truncatus-Befall liegen durchschnittlich 4fach über dem sonst üblichen Niveau. Schätzungen ergaben, daß eine landesweite Ausbreitung des Schädlings in Kenia, das durch seine direkte Nachbarschaft mit dem außerordentlich stark betroffenen Tansania potentiell gefährdet ist, zu einem Ernteverlust von mindestens DM 33 Mio. pro Jahr führen würde. Dieser Ausfall müßte durch entsprechend hohe Importe ausgeglichen werden.     

Organic carbon-14 in the Amazon river system

Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin.     

The dissemination of Salmonella by meat and meat products from swine

Pork and pork products which are consumed raw, e.g. mincemeat or fresh Bologna sausage, are relatively often contaminated with salmonellae. In the average of one year we detected salmonellae in about 5% of the samples investigated. Due to seasonal and local influences up to 45% of the minced meat samples can be positive for salmonellae. In minced meat salmonellae grow only at temperatures above 7 degrees C. During frozen storage of meat for several weeks, the salmonella count decreases on an average of about 50%. A damaging of surviving salmonellae by the freezing and thawing process was not observed. On the contrary, in thawed mincemeat stored at 8 degrees C the growth of salmonellae is stimulated, i.e. they grow better than in mincemeat not frozen before. Growth of salmonellae in Bologna sausage ("frische Mettwurst") can be inhibited by adding of at least 2.5% nitrit curing salt, 0.3% glucono-delta-lactone, and lactic acid starter cultures, even if the product is stored at temperatures up to 25 degrees C. Likewise in spreadible and sliceable fermented sausage ("streichf?hige und schnittfeste Rohwurst") no growth of salmonellae is to be expected, if a similar technology secures a sufficient microbiological stability during the ripening and smoking process. Therefore, the dissemination of salmonellae by pork and pork products can be avoided by technological measures, but also by a reasonable conduct of the consumer in the household.     

Untersuchungen zur Lagerung von Erdbeeren unter Berücksichtigung verschiedener Verpackungsmaterialien

In order to reduce the loss of quality of freshly harvested strawberries during storage, the effects of different packaging materials were examined with regard to storage time and temperature regime (20°C with relative humidity 75%, 4°C with relative humidity 88%). Strawberry containers (500?g) were used differing in form, alignment and number of ventilation openings, top and material. It was found that a drop in temperature to 4°C preserved the quality of strawberries longer in all packaging variants. Nevertheless, the used packaging material had different effects on the quality parameters. The packaging material made of polypropylene, which was closed with a lid and was equipped only with little ventilation openings, yielded the best results, e.?g. the transpiration losses were strongly reduced, thus favouring the preservation of pulp consistency and colour stability of the fruits. On the other hand, the fresh mass during storage was reduced by the materials polyethylenterephthalat, polyactid and groundwood. The quality loss was less dependent on the material, but more dependent on the number of ventilation openings. The results showed that with increasing numbers of ventilation openings the transpiration losses increased and the consistency and colour stability of the fruits decreased. In this context, a strong reduction of pathogenic infestation in relation to the ventilation openings could not be observed. As such, the loss of freshness was lowest with the packaging material of polypropylene, followed by the polyethylenterephthalat, polyactid and groundwood. Moreover, it was found that the kind of packaging material and the ventilation openings had an effect on the amount of pressure marks and the discharge of cell sap of the strawberries. The uneven ground surface of the materials made of polyethylenterephthalat and polyactid increased the punctual pressure on the strawberry fruits, which led to pressure marks and injuries of the fruit surface. Sharp-edged ventilation openings close to the ground surface of these variants favoured injuries and cell sap discharges of the packaging.     

Yield formation of five crop species under water shortage and differential potassium supply

A long‐term field experiment on a Haplic Phaeozem, established 1949 with four levels of potassium (K) supply (5, 69, 133, and 261 kg K ha^?1), was analyzed for the interaction between K supply and yield loss of five crop species by water shortage. The crop species were cultivated simultaneously side‐by‐side in the following rotation: potato (Solanum tuberosum L.), silage maize (Zea mays L.), spring wheat (Triticum aestivum L.), beet (Beta vulgaris L.), and spring barley (Hordeum vulgare L.). The treatment with 133 kg K ha^?1 supply had a nearly balanced K budget. In the treatments with lower supply, the soil delivered K from its mineral constituents. On the low‐K plots (especially on those with only 5 kg K ha^?1), crops suffered yield depressions of nearly all main harvest products (cereal grains, potato tubers, beet storage roots, silage maize) and by‐products (straw, beet leaves) by up to 40.7% of dry matter. Only wheat grains were an exception. Potassium concentrations in the harvested plant parts decreased nearly in parallel to the reduction of their dry matter yields, with the exception of cereal grains, which kept stable concentrations even in the treatment with only 5 kg K ha^?1. A comparison of four year‐pairs with differing levels of precipitation in yield‐relevant periods showed an average water shortage‐induced depression of dry matter yields by 19.7% in the main harvest products. The severity of this yield depression was not mitigated by elevated K supply, with the exception of beet leaves, where the dry matter production was stabilized by high K supply. In this crop, the reduction of storage‐root yield was associated with a decrease in harvest index and was therefore obviously caused by an inhibition of assimilate translocation from the leaves into these organs, in contrast to cereals, where water shortage primarily affected dry matter production in vegetative organs. It is concluded that the physiological causes of yield reduction by drought stress and the possibility of its amelioration by K supply differ between plant species and organs.     

Climate-sensitive modelling of site-productivity relationships for Norway spruce (Picea abies (L.) Karst.) and common beech (Fagus sylvatica L.)

The aim of the presented research project is to fit a site index model capable for predicting changes in site-productivity in a changing climate. A generalized additive model is used to predict site index as a function of soil and climate variables. The climate parameter values are estimated using the regional climate model WETTREG, based on global climate simulations with the global circulation model ECHAM5/MPI-OM for the reference period from 1961 to 1990. The climate values are further regionalized on a 200 m × 200 m grid. The generalized additive model quantifies the partial linear and non-linear effects of the predictor variables on site index. The model is parameterized for Norway spruce (Picea abies (L.) Karst.) and common beech (Fagus sylvatica L.) in Lower Saxony, Germany. Two case studies investigate the model's ability to generate information in order to support forest management planning decisions under a changing climate. One example analyzes the possible shift in site index of spruce along a precipitation gradient under the International Panel on Climate Change (IPCC) emission scenario A1B in the period from 2041 to 2050. The other case study shows possible future changes in site index of beech along a temperature gradient.