Bud development and dormancy in slash and loblolly pine. I. Speed of budbreak and second year height as related to lifting date

Slash and loblolly pine 1-0 seedlings were lifted from the nurserybed in late November, mid-December, late December, and mid-February. The buds of the seedlings were classified as set or growing two weeks prior to lifting and were re-examined upon lifting. For both species, buds that had set remained set whereas those that were classified as growing showed an decreasing trend of setting from November through December. A subset of seedlings was potted and maintained in a greenhouse to determine rate of budbreak; the remainder were field planted. In the greenhouse, loblolly pine broke bud fastest and slowest when lifted in mid-February and mid-December, respectively. The rate of slash pine budbreak increased over successive lifting dates. In the field, loblolly pine lifted in mid-December exhibited the highest percentage of growing seedlings; these seedlings were also tallest after one year in the field. Field-planted slash pine had the highest percentage of growing seedlings when lifted in late November. However, seedlings lifted in mid-December were tallest after one year.     

Performance of eight tree species in the highland Vertisols of central Ethiopia: growth, foliage nutrient concentration and effect on soil chemical properties

The coverage of trees in the highland Vertisol areas of Ethiopia is very scarce. A tree screening trial was conducted from 1997 to 2002 in Ginchi (central Ethiopia) to select fast growing and high biomass producing tree species; evaluate foliage macronutrient concentration of different tree species; and assess effects of trees on soil chemical properties beneath their canopies. Acacia decurrens Willd, A. mearnsii De Wild and Eucalyptus globulus Labill attained the highest height growth at 64 months as compared to other indigenous and exotic species. E. globulus provided better height increment from 24 to 36 and 36 to 64 months than other tree and shrub species. Acacia mearnssi and A. saligna Labill Wendl produced high biomass at 40 and 64 months. Differences between the highest and lowest dry biomass at 12, 40 and 64 months were 1.13, 29.19 and 38.89 kg tree⁻¹, respectively. None of the tree species resulted in a foliage to stem biomass ratio of >0.98 at 40 and 64 months. Sesbania sesban (L.) Merr had high N and P concentrations in its foliages and stems at 12 and 40 months. Total N under Acacia abyssinica Hochst. Ex Benth, A.␣saligna and S. sesban was slightly greater at 40 months than 12 months.     

Gespinstmottenraupen als Vogelvernichter

Ohne Zusammenfassung     

Wirkung einer simulierten Dauerbelastung durch HgCl2 auf die Generationsfolge der FeldheuschreckeAcrotylus patruelis (H.-S.) (Orthoptera,Acrididae)

A continuous treatment of the environment was investigated under simulated conditions using mercury and the acridideAcrotylus patruelis (H.-S.) as test animal. The insects were fed by wheat germs in hydroculture and rolled oats, both treated with mercury. The females layed their eggs in glass pots filled with sand treated with various amounts of HgCl₂. Two generations were bred under continuous treatment. By feeding treated food the oviposition increased significantly reaching the threefold number of eggs in the P-Generation. In the F₁ even more eggs were produced. Mercury stimulated the function of the ovaries. In this way the females have the possibility to prevent a toxic accumulation of Hg in their bodies. The increase of oviposition can be considered as a mechanism of decontamination. The females of both generations were not able to measure the content of mercury in the soil. At all investigated concentrations larvae hatched but in those higher than 6.05 mg HgCl₂/kg a significant reduction of hatching could be found. The hatching of the larvae of the F₂ generation was much less than that of the F₁. Larval development depended highly on the concentration of mercury. The larval period was prolonged up to 40% by feeding of contaminated wheat germs. By continuous contamination of the soil and of the food the larval period was increased up to twofold compared with the control. The imaginal rate was reduced by increasing mercury content in the soil. At least only 30% reached the adult stage. The imaginal life span also depended on the Hg amount of the soil in which the eggs developed and on the contamination of the food. At least only 20 days were reached (normally 3–4 months). The body weight of the treated adults did not differ from that of the control. During the larval period the accumulation of mercury in the body was threefold compared with the control insects. The mercury content was reduced at the beginning of oviposition. The amount of the heavy metal increased mainly in the gut and in the gonads of the males.     

Insektizidresistenz bei Dipteren

Zusammenfassung Einige grundsätzliche Probleme der Insektizidresistenz bei Dipteren scheinen heute geklärt zu sein. Vor allem besteht wohl kein Zweifel mehr, daß Insektizidresistenz ein genetisch verankertes Merkmal ist und daß das Insektizid bei der Entstehung einer Resistenz lediglich im Sinne eines positiven Auslesefaktors wirksam ist. Irgendwelche tatsächlich wirksamen und in der Praxis verwertbaren Möglichkeiten zur Verhütung einer Resistenzentwicklung oder ihrer erfolgreichen Bekämpfung bestehen bisher noch nicht. Der Praxis kann nur empfohlen werden, die Zahl der resistenten Individuen durch die Anwendung geeigneter Insektizidmischungen möglichst niedrig zu halten und somit der Ausbreitung der resistenten Populationen soweit wie möglich Einhalt zu bieten.

---

Summary A few basic problems of resistance to insecticides in Diptera appear to be cleared. Above all there is no doubt that insecticide resistance is a genetically interrelated characteristic and that the insecticides in the origin of resistance act solely in the sense of a positive selection factor. Until now no really effective practical possibilities for the prevention of the development of resistance or its successful control do exist.In practice it can only be recommended to keep the number of resistant individuals low by employing proper insecticide mixtures and thus to check as far as possible the spread of resistant populations.

     

Effects of environment, disease progress, plant height and heading date on the detection of QTLs for resistance to Fusarium head blight in an European winter wheat cross

In order to characterise quantitative trait loci (QTLs) for Type I and Type II resistance against Fusarium head blight (FHB) in wheat, a population of recombinant inbred lines derived from the cross Cansas (moderately resistant)/Ritmo (susceptible) was evaluated in spray-inoculated field trials over three seasons. Map-based QTL analysis across environments revealed seven QTLs on chromosomes 1BS, 1DS, 3B, 3DL, 5BL, 7BS and 7AL (QFhs.whs-1B, QFhs.whs-1D, QFhs.whs-3B, QFhs.whs-3D, QFhs.whs-5B, QFhs.whs-7A, QFhs.whs-7B) associated with FHB resistance. They accounted for 56% of the phenotypic variance. QFhs.whs-1D primarily appeared to be involved in resistance to fungal penetration, whereas the other QTLs mainly contributed to resistance to fungal spread. FHB resistance was significantly correlated with plant height (PH) and heading date (HD). Including all single environments, corresponding overlaps of QTLs for FHB resistance and QTLs for PH/HD occurred at six loci, among them two consistently detected QTLs, QFhs.whs-5B and QFhs.whs-7A. When significant effects of PH and HD on FHB resistance were eliminated by covariance analysis, a second QTL analysis revealed possible escape mechanisms for the majority of the coincidental loci.     

Nitrat-Verlagerung in Auenböden unter organischer und konventioneller Bewirtschaftung — Meßergebnisse,Modellierungen und Bilanzen

Nitrate transport in soils of a river flood plain under organic and conventional farming — analytical results, modeling and balances Over a period of two years the transport of nitrate was investigated in Fluvi-Eutric Cambisols of a river flood plain of the Rhine tributary Sieg (Nordrhein-Westfalen, Germany). The soils were cultivated according to organic and conventional farming systems. Time series of NO₃ concentrations in soil solutions sampled by ceramic cups down to a depth of 180 cm are given. The interpretation of the results was possible by model calculations using the model DELPHI, which had been calibrated before by tracer experiments. N-mineralization and N-leaching were quantified. For different crop residues reaction coefficients for the mineralization of the easily decomposed organic material were calculated. They were extremely high for bean residues (19.0 × 10¹²) × exp (-9800/T) and mustard-vetch residues (12.0 × 10¹² × exp (-9800/T). The lowest reaction coefficient of 3.0 × 10¹² × exp (-9800/T) was calculated for the decomposition process during winter time. For the two farming systems a detailed N-balance was calculated. It is shown that under conventional farming over a time period of two years 199 kg N/ha were leached. Within the same period 53 kg N/ha were leached under organic farming. These differences depend in part on different crop rotation. Especially intercropping on the organically cultivated plots reduced the leaching of nitrate.     

Nitratgehalte tieferer Bodenschichten bei unterschiedlichen Fruchtfolgen auf intensiv genutzten Ackerbaustandorten

Influence of rotation upon nitrate content of deep soil layers in intensiv cropping systems Soil samples were taken down to a depth of 10 m during winter 1985/86 in some fields in Lower Bavaria with and without vegetable production. Each core was cut into 50 cm increments and soil nitrate-N and exchangeable ammonium-N determined. The results can be summarised as follows:

• 1 The content of exchangeable ammonium in 0–10 m soil depth was much less than the amount of nitrate nitrogen. Effects of different supply of inorganic fertilizer upon the NH₄-content have not been observed.
• 2 In rotations without vegetables with high supply of mineral nitrogen much nitrate-N was concentrated in the root zone. However in a depth of 4–6 m the nitrate concentration was less than 50 mg/l.
• 3 In one field only the nitrate concentration in 2,8–3,8 m was 2 to 3 times higher than in comparable cases. This seems to be the result of much nitrogen mineralized but not used, because of fallow effects (winter killing without fertilization) in 1982.
• 4 The nitrate concentration in soil cores of arable land decreased generally with sampling depth. In fields with vegetable production soil layers of high nitrate content alterated with soil layers of low nitrate content.
• 5 Because of the strong correlation between the number of soil layers with high nitrate content and the frequency of vegetables in the rotation, it can be assumed that the soil layers with much nitrate are caused by unused inorganic fertilizer applied to vegetables. This hypothesis is also supported by the fact of high nitrogen efficiency (> 70%) of agricultural plants and low nitrogen efficiency (48–13%) of vegetables, caused by high amounts of fertilizer and only low nutrient requirement of vegetables.
• 6 The total amount of nitrate-N found in 0–10 m soil depth was in vegetable rotations 2 to 4 times higher than in fields without vegetable production. The nitrate concentration of the nitrate peaks found in fields with vegetable production decreased with sampling depth, but strongly differing gradients of nitrate decrease with soil depth were observed between the fields.