Occurrence of anholocylic strains of pest aphids on winter barley and wheat in South Moravia,Czech Republic

Anholocyclic strains ofSitobion avenae (F.),Rhopalosiphum padi (L.) andRhopalosiphum maidis (Fitch) were detected on winter barley and wheat in autumn, 1995 in South Moravia, the Czech Republic. Anholocycly was proved by samples docummenting the species composition and population structure of aphids in 20 localities throughout the area. Natural enemy presence was also determined and the species are listed. Anholocycly established in the cereal aphids in the target area is discussed in relation to a similar evidence known from the north-west Europe and some parts of the Mediterranean.     

Bending strength adjustments for moisture content for structural lumber

Summary Effects of moisture content on bending strength and section capacity have been studied assuming that strength properties are linearly related to moisture content below the fiber saturation point. The models developed using the linear strength vs. moisture content relationships are compared with quadratic models developed earlier. The linear representation of strength variation with moisture content leads to predicted member bending capacity relationships which show that increases in member bending strength with moisture content will compensate for section property decreases at all bending strength property levels. Comparisons of bending strength and bending capacity models show that the two modelling approaches lead to similar predicted member performance. Simplified procedures are provided for adjusting member bending strength for moisture content which are suitable for materials properties codes or standards.     

Suitability of the Citrus Brown Mite,Eutetranychus orientalis (Acari, Tetranychidae) as prey for nine species of phytoseiid mites

Nine phytoseiid species were tested to evaluate their potential as predators ofEutetranychus orientalis (Klein).Typhlodromus atbiasae Porath and Swirski,Amblyseius barkeri (Hughes) andAmblyseius olivi Nasr and Abou-Awad had a shorter developmental period thanTyphlodromus transvalensis (Nesbitt).Typhlodromus athiasae andAmblyseius barkeri showed the highest oviposition rates.Amblyseius olivi showed a low rate of oviposition althoughTyphlodromus transvalensis has not able to lay any eggs. Immatures survival ofTyphlodromus talbii Athias Henriot,Typhlodromus balanites El-Badry,Amblyseius badryi. Yousef and El-Borolossy,Amblyseius cabonus (Schicha) andAmblyseius lindquisti Schuster and Pritchard were very low onEutetranychus orientalis and all failed to develop to adulthood.     

Sekrete und Delta-16-Steroide als Lockmittel für die Rötelmaus (Clethrionomys glareolus)

Zusammenfassung Lebendfallen, die Nestmaterial oder Ausscheidungen von Rötelmäusen enthielten, wurden im Freiland von Artgenossen signifikant häufiger besucht als nicht-kontaminierte Fallen. Die Untersuchungen wurden im Spätsommer und Herbst in den Jahren 1986 und 1987 in Forstkulturen durchgeführt. In den Monaten August bis Oktober wurden Fallen, die kontaminierte Einstreu von Artgenossen enthielten, bevorzugt, in den Monaten November und Dezember Fallen mit Nestgeruch.Von den beiden Verbindungen 16-(5-alpha)-androsten-3-on (Androsten-on) und 16-(5-alpha)-androsten-3-alpha-ol (Androsten-ol) wurde die letztere signifikant von der Rötelmaus bevorzugt.

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Secretions and Delta-16-steroids as attractants for Bank Voles (Clethrionomys glareolus)

Bank Voles (Clethrionomys glareolus) preferred significantly live traps containing bedding or nesting material contaminated by conspecifics in comparision to clean traps (=control). The tests were conducted in forest cultivations in late summer and autumn of 1986 and 1987. In both years at the begin in August the traps contaminated with urin of conspecifics were most attractive. Females were significantly more frequently caught in traps contaminated by conspecific males and vice versa males visited preferably traps with bedding material of females. Later during October and November traps with nest odour were preferred by both sexes.It was assumed that derivatives of hormones could act as pheromones. Both compounds 16-(5-alpha)-androsten-3-one and 16-(5-alpha)-androsten-3-alpha-ol were tested in field plots. The latter was significantly preferred by Bank Voles but not by other species.

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Mit 7 Abbildungen und einer Tabelle     

Zur Möglichkeit des Einsatzes von Regulatoren des Pflanzenwachstums in der Schädlingsbekämpfung

Zusammenfassung In Anlehnung an ältere Untersuchungen mit holzigen Pflanzen ließ sich nun auch die Entwicklung von den krautigen Winterrapspflanzen durch eine Behandlung mit dem Wachstumsregulator Pydanon (Derivat der Pyridazinyessigsäure, 25 kg/ha) um etwa 2 Wochen verzögern.Im Durchschnitt der Versuche von 6 Feldern in 2 Jahren wurde durch diese Verzögerung die Populationsdichte der Kohlschotenmücke um fast 90% reduziert. Beim Kohlschotenrüßler betrug der entsprechende Wert 44%.Es werden die Ergebnisse, der kumulative Effekt von Herbiziden und Pydanon sowie die Ursachen der aufgetretenen Mindererträge diskutiert und die Voraussetzungen angedeutet, die für einen mehrjährigen Bekämpfungserfolg zu fordern sind.

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On the suitability of plant growth regulators for pest control

With reference to former investigations with wooden plants, the development of herbaceous winter rape could be retarded by treatments with the growth regulator PYDANON (derivate of pyridazinyl acetic acid, 25 kg/ ha) for about 2 weeks.In the mean of 6 fields in 2 years the population density of the brassica pod midge was reduced to about 90%. The respective value for the reduction of the cabbage seed weevil was 44%.The results, the cumulating effect between PYDANON and herbicides and the reasons for the observed yield reduction are discussed. Furthermore, the basic requirements are outlined, which are to be demanded for a control, lasting several years.

     

Arbeitszahlen für die Schädlingsbekämpfung

Zusammenfassung Auf Grund umfangreichen Beobachtungen bei einer Anzahl verschiedener Schädlingsbekämpfungsarbeiten werden durchschnittliche Erfahrungswerte für Arbeitsleistungen mitgeteilt, die allgemeine Gültigkeit beanspruchen können.     

Mitteilung von Beobachtungen bei Untersuchungen über die Einwirkung der neuen Kontaktinsektizide auf Wachsmotten und Seidenraupen

Ohne Zusammenfassung     

Beobachtungen zur Entwicklung der Frühjahrspopulationen vonMetopolophium dirhodum (Wlk.) auf dem Winterwirt

The rose-grain aphid,Metopolophium dirhodum (Wlk.), is a species living onRosa spp. as winter hosts and Gramineae as summer hosts. Thus, the planting of roses along roadsides and highways may be of importance in connection with the migration of the aphids to cereals. In March 1982 the nymphs hatched from eggs, which were laid in autumn on long shoots. One or two days after hatching they fed on buds in batches up to 15 individuals. Somewhat later they dispersed on the hostplants. The nymphal mortality of the first generation was high, namely about 79%. For further population development the number of fundatrices was less important due to their high reproduction capacity. Nymphs and adults of the first generation often changed their feeding site on the shoots. The specimens of the 2nd and 3rd generation were more stationary and formed dense colonies. The population density drastically increased during the 3rd generation. The development of the aphid populations on the primary host took place during 2–3 generations and lasted until the beginning of June, when the winged forms left the hosplant. In the second generation, i. e. at the beginning of May, the first emigrantes appeared and the size of the aphid colonies increased up to 115 individuals. Most colonies consisted of less than 11 aphids namely 30.9%. Natural enemies were present in large numbers during the end of May when the populations of aphids decreased due to emigration. They did not influence the density of aphid colonies, except the predacious larvae of hover-flies. Trophobiosis between ants and rose-grain aphids was not observed on the primary hostplant.