ALBERT

Notizen: The activity of GR7 and Striga germination stimulant(s) from Euphorbia aegyptiaca Boiss. showed adequate persistence (6–8 days) in acidic soils (pH 5·0–6·3), but residual activity was short (1–3 days) in alkaline soils. The compounds tended to lose activity at a faster rate in the alkaline clay Gezira soil (pH 7·8), than in its sandy equivalent (pH 8·1). In solution, pH had no influence on initial activity, but residual action was reduced more rapidly by alkalinity and high temperature. However, the rate of loss of activity in solution was slower than in soils.

Notizen: Germination of Striga hermonthica (Del.) Bentth seeds in response to the strigol analogue GR 24 was strongly influenced by soil moisture prior to, at, or after, stimulation. Exposure of seeds to excessive soil moisture contents (70% w/w) during conditioning resulted in a low response to GR 24. Transfer of Seeds from soil at 70% moisture to a lower moisture level (47%) for 2 days or more improved the response to GR 24 (37–58% germination), white air-drying restored germination (88%). In Gezira soil the optimum soil moisture contents for maximum response to GR 24 were 44, 38 and 40% during conditioning, stimulation and germination, respectively. The corresponding figures for the sandy soil were 20, 22 and 22%, respectively. Persistence of GR 24 was similar in both soil types, but was strongly influenced by soil moisture content. The stimulant was stable in air-dry soil, but a rapid loss was encountered in moist soil.

Notizen: Ethephon (2-chloroethylphosphonic acid), which generates ethylene, stimulated the germination of pre-conditioned seeds of Striga hermonthica when it was added to the alkaline Gezira clay soil at concentrations of 2.5 to 30 mg kg−1. As little as 5 min contact with treated soil was enough to stimulate germination. Ethephon in soil did not cause germination of unconditioned seeds for periods of up to 12 days and also had an adverse effect on seed germination when such seeds were given a second ethephon exposure after a storage period which was adequate, in untreated soil, to give the necessary pre-conditioning. Ethephon activity persisted in air-dry soil but declined over a 14 day period in moist soil. In the field ethephon at 0.6 to 4.8 kg ha−1 decreased the number of Striga shoots and increased sorghum height and flowering.

Notizen: Thidiazuron at 0.1 to 10 mg 1−1 induced concurrent germination and haustorium initiation in Striga asiatica (L.) Kuntze and S. hermonthica (Del.) Benth, but it had no effects on S. gesnerioides (Willd.) Vatke. Both millet and sorghum strains of S. hermonthica were equally responsive. The response of Striga seeds to thidiazuron increased with conditioning. Early applications of the compound induced some germination, but had adverse effects on the conditioning process. Induction de la germination des graines de Striga par le thidiazuron Le thidiazuron de 0,1 à 10 mg 1−1 a induit de façon conjointe le germination et l'initiation d'haustoria chez Striga asiatica et S. hermonthica, mais n'a pas eu d'effet sur S. gesnerioïdes. Les souches de S. hermonthica liées au millet et au sorgho ont un comportement équivalent. La réponse des graines de Striga au thidiazuron a augmenté par conditionnement préalable. Des applications précoces de produit ont induit quelques germinations, mais ont eu des effets contraires sur Ie processus de conditionnement. Einleitung der Samenkeimung bei Striga-Arten durch Thidiazuron Mittels Thidiazuron-Lösungen von 0,1 bis 10 mg 1−1 konnten eine gleichzeitige Keimung und Ausbildung der Haustorien bei Striga asiatica (L.) Kuntze und S. hermonthica (Del.) Benth. herbeigeführt werden, nicht jedoch bei S. gesnerioides (Willd.) Vatke. Der Rispenhirsen-und der Sorghum-Typ von S. hermonthica reagierten in gleichem Maße. Konditionierung der Striga-Samen förderte die Wirkung von Thidiazuron. Frühe Anwendung des Wirkstoffs führte zu einer geringen Keimung, beeinträchtigte jedoch die Konditionierung.

Notizen: Unrestricted weed growth resulted in serious yield losses (67–78%) in cotton (Gossypium barbadense L.). Hand-weeding once at 6 weeks after crop sowing was ineffective (48% loss). In plots treated with oxidiazon, cotton yield progressively decreased as applications were made earlier than planting time. Spraying with 1.07 kg ha−1 30 days prior to sowing gave 54–69% less yield than the same dose applied at or within 7 days of sowing. Oxadiazon at sowing gave better weed control than pre-sowing treatments and required less time for supplementary weeding. Air-dry weight of weeds as a percentage of the unweeded plots was 74% when the herbicide treatments were made 30 days before sowing, but was only 10% when the herbicide treatments were made at sowing. Chemical analysis of soil samples collected from the treated plots at sowing revealed that 6.5, 74 and 78% of the applied dose was recoverable from plots treated 30, 15 and 7 days before planting.Influence de l'époque d'application de l'oxadiazon sur l'efficacité de l'herbicide en culture de cotonnier au Gezira du SoudanLa libre croissance des mauvaises herbes a amené des pertes importantes (67–78%) dans le rendement du coton (Gossypium barbadense L.). Le désherbage manuel 6 semaines après le semis s'est montré inefficace (perte de 48%). Sur des parcelles recevant l'oxadiazon, les rendementsen coton ont diminuéà mesure que les applications préeédaient le semis. Une pulvérisation de 1,07 kg ha−1 30 jours avant le semis a donné un rendement inférieur de 54 a 69%à celui obtenu avec la même dose appliquée pas plus que 7 jours avant le semis. Appliqué au moment du semis, l'oxadiazon a permis une maîtrise des adventices supérieure à celle des traitements de pré-semis; il a également exigé un désherbage supplémentaire moins onéreux. Lors des traitements 30 jours avant le semis, le poids sec des mauvaises herbes etait 74% de celui des adventices sur les parcelles non-traitées mais les traitements au moment du semis ont réduit ce chiffre a 10%. Une analyse chimique d'échantillons de terre, prélevées au moment du semis sur les parcelles traitées, a révélé que 6,5%, 74% et 78% de la dose appliquée était récupérable sur les parcelles traitées 30, 15 et 7 jours avant le semis respectivement. Ueber den Einfluss des Zeitpunktes der Behandlung auf die herbizide Wirkung von Oxadiazon in Baumwolle im Sudan (Gezira) Ungehinderte Unkrautentwicklung in Baumwolle (Gossypium barbadense L.) verursacht grosse Ernteverluste (67–78%). Manuelle Unkrautbeseitigung 6 Wochen nach der Aussaat war praktisch wirkungslos (Verlust 48%). Je früher vor der Baumwollsaat die Parzellen mit Oxadiazon behandelt worden waren, deasto mehr nahm der Ernteertrag ab. Eine Behandlung mit 1,07 kg ha−1 30 Tage vor der Saat resulticrte in einem 54–69% geringeren Ertrag, als eine Behandlung mit derselben Dosierung bei der oder innert 7 Tagen nach der Saat. Oxadiazon zur Pflanzzeit appliziert, ergab eine bessere Unkrautbekämpfung als Behandlungen vor der Aussaat und erforderten weniger zusätzliche Zeit für ergäanzende Bekämpfungsmassnahmen. Das Trocken-gewicht (lufttrocken)der Unkräuler, bezogen auf die unbehandelten Parzellen, betrug 74% bei der Herbizidbehandlung 30 Tage vor der Saat, aber nur 10%, wenn die Applikation zur Saatzeit erfolgte. Eine chemische Analyse von Bodenproben zu diesem Zeitpunkt ergab, dass 6,5, 74 und 78%der 30, 15 und 7 Tage vor der Saat applizierten Dosis wiedergefunden wurden.

Notizen: Studies on the germination of Ischaemum afrum seeds showed that low temperature, presence of glumes and both low and excessive soil moisture contents were conducive to delayed and low germination. The inhibitory effect of the glumes was more pronounced in freshly harvested seeds. Germinability of seeds on the soil surface was poor, but shallow burial in soil increased germination.

Notizen: Unrestricted weed growth resulted in serious yield losses (60–75%) in rice (Oryza saliva L.). Hand-weeding once at 2 weeks after crop emergence was ineffective, but weeding at 2 and 2 weeks after crop emergence brought yield losses down to 20%. Pre-emergence application of bifenox and oxadiazon (12 l) and post-emergence application of molinate + propanil gave crop yields comparable to that of the clean weeded control (91–129%). Grain yields obtained with pre-emergence application of oxadiazon (25 EC) and post-emergence applications of propanil, bentazone + propanil, and bifenox alone or as a tank mix with propanil or bentazone were considerably less than those obtained from the clean weeded plots. Bifenox, oxadiazon (12 l) and propanil + molinate gave adequate and persistent weed control (72–97%), and did not damage rice. Oxadiazon (25 EC) gave good weed control but resulted in a serious stand reduction. Post-emergence application of propanil, propanil + bentazone bifenox alone or as a tank mix with propanil or bentazone had no adverse effect on crop stand, but gave poor control of grasses (0–40%).

Notizen: Amitrole (3-amino-l,2,4-triazole) penetration on foliar application to bracken (Pteridium aquilinum) is influenced by pre-spray conditions. With the exception of Triton X-405 all surfactants tested at a concentration of approximately 01% (w/v) viz., Tween 20, Triton GR-5, Triton X-100 and Tergetol NPX, improved penetration by more than 17%. Ammonium thiocyanate and ammonium nitrate both enhanced penetration while ammonium sulphate had no effect. Either phosphoric acid alone or in combination with ammonium nitrate reduced penetration. All humectants used were either deleterious or similar to the water control in their effect. Sucrose was shown to enhance penetration but the difference was not significant.Influence des conditions précédant le traitement, des mouillants et d'autres additifs sur la pénétration de l'amitrole dans le frondes de fougéresLa pénétration de I'amitrole (amino-3 triazole-1,2,4) en application foliaire sur la fougére aigle (Pteridium aquilinum) est influenceée par les conditions précédant le traitement. A l'exception du Triton X-405, tous les mouillants essayés à la concentration approximative de 0.1 % (pds/vol), à savoirile Tween 20, le Triton GR-5, le Triton X-100 et le Tergetai NPX, ont augmenté la pézétration de plus de 17 %. Le thiocyanate d'ammonium et le nitrate d'ammonium ont tous deux favorisé la pénétration, alors que le sulfate d'ammonium n'a pas eu d'effets. L'acide phosphorique, seul ou associé avec le nitrate d'ammonium, a réduit la pénétration. Tous les humidifiants utilisés se sont montrds soit néfastes soit analogues dans leurs effets au contrôle de l'eau. Le saccharose s'est révélé susceptible de favoriser la pénétration, mais la difference n'a pas été significative.Einfluss von Vorbehandlungen, Netzmitteln und anderen Zusätzen auf die Penetration von Amitrol in AdlerfarnDie Penetration von Amitrol (3-Amino-l,2,4-trizaol) in Adlerfarn (Pteridium aquilinum) bei Blattbehandiung, wird durch Vorbehandlungen beeinflusst. Mit der Ausnahme von Triton X-405 verbesserten alle geprüften Netzmittel, nämlich Tween 20, Triton GR-5, Triton X-100 und Tergetol NPX bei einer Konzentration von etwa 0,1% (Gew./Vol) die Penetration um mehr als 17%. Ammoniumthiocyanant und Ammoniumnitrat erhöhten die Penetration, wahrend Ammoniumsulfat keine Wirkung hatte. Die Anwendung von Phosphorsäure alleine, oder kombiniert mit Ammoniumnitrat, verminderte die Penetration. Alle verwendeten Substanzen die zur Steigerung der Feuchtigkeit dienen (humectants) waren entweder schädlich oder entsprachen in ihrer Wirkung der Wasserkontrolle. Sucrose verbesserte unbedeutend die Penetration.

Notizen: Experiments with the alkaline heavy clays of the Sudan Gezira showed that when the strigol analogue GR7 was applied to moist soil prior to subjecting Striga hermonthica seeds to moist conditions (‘conditioning’) for 7–14 days, there was no significant increase in germination. Conditioning of seeds in soils treated with GR7 had an adverse effect on the responsiveness of seeds when GR7 was added again after conditioning. Under ideal conditions, when GR7 was applied to conditioned seeds in moist soil, up to 75% germination could be induced by 2.0 kg/ha incorporated to 2–3 cm depth. Residual activity of GR7 persisted in air-dry soil, but at 50% moisture there was complete loss within 1 day. However, when conditioned seeds were put into the soil immediately after GR7 application its activity increased with increasing soil moisture.

Notizen: Aqueous extracts of fifteen Euphorbia species induced germination of Striga hermonthica (Del.) Benth. seeds to varying extents. Extracts from E. supina Raf., E. pilulifera Jacq., E. acalyphoides Hochst. ex. Boiss, E. prunifolia (Jacq.) Hort. Schoent., E. hirta L., E. aegyptiaca Boiss, E. splendens Boj., and E. granulata Forsk, were the most active. Extracts from E. acalyphoides and E. pilulifera were inhibitory at high concentrations. Undiluted extracts from E. pilulifera, E. aegyptiaca and E. hirta induced haustorial initiation. The stimulatory substance(s) were widely distributed in plants of E. aegyptiaca. Extracts from E. aegyptiaca also stimulated seed germination and haustorial initiation in a range of Striga species and strains.