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Growth experiments with unialgal cultures of 'red tide' flagellates Prorocentrum triestinum and Olisthodiscus luteus showed that relative growth rates of phytoplankton can be estimated from DCMU-~nduced fluorescence increase (DCMU-FI). This method was applied to the estimation of relative growth rate of a natural population in Tanigawa Harbor (Japan) where 0. luteus was dominant throughout the experiment. Measurements were made three times a day over a week. A steady increase of photosynthetic capacity indicated by DCMU-F1 was followed by a red t~d e of 0. luteus. Such increase of photosynthetic capacity was associated with accumulation of ammonia and low dissolved oxygen levels in the water colunln near the bottom.

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SUMMARYThe efficacy of a fumigant is determined by the gas concentration and exposure time. Typically, the gas concentration and exposure time are equally important in fumigation efficacy and their relationship is expressed as Ct = k, where C is the concentration, t is the time and k is a constant (Haber's rule). However, deviation from Haber's rule, i.e., the relative importance of time over concentration, has been reported for several stored-product pests, and a modified form (C n t = k) is used to express the relationship between C and t. This study aimed to determine if this modified form could be applied to phosphine fumigation of the cigarette beetle, Lasioderma serricorne (F.). Adult beetles from six cultures with different phosphine-resistance levels were exposed to phosphine (1-2000 ppm) at 25 °C for either 24, 72, 120, or 168 h, and the phosphine concentration necessary to achieve 50% lethality (LC 50 ) was calculated. The phosphine concentration (C) and the exposure time (t) relationship at the LC 50 for all six cultures were determined by regression analyses. The equation C n t = k was a good fit for all the cultures tested, irrespective of phosphine resistance. The results showed the exponent n was less than 1 (0.51 # n # 0.71, coefficient of determination 0.90-0.99), suggesting that time is more important than concentration in toxicity expression of phosphine against L. serricorne. Therefore, extending the exposure time rather than increasing the concentration should be emphasized to manage the future threat of resistance problems with phosphine. [Beitr. Tabakforsch. Int. 27 (2017) ordinaire, la concentration gazeuse et le temps d'exposition revêtent une importance égale pour une fumigation efficace et leur rapport est noté Ct = k, sachant que C désigne la concentration, t désigne le temps et k est une constante (règle de Haber). Cependant, une entorse à la règle de Haber, à savoir l'importance relative du temps sur la concentration, fut observée sur plusieurs nuisibles présents dans les produits entreposés et une formule modifiée (C n t = k) fut utilisée pour exprimer le rapport entre C et t. La présente étude vise à déterminer si cette formule modifiée pourrait être appliquée à la fumigation au gaz phosphine du coléop-tère des cigarettes, Lasioderma serricorne (F.). Des coléoptères adultes provenant de six cultures distinctes et présentant des niveaux différents de résistance à la phosphine furent exposés au gaz phosphine (1-2000 ppm) porté à 25 °C durant des périodes de 24, 72, 120 ou 168 heures et le calcul fut effectué de la concentration en phosphine nécessaire pour atteindre un taux de 50% de létalité (LC 50 ). Les rapports entre la concentration en phosphine (C) et le temps d'exposition (t) à une létalité de LC 50 pour la totalité des six cultures furent déterminés par des analyses de régression. L'équation C n t = k s'avéra bien convenir à toutes les cultures testées, quelle que soit leur résistance à la phosphine. Les résultats montrèrent que l'exposant n était inférieur à 1 (0.51 # n #...

RNA-seq data analysis of cigarette beetle (Lasioderma serricorne) strains having different sensitivities to pyrethroids identified sodium channel mutations in strains showing pyrethroid resistance: the T929I and F1534S mutations. These results suggest that reduced sensitivity of the sodium channel confers the pyrethroid resistance of L. serricorne. Results also showed that the F1534S mutation mostly occurred concurrently with the T929I mutation. The functional relation between both mutations for pyrethroid resistance is discussed.