Field trials on the retention of potato stocks in England

Summary Field trials done to supplement replicated smallplot trials showed that the incidence of leaf roll and Y viruses in potato crops remained low for several years in many parts of England when the crops were sprayed with insecticide, and in some parts, where aphids were few, without spraying. Four sprays with DDT emulsion at 2 lb. of active ingredient per acre per application, at intervals of 14 days, starting soon after the plants emerged, were enough to check spread from sources within the crop. Insecticides did no prevent viruliferous aphids, coming from outside the crop, from infecting sprayed plants. Although many growers could safely keep potato stocks for several years longer than they do now, others could not because virus Y is introduced by aphids from other crops in the same area. Risk from incoming infective aphids will remain until all potato crops are free from virus, but if all infected crops were sprayed with an efficient aphicide before the summer dispersal flight this should greatly decrease the amount of disease introduced into healthy crops.

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Zusammenfassung Feldversuche, die zur Erg?nzung wiederholter Kleinparzellenversuche durchgeführt wurden, ergaben, da? die H?ufigkeit des Auftretens der Blattroll- und Y-Viren bei Kartoffelbest?nden mehrere Jahre in vielen Teilen Englands gering blieb, wenn die Best?nde mit einem Insektenmittel gespritzt wurden; in manchen Teilen, in denen wenig Blattl?use vorkamen, war dies auch ohne Spritzen der Fall. Viermaliges Spritzen mit DDT-Emulsion zu 2 lb. aktiven Bestandteile pro “acre” pro Applikation in 14t?gigen Intervallen, wobei man bald nach dem Aufgang begann, reichten aus, um die Ausbreitung von Quellen innerhalb der Best?nde zu hemmen. Die Insektizide verhinderten nicht, da? virus-tragende Blattl?use, die von au?erhalb der Best?nde stammten, die gespritzten Pflanzen infizierten. Obwohl manche Züchter ihre Kartoffelbest?nde verschiedene Jahre l?nger halten k?nnten als sie es jetzt tun, würde anderen dies nicht gelingen, weil das Y-Virus von Blattl?usen aus anderen Best?nden des gleichen Gebietes eingeführt wird. Die Gefahr ansteckender Blattl?use wird bestehen bleiben, bis alle Kartoffelbest?nde virusfrei sind; wenn jedoch alle infizierten Best?nde mit einem wirksamen Blattlausmittel vor dem sommerlichen Befallsflug gespritzt würden, w?re der Umfang der Infizierung mit dieser Krankheit von gesunden Pflanzungen bedeutend zu verringern.

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Résumé Des essais en plein champ, effectués pour compléter des essais à différentes reprises sur petites parcelles, ont démontré que l'incidence des virus Y et de l'enroulement dans les cultures de pommes de terre restait faible pendant plusieurs années dans bien des régions d'Angleterre, pourvu que les cultures aient été traitées par pulvérisation d'un insecticide, et dans certaines régions, où les pucerons sont rares, mêmes sans pulvérisations. Quatre pulvérisations d'une émulsion de DDT à la dose de 2 lb. de substance active par “acre” et par pulvérisation, espacées de deux semaines, dont la première est effectuée peu après la levée, suffisaient pour enrayer la propagation à partir de sources situées à l'intérieur de la culture. Les insecticides n'empêchaient pas les pucerons porteurs de virus, venant d'en dehors de la culture, d'infecter les plantes traitées. Si bien des cultivateurs pourraient continuer sans inconvénient la culture de pommes de terre de la même semence pendant plusieurs années de plus que d'ordinaire, d'autres ne le pourraient pas parce que le virus Y est apporté d'autres cultures de la même région par les pucerons. Le risque de pénétration de puccrons infectieux continuera d'exister tant que toutes les cultures ne seront pas exemptes de virus. Mais si toutes les cultures infectées étaient traitées avec un insecticide efficace avant le vol de dispersion en été, il en résulterait une forte diminution de la maladie introduite dans des plantations saines.

     

Histological, digestive, metabolic, hormonal and some immune factor responses in Atlantic salmon, Salmo salar L., fed genetically modified soybeans

The paper reports the second and final part of an experiment aiming to study physiological and health-related effects of genetically modified (GM) soybean meal (SBM) type Roundup Ready soybean (RRS) in diets for post-smolt Atlantic salmon. For 3 months salmon were fed diets containing 172 g kg(-1) full-fat SBM from RRS (GM-soy) or an unmodified, non-isogenic line (nGM-soy), or a reference diet with fishmeal as the sole protein source (FM). Slight differences in anti-nutrient levels were observed between the GM and nGM-soy. Histological changes were observed only in the distal intestine of the soy-fed fish. The incidence of moderate inflammation was higher in the GM-soy group (9 of 10 sampled fish) compared with the nGM-soy group (7 of 10). However, no differences in the concomitant decreases in activities of digestive enzymes located in the brush border (leucine aminopeptidase and maltase) and apical cytoplasm (acid phosphatase) of enterocytes or in the number of major histocompatibility complex class II+ cells, lysozyme activity, or total IgM of the distal intestine were observed. GM compared with nGM-soy fed fish had higher head kidney lysozyme (11,856 vs. 10,456 units g(-1) tissue) and a tendency towards higher acid phosphatase (0.45 vs. 0.39 micromol h(-1) kg(-1) body mass in whole tissue) activities, respectively. Plasma insulin and thyroxin levels, and hepatic fructose-1,6-bisphosphatase and ethoxyresorufin-O-deethylase activities were not significantly affected. It is not possible, however, to conclude whether the differences in responses to GM-soy were due to the genetic modification or to differences in soy cultivars in the soy-containing diets. Results from studies using non-modified, parental line soybeans as the control group are necessary to evaluate whether genetic modification of soybeans in diets poses any risk to farmed Atlantic salmon.     

Movements by wild brown trout in a boreal river: response to habitat and flow contrasts

Abstract  Radio transmitters were implanted in wild brown trout, Salmo trutta L., in the River Måna at low summer water flows ( n  = 18), higher flow in summer ( n  =   20), and variable, peaking flows in autumn ( n  =   20), and tracked two to four times day and night for 4–5 weeks. Individuals were caught and released in a 4-km uniformly channelised section, and in a 4-km natural diverse river section. Substantial individual variation in home range and total movement (924–85 818 m² and 295–7014 m) suggested flexibility to adapt to local environmental conditions. Fish were stationary most of the time (median movement 0 m), but some individuals undertook few and apparently sporadic longer movements, sometimes involving shifts in home range. No consistent diurnal pattern in movements was found. Trout in the uniform habitat section appeared to have larger home ranges and moved more than trout in the natural section. Differences were, however, not statistically significant in most comparisons, due to large individual variation. Similarly, larger home ranges and movements between trials related to higher flow were found, but differences were generally not significant. No consistent effects of sudden, extreme peaking flows on area use or movements by the brown trout were observed.     

Effects of different angling practices on post-release behaviour of nest-guarding male black bass, Micropterus spp.

Abstract  This study evaluated how different angling practices affect the short-term post-release behaviour of nest-guarding male black bass, Micropterus spp. Male largemouth bass, M. salmoides (Lacepède), and smallmouth bass, M. dolomieu (Lacepède), were angled from their nests and subjected to treatments designed to simulate a variety of common angling practices associated with catch-and-release angling, including fishing tournaments. In addition, some nests had broods reduced (removal of the majority of the eggs or fry from the nest) during the angling treatments to simulate predation of offspring during the angling event. Fish subjected to procedures simulating fishing tournaments (including a 1-h livewell confinement and release 100 m from the nest) exhibited significantly longer rest periods prior to returning to their nest than did other treatment groups. This rest period was longer for largemouth bass than smallmouth bass. Brood removal and air exposure increased abandonment rates compared with controls. These results show that sublethal stressors inherent in some angling practices (such as air exposure and livewell confinement) may delay the return of male black bass to their nest. In the presence of nest predators, the delay in return time could result in increased nest abandonment.