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  • 1970-1974  (2)
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  • 1
    ISSN: 1573-8248
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary In western France, the aphidCapitophorus horni develops anholocyclic populations during the whole year on the globe-artichoke of which it is the major pest. A study of the parasites of this species was undertaken in 1967 and carried out until 1970. The observations have been done both on a plot of artichokes which never received any insecticidal treatment and on another one where such a treatment was done only once in April 1968. C. horni is attacked by such fungi asEntomophthora planchoniana andE. aphidis and by Hymenopterae, the main species beingAphidius matricariae and the other onePraon flavicorne (tab. 1). A number of hyperparasites have been record of whichCharips tscheki andAsaphes suspensus were the most numerous. Fig. 1 and fig. 2 show, comparatively on untreated and treated plots, the fluctuations of the populations ofC. horni on both young and older leaves of artichoke and the rate of parasitism by fungi and wasps. Fig. 3 gives numerical changes of the two main species of Hymenopterae encountered and shows the incidence of hyperparasitism. From this study it appears that a good regulation of the populations ofC. horni may occur, due to the high percentage and persistence of the parasitism. But in those natural conditions, epizootics occur too late for practical purpose and as a consequence, whole populations collapse, preventing other parasites from multiplying. Exposure of naturally or artificially lowered populations of aphids to constant parasitism seems far better for the prevention of outbreaks.
    Notes: Résumé Le puceronCapitophorus horni peut causer de graves préjudices aux cultures d’artichauts dans l’Ouest de la France. La présente note fait l’inventaire des parasites (Aphidiides et Entomophthorales) de cet aphide et précise leur rôle dans la régulation de ses populations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    BioControl 18 (1973), S. 61-75 
    ISSN: 1573-8248
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Summary A three-year study of the mechanisms involved in initiating epizootics onAphis fabae on field beans is reported. In 1969 and 1970, two field experiments were done at two sowing dates (with a month interval in 1969 and a fortnight in 1970); in 1971, only one could be conducted. Despite the two widely separated sowing dates, epizootics occurred at only a ten-day interval in 1969, and at the same time in 1970 in the two sowings. In 1971, there was a slow but steady progression of fungus attack, resulting in good control (fig. 1). Climatic factors, such as relative humidity above 90% for more than 10 hours per day, temperatures above 20°C and rains, are thought to be largely responsible for outbreaks; nevertheless, it is essential to have sufficient inoculum well-distributed among the population. It now seems that this quantity is better expressed as a minimum of 300 dead aphids per stem than as a percentage (table 1). As for inoculum distribution, dead aphids occur in any size of colony but, at the beginning they seem proportionately more numerous in the smaller colonies (fig. 2, 3). When epizootics are about to occur, the proportion of dead aphids is the same in all sizes of colony. Clearly, a well-spread production of inoculum will result from this apparent proportionality and from the distribution of aphid colonies in the field (fig. 3, 4, 5). Emphasis is laid on the difficulties of determining in field experiments whether the above factors are causal agents. Also, the threshold figure of 300 dead aphids per stem associated with the initiation of outbreaks may well vary under different ecological conditions.
    Notes: Résumé Le déclenchement dépizooties au sein de populations d'Aphis fabae sur féverole de printemps est largement dû aux facteurs climatiques et dépendant de l'hôte. Trois années d'expérimentations ont permis de préciser ces facteurs en conditions naturelles. Cette note insiste surtout sur les facteurs dépendant de l'hôte qui interviennent lorsque se prépare une épizootie: en particulier l'accent est mis sur la quantité minimum de pucerons mycosés requise et sur leur répartition au sein des colonies et de la culture.
    Type of Medium: Electronic Resource
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