Recherche Agronomique
Volume 4, Numéro 6, Pages 1-9
2000-05-06
Impact Of The Entomophagous Fauna On The Parlatoria Blanchardii Targ Population In The Biskra Region
Authors : Mohammedi S. . Salhi A. .
Abstract
Based on the Iperti scale (1987), infestation map of Parlatoria blan-chardii Targ on the date palm trees in the Biskra region shows different levels of infestation . These are du either to the presence or the absence of natural and local predators of P. blanchardii such as Pharoscymus semiglobusus and Cybocephalus palmarum. To elliminate or at least to decrease the white cochenial population, individuals of Pharoscymus semiglobusus and Cybocephalus palmarum were taken from oasis classified as free of P. blanchardii and relocated in infested ones. Two sites were selected ; the first one as a sampling site with an average mean of 59 white cochenial / ne and 10 predators in the same palm leaf , the second as a receiving site with an average mean of 171,4 white cochenial / cm' of palm leaf and where almost no predators were recorded . A known number of individuals of the predatory fauna were taken from the first site and relocated in the second one in a known number of date palm trees. Before relo-cating the predators, P.blanchardii population was measured in the receiving site and every 30 days during the two next months. After this period of time, popula¬tion of P.blanchardii decreased in some cases up to 50%. Besides that, the observed pattern proved that in presence of its natural predators, P.blanchardii population could be decreased or at least kept at an acceptable level.This relocating technique could be used as an alternative to the conventioa-nal one i.e. an increase of the predatory population in a breeding unit and then its release in infested oasis.
Keywords
levels of infestation, relocating, entomophagous fauna, taking site, receiving site.
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