Recherche Agronomique (2000), 6, 1-9 DSfRAA Impact of the entomophagous fauna on the Parlatoria blanchardii Targ Population in the Biskra Région Part II S.MOHAMMEDr &. A.SALHI^ 1 - DSA de Biskra 2 - S.R.P.V, Filiache , Biskra. Abstract: Based on the Iperti scale (1987), infestation map nf Parlatoria blan chardii Targ on the date palm trees in the Biskra région shows différent levels of infestation . These are du either to the presence or the absence ofnatural and local predators ofP. blanchardii such as Pharoscvmus semislobusus and Cvbocephalus palmarum. To elliminate or at least to decrease the white cochenial population, individuals of Pharosc\mus semiglobusus and Cvbocephalus palmarum were taken from oasis classified asfree ofP. blanchardii and relocated in infested ones. Two sites were selected ; the jïrst one as a sampling site with an average mean of 59 white cochenial / 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 ofindividuals ofthe predatoryfauna were takenfrom thefirst site and relocated in the second one in a known number ofdate 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 oftime, popula tion nf Phlanchardii decreased in some cases up to 50%. Besides that, the observed pattem proved that in presence ofits natural predators, Phlanchardii 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 Le. an increase ofthe predatory population in a breeding unit and then its release in infested oasis. Key Words : levels of infestation, relocating, entomophagous fauna, taking site, receiving site. 5 âL«'.,» jLa—œl ciiljj iti^il I g \\ «i" jlj-iâVl 4Jajj^ î '^loll 1987^ i^ljjLil i_i iii~> liUj ^ «L^jjJI 5jjjLaiLo cjLjI tt~i\ «âj^ mj ÂjjLàJl jjlj n frjj "•<" lA^lJJ (3^ Loi < «LaJîLj ùj^ SjLioVl j_pà ijl Lo (.y^ J .L^laail ^^1 j1 CybocephaliLS sp. Pharoscymnus semiglobosus. 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Il ■ "•! >j a II ■ ,-,! .J .^âll J 4jLioI Jbla-a ,_jic Jj Jl i4" ÛJ^ « I n(} jLâLljl^ ^ ^J*! a . , Loi CjIj iti*^ Il n <j ~ J 4juj_^l 4aI,,iiiO p m^Sj itiâ 17 I <4 4j m'ij p1 lAljjlll ijdO ~ ■■■ j^ J ' ■ ""^ 59 ■"•Ijj .T-all 4uL*til "(JjJLo tu ^ 4jjL^I olj iti-s II ^2>a J i—i"^ <<ii .diiL^I^I 4jjLâ ^ * JiA53 ^ ' •"*' I 'I 4-1 * ^ J~" ^ ^ I ..• f LAj-uÛ j ^1 .â" ...Vi ^^ I_i-«t mil (j-0 I J IJJ ^ "' J I (j-U'l ^ 4jjLàJl CjIj iti*> il Sjj itiT jl^^l ,2>0 I '<J ^ O ■ •! -^all 'lil jl ttll I 'mu O JiAC (_y^ I g ^ ^~K 2 -» H » a 11 iJ^ JQ ■" )J '^ *' Il ...A al ■ J« . .Il .-.I .J w.ôll « ^Ll^VI CjL^jJ Jlâ j 50 ''I J ( «1 ---J •■■■«■ " <1'° '•-I ■-~j41 .".I «J .^.âll JJ£ JjJLO ,__ytilâ3 < d,Àib JH < Ojjfl •" .^Lt.aJI )Jj^ '' Il ^_yàJLj 4.^a1Li I (]'' '.'*'''' 5jl '«^11 5j Mi~> il âJ^ ^LioVI Jdt.0 (jâJbLsjJI 4Jil OJ^I çuLljJI ûiÂA ^ a 4^1 \ Il ûi)lj Mi-^ il JJ J il I 'i 0 4 lj| Ijjb J t4« ijitl 111 o .4-mjiâJI .-jl^^îiaJl ji\£^<^^i^j}Parlatoriablanchardii TARG ■ Jl 14*1 iiiVI I i-i-h: liJi ' 4jjLâJI olj.itiTfc II < < ^1 1.0VI CjL^jJ : AJIjJI tZjlAlSJl INTRODUCTION 6 months (Mohammedi and Salhi, 1999). Througout this period, the main Among the many problems and activities were focused on the unders- constraints that face the date palm trees tanding of : in the Biskra région, Parlatoria blan- - The extent of the infestation by P. chardii Targ is actually a real threat not blanchardii in the Biskra région. only for the growth of the palm tree but - The relationship between P blanchar also for its fruits. dii and its local predatory fauna.(Table Notwithstanding the eradicating I). means used it is widely accepted that if The second part of this experiment the white cochenial is living in presence started in June 1998, where two oasis or of its natural predators, it could be pos expérimental sites were selected using sible to control its population . The two criteria : damages caused on date palm trees - Levels of infestation in the two oasis could be also kept at a relatively accep by P. blanchardii table level with préservation of the - The population of the entomophagous environment. fauna living in the same oasis To reach these two aims , this experi- A Known number of local predators of ment was conducted in two parts. The Pblanchardii was relocated from the first one started in april 1997 and lasted first oasis to the second one. Table I : Infestation levels by P blanchardii in the 17 oasis selected for the experiment throughout the Biskra région. (Mohammedi and Salhi 1999) Number of Date Number of white Infestation Districts palm Trees Gocheniis/cm' ievels(1) 1 Sidi Qkba 213100 101 2 2 Ourlai (Saâda) 110168 128 2 3 Ei Haouch 72 302 117 2 4 Oumache 106 011 112 2 5 Aïn Naga 32 777 125 2 6 Chetma 72 800 126 2 7 Bouchagroun 61 100 58 1 8 Ei Hadjeb 116739 51 1 9 Lichana 74 900 48 1 10 Ei Ghrous 85 600 38 1 11 Magtoufa 209 000 59 1 12 Ouied Djellal 166 500 12 0.5 13 Sidi Khaied 82 000 13 0.5 14 Lioua 155 520 05 0.5 15 Mekhadma 96 848 15 0.5 16 M'Iili 109 351 08 0.5 17 Ei Kantara 16 500 10 0.5 (1 ) According to the Iperti Scale (1987) This transfer or relocating individuals MATERIAL AND METHODS of the entomophagous species such as Pharoscymus semiglobusus and P. 1 - Sélection of the two sites: ovoidus should be able to reduce the white cochenial population in the recei- With its low level of infestation by P. ving site and will tend to create an equi- blanchardii and the presence of local librium between the two populations. predators in high nu^mber, Magtoufa This trend and/or control of P. blan- district was selected as the «taking» chardii by its natural predators such as site. The «receiving» site was located C. palmarum and P. anchorago was in Oumache district (Table II).The repoited by Balachowski (1926). same criteria as for the «taking» site Ipeiti and al (1970) confîrmed. the were used however with reversed same phenomena with Chilochrus values. Distance between the two bipustulatus. selected sites is around 62 Km. Table n : Criteria used in the experiment to select the receiving and the taking sites. Criteria used to Select the tow Taking site Receiving site Selected sites Sites Number of 59 171,4 Magtoufa white cochenials/cm^ Number of 10 0 Oumache predators/palm leaf 2 - Relocating Process: back to the laboratory for identifica tion , sélection and counting . Three predatory species were selec Ail selected individuals were settled ted for the experiment : Pharoscymus back in test tubes and taken to the semiglobusus^ P. ovoidus and receiving site. These were then freed Cybocephalus palmarum. Individuals onto the palm leaves of the date palm from this species were picket up from trees used for the experiment (Fig.1 ) the lowest crown of the date palm Seventeen date palm trees were taken trees. Each palm leaf was covered at random in the receiving site. 5 with a 1 m X 2m of white clowth and groups of 10 individuals of the preda shaken hardly. The white clowth was tory species were freed in each of the then layed down on the ground and ail 17 date palm trees. The first four predators found in this clowth were groups were put in opposite palm leaf, collected put in test tubes and taken the fifth in the middle of the crown. Each of the 4 palm leaves that received Three samples of 1cm were taken to be the predatory individuals was covered used for this counting. Two of the three with a piece of tulle. samples were taken on both end of the To measure the impact of the entomo- leaflet, the third one in its middle. With phagous fauna used in this experiment on a spécifie ruler, individuals of P. blan P. blanchardii population, three coun- chardii présent on the 12 leaflets were tings were carried ont. The first one befo- counted. Empty follicles were disrea- re the beginning of the treatment, while garded. The average mean of the three the next ones were done respectively at samplings were taken as the infestation the end of september and october 1998. average mean of each leaflet. The 12 Twelve leaflets were eut from each of means from the 12 leaflets were taken the date palm trees taken back to the as the infestation level of each date laboratory to be examined under a dis- palm tree (Table III).