OVIPOSITION OF RHYNCHOPHORUS PHOENICIS (F.) (COLEOPTERA: CURCUUONIDAE) IN PALMS OF THE NIGER DELTA

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1 Indian J Agric Res, 38 () : , 004 OVIPOSITION OF RHYNCHOPHORUS PHOENICIS (F) (COLEOPTERA: CURCUUONIDAE) IN PALMS OF THE NIGER DELTA CN Thomas l, OK Ogbalu and BA Okwakpam Department of Biological Sciences, Rivers State University of Science and Technology, P M B 5080 Nkpolu, Port Harcourt, Nigeria ABSTRACT Laboratory studies was carriedout between the months of May and July 001 on the oviposition of R phoenids Results showed thatthe adults (males and females) used the rosbum to make holes (l - 7 mm deep and 1-14 mm diameter), but only the females deposited an egg into a hole The relationship between the diameter depth of these holes showed good negative correlation (r ) The incubation period of the eggs was 3-4 days at temperature (6-301lC) and relative humidity (76-88%) The daily oviposition rate ranged between 3-50 eggs during the oviposition period of 5-0 days; least oviposition (09±061) occurred during the first week after pre-oviposition period of 1-5 days Maximum oviposition (449±104) occurred on the 9-13thdays of the second weekfollowed by (l663±506) onthe third and (l05±107) onthe fourth weeks respectively The ovipositionpatternwas generallyirregular, while the percentage egg-hatchabilitywas 6046 INTRODUCTION from western hemisphere species (R Rhynchophorus phoenicis (F) palmarum) and other related species (Hagley, (Coleoptera: Curculionidae) has been known 1965) The findings on the oviposition of R as a major secondary peslof coconut, oil and phoenicis presented here are crucial aspects raffia palms as well as the sago palm on which of on-going studies on the biology of this weevil the adults usually laid their eggs in entry holes in palms in the Niger Delta to achieve masscreated by the Orcytes monoceros (beetle), or rearing of the R phoenicis larvae in the sizeable wounds created during had pruning laboratory for human consumption and or harvesting (NRI, 1996) The economic commerce importance of R phoenicis does not only lie MATERIAL AND METHODS on the daage caused on palms but also on Trial on oviposition of R phoenicis the use of Its larvae for food In Cameron, were conducted in the Postgraduate laboratory te recipe of coconut larve was a favonte of the Department of Biological Sciences, dish offered only togoodfnends (Grimaldi and R' Ivers St a t e U' n1versi 't y f S d 0 clence an Blkla, 1987) The situation IS almost the same li ec hip no ogy, rt H t N' d 0 arcour, Igena urmg m Southern Nlgena where people cut down M ay 000 Se' xmgo f a dult f emaes I f rommaes I the young oil palms and mature raffia palms ' and leave the logs to be infested by adults of R was done usmg the morphol of the rostrum phoenicis in order to harvest the larvae latter In the femal, th rostrum IS curved and the (Ajiboye and Fasoranti, 1993) Inspite of the males have a straight and clubbed rostrum immense economic importance of this weevil, Ten (10) pairs of virgin females and detailed studies on its life history has not been male were collected from their cocoons after carried out on oil and raffia palms, which are their last pupal moult and put in pairs in ml abundant in the Niger Delta, thus available plastic containers that contained some decayed information on the subject are based on data tissues of previously infested oil palms The IDepartmentof Biology, Rivers State College of Education, Port Harcourt, Nigeria Corresponding author

2 Vol 38, No, 004 ' 17 males and females mated for 10days in these oviposition was 1±107 jars before h they were d 30 separated into different The percentage egg hatchability of jars,eac containe - 40g pieces of freshly female R phoenicis (Table 1) showed thai, out decaying palm sap and covered with muslin of the total number of six hundred and twelve cloths Daily monitoring and observations were conducted in order to study daily ovipostition (61) eggs laid by 10 fertile females, three hundred and seventy (6046%) eggs hatched rate of the mated females by transferring each to first instar larvae, while two hundred and female to new plastic container at 4 hours forty-two eggs (3954%) did not hatch interval and newly decayed palm saps were added todaily consecutively in their respective The results of correlation analyses plastic containers, before they were teased showed that the diameter and depth of the under water, using scapel and forcep The feeding holes which were made by both the fibrous tissues of the rotten saps were carefully males and females showed negative linear removed, and 30 ml of the resultant mixture correlation because the values of correlation was poured into different Petri dishes and coefficient was r = and r = 099 screened for the first instar larvae and un for thefemales and males respectively hatched eggs with a magnifying lens and The rate of oviposition in the females counted to know the total number of eggs and of R pheonicis was relatively high asthey had larvae produced by each female within the daily oviposition rate of 3-50 eggs and average oviposition period The depth and diameter weekly oviposition of 61±1185 for an of the holes made by the males and females oviposition period of 5-0 days under were taken separately using a Vernier caliper laboratory conditions of temperature (6 at 4 hours intervals for threedays Statistical 30 C) and relative humidity 06-88%); while and correlation analyses were computed using the ph of the decaying young oil palm saps SPSS (75 for Windows) was between RESULTS AND DISCUSSION The general pattern of oviposition by The results in Fig 1 showed that the the females was quite irregular as the females mated female adults of R phoenicis did not habitually suspended oviposition for - 3 days, lay eggs from the 1-5 days of their life span even during the periods of peak oviposition The weevils commenced oviposition on the 6 Similar irregulartty in oviposition was also - 9th days Out of the ten palm weevils (P _ reported on the females of R palmarum which PIJ studied, only one palm-weevil Oviposited stopped oviposition for 1-4 hours before on the 6th day (P ), 4 whereas four palm weevils they resumed ovisposition (Hagley 1965) The which commenced oviposition on the 8th day observed 1 - days period of quiescence and were PI P P and P ; while the remaining suspension of oviposition by the female adults 7 s IO for pal weevils (P ' 3 P ' P and S 6 PJ began and fairly high per cent of unhatched eggs oviposition on the 9th day Maximum (3954) could be attributed to the accumulation oviposition occurred on the 9-13thdays The of the organic by-products which could lead to mean weekly oviposition rates in Table 1 also asphyxiation of both the oviposition eggs, the showed that the first week had the least number newly hatched larvae and even the female of eggs laid (09±061), while the second week adults had the highest oviposition (449±1045), Thefemales and males of R phoenicis being followed by the third weekly used the rostrum to make holes on the palm (1663±506) and at the fourth week saps during their feeding activities This was

3 18 INDIAN JOURNAL OF AGRICULTURAL RESEARCH " 1 'i ' :J ] l!io to tel 30 ';0 lo ",_'--ta til F' W 060,,' "':', ' p, n P JJ' [jj No of larvae 11 No of eggs PI - PI0 denotes Individual palmweevlls -----, ---_ ' t '1 t4 It , -, ' 1:_ I Q,' _, )ll : J _m III _ a 1 I t 8 t ) I " ZO' t5 '0, N '_' "''''',,>0<'' ",',,,"','_ $ o,_i I S r I 1 10 S ss " l_m t I -" " II 18 IL '0 0 1:1 1:1 t, to n ' ij, t4 t$, 1 a 11 n t: : ::t : z- :, :--- D_a;;,ys_o_f_Ovipositlon ' ",, _ ),, j ' : 1$' 10 ' II " K-I " 1 (Copt

4 Vol 38, No, _,-- - '0 1 1,_---, , fo i i e, 4 o 1, "' -'--,,1' - f: ' 1 51I, 31 'I t 1 o P10 J Illl I 6 r 10 II I: '3!4 Days of oviposition 11 IS Fig 1 Indirect estimate of the number of eggs laid by female R phoenicis

5 possible due to modification of the mouth parts to form slender rostrum suitable for piercing and feeding on the substrates These findings agreed with the reports of Weissling and Giblin Davis (1997) which stated that most weevils used their modified mouth parts (rostrum) in feeding by preparing holes on plant materials due to the presence of modified mandibles at the end region of the rostrum Furthermore, the depth and diameter of the holes made by both males and females ranged between 1-7 mm and 1-14 mm respectively These holes showed negative linear correlation (r = -081 for the males, and r = -099 for the females) This means that the diameter of the feeding holes which were used for oviposition by the females, decreased as the depth increased These values agreed with the holes made by females, R palmarum on coconut pith in West Indies (Hagley 1965) However, it was only the females of R pheonicis that were observed to utilized the holes for oviposition During the egg-laying process, which was observed at night, a gravid female placed the tip of the pygidium of the last abdominal segment on the edge of a hole, used its clawed limbs to grip the decaying palm tissues and inserted the tubuliferious ovipositor into the hole anddeposited a single egg Hagley (1965) had reported that such a hole used for oviposition was immediately capped with a waxy secretion, which hardened and often adhered to the end of the egg This could be the reason for the slight difficulty experienced in separating the first instar larvae which were usually attached to the tissues of the palm at the posterior end 'The incubation period for the eggs was 3-4 days REFERENCES Ajiboye, DO and Fasoranti, JO (1993) Am Ent, 38: Grimaldi, J and Bikia, A (1987) La Grand Liver de la Cuisine Camerounaise, 136p Hagley, EA (1965) Ann Ent Soc Am, 58: -8 NRI (1996) Aguide to Insect Pest of Nigerian Crops Identification, Biology and control Federal Ministry of Agriculture and Natural Resources and Overseas Development Administration of British Government U K Wahua, TAT (1999) Applied Statistics for Scientific Studies Africa-Link Books University of Ibadan, Nigeria pp355 Wessling, TJ and Giblin-Davies, RM (1997) Introduction, Description, Life-l;ycle and Distribution of Rhynchophorus cruentatus (Fab) (Coleoptera:Curculionida:) Extention Digital Information Source (EENY-13) Dept of Entomology and Nematology University of Florida pp 5