PertanikaJ. Trop. Agric. Sci. 24(2): 109- 114 (2001) ISSN: 1511-3701© Universiti Putra Malaysia Press

Status of Rat Infestation and Recent Control Strategies in Oil PalmPlantations in Peninsular Malaysia

M. N. HAFIDZI 8c M.K. SAAYONDepartment of Plant Protection

Faculty of AgricultureUniversiti Putra Malaysia

43400 UPM Serdang, Selangor, Malaysia

Keywords: rattus sp, tyto alba, rat control, oil palm

ABSTRAKSatu soal selidik telah dijalankan untuk menentukan status serangan tikus dan kaedah kawalan tikus semasadi ladang-ladang kelapa sawit di Semenanjung Malaysia. Rattus tiomanicus (Miller), merupakan spesiestikus yang utama (68%) diikuti oleh Rattus argentiventer (Robinson and Kloss), (46%) dan Rattus rattusdiardii (L.), (28%). Walaupun 75% dari ladang tidak menganggap tikus sebagai masalah yang serius,kerugian yang diperolehi adalah dalam anggaran 0.01 hingga 0.1 t/ha. Burungpungguk jelapangTyto alba(Scopoli) kini merupakan komponen kawalan tikus yang penting dalam ladang kelapa sawit iaitu sebanyak82% daripada ladang yang mengambil bahagian. Ada ladang (21.4%) bergantung sepenuhnya kepada T.alba, tanpa menggunakan racun tikus. Sebahagian besar ladang (60.7%) menggabungkan mengumpan dankawalan menggunakan T. alba yang dapat menjimatkan kos mengumpan di antara RM2.64 sehingga RM30/ha/tahun.

ABSTRACTA survey was carried out to establish the status of rat infestation and recent rat control practices in oil palmplantations in Peninsular Malaysia. Rattus tiomanicus (Miller) constitutes a major rat species (68%),followed by Rattus argentiventer (Robinson and Kloss), (46%) and Rattus rattus diardii (L.), (28%).Although 75% of estates did not consider rats as a serious problem, the damage estimated ranges from 0.01 to0.1 t/ha. The barn owlTyto alba (Scopoli) is now an important rat control component in oil palm i.e. 82%of estates that participated in the survey. In some estates (2L4%) control is achieved entirely with T. alba,without baiting. In most estates (60.7%) baiting ivas done in combination with T. alba, whereby the latterreduced baiting cost from RM2.64 to RM30/ha/year.

INTRODUCTIONRat species that can be found in oil palmplantation in Peninsular Malaysia are Rattustiomanicus (Miller), Rattus argentiventer (Robinsonand Kloss), and Rattus rattus diardii (L.) (Wood1976). R. tiomanicus is the dominant speciesespecially in matured palms (Wood 1968),whereas the rice field rat R. argentiventer isnormally found in nurseries and young oil palms(Wood 1982). It is also a common species in oilpalm formerly planted with rubber (Wood 1976).R rattus diardii is normally associated with humandwellings, but has also become common in oilpalm (Mohd 1985) especially in areas where R.

tiomanicus has been controlled by baitingJSoh etal. 1982).

Apart from attacking matured palms, ratalso causes damage to young plantings. At thenursery stage, rat feeds on the apical tissuecausing death or affecting normal developmentof the young shoots. On young oil palms, themost favourite part is the petiole that forms thefronds. Damage to this suppresses the formationof fronds. In matured palm, attack isconcentrated on the inflorescence and the fruitbunch. Damage to inflorescence affects floweringwhile damage to fruits can reduce yield (Wood1982).

M. N. HAFIDZI 8c M.K. SAAYON

Baiting, with anticoagulant rodenticides isthe mainstay of rat control practices in oil palmestates in Malaysia. However, beginning mid-eighties, the barn owl Tyto alba (Scopoli) hasbeen identified as an effective predator of ratsand had since been relied upon to control ratswith encouraging results. Following successfultrials in estates in Selangor and Negeri Sembilan(Smal 1988), the biological control programmeusing barn owl has been implemented in manyestates throughout the country, by providingnest boxes to wild populations of barn owl. As aresult there has been a boost in the barn owlpopulation in oil palm. The purpose of thisstudy is to determine the current status of ratcontrol by the barn owl in oil palm estates vis-J-vis baiting in Peninsular ^Malaysia.

METHODA survey was carried out on 68 oil palm estates,all greater than 1000 ha, selected at randomfrom nine states in Peninsular Malaysia; thebreakdown were as follows; Kedah (6), Kelantan(6), Malacca (6), Negeri Sembilan (9), Pahang(9), Perak (8), Selangor (8), Terengganu (8),and Johore (8). The survey questions weredesigned to meet three major objectives. Firstly,to establish the common rat species recentlyfound in both mature and young oil palms inPeninsular Malaysia. Secondly, to gauge theseverity of rat damage, subjectively assessed interms of yield loss, and finally, the method ofcontrol currently employed with particularreference to baiting and natural predation bybarn owl.

RESULTS AND DISCUSSIONA total of 28 estates (41%) returned the surveyforms. Twenty of these or 71% came from fivestates namely Negeri Sembilan, Pahang, Selangor,Malacca and Kedah,

Rat Species Composition in Oil Palm

Seven estates (25%) reported the presence ofRattus tiomanicus only, three estates (11%)reported R. argentiventer only and two estatesreported R. rattus diardii only while seven estates(25%) reported the presence of both R.tiomanicus and ft argentiventer, three estates (11%)reported ft tiomanicus and R. rattus diardii andonly one estate reported ft argentiventer and R.rattus diardii. Only one estate reported the

presence of all three species. Three remainingestates were not sure of the identity of the ratspecies. The species composition is summarizedin Fig. 1. Based on individual species, R.tiomanicus was reported in 68% of the estates,followed by ft argentiventer 46% and ft rattusdiardii 28%.

The survey results show that ft tiomanicus isstill the dominant species in oil palm, as initiallyreported by Wood (1971), then Wood and Liau(1978) and the latest by Basri and Halim (1985).ft tiomanicus is well adapted to live in oil palmdue to its agility and arboreal habits as comparedto ft. argentiventer and ft rattus diardii, which liveon the ground, ft argentiventer is more commonin young palms (Wood 1982). Survey resultsindicate that 13 out of 33 (39%) rat damagereported by the estates occurred in youngplantings. Seven out of the 13 (54%) damage onyoung plantings was attributed to ft argentiventer.The survey also confirms the status of ft rattusdiardii reported by Basri and Halim (1985) asbecoming more common in oil palm. There areseveral factors to explain the higher occurrenceof ft rattus diardii in oil palm. Firstly, successfulcontrol on ft. tiomanicus has opened the way forinfestation by ft rattus diardii (Soh et al. 1982).Secondly, bait formulation and baitingtechniques has been designed primarily for Ktiomanicus, leading to ft rattus diardii developingresistance due to insufficient (sub-lethal dose)bait consumption (Lam et al. 1982). Finally, thepropagation of the pollinating weevil Elaeidobiuskamerunicus in oil palm has become an attractivesource of food (protein) to ft rattus diardii. Ratis more difficult to control after the introductionof the pollinating weevil (Mohd 1985). Theinclusion of the pollinating weevil in the rat diethas lead to juveniles growing faster and heavieradults (Liau 1985).

The particularly high percentage of estatesusing barn owl points to a greater reliance onbiological means to control rats in oil palm.Besides proven efficient and generally tolerantto baits, the high cost of rodenticides and theoperational cost of baiting have lead many estatesto start their own barn owl programme. Theresult of the survey indicates a departure fromthe control strategies normally employed in oilpalm in the 80's whereby control is primarilyachieved through baiting alone (Wood 1982;Basri and Halim 1985).

110 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 24 NO. 2, 2001

RAT INFESTATION AND RECENT CONTROL STRATEGIES IN OIL PALM PLANTATIONS

* , _

R. t - Rattus tiomanicusR. a - Rattus argentiventerR. r.d. - Rattus rattus diardii

Rat species

Nos. at the top of the bars represent actual numbers

Fig, 1. Composition of rat species present in the estates surveyed

80

in 60SiS 40UJ

s? 20 -

0

21

i *Not serious Moderate Serious

Level of seriousnessNos at the top of the bars represent actual numbers

Fig. 2. Percentage of estates based on level of seriousness of rat damage

Rate of Losses due to Rat DamageEstates were asked to subjectively assess the levelof rat damage as not serious, moderate or serious.Fig. 2 shows the percentage breakdown of estatesbased on these categories. Results of the surveyshow that 75% of estates assigned their ratdamage as not serious. Only 14.3% assigned ratdamage as moderate and 10.1% as serious. Table1 shows the estimated damage and loss incurredby some of the estates. The estimated damage inyield varies from 0.01 t/ha to 3 t/ha/yr. Thistranslates into losses ranging from RM 4/ha toRM1200/ha/yr. These figures were eitherestimated on a per hectare or per hectare on ayearly basis. Therefore it may not be comparable.However it can be deduced that damage to oilpalm lies in the range of 0.01 t/ha to 0.1 t/ha.When infestation is serious, the annual loss canexceed RM 1000 /ha. In terms of crude palmoil, Wood et al. (1973) estimated a loss of between

TABLE 1Estimated damage and loss due to rat damage

on oil palm

Estates

123456789

101112

Estimateddamage

0.4 t/ha0.7 t/ha0.32 - 0.93t/ha3t/ha/yr0.01 t/ha1 - 2 t/ha5 - lOKg/ha0.25t/ha3t/ha/yr2.2t/ha/yr0.02 t/ha0.1 t/ha

Estimated loss

RM 180 / h * -RM 200-300 /haRM 496 /haRM 1000 /ha/yrRM 4 /haRM 400 /haRM 5 - 10 /haRM 115 /haRM 1200 /ha/yrRM 594 /haRM 8/haRM 43 /ha

134 to 240 Kg/ha i.e. approximately 5% of totaloil production.

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 24 NO. 2, 2001 111

M. N. HAFIDZI 8c M.K. SAAYON

Among the factors identified by the estatesas contributing to the rat infestation in oil palmare; absence of rat control effort by surroundingsmall holding plantations, poor hygiene in thesurrounding area, heavy rainfall followed byflooding have caused rats to migrate to higherground, deposition of thinned fronds serving asnest sites for rats, wide area control cannot becarried out due to shortage of labour anddifficulties in controlling rats near forest fringesand swamp area which are sources of ratinfestation.

Present Status of Baiting and Barn Owl ControlProgram

Of the estates surveyed 17.9% relied on baitingonly, 21.4% relied on barn'owls only and 60.7%on both (Fig. 3). Interestingly one estateemployed snakes as a control agent apart frombaiting. These statistics show that 82% of the

estates implement the barn owl programme. Onthe other hand, baiting remained important as79% of estates surveyed continued to bait, singlyor in combination with barn owl. Six estates didnot bait and relied on barn owls only. Theseestates may have a sufficiently large populationof barn owl to keep rat infestation down thatbaiting is no longer necessary. Smal et al. (1990)proposed that the increase in barn owlpopulation may justify the suspension of baiting.

Fig. 4 compares the number estates usingfirst and second generation rodenticide singlyor in combination with barn owls. On the typesof rodenticide used by the estates, 76% used thefirst generation anticoagulant, namely warfarin(68%) and chlorophacinone (8%). This suggeststhat as in the 80's (Basri and Halim 1985),warfarin is still the rodenticide of choice in oilpalm estates. Chorophacinone, on the otherhand, although a first generation anticoagulant

1UJ

60 -I

50 -

40 •

30 •

2010 -

0 -

Baiting only

mm

BB

-—MBBarn owl only Baiting & Barn owl

Fig. 3. Percentage of estates surveyed using baits and barn owl in controlling ratsin oil palm

mm6 4

1st gen + 1st gen 2nd gen + 2nd gen.Barn Ovd only Barn O\M Only

Fig. 4. Number of estates using first and second generation rodenticide singly andin combination with barn owls

112 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 24 NO. 2, 2001

RAT INFESTATION AND RECENT CONTROL STRATEGIES IN OIL PALM PLANTATIONS

having similar effects like warfarin (Wood andLiau 1978), is not widely used, as revealed by thesurvey. This is probably due to the latter beingcheaper.

Warfarin is also a relatively safe rodenticidewhen used in combination with barn owl, asthere have been no known cases of secondarypoisoning to the latter (Duckett 1984). This isalso reflected from the survey whereby 10 estatesout of 16 (62.5%) that combines baiting andbarn owl used warfarin in their baits. Howeverwith reports of rats developing resistance to firstgeneration anticoagulant, as also revealed by thesurvey, some estates started to switch to secondgeneration rodenticide. The results from thesurvey show that 24% of the estates indeed usedsecond generation anticoagulant, namelybromadiolone (16%) and brodifacoum (8%).However, unlike first generation rodenticide,second generation poses a hazard to barn owls.Brodifacoum has been claimed to have a hightoxicity to barn owl (Mendenhall and Pank 1980).Duckett (1984) proposed that brodifacoumshould not be used in combination with barnowl. In spite of this, three estates combine barnowl and baiting with second generationrodenticide; one of which with brodifacoum.

Barn Owl and Reduction in Baiting CostThe estimated cost of baiting and that to sustainthe barn owl program, as indicated by some ofthe estates, are shown in Table 2. Not all estateshave provided the information needed and nostandard response was given. However, based onthe survey returns it can be deduced that baitingcost can be substantially reduced by implemen-ting the barn owl programmes. The cost ofbaiting varies from RMlO/ha/yr to RM64/ha/yrwith average cost of RM24.11/ha/yr. The averagebaiting cost was recorded by Basri and Halim(1985) as between RM10 - RM30/ha/yr. Duckettand Karuppiah (1989) indicated that in severecases the cost may reach RM60/ha/yr. From thesurvey, the reduction in baiting cost from usingbarn owl ranges from RM2.64/ha/yr to RM20 -RM30/ha/yr. This also generally fall's within therange quoted by Duckett and Karuppiah (1989)i.e. RM4.80 to RM20/ha/yr. Other estates gaveless objective response which include 50%reduction in baiting requirements, reduction inbaiting campaigns from twice to once a year,baiting campaigns continue at twice a year butwith a reduced intensity up to 50%/ha or baiting

TABLE 2Cost of baiting and reduction in baiting cost

B+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BOB+BO

B+BOB+BOB+BOBBBBB

from barn owl

Baiting Cost

RM 13/ha/yr-

RM 17.82/ha/yrRM40.82/ha/yr

-

RM40.60/ha/yrRM11.80/ha

RM12.60/ha/yrRM18.92/ha

__

--

-

4 campaigns/yrRMlO/ha/yrRM8.40/haRM5.80/ha

RM64/ha/yrRM11.50/ha/yr

B - BaitingBO - BarnNA - Not

owlapplicable

program

Reduction inBaiting Cost

RM 3.20/ha/yrYesYesYesYes

RM20/ha/yr< 10 n 20%

RM2.64/ha/vrNot much

50%Yes

RM20-30/ha/yrNo of baiting

rounds reducedNot sure

RM26/ha/yrNo reduction in cost

NANANANANA

rounds for each campaign reduced to 2 - 5rounds from 7 - 1 0 rounds. There is one claimhowever, that barn owl did not lead to anyreduction in cost.

CONCLUSION

The results of the survey show that R. tiomanicusremained the dominant species in oil palmfollowed by R. argentiventer. The survey alsoindicates that R. rattus diardii is becomingimportant in oil palm probably as a result ofbaiting strategy and methods of oil palmpropagation. Damage caused by rats is generallyconsidered not serious but can be substantialand control can be difficult, often hindered bycircumstances beyond the jurisdiction of theestates concerned.

The survey also shows that barn owl hasbecome an important component in the ratcontrol practices in oil palm estates in PeninsularMalaysia. First generation rodenticide namelywarfarin remained widely used and by virtue ofits low toxicity to barn owl would ensure the

PERTANIKAJ. TROP. AGRIC. SCI. VOL. 24 NO. 2, 2001 113

M. N. HAFIDZI & M.K. SAAYON

survival of the latter. Earlier claims that barn owlprogramme can considerably reduce baiting costhas been substantiated by this study.

ACKNOWLEDGEMENT

The author would like to thank all participatingestates in the survey. This project was funded byUniversiti Putra Malaysia under Research grantcode no. 50202-98-04.

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(Received: 18 April 2000)(Accepted: 28 June 2001)

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