The Weta 50:38-47

38

Extracts of the rosary pea, Abrus precatorius, aretoxic to the invasive termite, Coptotermes gestroi
Ravikash. R. Prasad*
Faculty of Science, Environment and Technology, The University of
the South Pacific, Suva, Fiji
Gilianne Brodie
Faculty of Science, Environment and Technology, The University of
the South Pacific, Suva, Fiji
Cas Vanderwoude
Hawaii Ant Laboratory, University of Hawaii (Manoa), Hilo, Hawaii,
USA
Simon Hodge
Faculty of Science, Environment and Technology, The University of
the South Pacific, Suva, Fiji, andFaculty of Agriculture and Life Sciences, Lincoln University,Christchurch, New Zealand* author for correspondence: email: researchravi@yahoo.com

Abstract
In 2009 an outbreak of the termite Coptotermes gestroi caused major
damage to buildings and vegetation in Fiji. Termite control is mostcommonly performed using synthetic insecticides, although many
botanically-derived toxins are also being evaluated. The woody
legume, Abrus precatorius, contains the toxic protein abrin, and has
been investigated previously for insecticidal properties. The current
study used laboratory experiments to evaluate extracts of A. precatorius
as potential control agents for C. gestroi. In Petri dish assays, exposure
to water- and methanol-based extracts of leaf and seed material
significantly increased mortality and shortened time to death of C.
gestroi. The results suggest that extracts of A. precatorius havepotential for use as control agents of C. gestroi and should be evaluatedfurther to determine their mode of action and efficacy under fieldconditions.

39

Ravikash Prasad et al.

Introduction
In 2009 an outbreak of the Asian subterranean termite, Coptotermes
gestroi (Wasmann 1896) (Isoptera: Rhinotermitidae), occurred in theLautoka district of Viti Levu in Fiji causing major damage to homes,schools and vegetation. According to the Biosecurity Authority of Fiji(pers. comm.) the Fijian government spent more than FJ$3 million
between 2009 and 2011 on the problem of C. gestroi infestation, which
involved application of chemical treatments, repair of damaged
structures and education of local residents. Control of C. gestroi in theLautoka area was primarily based on the commercially-available
product ‘Termidor’ (which contains the active ingredient fipronil)
imported from Australia, with prices to treat a typical Fijian house
ranging between FJ$170 to FJ$250. The Fiji Government indicatedthat new termite infestations would only be treated on a ‘user pays’
basis, and home owners that could not afford to pay for the chemicaltreatments would also be liable to pay for their own house repairs,estimated in the region of FJ$8000, close to the estimated per capita
gross national income of FJ$8300 in 2011 (Burese, 2011; Malo, 2011;
UNdata Fiji, 2013).
Coptotermes gestroi originates from South East Asia and isconsidered one of the most destructive, economically important, termite
species worldwide. Control of C. gestroi is still commonly performed
using synthetic insecticides, such as bistrifluron, hexaflumuron andimidacloprid (Lee et al.,2004; 2009; Hafiz and Hassan, 2008).
However, although these insecticides can be highly effective, theadverse effects of these chemicals on the wider environment andhuman health are of increasing concern and so alternative termite
control methods continue to be investigated (Verma et al., 2009).
A number of natural products and plant extracts have been
screened for inhibitory activities against invasive or pest social insects
such as ants, wasps and termites, with a view to controlling these
species in a more ‘environmentally friendly’ manner. For example,
extracts of boxthorn (Lycium shawii) and cassava (Manihot esculenta)
have recently been shown to have strong toxic effects against samsam
and leaf cutter ants respectively (de Cavalho Alves et al., 2013;
Mashaly et al., 2014), whereas the argentine ant, now a major invasive
species in New Zealand, was repelled from herbage treated with byessential oils of wintergreen, cinnamon, cloves, peppermint and(especially) spearmint (Scocco et al., 2012).
With regard toThe Weta 50:38-47

40

termiticides, extracts from white cedar Melia azedarach, aroeira
Myracrodruon urundeuva, teak Tectona grandis, stilt-mangrove
Rhizophora apiculata and the ‘suicide tree’ Cerbera odollum have all
been shown to have toxic effects against C. gestroi (Hashim et al.,2009; Khalil et al., 2009; Nascimento et al. 2009).
The leguminous plant Abrus precatorius L. (Fabaceae) (‘rosary pea’,‘jequirity’) is a high-climbing or trailing woody vine that grows intropical climates (Anand et al., 2010). The plant is native (or anancient introduction) to Fiji but, because of its tendency to smother orover-grow other native vegetation, is often considered as invasive or anuisance weed. Abrus precatorius has numerous and wide-ranging
bioactive properties and the insecticidal effects of this species havebeen investigated for over a hundred years (e.g. Stillmark, 1888; Bhatia
et al., 2013). The aim of this study was to use laboratory assays toevaluate water- and methanol-based seed and leaf extracts of A.
precatorius for toxicity towards C. gestroi by measuring both final
mortality and time to death.

Materials and Methods
Termites were collected from trees and posts in Tavakubu and Central
College School, Lautoka, and housed in glass tanks (90% relativehumidity; 28ºC) with wood fragments until used in assays. Abrus
precatorius leaves and seeds were collected from Malomalo Village
and the leaves and seeds washed, frozen for 3 days, freeze dried for 3days and then ground to a fine powder using an electric grinder.
Methanol extracts were prepared by mixing 500g of leaf or seed
powder with 1 L of methanol (99%) in a conical flask, shaking for 48
hours on an electric shaker and then repeatedly filtering until clear.
The filtrate was dried using a rotary evaporator at 60˚C and a stock
solution prepared by re-dissolving 10 g of the dried extract in 20 ml ofmethanol to obtain a 50% w/v solution, which was in turn seriallydiluted to give desired concentrations for bioassays (10% and 1% w/v).
Water extracts were made by direct mixing of A. precatorius leaf orseed powder in distilled water at the required concentrations (10% and1% w/v). The mixtures were placed on a shaker for 48 h and thenfiltered. All solutions were stored at 4oC until used.
Toxicity assays were performed using glass Petri dishes (9 cmdiameter) as the experimental arenas. Filter papers were dampened

41Ravikash Prasad et al.

with 2 ml of solution and excess fluid allowed to evaporate. There werethree replicate Petri dishes for all test solutions. Distilled water ormethanol (99%) were used as appropriate control treatments. Twenty
five termites were added to each of the Petri dishes, and daily mortalityof C. gestroi recorded in each dish for 10 days, with dead individuals
being removed each day to prevent contamination. The Petri dishes
were maintained in a hygrostatic tank at 28ºC and 90±10% RH and thehigh humidity ensured the filter papers remained moist throughout the10 d trial.
The mean time of death (MTD; d) for termites in each Petri dishwas calculated by:where di = the ith day since the assay started and Di = number oftermites which were recorded newly dead on di.

Results
There was a strong correlation between MTD and concentration forboth the water and methanol extracts (Figure 1: rs > |0.75|; P < 0. 0.005
for all extracts). Death was most rapid when termites were exposed tomethanol extracts compared to water extracts (cf. Figure 1a & 1b),
although mortality had still reached 100% in both of the 10% extracts
by Day 10 (Table 1).
Termite mortality exhibited a clear positive relationship with extract
concentration for all four types of extract after 1 d and 2 d exposure(Table 1). Mortality was more rapid when exposed to the methanolextracts compared to the water extract of comparable concentrations.
For the highest (50%) concentration of methanol extracts, all termites
were dead after 1 d exposure to the seed extract and after 2 d exposure
to the 50% leaf extract.
There was no control mortality in the water and methanol extracts after
1 d and 2 d (Table 1). However mortality of termites in the control
methanol treatment was high after 10 d (83%), suggesting exposure tomethanol residues was having some chronic inhibitory effects

Discussion
The results indicate that exposure to leaf and seed extracts of A.
precatorius can cause mortality and shorten time to death in the termite
C. gestroi. Previously, Setiawan et al. (2009) reported that methanol

The Weta 50:38-47

42

extracts of leaves and seeds of A. precatorius could produce 100%
mortality of C. gestroi in 12 days using a ‘force-feeding’ method. Our
study has reconfirmed the toxicity A. precatorius extracts against C.
gestroi, and extended these results by demonstrating that water-based
extracts are also toxic, and that mortality can be caused by contact withA. precatorius extracts or residues as well as by ingestion.
Bait toxicant systems, where active ingredients are incorporated into
food baits which are then carried into the termite colony by foraging
workers, can substantially reduce pesticide use (Su & Scheffrhan,1998). In these bait systems, a slow mode of action is important assufficient time is required for foraging termites to contact the toxin andthen return to the colony. This type of action was apparent for some A.
precatorius extracts: for example the 10% leaf extracts acted fairly
slowly (MTD ≈ 4-6 d) but still caused 100% mortality after 10 days. A
further desirable property of the A. precatorius extracts was that there
were no obvious repellent effects towards C. gestroi and this may have
prevented lethal doses being received.
Hoddle (2004) suggested there is scope to control invasive species in asustainable fashion if one problem species is utilized in some mannerthat helps to control another. Many other important insect pests ofSouth Pacific islands (e.g. mosquitoes and aphids) have also beenshown to be susceptible to A. precatorius extracts. Thus thedevelopment of viable and effective insecticides from this plant may
offer multiple advantages in a South Pacific setting, in terms of reduced
synthetic pesticide use, more environmentally sound pest control,management of a problem weed, and, ultimately, some economic
benefit to the local communities involved.
This study provides preliminary data describing the strong negative
effects of A. precatorius on C. gestroi. However we have not as yetidentified the active ingredient(s) and their concentrations in theextracts, and so could not estimate the actual doses of chemicals thetermites received. Further investigation of A. precatorius extracts isrequired to ascertain their mode of action and their effectiveness whenapplied to natural substrates (e.g. soil; foliage; timber) or incorporated
into bait toxicant formulations in a field setting.

43

Ravikash Prasad et al.

Acknowledgements
We wish to thank Lautoka Central College for allowing us to use theirlaboratories for experiments and officers of The Biosecurity Authorityof Fiji for helping locate and collect termites. This research was fundedby the University of the South Pacific.
References
Anand AR, Kishor OV, Rajkumar SV, Chandrashekhar U D & Tanaj
ND. 2010: Abrus precatorius Linnaeus: A phytopharmological review.
Journal of Pharmacy Research, 3: 2585-2587.

Bhatia M, Siddiqui NA & Gupta S. 2013: Abrus precatorius (L.):
an evaluation of traditional herb. Indo American Journal ofPharmacy Research, 3: 3295-3315.
Burese I. 2011: Chemical boost for eradication. In: The Fiji Times,
1/3/11, Fiji Times Limited, Suva.
http://www.fijitimes.com/story.aspx?id=167218
Hafiz AMA, Hassan AA. 2008: Preliminary field efficacy of transfer
effect of slow acting termiticide (imidacloprid) on subterranean
termites population (Coptotermes gestroi) (Wasmann) (Isoptera:Rhinotermitidae). Journal of Biosciences, 19: 101-106.
Hashim R, Boon JG, Sulaiman O, Kawamura F, Lee CY. 2009:
Evaluation of the decay resistance properties of Cerbera odollam
extracts and their influence on properties of particleboard.
International journal Biodeterioration and Biodegradation, 63:
1013–1017.
Hoddle MS. 2004: Restoring balance: Using exotic species to control
invasive exotic species. Conservation Biology, 18: 38-49.
Khalil HPSA, Kong NH, Ahmad MN, Bhat AH, Jawaid M, Jumat S.
2009: Selective solvent extraction of the bark of Rhizophora
apiculata as an anti-termite agent against Coptotermes gestroi.
Journal of Wood Chemistry and Technology, 29: 286-304.

The Weta 50:38-47

44

Lee LC, Lee CY, Vongkaluang C, Jaafar MA, Pornkulwat S, Ouimette
DG, Tolley M. & Borthe P. 2004 Field efficacy of Recruit® IIItermite bait (0.5% noviflumuron) against Coptotermes gestroi(Isoptera : Rhinotermitidae) in Southeast Asia. Presented at the2004 Annual Meeting and Exhibition.of the Entomological Societyof America.
Malo M. 2011: Termite user-pay system costly. In: The Fiji Times,
6/1/11.
FijiTimes
Ltd.,
Suva.
http://www.fijitimes.com/story.aspx?id=163401.
Mashaly AMA, Farooq M, Hozzein W, Al-Qahtani AM, Al-Mekhlafi
FA. 2014: Assessment of toxic baits for the control of the samsum
ant, Pachycondyla sennaarensis (Formicidae: Ponerinae). African
Entomology, 22: 204-209.
Nascimento SM, Franca TML, Ballesteiro PM, Barsanulfo ME. (2009):
Potential insecticidal effects of aqueous tree leaf extracts against
the subterranean termite Coptotermes gestroi (Isoptera:Rhinotermitidae). Sociobiology, 53: 719-728.
Sajap AS, Lee LC, Shah ZM. 2009: Elimination of subterraneantermite colonies with hexaflumuron in an improved bait matrix,
preferred textured cellulose (PTC). Sociobiology, 53: 891-901.
Santos MAI, Correa AD, Alves APD, Simao AA, Alves DS, deOlivereira RL, Saczk AA, Carvalho GA. 2013: Cassava leaf
methanolic extracts an an alternative to control of fall armywormand leaf cutter ants. Semina: Ciênces Agrárias, 34: 3501-3511.
Setiawan KH, Tarmadi D, Prianto AH, Yusuf S. 2009: Termicidal
activities of Abrus precatorius L. leaves extract against
subterranean termite Coptotermes gestroi. In: W. Diwanto and A.
Kusumaningtyas (eds.) Proceedings of The First International
Symposium of Indonesian Wood Research Society, Indonesia
Wood Research Society, Indonesia.

45Ravikash Prasad et al.

Scocco CM, Suiter DR, Gardner WA. 2012: Repellency of fiveessential oils to Linepithema humile (Hymenoptera: Formicidae).
Journal of Entomological Science, 47: 150-159.
Stillmark H. 1888: About ricin, a toxic enzyme from the seeds ofRicinus communis L. and some other Euphorbiaceae. Arbeiten aus
dem Pharmakologischen Institut Dorpat, 3: 59-151.
Su NY, Scheffrhan RH. 1998: A review of subterranean termite control
practices and prospects for integrated pest management
programmes. Integrated Pest Management. Reviews, 3: 1-13.
UNdata2013:
Fijidata.un.org/CountryProfile.aspx?crName=FIJI.
19/12/2013.

Islands.
AccessedVerma M, Sharma S, Prasad R. 2009: Biological alternatives fortermite control: A review. International Biodeterioration andBiodegradation, 63: 959-972.

46The Weta 50:38-47

109a) MeOH extracts

Leaf

8Seed

MTD (d)76543210011050

Concentration (%)

10Leafb) H2O extracts

9Seed

8MTD (d)765432100110

Concentration (%)

Figure 1. Mean time to death (MTD; days; mean ± SE; N = 3) of 25
Coptotermes gestroi exposed to filter papers treated with (a) methanoland (b) water extracts of Abrus precatorius leaves and seeds. The doses
given are relative concentrations (%) of original leaf and seed extracts(see Methods for details).

47

Ravikash Prasad et al.
Concentration

Solvent

TissueTime0%

1%

10%

50%

rS

P

Methanol

Leaf

1d0

1.3

20.0

74.7

0.931

< 0.001

2d0

8.0

45.3

1000.987< 0.001

10 d82.7

100

100

100

0.598

0.011

1d0

10.7

41.3

1000.986< 0.001

2d0

28.0

81.3

1000.941< 0.001

10 d82.7

100

100

1000.598

0.011

1d06.712.0-0.892< 0.001

2d0

6.7

16.0-

0.946

< 0.001

10 d26.7

52.0100-

0.834

0.002

1d06.7

10.7-0.897< 0.0012d010.7

24.0-0.942< 0.001

10 d

26.7

100100-

0.845

0.002

Seed

Water

Leaf

Seed

Table 1. Mortality (%; mean; N = 3) of 25 Coptotermes gestroi after
1, 2 and 10 days exposure to methanol and water extracts of Abrus
precatorius leaves and seeds in Petri dish toxicity assays. The doses
given are relative concentrations (%) of original leaf and seed extracts(see Methods for details). (rS - Spearman’s rank correlation coefficient).