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A Nevek-Endinc Problem

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A Nevek-Endinc Problem tssN1562-5192 h#@ffi&gdtu Ministry of Agriculture,Water and Forestry,Directorate of AgriculturalResearch and Training,Private Bag 13 184, Windhoek No 90April 2005 D i c h ap e t alunt cy ttto s utlt (PO I S O N-LEAF lC I F'BLAAR) : A NEVEK-ENDINCPROBLEM INTRODUCTION Dichapetalumcymosum, known as poison-leafin English(E,d.'s note: accordingto the Afr./Eng. BilingualDictionary by Bosmanet al. 1988)but morecommonly referred to by itsAfrikaans common name,giJblactr or magou,is an extremelypoisonous plant that kills livestock.In Namibia,gifblaar occursto the eastand north-eastofthe countryand is confinedmainly to the fine sandysoils ofthe Kalaharigeological system underlain with Karoobasalt (Opperman & La Grange1969). According to Correia& Van Rensburg(2000), the generalecological characteristics of the distributionarea of gifblaarare soils that aresandy, well-drained and deficient in nutrients.Gifblaar grows in association with treessuch as various Combretumcollinum (C. mechowianumO. Hoffm.), Burkea africana and Terminaliasericea (Du Plooy 1972;YanVuuren 1960). LITERATUREREVIEW The first recordingof gifblaarpoisoning was in 1890, althoughresearch on it only commencedin 191l0 (SWAA l96l). Steyn's(1928) study and descriptionof the Gifblaarplant symptomsof gifblaarpoisoning - its toxicology- were complernentedby Leemann's( 1 935) work on theanatomy, motphology and physiology of the plant.Nearly a decadelateq Marais ( 1943)isolated and synthesised monofluoroacetate asthe activetoxic compoundin theplant. This breakthrough enabled further research on theplant's toxicologyand pharmacology.Nonetheless, by the 1960s,the vaguenessin the literature Cluster of gifblaar leaves regardingthe treatmentof poisonedanimals was being lamented (SWAA 1961).And despite "the fuftherresearch, Remington's (1 935) despair that hopeoffinding anyspecific prophylactic or curativesubstance (antidote) for use in gifblaarpoisoning has become very remote"remains true today. E STATEINTERVENTION TO CURB STOCKMORTALITIES DUE TO GIFBLAAR During the 1960s,the farmersin the GrootfbnteinDistrict approachedthe SouthWestAfricaAdministration (SWAA) for assistance regardinglivestock deaths due to gifblaarpoisoning. An extensionofficer in Grootfontein,LF la Grangeand an Administration botanist, DRJ vanVuuren, were appointed to investigatethe issue of livestockmorlality in gifblaar-infestedareas and compiled a reporton gifblaar "Gifkommissie" poisoningand livestockmortality (Van Vuuren 1960).During 1961the (Departmentof AgriculturalTechnical Services in SouthAfrica) werealso tasked to investigatethe issueof livestockmortality due to gifblaarpoisoning in the GrootfonteinDistrict. The SWAA then purchasedproperty in the District fbr the solepurpose of establishingthe SonopResearch Station to conductresearch on gifblaar.Two projectswere launched by the livestockresearcher, PAJ Brand, and the pasture researcher, DPJ Opperman. The objectivesof thesetwo projectswere (a) to determinethe possibility of managementsystems and lick supplementationto alleviatelivestock mortality, and (b) to eradicategitblaar whereverit grew.Eradication was effectedby the foliar applicationof herbicides, or by diggingthe plantsopen and treating their stemswith herbicides. CHARACTERISTICSOF GIFBLAAR R Leemann ( 1935) provides an in-depth description of the anatomical and morphologicalproperties of the plant, which are of interestnot only from a botanicalpoint ofview, but alsoinsofar as its eradicationis concerned.A typical gifblaarplant hasa main stemthat penetratesthe soil verlically.From this main stem,further sets of stemsand branchesproliferate horizontally just below soil level.Here and there, the branches produce tufts ofleaves above ground. These are Gifblaar leaves,showing the characteristicarches made by the veins the leavesthat stock qraze on. 'g -- ,=D--- ry &"@qtr '\i:')@. ,a ',- //t-.'5/ ' 7' " rc)15 Damagedplant sprouting The undergroundbranching of the stemmay continuefor manymetres, forming an extensivenetwork of horizontaland vertical stems far awayfrom themain stem. This undergroundnetwork may look like theplant's roots system, but anatomically,it is theplant's stem. From a botanicalpoint of view,gifblaar is a climberthat has gone underground. The plant retains the characteristics of climbingplants but below ground,where it "takesevery opportunity to twist andclimb" (SWAA 1961). A few otherplants that occur in the samehabitat as gifblaar are very similarin their growthhabits, in that they alsohave well-developed underground stems and sprout intermittent clumps of leavesabove ground. The leaves oftheseplants are also practically identical to thoseofthe gifblaarplant, and can easily be confusedwith it. In this regard,in NamibiaOchna pulchra is probablythe mostlikely candidate.However, a uniquedifferentiating anatomicalfeature of thegifblaar plant's leaves is its peculiarvenation: the mainveins are arched. In 1935,the VeterinaryServices Division in SouthAfrica conductedfeeding trials in orderto determinethe exactstage in theplant growth's cycle when the toxicity was at its highest.They established that this occurred in spring,when the plant produced new shoots,and in autumn,when it formednew leaves(Leemann 1935). Thus, the concentrationof monofluoroacetateis highest when the plantsprouts. It is obvious,therefore, that climatic conditionsplay a role in determiningwhen and for how long the plant is toxic enoughto kill livestock.Even as it matures,although the concentrationof aciddecreases, the plant never ceases to be toxic (ibid.).Moreover, furlherresearch (SWAA 1961)found that ail partsof theplant contained the toxin. Afeature of gifblaarthatis of utmostimpoftance in its controlis the plant'sability to sproutwherestems have beendamaged or, evenworse, to propagateitself by settingroots and forming a new plantfrom cuttingsof the Extensivestem system of stemthat may remainin the soil aftereradication (Leemann 1935). Another feature in relationto theabsorption the gifblaar plant € of herbicideis the high propofiionof stemsbelow ground,compared with the fewer numberof leavesabove sroundlevel. DISCUSSIONAND CONCLUSION .-'E/d" Fromthe above it is clearthat, despite the volume of researchon gifblaar,the plant remains A a problemin respectof livestockmortalities. Since finding an antidoteto gifblaarpoisoning seemsremote, there is an urgentneed for researchto find a way to successfullyeradicate theplant or at leastdevise measures to reducethe livestockdeaths it causes. Farmerstoday continue to requestinfbrmation on gifblaarpoisoning. The next three issues of Spotlighton Agriculture (No.'s 91, 92 and93)will attemptto addressthis need. The two issuesreview the research conducted in Namibiaand South Africa in respectof eradicating Mainunderground stem, with leaves growing above ground gifblaarand devising possible measures to reducethe animaldeath toll. References "Geographical Correia,RIDES & L van Rensburg.2000. distributionand local occurrenceof Dichapetalumcymosum (Hook)Engl. (Gifblaar)in Namibiaand surroundingareas". Agricola, 11. Du Plooy, PJ. 1972. Ondersoekna die voorkoms van gifblaar (Dichapetalumcymosum) wat die weidings potentiaal van Boesmanlandbeinvloed. & Windhoek:Depadement van Bantoe-Administrasieen -Ontwikkeling. Leemann,AC. 1935."The eradication of Gifblaar".Boerdery in Suid-Afrika,June. Marias,JSC. !943."Mono-fluor-acetic acid: The toxic principleof gifblaal'. TheOnderstepoori Journal of VeterinaryFesearch, 19. "Gifblaar Opperman,DJP & LA la Grange.1969. controlin SouthWest Africa"" Boerdery in Suid-Afrika,May. Steyn,DG. lg2B. "Gifblaarpoisoning".Directorateof Veterinarian Educationand Research. Reports13and15,187-198. "Die WlrS SWAA/SouthWest Africa Administration. 1961 . Gifkommissie".South West Africa Administration Report, March-July. VanVuuren, DRJ. 1960. Verslag van die planikundigeoor die ondersoekna gifblaar(Dichapetalum cymosum) in die Horabeblok.Soufh WestAfrica rv Ad min i strati on Repo rt, August. Author: FV Bester;Directorate of AgriculturalResearch and Training;Ministry of Agriculture,Water and Forestry,Private Bag 13184, Windhoek,Namibia. Photographs: A Leemann;Department of Agricultureand Forestry,South Africa; and FV Bester(as above) Content Editor.' Paulvan der Merwe;Directorate of AgriculturalResearch and Training;Ministry of Agriculture,Water and Forestry PrivateBag 13184,Windhoek, Namibia. WLanguage Editor: fhe Word Factory,PO Box 11465,Windhoek. .
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