sess11 4 were h.k., kabira j., olubayo f & torrance l – aphids infesting potatoes in kenya
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APHIDS INFESTING POTATO IN KENYA
H K WERE, J KABIRA, F OLUBAYO AND L TORRANCE
SCHOOL OF GRADUATE STUDIES
MASINDE MULIRO UNIVERSITY, KAKAMEGA, KENYA
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PotatoThe potato is a starchy tuberous cropBelongs to the Solanaceae (night shades) familyThe family consists of about 2,000 speciesApart from calories, potato is vital source of vitamins, K and fibreIt provides more calories, nutrients and vitamins per area of land sown than any other crop
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Uses contédExcellent novel source of natural health promoting compounds such as vitamine CCash cropFeed cropRaw material for starch
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Top potato producers in 2011
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China
Russia
India
United StatesUkraine
Germany
PolandFrance
88.442.332.724.219.411.8
8.28.0
Bangladesh 8.3
(16)
(48)(20)(18)
(42)(17)(15)(22)
(46)
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Potato production in KenyaPotato is Kenya’s second most important food crop after maizeGrown in high altitude areas between 1,500 and 3,000 maslCurrent yields of 5 – 10 ton per ha are low compared to 50 ton per ha obtained in Belgium Lower yields are blamed on diseases and pests. Most varieties in Kenya are badly degenerated Aphid transmitted viruses PLRV and PVY are thought to be the main causes degeneration
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Aphid pests of potatoThose with piercing‐sucking mouthparts damage potatoes by direct physical injury, extracting phloem, injecting toxic saliva Many aphids are potential vectors of potato pathogens. This association can be
casual with the insect serving as a mechanical vector or providing entry for invasion by pathogens present in the environment
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Mean aphid counts Vs virus diseases incidence
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Major aphid transmitted viruses in Kenya
Six viruses: PLRV, PVA, PVM, PVS, PVX and PVYMore?
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Objectives
Monitor aphid populations in different eco zones in order to determine areas suitable for potato seed multiplication
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APHID MONITORINGDone in five major growing regions.Meru Njabini Mt Elgon Molo Nairobi Altitudes between 1,794 and 2630.
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Monitored areas
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samplingTwo methods used:
i. Wingless (apterae) aphids colonizing potato leaves were sampled weekly ii. For winged (alate) aphids, four circular YWTs on a platform at a spacing ranging from 8 m to 15 m were used.the aphids caught in YWTs were collected weekly – identified and counted
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i. On leaves
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ii. Yellow water traps
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On potato leavesFour aphid species were found colonising potato
Macrosiphum euphorbiae, Aphis gossypi, Myzus persicaeand Aphis fabae
A. fabae was most abundant in all districts while M. persicae was least abundantMean aphid counts were highest (1133.5) in Mt Elgon and lowest (50.8) in Meru
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In YWTsTen aphid species, Aphis gossypii A. fabae, Aulacorthum solani, Acyrthosiphon pisum,Brevicoryne brassicae, Cavariella aegopodii, Macrosiphum euphorbiae, Myzus persicae, M. ascalonicus and Rhopalosiphum maidis.The total aphid counts were highest in Mt Elgon and lowest in Njabini.The most abundant aphid species in all areas was R. maidis, while M. euphorbiae was least
16
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Results of aphid data analysis
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Monthly total aphid counts (YWTs)
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0
10
20
30
40
50
60
70
80
90
Meru(YWT)Mt Elgon
Molo
Njabini
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Aphid counts Vs altitude
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Conclusions Mt. Elgon has the highest aphid population while Njabini has the lowestIn all areas, R. maidis and B. brassicae occur in large numbers indicating the presence of cereals and brassicas around potato farmsAphids that transmit non persistent viruses such as R. maidis are more abundant than M. persicae an efficient transmitter of PLRV
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Conclusions cont’edOnly 4 aphid species colonise potato in KenyaAlthough A. fabae and A. gossypii, usually colonisebeans and cotton, respectively, they colonisepotato in Kenya and have largely displaced potato aphids A. fabae is the dominant species on the leaves, but not in YWTs suggesting the aphid is more of a coloniser than a migrant.Nairobi and Njabini consistently had low aphid incidence and may be well suited for basic potato seed multiplication
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AcknowledgementsFinancial support was provided by The Monsanto Fund and the work of LT and BF by the Scottish Government’s Research and Analytical Services (RESAS) Division.
We Thank J Pickup and F Highet of SASA, Edinburgh UK for providing the Scottish suction traps data
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