An Investigation on the Possibilities of Biological Control of Orobanche Spp. In Ethiopia
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Date
1996-06
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Addis Ababa University
Abstract
In th is srudy. the poss ibilities of biolog ical comrol of Orobanche spp. (b roomrapes). a
serious root parasites of tomato (Lycopersicofl escelentum ~f i[[ .) and other members of the
family Solanaceae in Ethiopia have been investigated . Intensi\'e surveys were conducted
for insect parasites of Orobanche spp. in tomato production areas. namely. Nura Era.
Meni Jeju and Malima Farms. The surveys showed that, the fly PhytomyZIJ orobanchia
(Diptcra: Agromyzidae) occurs only in Malima Farm where it exhibited destructive ab ility
to thc seed capsules of O. ramosa and O. cemua up to 81.4% and 7 1. 7%, respective ly.
Surveys were also conducted in Ziway. Nura Era. Meni Jeju and Malima farms for
mic roorganisms pathogenic 10 Orobanche spp . for the purposes of their isolat ion.
identi fication and explorat ion of their potential as biological control agents. Twenty fungal
isolates were isolated and identified from infected Orobanche plants. These were:
FusariulII. gibbosum: (2) F. nygamai: (1 I) F. Orysporum: (2) F. proli!eralUm: F. Solalli
\"{Ir. Solani and (3) Fusarium sp. All the identified fungal isolates belong to Ihe ge nus
Fusarium and have not been reponed before in Ethiopia. Two of them F. nygamai and
F. pro!i!eratum were identified for me first time on Orobanche plants as paras ites.
Pre lim inary pathogenici ty tests showed that F. gibbosum, F. rrygamai, F. oxysporum and
Fusarium spp . were promising as pathogens to O. ramosa. They significantly reduced the
number of emerged shoots when applied at a rate of 10 gkg·1 of soil under glasshouse
conditions. The same isolates sig nificantly decreased the dry weight of O. ramosa and
resulled in signi ficant increase of tomato dry weight by 30.3%. 30.3%. 32 .1 %, and
30.3. %. respect ive ly.
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F oxysporum and F. lIygamai signific.:mtly killed O. aeg\pllOCO IUbe rcles v. hen appl ied
at a rate of 0. 5 X 100 spore mI'] in the roOt chamber. F. oxysporum killed 81 ~ and 8] C'f .
\\hilc F. nygamai killed -H % and 48% of the tubercles after 10 and 15 da ys of inoc ulat ion.
re spect ive ly. The colour of the diseased IUbercles was changed to dark brown or black .
Symptoms like wet rotting were also obse rved .
Recommendations and suggestions are forwa rded for furthe r wo rk on the biological comrol
of Orobanche spp. in Ethiopia . This should include comprehens ive evaluation of the role
played by the PhylOmyza orobanchia as an effect ive bioagenl
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Keywords
Biological Control