Full text for subscribers

WFL Publisher
Science and Technology
Meri-Rastilantie 3 B, FI-00980
Helsinki, Finland
e-mail: [email protected]
Journal of Food, Agriculture & Environment Vol.11 (3&4): 1404-1408. 2013
www.world-food.net
Leafspot disease of taro cocoyam (Colocasia esculenta (L.) Schott) caused by
Botryodiplodia theobromae and in-vitro control with some agrochemicals
E. M. Ilondu
Department of Botany, Delta State University, P.M.B. 1, Abraka, Nigeria. *e-mail: [email protected]
Received 22 July 2013, accepted 30 October 2013.
Abstract
Fungi associated with leafspot disease of taro cocoyam (Colocasia esculenta (L.) Schott) in naturally infected farms at Ora-Eri, Aguata L. G. Area of
Anambra State were investigated. The isolation study was conducted in the laboratory using Potato Dextrose Agar medium. The fungi identified with
their percentage frequency of occurrence included Humicola fusco-atra (11.11%), Botrydiplodia theobromae (36.61%) Fusarium solani (15.03%),
Fusarium moniliforme (16.34%) and Gliomastrix cerealis (20.92%). Only B. theobromae produced leafspot lesions when healthy cocoyam leaves
were inoculated with the spore suspension of the fungi in the pathogenicity tests. Three commercial fungicides (Benlate, Mancozeb and Ridomil plus)
at the concentrations of 10 - 5000 ppm were evaluated for their in-vitro effect on the mycelial growth of B. theobromae seven days after inoculation
in pre-amended Potato Dextrose Agar medium. The fungicides showed a variable response in inhibiting the growth of the pathogen with a dosedependent effect. B. theobromae was 100% sensitive to Benlate at 1000 ppm, Mancozeb at 3000 ppm and Ridomil plus at 5000 ppm. The results
of this study will be helpful to adopt most suitable fungicidal application to curb leafspot disease occurrence in cocoyam farms.
Key words: Leafspot, Colocasia esculenta, Botryodiplodia theobromae, agrochemicals.
Introduction
Cocoyam, a member of the Araceae family, is an ancient crop,
grown throughout the humid tropics for its edible corms, carmels
and leaves as well as other traditional uses 1. Taro cocoyam
(Colocasia esculenta (L.) Schott) is a staple food for many people
in developing countries in Africa, Asia and the Pacific. It is
produced mainly in Africa especially in Nigeria and Asia mainly in
China 2. It has been reported to be third most important staple root
and tuber crop after yam and cassava in Nigeria, second to cassava
in Cameroon and first in Ghana 3. The total taro production in the
world is about 9.22 million tons from the area of 1.57 million hectares
covering Southeast Asia, Pacific Island, Hawaii, Philippines, Africa,
West Indies and certain areas of South America 4. In terms of
volume of production, Nigeria is the largest producer in the world
accounting for about 40% of total production 5. The most widely
cultivated crop in both western and eastern regions of the country
in terms of area devoted to it and number of farmers growing it 3.
Diseases of taro cocoyam caused by fungi and other pathogens
result not only in subsequent reduction in vigour, quality and
yield of the crop but also constitute a barrier to international
exchange of germplasm 6. Cocoyam has a wide range of uses: in
religious festivals, as contact poison, mild laxative, in treatment of
wounds and snake bites, reducing body temperature in a feverish
patient 7, 8. It is a good source of starch (70-80 g/100 g dry taro),
fibre (0.8%) and ash (1.2%) Starch derived from the taro corm is a
good source of carbohydrate for excluded special products such
as infant weaning diet and low glycemic index foods 9. Processed
cocoyam tuber has been used as carbohydrate source in the diet
of juvenile catfish 10 and a good substitution of wheat flour in
bread making 4. The leaves are important source of proteins and
vitamins 11. The leaves which are cooked and eaten as vegetable
1404
contain about 23% protein on a dry weight basis. It is also a rich
source of calcium, phosphorus, iron, vitamin C, thiamine, riboflavin
and niacin which are important constituents of human diet 2. C.
esculenta and C. antiquorum can be used as brewing adjuncts in
the production of larger beer in Nigeria 12. The flowers (locally
called Opi-ede) are dried and used in soup preparation. Cocoyam
is important, not only as food crop but even more as a major
source of income for rural households at Ora-Eri. Field losses of
cocoyam are mainly due to fungal diseases and pests. Fungal
invasion of the crop can lead to formation of dark brown leafspots,
rotting of the roots, corms and stunting of the entire plant. Leaves
initially appear pale green, then turn yellowish and hang down,
and finally shrivel and die 13. Chemical control measures have
been tested and found effective in the control of plant diseases 14.
Certain protective fungicides, although hazardous to the
environment are still used for the control of fungal diseases 15-17.
Several reports have shown that the status of minimum inhibition
concentration (MIC) of some plant extracts have been fungistatic
in nature. For instance, the MIC of Artemisia nilagrican
(Asteraceae) oil was found to be 200 mg/ml with a broad fungitoxic
spectrum on dermatophytes but was found to be fungistatic in
nature 18. Ranasingha et al. 19 reported that the effect of essential
oils of Cinnamonum zeylanicum and Syzgium aromatium were
fungistatic against Fusarium proliferatum isolated from banana
while total inhibition of Fusarium oxysporium f. sp. glandioli
was from 100-300 ppm of the essential oils and their effect was
fungistatic 20. Similarly Ilondu 21 reported that the antifungal
potency of extracts from some Asteraceae against leafspot fungi
of sweet potatoes showed fungistatic effect. Therefore,
agrochemicals remain the primary means of control of plant
Journal of Food, Agriculture & Environment, Vol.11 (3&4), July-October 2013
diseases. Previously leafspot disease of taro cocoyam (Colocasia
esculentus) in Ghana was effectively managed with thophanate
methyl (Topsin M) fungicide 22. This study was therefore carried
out with the following objectives: 1. to isolate and identify the
causal organisms of leafspot diseases of cocoyam and 2. to
determine the efficacy of some agrochemicals against the leafspot
pathogens in-vitro.
Materials and Methods
Study location: The study was conducted at Ora-Eri which is a
Sub-urban town in Aguata Local Government Area of Anambra
State. Aguata Local Government Area lies within 5°57’-6° and
7°02’-7°07’ E of Anambra state, Nigeria, at an altitude of about
1300 ft – 1500 ft above sea level and made up of Sub-urban town
(Fig. 1). The Southwest monsoon and the Northeast trade wind
dominate the wind system and influences the rainy (May - October)
and dry season (November-April), respectively. The cool dry
Harmattan Northeast trade wind in the dry season usually
dominates the wind system from December to January. The
temperature range fluctuates between 21°C and 32°C with the
relative humidity of 60–80% and the annual rainfall as high as
3,000 mm at the peak of rainy season 23.
0
2
Collection of experimental materials: Cocoyam leaves with
leafspot symptoms were observed and collected randomly from
different farms at Ora-Eri. Voucher specimens were brought to the
Department of Botany Laboratory, Delta State University, Abraka,
and stored in refrigerator at 4°C till use. The fungicides used in
this study which included Benlate, Mancozeb and Ridomil plus
were obtained from Delta State Agricultural Procurement Agency
(DAPA) Ibusa near Asaba.
Isolation and identification of leafspot fungi: Isolation and
identification of leafspot fungi from diseased cocoyam leaves was
carried out using the method adopted from Ilondu et al. 24. Sections,
4 mm long, excised from the margins of necrotic leafspot (Fig. 2)
with sterile razor blade were surface-sterilized for 2 min in 2%
aqueous solution of commercial bleach (sodium hypochlorite
solution), rinsed in two changes of sterile distilled water. The
disinfected tissue pieces were blotted between sterile Whatman
No. 1 filter paper and aseptically plated on potato dextrose agar
(PDA) plates (3 pieces per plate). The plates were then incubated
at room temperature (32± 2oC) for five days. Any observed mycelial
growth was repeatedly transferred to fresh PDA plates until pure
cultures of isolates were obtained.
4 Km
Figure 1. Map of Aguata Local Government Area, Anambra State Nigeria showing the study location23.
Journal of Food, Agriculture & Environment, Vol.11 (3&4), July-October 2013
1405
a.
b.
Laboratory screening of fungicides on fungal growth: In-vitro
evaluation of three fungicide (Table 1) to check the colony growth
of Botryodiplodia theobromae was done through poisoned food
technique 17. Appropriate quantity of the fungicides were added
into 500 ml conical flask to prepare for each level of concentration.
The concentrations used were 10, 25, 50, 100, 200, 500, 1000, 2000,
3000, 4000 and 5000 ppm of the active ingredient 27. One millilitre
of each level of concentration was aseptically incorporated into
20 ml of cool molten PDA in each of test-tube. Each medium was
homogenised by gentle agitation for uniform dispersal of fungicide
before dispensing into 9 cm diameter sterile Petri dishes. The Petri
dishes were allowed to set on a laboratory bench for 6 hours. The
mycelia disc of 4 mm diameter taken from 5 days-old culture of the
test fungi were aseptically placed in the centre of solidified
poisoned PDA. Three replicates were maintained for each
concentration and the plate were incubated at 30± 2°C in a complete
randomized design. Observations on the mycelia growth were
recorded after seven days of incubation, growth of the fungus on
non-poisoned PDA served as a control. The experiment was
repeated twice. The percentage inhibition in growth due to various
fungicidal treatments at different concentration was computed 27
as follows:
Diseased leaf Abaxial surface and Adaxial surfaces
Flecking diseased lesions
FP =
c.
Leafspot showing concentric ring effect
Figure 2. Various degrees of leaf pot disease of cocoyam in the study.
Percentage frequency of isolation (PFI) of all fungi was
calculated by the equation:
PFI =
No. of times a fungi is encountered
x 100
Total no. of times all fungi was encounted
(1)
Identification of isolates was done using Olympus microscope at
x40 magnification and standard mycological manuals 25, 26.
Pathogenicity of isolates: Top loamy sand, pH 5.9, from the
Department of Agricultural Education Teaching and Research farm
was used for this study. The soil was sterilized by autoclaving at
1.1 kg/cm2 pressure and temperature of 121°C for 1 h and after 24 h
for another 1 h and left to cool for 2 days before use. Cocoyam
corms purchased from Oye market, Ora-Eri, were planted in black
polythene bags each containing 5 kg of the sterile soil and
maintained in screen house under the prevailing conditions of
temperature (24-32°C) and light for three weeks before inoculation.
The inoculum of the fungal isolates were prepared by washing off
the propagules from 10 days old cultures of each isolate with
sterile distilled water into 250 ml Erlenmeyer flask. The propagule
suspension of each isolate was filtered through two layers of
sterile Muslin cloth and adjusted to the concentration of 5x104
spores/ml using a haemocytometer 13. The upper and lower
surfaces of the leaves were artificially sprayed with the suspension
using a spray atomizer. The plants were arranged in a complete
randomised design with two replicates including the control. Both
inoculated and un-inoculated (control) plants were covered with
transparent polythene bags to create a humid atmosphere for 24
hours. The plants were inspected daily for leafspot symptom
development up to 21 days after inoculation.
1406
dc - dt
x 100
dc
(2)
where FP = Percentage inhibition of fungal growth, dc = average
diameter of fungal colony in control Petri dish, dt = average
diameter of fungal colony in treated Petri dish
Table 1. Common name, trade name, chemical name and
formulation of the fungicides evaluated in-vitro for their
efficacy against Botryodiplodia theobromae.
Common
name
Trade
name
Benomyl
Benlate
Mancozeb
Dithane M45
Metalaxyl
Ridomil
Chemical name
Methy-1-butylcarbomyl-2
-benximidazole-2-Carbonic acid
Zinc Manganese ethylene
bis dithiocarbamate
Methyl N-(2,6-dimethyl-phenyl)N-(methoxyacetyl) -D-alaninate
Formulation
50% WP
80% WP
66% WP
Data analysis: Data obtained were subjected to analysis of
variance (ANOVA) using statistical package for social science
SPSS version 17.0 and means were separated according to
Duncan’s Multiple Range Test (DMRT) at 5% probability level.
Results and Discussion
Leafspot lesions were observed in every cocoyam farm visited in
the study area. The lesions (Fig. 2) were characterized by round to
irregular shaped brown spots shining on the abaxial surface of
the leaf but dull on the adaxial surface with gummy droplets and
water-soaked edge as the lesions advance. In some leafspots the
central portion had often cracked and flecked off leaving a shothole effect. In severe cases, lesions had coalesced to give extensive
leaf necrosis. Ilondu 21 made a similar observation in assessing
the leafspot disease of sweet potato in Delta State. As pointed
out by Okoi and Olufolaji 13, fungal invasion of such crop can lead
to stunting of the entire plant which shrivelled and die. Some
lesions showed concentric ring appearance which according to
Mehrotra and Aggaarwal 28 is common in many leafspot diseases.
This could be due to diurnal periodicity of light and darkness as
Journal of Food, Agriculture & Environment, Vol.11 (3&4), July-October 2013
reported by Bilgrami and Verma 29. The implication of this foliar
disease is obvious: Photosynthesis may be drastically reduced
by pathogen growing or killing areas of green leaf, leading to
possible yield losses the quality and quantity of leaves used as
vegetables will be reduced.
The fungi isolated from cocoyam, leaves showing leafspot
symptoms and their percentage frequency is presented in Table 2.
Of all the fungi associated with the leafspot diseases of cocoyam,
only Botryodiplodia theobromae produced leafspot lesions when
healthy leaves of cocoyam were inoculated with the spore
suspension of the fungi in the pathogenicity tests (Table 2). This
pathogen was consistently re-isolated from the lesions which
developed following inoculation. The control plants did not show
any sign of infection throughout the period of observation. B.
theobromae had been reported as one of the pathogens of leaf rot
of cocoyam in Nsukka zone of Nigeria 12. Similarly, B. theobromae
had been implicated as leafspot pathogen of other crops such as
mango 26 and orange 21 in south-eastern Nigeria.
Table 2. Percentage frequency and pathogenecity of fungi
isolated from leafspot disease of cocoyam
(Colocasia esculenta).
Fungi
Gliomastix cerealis
Humicola fusco-atra
Botryodiplodia theobromae
Fusarium solani
Fusarium moniliforme
No. of times
Isolated
32
17
56
23
25
Percentage
frequency
20.92
11.11
36.61
15.03
16.34
Pathogenicity
of isolates
+
-
Key: - = non pathogenic, + = pathogenic
The in-vitro effect of three fungicides on the colony growth of
B. theobromae in pre-amended potato dextrose agar (PDA)
medium is presented in Table 3. The fungicides showed variable
response in inhibiting the growth of the pathogen at different
minimum inhibition concentrations their effectiveness increased
with increased in the concentration of the active ingredient.
However, Benlate at 1000 ppm concentration caused 100%,
reduction in mycelia growth of the fungus, followed by Mancozeb
at 3000 ppm and the least was Ridomil at 5000 ppm. Nwanosike
and Adeoti 30 reported that 100% inhibition of mycelial growth is
considered effective dosage of fungicides. Many researchers have
reported the effectiveness of Benlate and Dithane M45 for the
control of pathogens of leafspot disease of other crops:
Corynesspora cassiicola on tobacco 31; Coniella musalansis on
Table 3. Effect of different concentrations (mg/ml) of
three fungicides on the redial mycelial
growth (cm) and percentage inhibition of
B. theobromae in-vitro.
0
10
25
50
100
200
500
1000
2000
3000
4000
5000
Benlate
4.30 (0.00h)
3.90b (9.30g)
3.30c (23.26f)
2.50d (41.86e)
1.60e (62.79d)
0.90f (79.07c)
0.04g (90.70b)
0.00h (100a)
0.00h (100a)
0.00h (100a)
0.00h (100a)
0.00h (100a)
a
Mancozeb
4.30a (0.0h)
4.10a (2.33h)
3.90b (9.30g)
3.60b (16.28g)
2.70c (37.21f)
2.20d (48.84e)
1. 80e (58.14d)
1.10f (74.42c)
0.6g (86.05b)
0.00h (100a)
0.00h (100a)
0.00h (100a)
Ridomil
4.30 (0.0j)
4.30a (0.0j)
4.10a (2.33j)
3.70b (13.95i)
2.80c (34.88h)
2.40d (44.19g)
2.00e (53.49f)
1.70f (60.47e)
1.20g (72.09d)
0.80h (81.40c)
0.30i (93.02b)
0.00j (100a)
a
Values with the same superscript(s) is the same column are not significantly different
at P>0.05 by DMRT. Values in parenthesis indicated percentage growth inhibition.
Hibiscus cannabinus 32; Curvularia clavata on oil palm
seedlings 33; Alternaria macrospora on cotton 30, Cercosporella
leafspot of sweet potato 24 and Sclerotium rolfsii isolated from
ginger 27. Idowu 34 reported that benomyl, metalaxyl and mancozeb
inhibited the mycelia growth of Colletotricum graminicola
causing anthracnose disease of sorghum. Benlate was classified
as type 1 fungicides because it gave 100% suppression of colony
growth Fusarium mangiferae at the minimum inhibition
concentration tested 35. Benlate (Benomyl) is a systemic fungicide
with a wide range of antifungal spectrum and Dithane M45 (zincmanganese ethylene-bis-dithiocarbamate) is a broad spectrum
fungicide recommended against many fungi that attack crops14.
The efficacy of mancozeb may be due to unique combination of
zinc and manganese ethylene. Bis-dithiocarbonate and it is
particularly suitable under tropical condition 36.
Ridomil was least effective in reducing the growth of the test
fungus. Similar results were report by Okonkwo and lbiam 37 and
Wokocha and Nwaogu 38 of Ridomil on other fungi. As pointed
out by Wokocha and Nwaogu 38 the pathogen must have
developed resistance to Ridomil which may be responsible for its
relative inefficacy in inhibiting the mycelia growth of the test fungus
when compared to Benlate and Mancozeb.
The use of fungicides in the laboratory visa-vis the field depends
on their in-vitro efficacy at minimal, economically acceptable
dosages and their efficient and rapid transport to the infection
site
Conclusions
This study revealed that Botryodiplodia theobromae was the
causal pathogen of leafspot disease of cocoyam (Colocasia
esculenta (L) Schott) in the study location. The study also found
out that the best fungicide that could arrest the growth of this
pathogen is Benlate, followed by Mancozeb. Their use will be
helpful to adopt most suitable fungicidal application to curb
leafspot disease occurrence in cocoyam farms usually experienced
during the growing season. The limited number of fungicides
screened in this study was as a result of the urgency to find a
control measure for this devastating disease in the study area.
Further study is in progress with other chemicals and biocontrol
agents to ascertain their efficacies in integrated approach to
disease management.
Acknowledgements
Mr. Vincent Ojieh is acknowledged for the statistical analysis in
the work and Sandra Idehen for the collection of diseased leaves
of the plant.
References
Njoku, P. C. and Ohia, C. C. 2007. Spectrophometric estimation studies
of mineral nutrient in three cocoyam cultivars. Pakistan Journal of
Nutrition 6(6):616-169.
2
Tumuhimbise, R., Talwana, H. L., Osiru, D. S. O., Serem, A. K.,
Ndabikunze, B. K., Nandi, J. O. M. and Palapala, V. 2009. Growth
and development of wetland-growth taro under different plant
populations and seedbed types in Uganda. African Crop Science
Journal 17(1):49-60.
3
Ogunniyi, L. T. 2008. Profit efficient among cocyam producers in Osun
State, Nigeria. International Journal of Agricultural Economics and
Rural Development 1(1):38-45.
4
Ammar, M. S., Hegazy, A. E. and Bedeir, S. H. 2009. Using of taro flour
1
Journal of Food, Agriculture & Environment, Vol.11 (3&4), July-October 2013
1407
as substitute of wheat flour bread making. World Journal of Dairy and
Food Sciences 4(2):94-99.
5
Okoye, B. C., Onyenweaku, C. E. and Asumugha, G. N. 2007. Allocative
efficacy of small holders cocoyam farmers in Anambra State, Nigeria.
Nigerian Agricultural Journal 38:70-87.
6
Wagih, M. E. 1997. Eradication of taro viruses from seed rescue culture
coupled with thermotherapy. African Crop Science Journal 5(4):419424.
7
Emmanuel-Ikpeme, C. A., Eneji, C. A. and Essiet, U. 2007. Storage
stability and evaluation of taro chips fried in palm oil, palm olein oil,
soybean oil and their blends. Pakistan Journal of Nutrition 6(6):570575.
8
Zarafi, A. B., Shenge, K. C., Chindo, P. S. and Alao, S. E. L. 2011.
Incidence of cocoyam leaf blight disease in Kaduna State, Nigeria.
Nigeria Journal of Plant Protection 25(1):33-42.
9
Amon, A. S., Soro, R. Y., Koffi, P. K. B., Due, E. A. and Kouame, L. P.
2011 Biochemical characteristics of flour from Ivorian taro (Colocasia
esculenta, cv. Yatan) corn as affected by boiling time. Advance Journal
of Food Science and Technology 3(6):424.
10
Aderolu, A. Z., Lawal, M. O. and Oladipupo, M. O. 2009. Processed
cocoyam tuber as carbohydrate source in the diet of juvenile African
catfish (Clarias gariepinus). European Journal of Scientific Research
35(3):453-460.
11
Serem, A. K., Palapala, V., Talwana, H., Nandi, J. M. O., Nwabikunze,
B. and Korir, M. K. 2008. Socioeconomic constraints to sustainable
cocoyam production in the lake Victoria crescent. African Journal of
Environment Science and Technology 2(10):305-308.
12
Ugwuja, F. N. and Chiejina, N. V. 2011. Preliminary investigation of the
causes of leaf rot of cocoyam in Nsukka zone of Nigeria. Nigerian
Journal of Plant Protection 25(2):203-213.
13
Okoi, A. I. and Olufolaji, D. B. 2008. Pathogenicity of fungi isolated
from oil polluted soil on cocoyam (Colocasia esculenta L.) in River
State, Nigeria. Nigerian Journal of Botany 21(2):266-272.
14
Nene, Y. L and Thapliyal, P. N. 1993. Fungicides in Plants Disease
Control. 3rd ed. Oxford and IBH Publishing Company, New Delhi,
691 p.
15
Patel, N. A., Dange, S. R. S. and Patel, S. I. 2005. Efficacy of chemicals
in controlling fruit rot of tomato caused by Alternaria tomato. Indian
Journal of Agricultural Research 39:1.
16
Sharma, R. L. 2006. Efficacy of fungicide impregnated paper liners
against storage rot of tomato fruit. Journal of Mycoloy and Plant
Pathology 26(2):310-311.
17
Taskeen, U. N., Wani, A. H., Bhat, M. Y., Pala, S. A. and Mir, R. A.
2011. In-vitro inhibitory effect of fungicides and botanicals on mycelia
growth and spore germination of Fusarium oxysporum. Journal of
Biopesticides 4(1):53-56.
18
Kishore, N., Dubey, N. K. and Chansouria, J. P. N. 2001. Antimycotic
activity of the essential of Artemisia nilagirica. Flavour and Fragrance
Journal 16(1):61-63.
19
Ranasingha, L., Jayawardena, B. and Abeywickrama, K. 2002.
Fungicidal activity of essential oil of Cinnamomum zeylanicum (L).
and Syzygium aromaticum (L.) Merr and I. M. Perry against crown rot
and anthracnose pathogens isolated from banana. Letters of Applied
Microbiology 35:208–211.
20
Barrera-Necha, L. L., Gardino-Pizana, C. and Barcia-Barrera, L. J. 2009.
In-vitro antifungal activity of essential oils and their compounds on
mycelial growth of Fusarium oxysporium f. sp.gladioli (Massey)
Snyder and Hansen. Plant Pathology Journal 8(1):17–21.
21
Ilondu, E. M. 2012. Etiology and Managament of Leafspot Disease of
Sweet Potato (Ipomoea batatas (L.) Lam) in Delta State. Nigeria Ph.D.
thesis, Department of Agronomy, Faculty of Agriculture, Delta State
University, Asaba campus, 180 p.
22
Awuah, R. T. 1995. Leafspot of taro (Colocasia esculenta (L.) Schott)
in Ghana and suppression of symptom development with thiophanate
methyl. African Crop Science Journal 3(4):519-523.
23
Ofomata, G. E. K. 2002. Nigeria in Maps, Eastern States. Ethiope
1408
Publishing House, Benin City, Nigeria, 86 p.
Ilondu, E. M., Ayodele, S. M. and Ofere, B. K. 2010. Comparative
efficacy of neem leaf extract (Azadirachta indica A. Juss) and there
commercial fungicides in control of Cercosporella leaf spot of sweet
potato (Ipomeaea batatas L.). Nigerian Journal of Botany 23(1):157164.
25
Barnett, H. L. and Hunter, B. B. 1999. Illustrated Genera of Imperfect
Fungi. 4th edn. The American Phytopathological Society, St. Paul,
Minnesota, U.S.A., 218 p.
26
Alexopoulus, C. J., Mims, C. W. and Blackwell, M. 2002. Introductory
Mycology. 4th edn. John Wiley and Sons Inc., Singapore, 869 p.
27
Ilondu, E. M. 2011. In-vitro evaluation of four fungicides for the control
of Sclerotium rolfsii Sacc., the casual agent of rhizome rot of ginger
(Zingiber officinale Rosc). Nigerian Journal of Science and Environment
10(1&2):242-250.
28
Mehrotra, R. S. and Aggarwal, A. 2004. Plant Pathology. 2nd edn. Tata
McGraw-Hill Publishing Company Limited, New Delhi, 846 p.
29
Bilgrami, K. S. and Verma, R. N. 1978. Physiology of Fungi. 2nd rev.
edn. Vikas Publishing House PVT Ltd., New Delhi, 493 p.
30
Nwanosike, M. R. O. and Adeoti, A. A. 2002. Evaluation of four
fungicides for control of cotton leaf spot caused by Alternaria
macrospora Zimm. in Nigeria. ASSETS Series A: Agriculture and
Environment 2(2):165-171.
31
Oke, O. A. 1990. Chemical control of Corynespora cassiicola (Berk
and Curt) Wei tobacco leafspot disease. Nigerian Journal of Plant
Protection 13:100-104.
32
Adeoti, A. A. 2000. Evaluation of four fungicides for the control of leaf
spot disease of Hibiscus cannabicus caused by Coniella musaiansis.
Nigerian Journal of Botany 13:55-60.
33
Nwatu, C. M. and Okigbo, R. N. 2011. Fungal leafspot disease of
orange tree in Southeastern Nigeria. In Book of Abstracts, 20th Annual
Conference of Botanical Society of Nigeria (BOSON) held at Nnamdi
Azikiwe University, Awka, Anambra State, Nigeria, June 6th-9th, p. 27.
34
Idowu, O. T. H., Salaam, A. M., Popoola, A. R. and Adeoti, A. Y. A.
2012. In-vitro assessment of fungicides for the control of sorghum
anthracnose induced by Colletotrichum graminicola (Cesati) Wilson.
Nigerian Journal of Mycology 4:76-83.
35
Iqbal, Z., Pervez, M. A., Iftikhar, S. A. Y., Yasin, M., Nawaz, A.
Ghazanfar, M. U., Dasti, A. A. and Saleem, A. 2010. Determination of
minimum inhibitory concentrations of fungicide against fungus
Fusarium mangiferae. Pakistan Journal of Botany 42(5):3525-3532.
36
Odigie, E. E. 2000. Efficacy of some fungicides for the effective control
of the seedling blight disease caused by Curvularia clavata. Nigerian
Journal of Microbiology 14(2):123-128.
37
Okonkwo, A. A. and Ibiam, O. F. A. 2006. Post-harvest rot of cocoyam
species Colocasia esculenta (L) Schott and Xanthosora sagittifolium
(L) Schott tubers by Fusarium moniliforme, Fusarium oxysporum
and Odium monilioides. Plant Product Research Journal 10:30-32.
38
Wokocha, R. C. and Nwaogu, G. A. 2008. Comparative toxicity of
extracts of three tropical medicinal plants and Ridomil (metalaxyl) on
Phytophthora palmivora and varietal resistance of cocoa to black pod
disease in Ikwuano area of Abia State. Nigerian Journal of Botany
21:428–436.
39
Okigbo, R. N. and Osuide, M. I. 2003. Fungal leafspot diseases of
mango (Mangitera indica L.) in south-eastern Nigeria and biological
control with Bacillus subtilis. Plant Protection Science 39(2):70-77.
24
Journal of Food, Agriculture & Environment, Vol.11 (3&4), July-October 2013