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Sci. Agri.

17 (2), 2017: 55-76

© PSCI Publications

Scientia Agriculturae www.pscipub.com/SA

E-ISSN: 2310-953X / P-ISSN: 2311-0228

DOI: 10.15192/PSCP.SA.2017.17.2.5576

Effect of Four Copper-Based Fungicides on Soil Fungi in A

Cocoa Farm at Tafo, Eastern Region, Ghana

J.K Kwodaga1, G.T Odamtten1, E Owusu1, A.Y Akrofi2 , M Wiafe-Kwagyan1

1. Department of Botany, University of Ghana, Box LG 55, Legon-Accra, Ghana.

2. Cocoa Research Institute of Ghana (CRIG), P. O. Box 8, AkimTafo, Ghana

Corresponding author email: [email protected]

Paper Information A B S T R A C T

Received: 11 October, 2016

Accepted: 24 January, 2016

Published: 20 February, 2017

This study was designed to elucidate the effects of four fungicides (ALM

600, Famous, Metacide Super, and Ridomil Gold) used for control of black

pod disease of cocoa on mycoflora of the topsoil (0-5 cm) and subsoil (5-10 cm) in a cocoa farm at Akim Tafo, Eastern Region, Ghana. Soil

mycoflora and the effect of the fungicides on their populations were

determined along a transit from the base of a cocoa tree (0 m, 0.75 m, and 1.5 m distances) by the conventional, decimal serial dilution technique up

to 1:104 and population recorded as log10 CFU/g sample. The percentage

occurrence of individual fungi was recorded on Cooke’s medium at 30oC after 5 days. The variation in occurrence of fungi along the transit from the

base of the cocoa plant in both the dry and wet season was influenced by

distance and type of fungicide applied. There was also higher species diversity (p ≤ 0.05) in the topsoil than in the subsoil. Generally, fungal

population decreased by 0.3-0.9 log cycles as one moved from base of the cacao tree to about 1.5 m away. Twenty four fungal species belonging to

12 genera (Aspergillus, Cladosporium, Fusarium, Mucor, Mycelia sterilia,

Neosartorya, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, Trichoderma, Scopulariopsis) were isolated during the dry season while in

the wet season, 23 fungal species belonging to eleven genera (Aspergillus,

Botrytis, Cladosporium, Fusarium, Mucor, Paecilomyces, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, and Trichoderma) were isolated.

Practical implications of these findings are discussed and future work

suggested.

© 2017 PSCI Publisher All rights reserved.

Key words: Black pod disease, Cocoa, Fungi, Fungicide, Phythophtora

Introduction

Theobroma cacao L. (cocoa), an economic crop suffers from severe losses due to pests and diseases everywhere it is

cultivated (Bowers et al, 2001; Bartley, 2005). Black pod disease caused by Phytophthora spp has been reported as the most

devastating disease in cocoa production worldwide; capable of causing massive losses in all cocoa growing areas in the world

(Gregory 1974; Evans 2001; Brasier et al, 1981; Fulton 1989; Brasier and Griffin 1979; Evans and Prior 1987). Although,

Phytophthora species attacks all parts of the cocoa plant, the major economic loss is from infection of the pod (Gregory, 1974;

Evans and Prior, 1987). The infection of West Africa cocoa by Phytophthora species has the potential to significantly reduce

the world's cocoa production and also impact on resource-poor farmers, leading to socio-economic, and possibly political as

well as ecological, instability (Rice & Greenberg, 2000). ). In Ghana, Phytophthora palmivora and P. megakarya are the main

causes of black pod disease of cocoa (Dakwa, 1988; Luterbacher and Akrofi, 1993; Opoku et al, 1999). Research has shown

that the disease can cause a loss of 44% of global cocoa production annually (Van der Vossen Ham, 1997). There is therefore

the need to control black pod disease of cocoa. Some of the control measures employed to manage the disease are biological,

cultural and chemical methods. The use of fungicides is usually the method of choice for the control of black pod disease of

cocoa since it has proven to be the most effective. This is not surprising since pesticides application has become an integral

part of modern agriculture. According to Hajnis et al. (1979), 20% of crop farming production and 60% of fruit production are

based on pesticides protection. Also data from FAO indicates that agricultural crop yield may reduce by 30-50% resulting in a

loss of 75 billion dollars if the use of pesticides is discontinued (Ejhler, 1986).

Sci. Agri. 17(2), 2017: 55-76

56

In cocoa cultivation, the effective control of black pod disease is achieved by spraying with copper fungicides

(Duguma et al, 2001). To achieve effective control, fungicides must be applied at four-weekly intervals, at about 6-9

applications per year during the rainy season (Hislop and Park, 1960). In Ghana, all fungicides recommended for the control of

black pod diseases of cocoa are copper-based (Opoku et al 2007).

An ideal fungicide should not be persistent and should selectively kill or inhibit the growth of pathogenic fungi,

without affecting non-target saprophytic micro-organisms (Corden and Young, 1965). However, many fungicides have toxic

effects which are not confined to their target species, and may impact negatively on other organisms which benefit the wider

agro-ecosystem. Applied fungicides may enter the soil as runoff from treated areas or from drifting sprays.

Fungicide application results in a decrease in numbers of soil fungi (Corden and Young, 1965; Elmholt and

Smedegaard-Petersen, 1988) as well as organic matter breakdown (Karanth and Vasantharajan, 1973) and a reduction in the

proportion of water stable aggregates in the soil (Karanth and Vasantharajan, 1971). Therefore, in fungicide control of black

pod disease of cocoa, it is important to avoid serious injury to a great variety of soil-dwelling organisms whose functions are

vital to maintaining soil fertility. It is also necessary to know the side effects of these fungicides on different forms of life

inhabiting the soil (Ojo et al., 2006).

Use of pesticides in agriculture may result in the reduction of the number of microorganisms, biochemical activities,

and microbial diversity and also change the structure of microbial community in soils (Martinez-Toledo et al 1998, Cycon and

Kaczynska 2004, Cycon 2006). Fungicides have been reported to have a larger inhibition effect on soil microorganisms than

other pesticides (Kruglov 1991). Findings by Ojo et al. (2007) indicated that fungi and protozoa are more susceptible to

fungicides than bacteria and Actinomycetes. Nonetheless, when fungicides are applied at recommended rates, they usually

have no significant effects or transitory effects on soil microbial characteristics (Ahtiainen et al., 2003). Studies have also

shown that initial soil fungal potential decreased when exposed to fungicides, but very rapidly establish normal metabolism

enabling them to restore their population with time (Leka et al, 2005; Wainwrght, 1977).

It is difficult to generalize the effects of fungicides on non-target soil microorganisms in fields, because soil properties

and environmental conditions also play a role in how soil microorganisms respond to the applied fungicides. Since fungicides

enter the soil as runoff from treated area systems or from drifting sprays, it is important to investigate the non-target effect of

fungicides used to control black pod disease of cocoa on fungal population in the soil of cocoa growing areas in order to

ascertain their specific effects in the soils. This would help in understanding the effect of fungicides on the beneficial activities

of microorganisms in soils of cocoa growing areas and also assess the hazards associated with the use of fungicide in general.

The fungicides used in this study were ALM 600, Famous, Metacide Super and Ridomil Gold at the various concentrations;

ALM 600 at 75g/15L of water, ALM 600 at 50g/15L of water, Famous at 100g/15L of water, Famous at 75g/15L of water,

Metacide Super at 50g/50L of water, Metacide Super at 75g/15L of water and Ridomil Gold at 50g/15L of water. They were

assessed in the field fungicide trial plots at CRIG Tafo to ascertain their comparative efficiency in controlling black pod

disease pathogens namely P. megakarya and P. palmivora and their effect on the non-target organisms (fungi).

Materials and methods

Study area

Soil samples were obtained from Cocoa Research Institute of Ghana (CRIG) at New Tafo, Akim in the Eastern

Region of Ghana with geographical location 06o13’25.8”N and 00o21’51”W. The topography is undulating and rises about 240

metres to 300 metres above sea level. The soil type is the WACRI series, typical forest ochrosols or rhodicferrassols

(FAO/UNESCO, 1968). The area is characterized by double rainfall regime with the major one in March to June and the minor

one in September to November. The mean annual rainfall is between 1250mm and 1750mm. the temperature ranges between

26oC in August and 30oC in March. The relative humidity ranges between 70%-80% in the dry season and 75%-80% in the wet

season.

Soil sampling

Soil samples were collected during the month of December, 2013 (dry season) and April, 2014 (wet season) from a

farm plot at the Cocoa Research Institute of Ghana (CRIG) Tafo earmarked for trial experiments on fungicides. Nine

experimental fields were used in this study. Each of seven of the fields under study were consistently treated with only one of

the following fungicides: ALM 600 50g/15L, ALM 600 75g/15L, Famous 75g/15L, Famous 100g/15L, Metacide Super

50g/15L, Metacide Super 75g/15L and Ridomil Gold 50g/15L on the 13th August, 10th September, 9th October and 5th

November 2013 to control Phytophthora black pod disease of cocoa.. The other two experimental fields were control field

within the treated fields and a forest area that has not been treated with any of the fungicides. The first soil samples (dry

season) were collected a month (i.e. December, 2013) after the last fungicide treatments for the cocoa spraying season. The

second soil samples (i.e. for the wet season) were also collected in April, 2014.The inter spacing between the cocoa plants on

the experimental field was 3 meters. On each field, the soil samples were randomly collected from three points as follows: the

base of the tree (0 meter), 0.75 metre and 1.5 metres away from the base of the tree. The soils were sampled from the top 0-

Sci. Agri. 17(2), 2017: 55-76

57

5cm (top soil) and 5-10cm (subsoil) depths using a soil auger. The samples were properly labelled and kept in clean plastic

bags and transported to the Department of Botany laboratory, University of Ghana, Legon for analysis.

Soil pH

The pH readings of soil samples were made with TOA pH HM-60 (Ogawa Seiki Co. Ltd. Japan) using a 1:2 soil:

water ratio (Mclean, 1982).

Soil moisture content

10g of fresh soil sample was placed in a porcelain dish and the dish placed in an oven at 105oC and the contents dried

for 24 hours before cooling in a desiccators and weighing. The soil was reheated and reweighed until a constant weight was

achieved. The result was expressed as follows (Purvis et al., 1966):

Moisture content(%) =weight of original sample − weight of dried sample

weight of original samples× 100

Determination of Total Fungal Population Fungal colony counts were determined by placing 10.0g of each soil sample into 100ml distilled water with 0.1%

peptone as diluents in 250ml Erlenmeyer flasks and then shaken in a Gallenkamp Orbital Shaker Series 320 at 140 rpm for 5

min. From this stock suspension, the serial decimal dilution technique was employed (up to 1: 104) for each soil sample

prepared. The fungi spores were raised on Cooke’s modified medium on Petri plates (9.0cm diameter). Counting of fungal

colonies

Results

Mycoflora profile of dry season soil samples

The variation in occurrence of fungi along the transit from the base of the cocoa plant in the dry season was

influenced by distance and the type of fungicide applied in the field (Fig1- 9). There was also higher species diversity in the

top soil (0-5cm) than in the subsoil (5-10cm) (Figs 1- 9). There was generally a decline in the number of fungi encountered as

one sampled away from the base of the plant i.e. from 0 – 1.5m distance, and the top soil recording higher fungi numbers than

the subsoil at each sampled point along the transit (Figs 10-18).

Generally, the control cocoa farm with no fungicide treatment harboured four Aspergillus species (A. alutaceus, A.

niger, A. oryzae and A. penicilloides) (Fig 1) and two Penicillium species (P. expansum, P. italicum) in addition to

Trichoderma harzianum, Mucor haemalis and Cladosporium macrocarpum, Phyllosticta citricarpa and Scopulariopsis fusca

(Fig 1). Rhodotorula was not recorded in this soil during the dry season. However, Scopulariopsis fusca featured prominently

in this soil (Fig 1).

On the other hand, the Forest soil away from the field cocoa plots (also acting as control) did not record presence of

Aspergillus species (Fig 2) but Penicillium (P. citrinum and P. italicum) were recorded as well as T. harzianum and

Phyllosticta citricarpa. Rhodotorula predominated in this soil not excepting Rhizopus oryzae which occurred only in the top

soil (0-5cm) at the base of the plant (Fig 2).

On the part of the field plots treated with ALM 600 50g/15L, no Aspergillus species were isolated (Fig 3) whereas A.

niger was isolated from the (5-10cm) subsoil in the portion of the plot at the base of the tree (Fig 4) treated with ALM 600

75g/15L.

Fusarium species (F. poae, F. oxysporum) and Rhizopus stolonifer were isolated from the ALM 600 75g/15L treated

soil which were not encountered in the control soil in the dry season (Fig 3) whereas Scopulariopsis fusca and T. harzianum

featured prominently in the soils treated with ALM 600 fungicide (Figs 3 and 4) not expecting Rhodotorula which was

frequently isolated in the ALM 600 50g/15L and ALM 600 75g/15L treated soil (Figs 3 and 4).

Rhodotorula species and T harzianum featured prominently in the soil treated with Famous 75g/15L and Famous

100g/15L (Figs 5 and 6) while no Aspergillus species was encountered in the soil treated with Famous 100g/15L (Fig 6). Three

Aspergillus species (A. alutaceus, A. flavus and A. penicilloides) were encountered at various distances in the soil from the

farm section sprayed with Famous 75g/15L fungicide (Fig 5). However, Penicillium species (P. camemberti, P. italicum) were

isolated from the farm section sprayed with Famous fungicide at different application rates (Figs 5 and 6).

While Metacide Super 50g/15L applied to the soil permitted isolation of Aspergillus species (A. alutaceus, A. flavus,

and A. penicilloides) and Penicillium species (P.camemberti, P. glabrum, P. italicum) (Fig 7), no Aspergillus species could be

isolated from the farm soil sprayed with Metacide Super 75g/15L (Fig 8) but P. camemberti and P. italicum were encountered.

Interestingly the same soil permitted survival of Rhodotorula species and T. harzianum in both fields sprayed with Metacide

Super fungicide (Fig 8).

Finally, the Ridomil Gold-treated soil harboured the widest diversity of fungal species along the transit in the field

plots namely Aspergillus (A. flavus, A. tamari), Fusarium, Penicillium (P. camemberti, P. citrinum, P. corylophilum, P

Sci. Agri. 17(2), 2017: 55-76

58

italicum) Scopulariopsis, Rhodotorula and Trichoderma and Mucor (Fig 9). Rhodotorula and Trichoderma predominated over

the other species encounteerd.

Figs 10-18 show the changes in soil fungal population along the transit in the farms treated with fungicides including

the Control and Forest fields. Generally, population decreased by about 0.3-1.0 log cycles as one moved from the tree to about

1.5m away. The top soil fungal population was higher than what existed in the subsoil.

Generally, 25 fungal species belonging to 12 genera (Aspergillus, Cladosporium, Fusarium, Mucor, Mycelia sterilia,

Neoserterya, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, Trichoderma, and Scopulariopsis) were isolated from the dry

season soil samples (Table 1).

Mycoflora profile of wet season soil samples

Figures 19-36 and Tables 2 summarize the results obtained. The variations in occurrence of fungi along the transit

from the base of the cocoa plant in the wet season was also influenced by distance and type of fungicide applied in the field

(Figs 19-27). There was similar higher species diversity in the top soil (0-5 cm) than in the subsoil (5-10 cm depth) (Figs 19-

27). The general decline in number of fungi encountered as one sampled away from the base of the plant was also evident, with

the top soil at each sampled point recording a higher fungi population than the subsoil (Figs 28-36).

There was a drastic shift in species diversity in the control soils; A. flavus, B. cinerea, Fusarium oxysporum, F. poae,

Paecilomyces spp and Mucor plumbens, Penicillium citrinum and Rhodotorula which were absent in the soil during the dry

season appeared after the rains (figs 1 and 19). On the other hand, A. niger, A. oryzae, Cladosporium macrocarpum,

Penicillium expansum, P. italicum, and S.fusca were not isolated from the same soil in the wet season (Figs 1 and 19).

Interestingly, Rhodotorula was the most frequently encountered fungi in the soil during the wet season (Fig 19).

The forest soil away from the field cocoa plots (also acting as control) showed a similar shift in species diversity

during the wet season. While no Aspergillus species were recorded in the dry season in the Forest soil, three Aspergillus (A.

alutaceus, A. niger, A. penicillioides) were isolated in the wet season (Fig 20). R. oryzae and Phyllosticta citricarpa, could not

be isolated in the rainy season although they featured prominently in the dry season. New fungal species which were absent in

the dry season samples were isolated from the Forest soil during the wet season namely C. macrocarpum, F. oxysporum, M.

racemosus, P. expansum, and P. glabrum (Fig 20).

There was a drastic decrease in mycoflora diversity in the cocoa farm plots treated with both ALM 600 50g/15L and

ALM 600 75g/15L fungicides (Figs 21 and 22) at both the top soil (0-5 cm) and subsoil (5-10 cm) depths. While no

Aspergillus sp was present in the dry season, A. flavus and A. penicillioides as well as Mucor racemosus were detected in

small proportions whereas Rhodotorula sp predominated at all levels and distance from the cocoa plant in the ALM 600

50g/15L treated soil during the wet season (Fig 21).

In the soil treated with fungicide ALM 600 75g/15L, A. flavus was isolated in small proportions whereas Rhodotorula

and P. citrinum predominated in the soil during the wet season (Fig 22). F. oxysporum and F. poae remained but in very small

suppressed proportions and T. harzianum could not be isolated in wet season (Fig 22).

In the wet season, Rhodotorula sp was again the most frequently isolated species in the soil treated with Famous

75g/15L and Famous 100g/15L fungicide (Fig 23 and 24). Penicillium species which were present in the soil treated with

Famous fungicide (Figs 5 and 6) during the dry season, could not be isolated in the rainy season (Figs 23 and 24), while

Aspergillus species (A. alutaceus, A. niger, A. flavus, A. terreus) were persistent albeit in small percentages in the Famous-

treated soil (Figs 23 and 24). Two Fusarium species (F. oxysporum and F. poae) were also present in the soils in low

proportions (Figs 23 and 24).

In the wet season Metacide Super 50g/15L and 75g/15L-treated soil were predominated by Rhodotorula (Figs 25 and

26) taking over from T. harzianum with depressed occurrence (Fig 25). A. niger and A tamarii had replaced A. alutaceus and

A. penicilloides found in the soil during the dry season (Fig 7). P. citrinum, P. funiculosum. P.italicum replaced P. camemberti,

P. glabrum and P. italicum isolated during the dry season. F. oxysporum and F. poae not encountered in the dry season also

were present in the wet season. Botrytis cinerea not found in dry season appeared in the wet season (Fig 25) and F. poae also

was isolated in the soil treated with the higher concentration of Metacide super (50g/15L) (Fig 26).

Finally, the Ridomil Gold 50g/15L treated soil was predominated by Cladosporium macrocarpum (Fig 27) in contrast

with the dry season data predominated by Rhodotorula and T. harzianum (Fig 9). The dry season soil yielded eleven species

belonging to seven genera (Aspergillus, Fusarium, Mucor, Penicillium, Rhodotorula, Scopulariopsis and Trichoderma) (Fig 9).

The wet season soil harboured thirteen fungal species predominated by Aspergillus species (A. alutaceus, A.flavus, A. niger,

A. oryzae); with other genera being Botrytis, Cladosporium, Fusarium, Mucor, Penicillium (P. camemberti, P. citinum, P.

funiculosum), Rhodotorula and Trichoderma (Fig 27). Figs 28-36 show changes in soil fungal population along the transit in

the control and fungicide-treated field plots during the wet season. Generally population decreased minimally by 0.1 - 0.4 log

cycles (i.e. less than one log cycle) as one moved from the tree to about 1.5 m away. The top soil was generally slightly high in

fungal count than the subsoil (Figs 28-36).

Sci. Agri. 17(2), 2017: 55-76

59

Generally 23 fungal species belonging to eleven (11) genera (Aspergillus, Botrytis, Cladosporium, Fusarium, Mucor,

Paecilomyces, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, Trichoderma) were isolated and Aspergillus species (7)

predominated, followed by Penicillium (6) (Table 1 and 2). Species isolated in the wet season and not in the dry season were;

A. terreus, Botrytis cinerea, Cladosporium macrocarpum, F. oxysporum, M. plumbens and Paecilomyces sp.

Fungi species isolated in the dry season and not in the wet season were: C. herbarum, M. hiemalis, Mycelia sterilia,

Neosartorya fisheri, P.corylophilum, P.italicum, S. fusca (Tables 1 and 2).

Table 1: Summary of pooled data of fungal species isolated for the dry season soil samples under study.

Fungi isolate Field

Aspergillus alutaceus Wilhelm F75,M50,CON

A. flavus Link. F75,M50,R50 A. niger van Tieghem CON

A. oryzae (Ahlburg) Cohn CON

A. penicilloides F75,M50,CON A. tamarii Kita R50

Cladosporium herbarum (Pers.) Link A50,A75,M50,M75,CON

Fusarium poae (Peck) Wollenweber A75,M75,R50

Mucor hiemalis Wehmer f. hiemalis A75 F100,M75,CON

M. racemosus Fres. F75,M50

Mycelia sterilia A75,M75 Neosartorya fischeri (Wehmer) Malloch &Cain A50

Penicillium camemberti Thom A75,F75,F100,M50,M75,R50

P. citrinum Thom A50,R50,FOR P. corylophilum Dierckx R50

P. expansum Link CON

P. funiculosum Thom A50 P. glabrum (Wehmer) Westling M50

P. italicum Wehmer A75,F75,F100,M50,M75,R50CON,FOR

Phyllosticta citricarpa F75,F100,CON,FOR R. oryzae Went and Prisen-Geerlings A50,FOR

Rhodotorula spp A50,A75,F75,F100,M75,R50,FOR

Trichoderma harzianum Rifai A50,R50,CON Scopulariopsis fusca A50,A75,F75,F100,M50,M75,R50,CON,FOR

Key: A50= ALM 600 50g/15L-treated field, A75= ALM 600 75g/15L-treated field, F750= Famous 75g/15L-treated field, F100= Famous

100g/15L-treated field, M50= Metacide super 50g/15L-treated field, M75= Metacide super 75g/15L-treated field, R=Ridomil gold 50g/15L-

treated field, CON. = control field, FOR. = forest field.

Table 2: Summary of pooled data of fungal species isolated for the wet season soil samples under study. Fungi isolate Field

Aspergillus alutaceus Wilhelm F75,R50,CON,FOR

A. flavus Link. A50,A75F75,F100,M50,R50,CON A. niger van Tieghem F75,F100,M50,R50,FOR

A. oryzae (Ahlburg) Cohn M75,R50

A. penicilloides Speg. A50,FOR A. tamarii Kita M50,M75

A. terreus Thom F100

Botrytis cinerea Pers M50,R50,CON Cladosporium macrocarpum Preuss F100,R50,FOR

Fusarium oxysporum Schlecht. A75,F75,F100,M50,R50,FOR

F. poae (Peck) Wollenweber A50,A75,F100,M75 Mucor plumbens Bon. CON

M. racemosus Fres. A50,M50,R50,FOR

Paecilomyces sp Bain. CON Penicillium camemberti Thom R50

P. citrinum Thom A50,A75,M50,M75,R50,CON,FOR

P. expansum Link CON P. funiculosum Thom M50,M75,R50

P. glabrum (Wehmer) Westling CON

Phyllosticta citricarpa CON Rhizopus oryzae Went and Prisen-Geerlings M75

Rhodotorula spp A50,A75,F75,F100,M50,M75,R50,CON,FOR

Trichoderma harzianum Rifai A50,F100,M50,M75,R50,CON,FOR

Key: A50= ALM 600 50g/15L-treated field, A75= ALM 600 75g/15L-treated field, F750= Famous 75g/15L-treated field, F100= Famous

100g/15L-treated field, M50= Metacide super 50g/15L-treated field, M75= Metacide super 75g/15L-treated field, R=Ridomil gold 50g/15L-

treated field, CON. = control field, FOR. = forest field.

Sci. Agri. 17(2), 2017: 55-76

60

Table 3a: Comparison of Mean log10 CFU/g of fungi population of soil sampled at 0-5cm and 5-10cm during the dry season.

Soil depth

(cm)

Treatments

Control Forest ALM 600

50g

ALM 600

75g

Famous

75g

Famous

100g

Metacide

Super 50g

Metacide

Super

100g

Ridomil

Gold 50g

0-5 4.41a 4.11a 4.26a 4.36a 4.48a 4.24a 4.32a 4.25a 4.41a

5-10 3.99b 4.05a 4.13a 4.09a 4.20a 4.02a 4.12a 4.15b 4.28b

Means with different letters within the same column are significantly different (p ≤ 0.05)

Table 3b: Comparison of Mean log10 CFU/g of fungi population of soil sampled at 0-5cm and 5-10cm during the wet season.

Soil depth

(cm)

Treatments

Control Forest ALM 600

50g

ALM 600

75g

Famous

75g

Famous

100g

Metacide

Super 50g

Metacide

Super 100g

Ridomil

Gold 50g

0-5 4.48a 4.40a 5.24a 4.96a 4.58a 5.21a 4.39a 4.40a 4.30a

5-10 4.32b 4.29b 5.13b 4.83b 4.25a 4.88a 4.28a 4.23a 4.15a


Table 4: Mean values of soil properties

Soil property Seasons

Dry season Wet season

pH 7.42a 7.74a

Moisture content (%) 8.67a 12.9b

Means with different letters within the same row are significantly different (p≤0.05)

Table 5: Mean values (log10 CFU/g) of fungi population in dry and wet seasons for the two soil depths.

Season Soil depth (cm)

0-5 5-10

Dry season 4.316a 4.114b

Wet season 4.662a 4.504b


Figure 1: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Control

field.

0

10

20

30

40

50

60

70

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10

distance from tree (m)/depth of soil (cm)

Aspergillus alutaceus

Aspergillus niger

Aspergillus oryzae

Aspergillus penicilloides

Cladosporium macrocarpum

Mucor hiemalis

Penicillium expansum

Penicillium italicum

Phyllosticta citricarpa

Scopularriopsis fusca

Trichoderma harzianum

% s

pec

ies

com

posi

tion

Sci. Agri. 17(2), 2017: 55-76

61

Figure 2: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Forest field.

Figure 3: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from ALM 600

50g/15L-treated field.

0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10

distance from tree(m)/depth of soil (cm)

Penicillium citrinum



Rhizopus oryzae

Rhodotorula

Trichodermaharzianum

% s

pec

ies

com

po

siti

on

0

10

20

30

40

50

60

70

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Cladosporiummacrocarpum

Penicilliumcitrinum

Penicilliumfuniculosum

Neosarteryafisheri

Rhizopus oryzae

Rhodotorula

Scopulariopsisspp


% s

pec

ies

com

posi

tion

Sci. Agri. 17(2), 2017: 55-76

62



Figure 5: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Famous


0

10

20

30

40

50

60

70

80

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus niger

Fusariumoxysporium

Fusarium poae

Cladosporiummacrocarpum

Penicilliumexpansum

Rhizopusstolonifer

Rhodotorula


% s

pec

ies

com

po

siti

on

0

10

20

30

40

50

60

70

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10



Aspergillus flavus



Mucor racemosus

Penicillum camemberti

Penicillum italicum


Rhodotorula


% s

pec

ies

com

po

siti

on

Sci. Agri. 17(2), 2017: 55-76

63



Figure 7: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Metacide

Super 50g/15L-treated field.



05

101520253035404550

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


PenicilliumcamembertiPenicilliumitalicumPhyllostictacitricarpaRhizopushiemalisRhodotorula

% s

pec

ies

com

posi

tion

0

10

20

30

40

50

60

70

80

90

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10



Aspergillus flavus



Mucor racemosus

Penicillium camemberti

Penicillium glabrum


%sp

ecie

sco

mp

osi

tio

n

0

10

20

30

40

50

60

70

80

0/0

-5

0/5

-10

o.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


CladosporiummacrocarpumFusarium poae

Mucor hiemalis

Mycelia sterilia

PenicilliumcamembertiPenicilliumitalicumRhodotorula

% s

pec

ies

com

posi

tion

Sci. Agri. 17(2), 2017: 55-76

64

Figure 9: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Ridomil gold


Figure 10: Changes in fungal population (log10 CFU/g sample) along a transit from base of cocoa tree up to 1.50m at varying depth (0-5cm;

5-10cm) in soils sampled from the untreated cocoa farm plot (control) during the dry season.


5-10cm) in soils sampled from an untreated native Forest soil during the dry season.

0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus flavus

Aspergillus tamarii

Fusarium poae

Mucor hiemalis



PenicilliumcorylophilumPenicillium italicum

Rhodotorula

Scopulariopsis spp


% s

pec

ies

com

po

siti

on

3.43.63.8

44.24.44.64.8

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10

distance from tree (m)/soil depth (cm)

Log 1

0C

FU/g

3.83.85

3.93.95

44.05

4.14.15

4.24.25

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

65

Figure 12: Changes in fungal population (log10 CFU/g sample) along a transit from the base of cocoa tree up to 1.50m at varying depths (0-

5cm; 5-10cm) in soils from the Metacide super 50g/15L-treated cocoa plots during the dry season.


5cm; 5-10cm) in soils from the Metacide super 75g/15L-treated cocoa plots during the dry season.


5cm; 5-10cm) in soils from the Famous 75g/15L treated cocoa plots during the dry season.

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.8

3.9

4

4.1

4.2

4.3

4.4

4.5

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.7

3.8

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

4.7

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

66


5cm; 5-10cm) in soils from the Famous 100g/15L treated cocoa plots during the dry season.


5cm; 5-10cm) in soils from the ALM 600 75g/15L treated cocoa plots during the dry season.


5cm; 5-10cm) in soils from the ALM 600 50g/15L treated cocoa plots during the dry season.

3.7

3.8

3.9

4

4.1

4.2

4.3

4.4

4.5

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10distance from tree (m)/soil depth (cm)

Log 1

0C

FU/g

3.4

3.6

3.8

4

4.2

4.4

4.6

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.7

3.8

3.9

4

4.1

4.2

4.3

4.4

4.5

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

67


5cm; 5-10cm) in soils from the Ridomil gold 50g/15L treated cocoa plots during the dry season.

Figure 19: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Control

field.

Figure 20: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Forest

field.

0

10

20

30

40

50

60

70

80

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10



Aspergillus flavus

Botrytis cinerea

Fusarium oxysporum

Fusarium poae

Mucor plumbens

Paecilomyces spp


% s

pec

ies

com

po

siti

on

0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10



Aspergillus niger



Fusarium oxysporum

Mucor racemosus


Penicillium expansum

Penicillium globrum


% s

pec

ies

com

po

siti

on

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

4.7

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

68







0

20

40

60

80

100

120

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus flavus


Fusarium poae

Mucor racemosus


Rhodotorula


% s

pec

ies

com

po

siti

on

0

10

20

30

40

50

60

70

80

90

100

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus flavus

Fusarium oxysporum

Fusarium poae


Rhodotorula

% s

pec

ies

com

posi

tion

0102030405060708090

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


AspergillusalutaceusAspergillusflavusAspergillusnigerFusariumoxysporumRhodotorula

% s

pec

ies

com

po

siti

on

Sci. Agri. 17(2), 2017: 55-76

69






Ssuper 75g/15L-treated field.

0

20

40

60

80

100

120

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus flavus

Aspergillus niger

Aspergillus terreus

CladosporiummacrocarpumFusariumoxysporumFusarium poae

Rhodotorula

% s

pec

ies

com

po

siti

on

0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus flavus

Aspergillus niger

Aspergillus tamarii

Botrytis aclana

Fusarium oxysporum

Mucor racemosus


Penicillium funiculosum

Rhodotorula


% s

pec

ies

com

posi

tion

0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10


Aspergillus oryzae

Aspergillus tamarii

Fusarium poae



Rhizopus oryzae

Rhodotorula


% s

pec

ies

com

posi

tion

Sci. Agri. 17(2), 2017: 55-76

70

Figure 27: Percentage occurrence of fungi at varying distances (0 - 1.5m) from tree at different depths (0-5, 5-10cm) of soil from Ridomil

gold 50g/15L-treated field.


5-10cm) in soils sampled from the untreated cocoa farm plot (control) during the wet season.


5-10cm) in soils sampled from an untreated native Forest soil during the wet season.

4.1

4.15

4.2

4.25

4.3

4.35

4.4

4.45

4.5

4.55

4.6

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10

Log 1

0C

FU/g


0

10

20

30

40

50

60

0/0

-5

0/5

-10

0.7

5/0

-5

0.7

5/5

-10

1.5

0/0

-5

1.5

0/5

-10



Aspergillus flavus

Aspergillus niger

Aspergillus oryzae

Botrytis aclana


Fusarium oxysporum

Mucor racemosus




Rhodotorula


% s

pec

ies

com

po

siti

on

Sci. Agri. 17(2), 2017: 55-76

71


5cm; 5-10cm) in soils from the ALM 600 50g/15L-treated cocoa plots during the wet season.


5cm; 5-10cm) in soils from the ALM 600 75g/15L-treated cocoa plots during the wet season.


5cm; 5-10cm) in soils from the Famous 100g/15L-treated cocoa plots during the wet season.

4.8

4.9

5

5.1

5.2

5.3

5.4

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

4.65

4.7

4.75

4.8

4.85

4.9

4.95

5

5.05

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

4

4.2

4.4

4.6

4.8

5

5.2

5.4

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

72


5cm; 5-10cm) in soils from the Famous 75g/15L-treated cocoa plots during the wet season.


5cm; 5-10cm) in soils from the Metacide super 50g/15L-treated cocoa plots during the wet season.


5cm; 5-10cm) in soils from the Metacide super 75g/15L-treated cocoa plots during the wet season.

4.1

4.15

4.2

4.25

4.3

4.35

4.4

4.45

4.5

4.55

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

3.8

3.9

4

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

73


5cm; 5-10cm) in soils from the Ridomil gold 50g/15L-treated cocoa plots during the wet season.

was done after 5 days of incubation at 30oC. Counted colonies were converted into Log10 CFU/g. This method was

used to determine the mycoflora profile of soils sampled in both the dry and wet seasons. In both seasons, soil samples were

collected from different depths (0-5 cm, 5-10 cm) and distances from the cocoa farm trees (0, 0.75 m, 1.50 m).

Fungal Identification Fungi were identified by their morphological, cultural and colour characteristics using the criteria outlined by Smith

(1960), Barnett and Hunter (1972), Samson and Van Reenen – Hoekstra (1988), Ramirex (1982), Von Arx (1970) and Booth

(1971). A binocular microscope (Nikon, Japan, Optiphot-2) was used in identification. The percentage occurrence of each

species at different depths (0-5cm, 5-10cm), total population and the changes in fungal profile were recorded along the transit

starting from the base of the tree.

Statistical Analyses Statistical analyses were conducted with SPSS version 16.0 software at 5% significance level using Paired-Samples T

Test.

Discussion

Cocoa production in the West and Central African sub-region (predominantly Côte d’ Ivoire, Ghana, Nigeria and

Cameroon) in 2005/2006 was 2,626 metric tonnes; 71.5% of the world total output of 3,674 metric tonnes (ICCO, 2007).

Cocoa therefore plays a major role in the economy of developing economies in West Africa and especially Ghana in terms of

foreign exchange generation, domestic income and sources of revenue for the provision of socio-economic infrastructure.

Undoubtedly, there is an increasing demand for cocoa beans worldwide (Taylor, 1998) but the changing fortunes of the cocoa

industry in Ghana owing to pests and diseases may be a major challenge to its production (Bowers et al. 2001).

Phytophthora pod rot (black pod disease) caused by P. palmivora and P. megakarya (Dakwa, 1987, Luterbacher and

Akrofi 1993; Opoku et al.1999; Opoku et al, 2000) is the most prevalent disease of cocoa in Ghana. The testing of fungicides

for the control of black pod disease of cocoa in Ghana is the sole preserve of the Ghana Cocoa Marketing Board which

mandates the Cocoa Research Institute of Ghana, CRIG to carry out laboratory and field tests for ascertaining efficacy before

being recommended to the farmers for mass application under GRIG’s guidance.

In Ghana, all the fungicides recommended for the control of black pod disease of cocoa are copper-based (Opoku et

al. 2007). Repetitive applications (6-9 sprays in a year) of high copper doses as recommended for control of black pod disease

may have detrimental consequences on human health and may impair the ecological balance of microorganisms and

mcarofauna which play a role in nutrient cycling and plant health.

This study was designed to elucidate the impact of the application of fungicides on the soil mycoflora, in the

fungicides trial field at the Cocoa Research Institute of Ghana at Tafo in the Eastern Region. This is because of the report in

3.9

3.95

4

4.05

4.1

4.15

4.2

4.25

4.3

4.35

4.4

0/0-5 0/5-10 0.75/0-5 0.75/5-10 1.50/0-5 1.50/5-10


Log 1

0C

FU/g

Sci. Agri. 17(2), 2017: 55-76

74

many publications that fungicide application results in decrease of number and population of soil fungi (Corden and Young,

1965, and Elmholt and Smedegaard- Peterson, 1988) as well as organic matter breakdown (Karanth and Vasantharajan, 1973)

and a reduction of proportion of water stable aggregates in soil (Karanth and Vasantharajan, 1971).

The mycoflora profile of the soil sampled along a transit gradient showed that resident mycoflora was influenced by

distance from the tree and type of fungicide applied during the dry season. There was also a significant difference (p ≤ 0.05) in

population of resident fungi in the top soil (0-5 cm) than in the subsoil (5-10 cm) (table 5) and there was a general decline in

fungal diversity as one sampled away from the base of the plant (i.e. from 0-1.5 m distance away) (figs. 1-9 and 19-27).

Rhizophere and rhizoplane chemicals influence fungal growth and the root exudates are likely to stimulate fungal growth near

the plant and decrease away from the tree as competition for nutrients increases away from the source. This may partly explain

why resident fungal population decreased as one moved away from the tree to about 1.5 m away (Figs. 10-18 and 28-36).

No significant difference was observed for top soil samples (0-5cm soil depth) among the various treatments for both seasons

(fig 3a and 3b). However, at 5-10cm soil depth samples there were significant difference (p≤ 0.05) for control, Metacide Super

75g/15L and Ridomil Gold 50g/15L treated fields and the rest of the other fields during the dry season (Table3a and 3b). Also

at 5-10cm soil depth samples, significant difference (p≤0.05) existed for control, forest, ALM 600 50g/15L, ALM 600 75g/15L

treated fields and the other fields during the wet season (Table 3a and 3b). These differences can be attributed to differences in

chemical composition and concentration of the various fungicides, hence their different effects on the soil mycoflora.

The moisture content of the soil in the wet season in all field plots was significantly higher (p ≤ 0.05) in the wet season than in

the dry season while the pH did not change significantly (p ≥ 0.05) in the wet season (Table 4).

Generally 24 fungal species belonging to 12 genera (Aspergillus, Cladosporium, Fusarium, Mucor, Mycelia sterilia,

Neosartorya, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, Trichoderma, Scopulariopsis) were isolated from the soil of the

farms during the dry season (Table 1). Aspergillus and Penicillium species predominated over the other genera. This is a well-

known phenomenon that Penicillium and Aspergillus species are isolated frequently from soil (Alexander, 1977).

Surprisingly, Aspergillus species could not be isolated in the dry season in the Forest soil away from the cocoa field plots (Fig

2) but Penicillium spp were recorded in addition to Trichoderma harzianum. Rhodotorula sp predominated in this soil followed

by Rhizopus oryzae in soil treated with Famous fungicides. The survival of Rhodotorula in soil is attributed to its strong

competition for nutrients and probably also from its ability to utilize aromatic compounds from degradation of native leaves in

soil (Kirt et al 2004). The variation in phenology of the soil mycoflora may be partly attributed to the effect of the fungicides

on the metabolism of the individual fungal species (Figs 1-9). There was a drastic shift in species diversity in the soils during

the wet season (Fig 19-36; Table 2). For example A. flavus, B. cinerea, F. oxysporum, F. poae, Paecilomyces, M. plumbens, P.

citirinum and Rhodotorula which were absent in the control soil during the dry season appeared after the rains (Figs 1 and 19).

On the other hand, A. niger, A. oryzae, C. macrocarpum, P. expansum, P. italicum, and S. fusca could not be isolated from the

control soil in the wet season (Figs 1 and 19). The change could be attributed to antibiosis effect of the chemicals produced in

vitro in the soil by strong competitors or soil fungistasis (Alexander, 1977). The Forest soil away from the trial cocoa plots

(also serving as control) showed a similar shift in species diversity during the wet season while no Aspergillus were recorded

in the dry season in the forest soil, three Aspergillus species (A. alutaceus, A. niger and A. penicilloides) were isolated in the

wet season (Fig 20). P. italicum, Phyllosticta citricarpa and R. oryzae (fig 2) could not be isolated in the rainy season although

they featured prominently in the dry season. New fungal species which were absent in the dry season were encountered in the

wet season; for example C. macrocarpum, F. oxysporum, and M. racemosus (Table 2 and 20). All living things require

moisture, and it is not surprising, therefore that soil water has direct effect upon the abundance and functions of fungi

(Alexander, 1977; Wolters, 1997).

The application of fungicides changed the fungal profile and eliminated some species in the process (Fig 1-9 and 19-

27). However, the preponderance of Rhodotorula and P. citrinum is well noted because they are presumably strong competitors

for nutrients and space or probably their metabolites are unfavourable for growth of other species. It is reported that application

of even inorganic fertilizers may modify the abundance of fungi but such alterations are frequently more of the result of

acidification (Alexander, 1977). The abundance and physiological activity of the fungus flora of different habitats vary

considerably and the community and its biochemical activities undergo appreciable fluctuation with time at any single site.

Both the genus composition and the diversity of the fungi varied for the various plots. So whether a fungus or

(microorganism) will be able to survive, adapt itself, and become established in a specific habitat will be determined by the

surrounding environment (Alexander, 1977) such as the case in this study when fungicides were applied to the farm soil. The

major external influences imposed on the fungus community include the organic matter status, (which was not determined in

this study), hydrogen ion concentration (pH) (Table 4), organic and inorganic fertilizers, chemical sterilants, the moisture

regimes (Table 4), aeration, temperature, position in the soil profile, season of the year and composition of the vegetation

(mainly cocoa leaf litter) in this case. Generally, population of the fungi decreased minimally as one moved away from the tree

to 1.5m away and the top soil (0-5 cm) was generally higher in fungal population than the subsoil (5-10 cm) which was

expected (Figs 10-18 and 28-36). In generally, 23 fungal species belonging to eleven genera (Aspergillus, Botrytis,

Cladosporium, Fusarium, Mucor, Paecilomyces, Penicillium, Phyllosticta, Rhizopus, Rhodotorula, and Trichoderma) were

Sci. Agri. 17(2), 2017: 55-76

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isolated in the wet season (Table 2). Again Aspergillus species (7) predominated over the other followed by Penicillium (6)

species. Species which were isolated in the wet season and not in the dry season were: A. terreus, Botrytis cinerea,

C.macrocarpum, F. oxysporum, M. plumbens and Paecilomyces sp (Tables 1 and 2): Fungal species isolated in the dry season

and not in the wet season were: C. herbarum, M. hiemalis, Sterile mycelia (Mycelia sterilia), N. fischeri, P. corylophilum, P.

italicum, S. fusca (Tables 1and 2).

Conclusion

This study has provided novel information on the soil resident fungi of the fungicide trial plots at CRIG, Tafo, Ghana

in the top and sub soil levels with the view to ascertaining the four fungicides tested for their efficacy to control black pod

disease as well as their influence on non-target organisms. The soil mycoflora was predominated in most instances by

Aspergillus species followed by Penicillium. Population of the resident fungi was higher in the top soil (0-5 cm) than in the

subsoil (5-10 cm). The population decreased proportionately as one moves away from the tree to about 1.5 meters away.

Generally the fungicides did not have adverse effect on the soil mycoflora as at the time of this study. This could be an

indication that the fungicides contain acceptable levels of active ingredients and also CRIG being a research institute, the

fungicides were applied at the recommended rate.

It is recommended that studies on the impact of fungicides on soil microflora and macrofauna especially earthworms

should continue since this can be used as a bioindicator for pollution by copper (from copper based fungicides) in cocoa farm

soils

Acknowledgements

The authors wish to thank Mr George Akwetey and Mr C. O. Agyeman of the Department of Botany, University of

Ghana for their technical support. Special thanks also goes to the Head, Pathology Division of CRIG, Tafo and his colleagues

for their immerse assistance in the field work.

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