Greener Journal of Biological Sciences Vol. 11(2), pp. 37-44, 2021 ISSN: 2276-7762 Copyright ©2021, the copyright of this article is
retained by the author(s) |
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Assessment of the infestation of
Loranthaceae on shade trees in cocoa-based agrosystems: case of the
experimental field of the site of the University Jean Lorougnon Guédé (Côte
d'Ivoire)
*
Agroforestry Training and Research Unit,
University Jean Lorougnon Guedé, Daloa, Côte
d’Ivoire.
ARTICLE INFO |
ABSTRACT |
Article No.: 07231071 Type: Research |
In Côte d'Ivoire, in agrosystems, many trees and
shrubs are tolerated because of the shade they provide to crops. However,
these woody plants are attacked by Loranthaceae and make them privileged hot
of infestation in orchards. The inventories by surface surveys were carried
out in the experimental cocoa field on the Jean Lorougnon Guédé University
site to identify the species of Loranthaceae and their host. In total, two
(2) parasitic species (P. capitata and T. bangwensis) were encountered. The
taxonomic diversity of host plants is 23 species belonging to 20 genera and
14 families. Fabaceae (13.63%) is the richest family in infested species.
The results revealed a high infestation rate based on the DBH of the host
taxa. The infestation rate of the hosts taken together is in the order of 27.624%
and the infestation intensity is 1.87 tufts/tree. The field presented an
infestation rate of the order of 15.97±6.81% and an infestation intensity of
2.39±0.34 tufts/tree. |
Accepted: 24/07/2021 Published: 26/08/2021 |
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*Corresponding Author Denis-Esdras A. Amon E-mail: amonson77@yahoo.fr |
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Keywords: |
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INTRODUCTION
In sub-Saharan Africa, the destruction of forests year after year by the improper felling of trees and shrubs has manifold ecological consequences. In Côte d'Ivoire in agrosystems, the woody species spared in orchards for the shade they provide to crops have over time become focal point of Loranthaceae infestation commonly called ‶African mistletoe'' for these crops (Amon et al., 2010). Today, few trees and shrubs are not parasitized by Loranthaceae (Amon, 2006). Indeed, these epiphytoid hemiparasitic phanerogams attack and invade in large numbers the shade species encountered particularly in cocoa field (Soro et al., 2009). According to Boussim (2002), the Loranthaceae, once implanted on the trunk or the branches of the host, take with the helper of a system called sucker, the water and the mineral salts of the latter to ensure their own development. By this process of infestation, they are able to produce their own photosynthesis and live as long at the expense of this host; which makes these parasitic plants real dangers for any cultivated or spontaneous woody species that they parasitize (Salle, 2004; Soro, 2006). Despite the numerous inventories carried out in Côte d'Ivoire, in order to understand these parasitic plants and their host plants (Traoré et al., 2003, Soro, 2010; Amon, 2014), no specific study on the degree of infestation of species shading by these same phytoparasites in cocoa-based agrosystems has not been carried out to our knowledge in the Central-West of Côte d'Ivoire, an important cocoa production area (N'Guessan et al., 2014). It therefore seems important to carry out a qualitative inventory of woody plants tolerated as shade species in the experimental cocoa growing field on the site of the University Jean Lorougnon Guédé and to assess their state of infestation by species of the family of Loranthaceae.
MATERIAL AND METHODS
Study area
The study area is located in the department of Daloa, in the Central-West of the Côte d'Ivoire between 06º51′40.7″ North latitude and 006º21′22.6'′ West longitude (Fig. 1). It is in the Guinean domain characterized by an equatorial type climatic regime comprising two rainy seasons and two dry seasons (Eldin, 1971). Monthly precipitation varies between 1300 mm and 1800 mm. Its vegetation is from the mesophilic sector of the Guinean domain, today, made up of a mosaic of forests and savannas (Guillaumet & Adjanohoun, 1971; Monnier, 1983).
Material
The plant material was composed of Loranthaceae and woody plants found in the experimental field of cocoa. The technical equipment includes a geographical positioning device (GPS), a digital camera, a tape measure, sisal wires and data sheets.
METHODS
Data collection
For the floristic inventory of shade species, hosts of vascular plants of the Loranthaceae family, the surface survey method which consists of listing shade trees and shrubs encountered on square or rectangular areas (Hall & Swaine, 1981), coupled by direct observations in order to note the presence or absence of Loranthaceae species (Soro, 2010) were adopted in the experimental cocoa field on the Jean Lorougnon Guédé University site. The inventory consisted of counting the non-parasitized individuals and those parasitized of shade trees and shrubs, the parasitic species and the number of their tufts on each woody plant was carried out from three survey plots of 20m×20m (400m²) delimited in the field. The total height of individuals of shade trees and shrubs and their diameter at breast height (DBH at 1.30 m from the ground) were also registered. The presence or absence of the parasite and the number of its clumps by these woody plants have been noted. The data collected made it possible to determine the rate and intensity of infestation of Loranthaceae in the experimental cocoa cultivation plantation according to the formula used by Amon (2006):
§ Infestation rate (Txi):
with Txi - Infestation rate; Nip - Number of parasitized individuals; Nti - Total number of individuals identified;
§ Intensity of infestation (Ii):
with Ii - Intensity of infestation; Nt - Total number of Loranthaceae tufts; Ntii - Total number of infected individuals identified.
Statistical analysis
The data generated were subjected to one-way analysis of variance (ANOVA) to compare the mean values of the infestation rates and intensities of Loranthaceae on shade species. Statistical analysis was performed using STATISTICA version 7.1 software. This program provides, in the event of significant differences, for a comparison of the means (Dagnelie, 1980), by Duncan's test at the 5% threshold (α < 0.05).
RESULTS
Loranthaceae species encountered
Two species of Loranthaceae were found on cocoa trees and woody shade plants in the orchard. These are Phragmanthera capitata (Spreng.) Ballé (Fig. 2) and Tapinanthus bangwensis (Engl. And K. Krause) Danser (Fig. 3). T. bangwensis is the most common and abundant species with 77% of the host spectrum registered.
Loranthaceae host shade species
Twenty-two (22) shade species hosts of Loranthaceae belonging to 20 genera and 15 families were inventoried in the experimental field in cocoa trees studied on the University Jean Lorougnon Guédé site (Table 1). The Fabaceae are the richest family in host species with 3 species, either 13.63% of the total host species. It is followed by the Apocynaceae the Bignoniaceae, the Bombacaeae, Meliaceae and the Rubiaceae with each 2 species (9.09%). The remaining families each have between 1 species (4.54%). In terms of numbers of species, the richest genus are Albizia (3 species, either 15% of total genera) and Citrus (3 species, or 7.31% of total genera). All other 21 genera have a separate taxon (4.54%). We cite other Annona, Adansonia, Alstonia, Bombax, Ceiba, Cola, Morinda, Newbouldia and Persea.
Morphologically, the shade host species identified are divided into 4 groups: mesophanerophytes (mp) with 13 infested species (59.09%), microphanerophytes (mP) with 5 infested species (27.72%), megaphanerophytes (MP) with 3 infested species (13.63%) and lianescent mesophanerophytes (Lmp) with 1 infested species (4.54%).
Table 1: Lists of shade species hosts of Loranthaceae and their degree of infestation
Nº |
Epecies |
Families |
Types
biological |
Parasitic species |
Inft rate (%) |
Intensity inft |
|
Pc |
Tb |
||||||
1 |
Spondia
mombin Linn. |
Anacardiaceae |
mP |
+ |
+ |
31.57 |
2.50 |
2 |
Annona
sp Linn. |
Annonaceae |
Lmp |
- |
+ |
7.15 |
1.25 |
3 |
Alstonia
boonei De Wild |
Apocynaceae |
MP |
- |
+ |
45.33 |
2.10 |
4 |
Hollarhena
floribona (G. Don) Dur. & Schinz var. |
Apocynaceae |
mP |
+ |
- |
21.70 |
1.18 |
5 |
Albizia adianthifolia (Schumach.) W. Wight |
Fabaceae |
mP |
+ |
+ |
35.44 |
2.46 |
6 |
Albizia
lebbeck (Linn.) Benth. |
Fabaceae |
mp |
|
+ |
40.33 |
2.09 |
7 |
Albizia zygia (DC.) J. F. Machor. |
Fabaceae |
mP |
+ |
+ |
41.25 |
2.20 |
8 |
Newbouldia laevis (P. Beauv.) Seemann |
Bignoniaceae |
mp |
- |
+ |
8.22 |
1.00 |
9 |
Spathodea campanulata P.
Beauv. |
Bignoniaceae |
mp |
+ |
- |
11 |
1.85 |
10 |
Bombax
buonopozense P. Beauv. |
Bombacaceae |
MP |
+ |
+ |
50 |
2.50 |
11 |
Ceiba
pentadra (L.) Gaertn. |
Bombacaceae |
MP |
- |
+ |
47.85 |
3.53 |
12 |
Persea
americana Mill. |
Lauraceae |
mP |
+ |
+ |
43.27 |
2.48 |
13 |
Theobroma
cacao Linn. |
Malvaceae |
mp |
+ |
+ |
25 |
1.60 |
14 |
Milicia
excelsa (Welw.) C. C. Berg |
Moraceae |
mP |
- |
+ |
17 |
1.00 |
15 |
Cedrela
odorata C. V. Linné |
Meliaceae |
mp |
+ |
- |
18.95 |
1,00 |
16 |
Trichilia
megalantha Harms |
Meliaceae |
mp |
+ |
- |
9.25 |
1.15 |
17 |
Psidium
guajava Linn. |
Myrtaceae |
mp |
- |
+ |
35 |
2 |
18 |
Margaritaria discoidea (Baill.) G.L.Webster |
Phyllanthaceae |
mp |
- |
+ |
8.33 |
1.25 |
19 |
Morinda
lucida Benth. |
Rubiaceae |
mp |
+ |
- |
25 |
1.80 |
20 |
Citrus
sinensis (L.)
Osbeck |
Rutaceae |
mp |
+ |
+ |
35.38 |
2.25 |
21 |
Coffea
canephora A. Froehner |
Rutaceae |
mp |
- |
+ |
7.35 |
1.15 |
22 |
Cola
nitida (Vent.) Schott & Endl. |
Sterculiaceae |
mP |
+ |
+ |
43.35 |
3.00 |
Total |
13 |
17 |
27.62 |
1,87 |
Prevalence of shade species infestations
Table 1 shows the rate and intensity of infestation of Loranthaceae on the 22 shade species inventoried in the experimental cocoa field. Loranthaceae host infestation rates vary between 7.15 in Annona sp. and 50% in Bombax buonopozense. Among these host taxa, field megaphanerophytes (PM) have high rates of infestation (Fig. 4). Mention is made of Bombax buonopozense (50%), Ceiba pentadra (47.85%) and Alstonia boonei (45.33%).
Then come the microphanerophytes (mP) among others Cola nitida with an infestation rate of 43.35%, Persea americana (43.27%), Albizia zygia (41.25%), A. lebbeck (41.25%) and A. adianthifolia (39.44%). Likewise, in the cohort of 22 hosts, the weakest attacks were registered in mesophanerophytes with the species Annona sp. (7.15%).
Regarding the intensity of the infestation, the averages obtained vary between 1 and 3.53 tufts/tree (Table 1). Shade host species such as C. pentadra (3.53 tufts/tree), Cola nitida (3 tufts/tree), Spondia mombin, B. buonopozense and P. americana (2.48) show high infestation intensities. In addition, the lowest infestation intensities (1%) were registered in two host species. We cite: Newbouldia laevis and Milicia excelsa.
Overall, the rate of infestation of shade species inventoried by Loranthaceae in the experimental cocoa farming field of the Jean Lorougnon Guédé University site is around 27.62% and the infestation intensity is 1.87 tufts/tree (Table 1).
Infestation according to the height and diameter classes of shade species
Figure 5A indicates the levels of infestation of Loranthaceae in relation to the diameter classes of individuals of trees and shade shrubs identified. The rate of infection increases with the diameter of the host species. The strong hosts are the most infested. The classes determined differ from others in terms of the rate of infestation. In the diameter classes (16-20 years) and (> 20 year), the average rates of infested individuals are 21.60±10.50% and 29.08±10%, respectively. The low rate of infestation (5.33±2.90%) is recorded in the diameter class (0-5 years). Analysis of variance indicates a significant difference according to Duncan's test (p=0.02; F=4.77) between 5 statistically different groups a, ab, abc, bc and c (Figure 5A).
Regarding the height analysis, we also note a significant difference between the infestation rates of Loranthaceae on shade species according to their height classes. The infestation rates are statistically distinguished according to Duncan's test (p=0.03; F=6.33) through 3 homogeneous groups a, ab and b for the different height classes of shade trees and shrubs with a higher class infestation rate (> 20 year) (Figure 5B).
Infestation of the experimental field
The values of the infestation rate of cocoa trees by Loranthaceae registered in the experimental field of the Jean Lorougnon Guédé University site vary from 18.18% to 21.42% (Table 2). Individuals of cocoa trees in plot 1 (Pl1) are the most parasitized with an infestation rate of around 21.42%. Then come those of plot 3 (Pl3) with a rate of 18.18%. The cocoa trees in plot 2 (Pl2) are the least infested with Loranthaceae (8.33%). Regarding the infestation intensity, Pl1 registered a high infestation intensity of the order of 2.67 tufts/tree (Table 2). Likewise, the lowest intensity of infestation is recorded in individuals of Pl2.
Table 2: State of infestation of the experimental field by Loranthaceae
Experimental field |
Total number of plants/plot |
Number of parasitized plants/plot |
Number of tufts/plot |
Infestation rate (%) |
Infestation intensity |
Plot
1 |
14 |
3 |
8 |
21.42 |
2.67 |
Plot
2 |
12 |
1 |
2 |
8.33 |
2 |
Plot
3 |
11 |
2 |
5 |
18.18 |
2,5 |
Total |
37 |
6 |
15 |
15.97±6,81 |
2.39±0.34 |
DISCUSSION
The study identified two species of Loranthaceae (Phragmanthera capitata and Tapinanthus bangwensis), parasites of shade trees and shrubs in the experimental cocoa cultivation field at the Jean Lorougnon Guédé University site. The number of two species encountered is lower than the four Mrankpa species (2018) inventoried on the University Jean Lorougnon Guédé site. The difference noted could be explained by the size of the prospected area. Indeed, Mrankpa (2018) made an inventory over the entire Jean Lorougnon Guédé University site.
Twenty-two (22) shade host species of Loranthaceae belonging to 20 genera and 15 families were inventoried in this experimental field. This number is significantly lower than those of the 41 host species and 21 families obtained by Sako (2019) in the village fields in the surrounding areas of the University Jean Lorougnon Guédé. These results also corroborate those of Amon (2006), in Côte d'Ivoire and Houenon (2012), in Benin who have already reported the polyphagous character of parasitic vascular plants of the Loranthaceae family which parasitize different families of trees and shrubs in sub-Saharan Africa.
The rate of infestation of shade species by Loranthaceae registered in the experimental cocoa field is of the order of 27.62%. This value of the infestation rate obtained is significantly lower than that of 35.25% registered by Sako (2019) in cocoa agrosystems in surrounding areas of the University Jean Lorougnon Guède. This observed difference could be explained by the level of cared of the plots. Indeed, the field studied by this author were fewest cared and aged.
The enumerated cohort of shade host species exhibited numerically high infestation rate values according to diameter and height classes. These results confirm the work of Mranpka (2018).
The infestation rate of the experimental cocoa field is of the order of 15.97±6.81%. This rate is clearly lower than the 42.86±7.02% of Amon et al. (2020) obtained by in agrosystems based on cocoa trees in riparian areas of the University Jean Lorougnon Guédé. This difference could be justified by the age of the farms as well as by the care. Indeed, the plantations studied by this author are older and poorly cared.
CONCLUSION
Loranthaceae pose a serious threat to cocoa trees and other woody shade plants in orchards. The experimental cocoa farming field at the Jean Lorougnon Guédé University site parasitized by two species of Loranthaceae (P. capitata and T. bangwensis). This field abounds within 22 species of shade hosts of Loranthaceae belonging to 20 genera and 15 families. The infestation rate values of these woody plants by Loranthaceae vary from species to species and also according to their diameter and height classes. The field presented an infestation rate of the order of 15.97±6.81% and an infestation intensity of 2.39±0.34 tufts/tree. The results of this study could be used as an implement in making decisions concerning the conservation of certain species in fields for a sustainable agriculture.
Acknowledgements
Authorities from Jean Lorougon Guédé University in Daloa, Côte d'Ivoire.
Conflict of Interests
Authors declare that they have no conflict of interest.
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Cite this Article: Amon DA; Mrankpa SA (2021). Assessment of the
infestation of Loranthaceae on shade trees in cocoa-based agrosystems: case
of the experimental field of the site of the University Jean Lorougnon Guédé
(Côte d'Ivoire). Greener Journal of
Biological Sciences 11(2): 37-44. |