Diversity of yam insect pests at Kalonge, Kalehe territory, South Kivu, East of Democratic Republic of Congo

The present study revealed a total of 6 orders and 17 families such us Thysanoptera (Thripidae), Lepidoptera (Lymantriidae, Sphingidae, Noctuidae, Hesperiidae), Isoptera (Termitidae), Hemiptera (Cercopidae, Aphididae, Coreidae, Aleyrodidae, Pseudococcidae), Coleoptera (Cerambycidae, Chrysomelidae, Dynastidae, Scarabaeidae, Scolytidae) and Diptera (Cecidomyiidae). Again 28 species of yam pests include Ancistrotermes sp showed the maximum species diversity, followed by Ferrisia virgata, Planococcus citri, Tagiades litigiosa, Pseudoplusia sp, Dialeurodes sp, Tagiades nestus, Heteroligus meles, Rhopasosiphum maidis, Aspidiotus destructor, Aphis gossypii, Aphis craccivora, Toxoptera citricida, Thrips crawfordi, Dasychira mendosa, Leptoglossus australis, Ptyleus grossus, Lasioptera sp, Apomecyna saltator Clytocera chinospila, Heteronychus spp, Galerucida bicolour, Apomecyna dioscorea, Heteroligus meles and least species diversity were observed in Crioceris livida, Heteroligus appius and Xyleborus ferrugineus. Those yam pest cause damage on root, tuber, foliage, vine borer, galls on leaves, xylem sap feeder, phloem sap feeder, virus vector, sap sucker and sap feeder, dried roots. The study showed a rich yam pest diversity mainly attributed to the study area.

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Yam Pest Damage ZonesClose ×

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No. of individuals: Ancistrotermes sp vs Macrotermes spp vs F virgata vs P citri vs T litigiosaClose ×

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Introduction

Yams (Dioscorea sp., family Dioscoreacea) are annual or perennial tuber-bearing and climbing plants. Of the 600 or so species of Dioscorea recognized worldwide, only 10 are grown for food in various tropical and subtropical parts of the world by Asiedu et al.(2001) [1] ; Korada et al. (2010) [2] , Didi Konan et al. (2016) [3] and Wembou et al. (2017) [4] . Asiedu et al. (2001) [1] reported a few species are grown on a small-scale for extraction of the pharmaceutical compounds dioscorin and diosgenin. Then, the tubers have organoleptic qualities that can make them the preferred carbohydrate staple and can contribute up to 350 dietary calories per person each day. Adeniji et al. (2012) [5] and Cornet (2015) [6] report that yam constitutes an important food crop in intertropical zones and plays a major role in the food security of millions of people. According IITA (2007) [7] and Korada et al. (2010) [2] , yams are produced over 5 million hectares in 47 countries in tropical and subtropical regions of the world. However, more than 95% of the world's 47 million metric tonnes of yam produced annually comes from Sub Saharan Africa. Moreover, in Africa, yields varied from 8.5 t/ha to 9.5 t/ha between 1990 and 2002. This increase is almost exclusively due to the increase in cultivated areas and the increase in yields. This low yam productivity is due to several factors including pressure from insect pests and diseases. Insects act in two ways: as vectors of viral diseases (generally biting suckers) on aerial parts and as pests of both leaves and tubers (Diby, 2005 cited by Soro et al., 2010) [8] . According to Degras (1986) cited by Soro et al. (2010) [8] , most of the damage observed on tubers has its origin in the fields. Foua Bi, (1982) cited by Soro et al. (2010) [8] reports that regarding losses due to insect pests, a reduction in the emergence rate of more than 30% due to scale insects has been reported. Manyong and Oyewole (1997) cited by Korada et al. (2010) [2] , the productivity of yam cultivation has been severely constrained by reduction in soil fertility, increases in infestation of coleopteran pests and increases in production costs. In addition to these problems, yam is increasing pressure from a range of insect pests (e.g. leaf and tuber beetles, mealybugs, scales), fungi (anthracnose, leaf spot, leaf blight, tuber rots) and viruses, as well as nematodes; contribute to sub-optimal yields and the deterioration of tuber quality in storage. The high-risk area for nematode infestation is estimated to be 45% in yam growing regions of West Africa. Bankole and Adebanjo (2003) [9] reported dried yam chips are also containing mycotoxins. Dans la zone d'étude, une espèce d'igname principalement Dioscorea alata (L) en fonction de provenance paysanne a fait l'objet de l'étude repartie en dix variétés locales d'ignames suivant leurs caractéristiques morphologiques et a été classée en trois groupes et/ou catégories basées sur les facteurs productivité et rendement dont : Haut rendement(HR), moyen rendement (MR) et faible rendement (FR).Parmi elles, Katesha, Nyalushuli, Kasakura et Kabeyabeyabeya ont un rendement moyen, Nyamishi et Nyabisu (RF), Nyabongwa, Bitarama, Nyaluliga et Kazanga (HR). Certaines de ces variétés ont manifestés la sensibilité aux maladies et d'autres aux insectes. On the markets and in the industry, there is a certain varietal preference among consumers, sellers and producers. This would be explained by the level of shelf life in the field, cooking time, precocity, vigor, productivity, resistance to diseases as well as organoleptic qualities (its improved flavor/taste), thus allowing customers to be attracted. In the present study, the overall strategy consisted of updating the data on the fauna of yam insects (diversity) on local varieties in farming environments.

Materials and Methods

Materials and Methods

Study area

This study was carried out in the Kalonge group located in the territory of Kalehe, province of South Kivu, in the east of the Democratic Republic of Congo. This group constitutes the large area where yams are produced, thus partly supplying neighboring territories as well as the city of Bukavu, apart from the quantity consumed by the indigenous population. Kalonge is a group of trees with average annual temperatures of 18 °C and rainfall which can reach 2114 mm.It borders with Ninja to the south, to the north by the Kahuzi Biega National Park (PNKB), to the east by Shabunda and to the west by the other villages of the Kabare Territory.

Choice of experimental plots

Six localities form the Kalonge group. The choice of these localities was precise. However, the choice of experimental plots was based on criteria linked to fallowness and not being next to another yam field to avoid any pre-existing entomological influence in the plot and surrounding areas, thus transmitting insect pests and vectors and of course diseases.

Insect trapping

Insects were captured using sweep nets. As for the flying insects, they were also captured using sweep nets and by hand between 6 a.m. and 8 a.m. and between 4:30 p.m. and 6:30 p.m. during the 3 phases, mainly in the tuber germination phase, in the growth phase as well as in the maturation, i.e. twice a week for 60 days for each phase.

Transport of samples (captured insects)

After capturing the insects, they were directly placed in alcohol (ethanol) concentrated at 95 percent and sent directly to the packaging location while awaiting their transfer to the agricultural entomology laboratory where they were identified.

Insect Identification

The insects captured and preserved in alcohol measured at 95 percent were made using a special identification key from Kouadjo et al. (2018) [10] at the Agricultural Entomology laboratory of the Department of Biology, from the Natural Sciences Research Center/CRSN-Lwiro. The identification was based on the external morphological characteristics of the insects using a binocular magnifying glass capable of enlarging the image of each insect 10 to 20 times larger, while referring to the collection of other insects found at Agricultural Entomology laboratory of the same Department and the same Center.

Data Analysis

In this study, for biodiversity analysis the data from collected insect samples were grouped according to source. The averages were calculated and there are several ways to test the species diversity. The biodiversity count was made using the Shannon diversity index (Shannon, 1948) [11] to estimate species richness uniformity and species diversity.

Species Diversity

The species diversity index was calculated by using the Shannon-Wieners Diversity index formula. H= -

Where p is the proportion ( N n ) of individuals of one particular species found (n) divided by the total number of individuals found (N), ln is the natural log, Σ is the sum of the calculations, and is the number of species.

Diversity index of different pests from Kalonge

The total of 1). My research is also consistent with Maliki et al. (2012) [12] , Andres et al. (2017) [13] , Kouadjo et al. (2018) [10] . Yam is attacked and damaged by field and storage pests wherever it is grown elsewhere, resulting in yield and storage losses (Taylor, 1964 [14] and Korada et al. (2010) [2] . Some of the most common pests include yam beetle, mealy bugs, termites, and nematodes. Pests may damage the yam tubers by decreasing their dry matter content, thus reducing germination capacity. Furthermore, the damage they cause to the epidermis may trigger secondary infections by rot fungi (i.e., molds), which can lead to high storage losses. Yam farmers hardly use synthetic pesticides. Effective control of pests is necessary to optimize yam yields (Andres et al., 2017) [13] . The species diversity index was calculated by Shannon-Weiner index formula comprising(2.8721), Ancistrotermes sp showed the maximum species diversity, followed by Ferrisia virgata, Planococcus citri, Tagiades litigiosa, Pseudoplusia sp, Dialeurodes sp, Tagiades nestus, Heteroligus meles, Rhopasosiphum maidis, Aspidiotus destructor, Aphis gossypii, Aphis craccivora, Toxoptera citricida, Thrips crawfordi, Dasychira mendosa, Leptoglossus australis, Ptyleus grossus, Lasioptera sp, Apomecyna saltator Clytocera chinospila, Heteronychus spp, Galerucida bicolour, Apomecyna dioscorea, Heteroligus meles and least species diversity were observed in Crioceris livida, Heteroligus appius and Xyleborus ferrugineus (Table 2). Goergen et al. (2010) [15] reported not similar results during the study.

Genus	Species	No. of individuals	Proportion (pi)	(Σ (sum) of pi2 (n/N)2	ln pi	Σ (sum) of pi ln pi
Ancistrotermes	Ancistrotermes sp	400	0.1368	0.0187	-1.9892	-0.2721
Macrotermes	Macrotermes spp	390	0.1334	0.0178	-2.0146	-0.2687
Ferrisia	F virgata	190	0.0649	0.0042	-2.7337	-0.1776
Planococcus	P citri	168	0.0574	0.0033	-2.8567	-0.1641
Tagiades	T litigiosa	165	0.0564	0.0032	-2.8748	-0.1622
Pseudoplusia	Pseudoplusia sp	148	0.0506	0.0026	-2.9835	-0.1510
Dialeurodes	Dialeurodes sp	145	0.0496	0.0025	-3,0039	-0,1489
Tagiades	T nestus	143	0.0489	0.0024	-3.0179	-0.1476
Hippotion	H celerio	139	0.0475	0.0023	-3.0462	-0.1448
Rhopasosiphum	R maidis	135	0.0462	0.0021	-3.0754	-0.1419
Aspidiotus	A destructor	132	0.0451	0.0020	-3.0979	-0.1398
Aphis	A gossypii	130	0.0445	0.0019	-3.1132	-0.1384
Aphis	A craccivora	129	0.0441	0.0019	-3.1209	-0.1377
Toxoptera	T citricida	126	0.0431	0.0018	-3.1444	-0.1355
Thrips	T crawfordi	120	0.0410	0.0017	-3.1932	-0.1310
Dasychira	D mendosa	100	0.0342	0.0012	-3.3755	-0.1154
Leptoglossus	L australis	27	0.0092	8.5265E-05	-4.6848	-0.0433
Ptyleus	P grossus	25	0.0085	7.3101E-05	-4.7618	-0.0407
Lasioptera	Lasioptera sp	18	0.0061	3.7896E-05	-5.0903	-0.0313
Apomecyna	A saltator	17	0.0058	3.3802E-05	-5.1475	-0.0299
Clytocera	C chinospila	13	0.0044	1.9767E-05	-5.4157	-0.0241
Heteronychus	Heteronychus spp	12	0.0041	1.6843E-05	-5.4958	-0.0225
Galerucida	G bicolour	11	0,0038	1,4152E-05	-5.5828	-0,0210
Apomecyna	A dioscorea	10	0.0034	1.1696E-05	-5.6781	-0.0194
Heteroligus	H meles	10	0.0034	1.1696E-05	-5.6781	-0.0194
Crioceris	C livida	8	0.0027	7.4856E-06	-5.9013	-0.0161
Heteroligus	H appius	7	0.0024	5.7311E-06	-6.0348	-0.0144
Xyleborus	X ferrugineus	6	0.0020	4.2106E-06	-6.1889	-0,0127
Total no. of species collected	28
Total no. individuals		2924	1
Shannon diversity index (H)		2.8721

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Species Diversity Index.

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Conclusion

The study area supports a rich diversity of insect pests with wide varieties of yam which provide an ideal breeding environment for yam insect pest. It is estimated that there are more than 28 yam insect pests' species on the Kalonge, Kalehe Territory, South Kivu, East of Democratic Republic of Congo as they are specific to different seasons and this survey was conducted for only six months. Therefore, it is difficult to collect, preserve, photograph and identify all species within the study area. The study is an attempt to provide a checklist for yam insect pests in the study area and will be continually updated for future reference. It was observed that Ancistrotermes sp was the most abundant species and had the highest number of individual species observed during the study, and Xyleborus ferrugineus had the least number of species observed respectively from the survey. Yam insect pests' diversity depends upon the cultural strategies or among other factors as climatic and soil. Therefore, it is possible that yam can be protected against those insect pests by improving the yam yield the study area.

Acknowledgement

AcknowledgementWe express thankfulness to my respected advisor Prof. Gueye Badara and all the laboratory members of Agricultural Entomology Research Centre in Natural Sciences, South Kivu/ DRC and others like Elie Misengero, Bisimwa Shamavu, Bacubizala Mutimirwa, Cubaka Mushunju and Bunani Lishombo.

Figures and tables from the paper

Order	Family	Species	Damage
Coleoptera	Cerambycidae	Apomecyna dioscorea Pierce	Root, tuber
		Apomecyna saltator Fab.	Vine borer
		Clytocera chinospila Gahan	Vine borer
	Chrysomelidae	Crioceris livida Dalman	Foliage
		Galerucida bicolour Hope	Foliage
	Dynastidae	Heteroligus appius (Burmeister)	Tuber
		Heteroligus meles	Tuber
	Scarabaeidae	Heteronychus spp.	Tuber
	Scolytidae	Xyleborus ferrugineus (Fab.)	Foliage
Diptera	Cecidomyiidae	Lasioptera sp.	Galls on leaves
Hemiptera	Cercopidae	Ptyleus grossus Fab.	Xylem sap feeder
	Aphididae	Aphis craccivora Koch	Phloem sap feeder & virus vector
		Aphis gossypii Glover	Phloem sap feeder & virus vector
		Aspidiotus destructor Signoret	Foliage
		Rhopasosiphum maidis (Fitch)	Sap sucker & virus vector
		Toxoptera citricida (Kirkaldy)	Sap sucker & virus vector
	Coreidae	Leptoglossus australis Fab.	Foliage
	Aleyrodidae	Dialeurodes sp.	Sap feeder
	Pseudococcidae	Ferrisia virgata Cockerell	Foliage
		Planococcus citri (Risso)	Foliage, virus vector, tuber
Isoptera	Termitidae	Ancistrotermes sp.	Dried roots and tuber
		Macrotermes spp.	Dried roots and tuber
		Microtermes spp.	Dried roots and tuber
Lepidoptera	Lymantriidae	Dasychira mendosa Hubner	Foliage
	Sphingidae	Hippotion celerio L.	Foliage
	Noctuidae	Pseudoplusia sp.	Foliage
	Hesperiidae	Tagiades litigiosa Moschler	Foliage
		Tagiades nestus (C. Felder)	Foliage
Thysanoptera	Thripidae	Thrips crawfordi Nakahara	Foliage

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List of insects of yam: field/pre-harvest

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