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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 5, Num. 3, 1997, pp. 295-302
African Crop Science Journal, 1997, Vol. 5. No. 3, pp. 295-302.

SHORT COMMUNICATION: Incidence and damage caused by maize stemborers on farmers' fields in south western nigeria

O.N. OIGIANGBE, M.F. IVBIJARO, F.K. EWETE and H.J.W. MUTSAERS^1

Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan, Nigeria
^1 International Institute of Tropical Agriculture, PMB 5320, Oyo Road, Ibadan, Nigeria

(Recieved 17 August, 1995; accepted 12 December, 1996)


Code Number: CS97036
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ABSTRACT

The incidence and damage of maize (Zea mays L.) by stemborers complex of Eldana saccharina Walker, Sesamia calamistis Hampson, Acigona (Syn = Coniesta ignefusalis Hampson) and Mussidia nigrivenella Roganot were assessed in 17 and 6 small-scale farmers' fields in southwestern Nigeria during the early and late cropping seasons of 1991, respectively. The incidence, numbers of borer larvae and pupae as well as the damage caused were significantly higher in the late compared to the early season. Eldana saccharina and S. calamistis were the most abundant species while A. ignefusalis and B. fusca occurred in lower numbers at harvest. Mussidia nigrivenella occurred only during the late season. Eldana saccharina (r=0.96) and S. calalmistis (r=0.88) caused the highest percentage stalk length damage while A. ignefusalis (r=0.76) and E. saccharina (r=0.53) accounted more for the percentage node damaged during the early season. During the late season, B. fusca significantly increased the percentage nodes damaged (r=-0.86) while A. ignefusalis significantly reduced yield (r=-0.998). Combining the data for the two seasons revealed that 94.8% of the variation in yield was accounted for by cob weight, percentage of node damaged, number of plants damaged and the incidence of stemborers per farm. The percentage length damaged accounted for 30.9% of the variance in cob weight, while the number of S. calamistis per stalk accounted for another 17.7%. Of the variance in cob weight, 18.7% were accounted for by the total number of stemborers per stalk. The need to further investigate factors affecting oviposition choice by female maize stembores is highlighted.

Key Words: Cob weight, Eldana saccharina, Mussidia nigrivenella, oviposition, Sesamia calamistis, stalk damage, Zea mays

RESUME

La frequence et les degets des foreuses des tiges du Mais, Eldana saccharina Walker, Sesamia calamistis Hampson, Acigona (Syn = Coniesta ignefusalis Hampson) et Mussidia nigrivenella Roganot ont ete evalues dans 17 et 6 champs de paysans du Nigeria, respectivement au debut et a la fin des saisons de culture en 1991. Cette evaluation fait partie d'un project visant a identifier les contraintes de la production du Mais dans la region. La frequence, le nombre de larves d'insectes et de chrysalides et les degets causes etaient sensiblement eleves a la fin de la saison de culture comparativement a ceuxs trouves au debut de la saison de culture. E. saccharina et S. calamistis etaient les especes les plus abondantes alors que A. ignefusalis et B. fusca se sont presentes en nombres reduits. Mussidia nigrivenella s'est presente seulement a la fin de la saison. E. saccharina (r=0,96) et S. calamistis (r=0,88) ont cause le pourcentage le plus eleve des degets de la tige alors que A. ignefusalis (r=0,76) et E. Saccharina (r=0,53) ont ete la cause d'un pourcentage plus eleve des degets du noeud au debut de la saison. B. fusca augmente sensiblement le rendement (r=0,90) et le nombre de pieds (r=0,96). En fin de saison, B. fusca, a sensiblement augmente le pourcentage des noeuds endommages (r=0,86) tandis que A. ignefusalis a reduit de facon significative la production (r=-0,998). Pour les deux saisons, 94,8% de variation de la prodution ont ete attribues aux poids des epis, au pourcentage des noeuds endommages au nombre de plantes attaquees et a l'incidence des insectes par champ. Le pourcentage de la longueur de la tige endommagee representait 30,9% de la variance entre les poids de l'epi, tandis que le nombre de S. calamistis par tige comptait par ailleurs pour 17,7% tandis que 18,7% de cette variance a cause par le nombre total d' insectes terebrants par tige. ll y a des lors lieu d'etudier les facteurs qui affectent le choix du lieu de ponte par les insectes femelles foreuses de tiges de mais.

Mots Cles: Poids de l'epi, Eldana saccharina, Mussidia nigrivenella, lieu de ponte, Sesamia calamistis, degets de la tige, Zea mays

INTRODUCTION

South western Nigeria straddles the semi-decidous forest-savanna transition vegetation zones. The area has a bi-modal rainfall pattern with two rainy seasons. The first season starts in late March or April and ends in early August. The second starts in late August or early September after a short break which is rather erratic and sometimes does not occur at all. Second season planting of food crops is of minor importance and the main food crop operations are carried out in the first season with the maize + cassava intercrop as the dominant pattern (Mutsaers, 1991a).

Maize stemborers are the most important field pests of maize (Bowden, 1954; Harris, 1962). Usua (Unpub.) indicated that the presence of one or two borer larvae in a maize plant reduced yield by about 25%. Yield reductions of 10-100% have been reported in southwestern Nigeria as a result of stemborer attack (Usua, 1968). More damage usually occurs in the late season crop (Adayemi et al., 1966; IITA, 1986; Mutsaers, 1991a) and this has made late season maize cultivation unprofitable (IITA, 1987). Harris (1962) and Usua (Unpub.) reported that Busseola fusca Fuller and Sesamia calamistis Hampson were the dominant maize stemborer species in southwestern Nigeria, with Eldana saccharina Walker and Acigona (Syn = Acigons (Syn = Conista) ignefusalis Hampson occurring as minor pests. But in recent times, S. calamistis and E. sacharina have also become important (IITA, 1986; Bosque-Perez and Mareck, 1990). Bosque-Perez and Mareck (1990) reported that S. calamistis attacks maize plant at 2 to 3 weeks after emergence (WAE) resulting in stand loss while E. saccharina attacks the plant at the tasseling stage (6 to 8 WAE) causing yield reduction. Under the multiple cropping system of south-western Nigeria, vertebrate pests also account for a significant level of stand loss (Mutsaers, 1991b). It is therefore necessary to assess the relative importance of stemborer species as they affect crop damage and yield with a view to formulating control strategies.

MATERIAL AND METHODS

A total of 17 and 6 small-scale farmers' fields were surveyed during the 1991 early (April-August) and late (August- December) cropping seasons, respectively, in five villages near Ibadan, southwestern Nigeria. The number of farms surveyed depended on availability of the maize crop during the season. Only 6 out of the 17 farmers who were surveyed during the first season cultivated a second season crop but not on the same plot. Most of the farmers planted improved maize varieties (TZPB and TZSR-W) developed at the International Institute of Tropical Agriculture (IITA), Ibadan, while the rest planted local varieties. In each farm, 10% of the estimated maize population in randomly selected rows were sampled at harvest. The stems were cut at ground level, taken to the laboratory and dissected for the presence of stemborers. The total length of each stem (from the ground level to the base of the terminal leaf), the length of the damaged nodes or internodes were recorded and expressed in percentage. The stemborer larvae found were sorted out according to their morphological features (Harris, 1962; Usua, Unpub.) and reared to adults on short maize stalks in plastic dishes (17 x 12 x 8 cm). The stalks were changed frequently to ensure adequate food supply. Identification was done in the Insect Museum of the Department of Crop Protection and Environmental Biology, University of Ibadan, Ibadan. The t-test was used to compare the data for the two seasons according to the independent and unequal variance model (Steel and Torrie, 1980). The data were also subjected to simple correlations, regressions and stepwise regressions where necessary.

RESULTS

Table 1 shows the incidence, numbers and damage of all the stem borer species during the first and second cropping seasons. Their respective values were significantly higher during the late season compared to the early season. Eldana saccharina and S. calamistis were the most abudant species during each season (Table 2). While the abundance of E. saccharina and A. ignefusalis were not significantly different during the two seasons, those of S. calamistis and B. fusca were significantly higher during the late season. Mussidia nigrivenella was recorded only during the late season. There was a significant positive correlation between yield and number of S. calamistis during the first season (r=0.516) but the number of A. ignefusalis had a significant negative correlation (r=-0.899) with yield during the second season (Tables 3 and 4). While there was no significant correlation between the number of any of the stemborer species and cob weight during the first season, the number of M. nigrivenella showed a significant negative correlation (r = -0.627**) during the second season. When the data from the first and second farms were combined, cob weight and yield had significant negative correlations with stemborer damage (Table 5). Table 6 shows a summary of the stepwise regression on this combined data with yield as the dependent variable. Cob weight accounted for 69.4% of the variance while incidence of stem borers accounted for another 16.1%. The number of nodes and plants damaged collectively accounted for only 9.2% of the variance. Table 7 shows the summary of the stepwise regression for the dependent variable cob weight. Percentage stalk length damaged, number of S. calamistis and the total number of stemborers significantly affected cob weight, accounting for 30.9%, 17.7% and 18.7% of the variance, respectively.

DISCUSSION

This study agrees with previous reports which indicated that the incidence, abundance and damage caused by maize stemborers in southwestern Nigeria are significantly higher during the late cropping season than in the early season (Adeyemi et al., 1966; Daramola, 1985). Eldana saccaharina and S. calamistis were the most abudant species at harvest while B. fusca and A. ignefusalis occur in much lower numbers as earlier reported (IITA, 1986; Bosque-Perez and Mareck, 1990). Harris (1962) and Usua (Unpub.) observed higher population of B. fusca on maize in Ibadan when they sampled the plants before harvest. Our results suggest most of the B. fusca larvae that infested the young plants had developed into adults before harvest and only one generation is possible on a single maize crop. In the case of S. calamistis, however, two generations are possible on the same crop, the first attacking the plant between 2-6 WAE and the second between 7-11 WAE. It is this second generation larvae that account for much of the larvae present at harvest. Busseola fusca and C. ignefusalis are dominant species in the savanna zone where they are important pests of sorghum and millet, respectively (Harris, 1962; Macfarlane, 1990).

Leyennar and Hunter (1977) working in the humid forest zone of Ghana, reported that maize plants which died prematurely as a result of insect damage usually had S. botanephaga while a larval count at harvest indicated that E. saccharina was the most plentiful. Eldana saccharina infests the crop as from 6 WAE and only one generation can develop on one crop. In most cases E. saccharina larvae recovered from maize stem at harvest were young. Thus sampling at harvest gives a better estimate of the abundance of E. saccharina than B. fusca and S. calamistis.

The significant positive correlation between the number of S. calamistis and yield during the first season indicates that ovipositing females select vigorous plants for egg laying. This is consistent with the report of Martin et al. (1989) which indicated that maize growth quality affect oviposition choice and damage by stemborers. The activity of A. ignefusalis significantly reduced the yield during the second season mainly as a result of multiple node damage larva. The presence of M. nigrivenella in stalks during the second season confirms the observation of Adeyemi (1969) and IITA (1986) which indicated that this insect survives the dry season in maize stalk but re-infest the cobs and increases in number during the first season. It is the dominant maize earworm in West Africa (Daramola, 1985; Moyal, 1988), and having increased in number during the first season is able to reduce cob weight by feeding on the ear stalk (peduncle) and developing seeds during the second season.

Although damage to stalk had been shown to significantly reduce grain weight (Bosque-Perez and Mareck, 1990), crop density and cob weight were largely responsibe for the final yield per farm in our study. Mutsaers and Walker (1990) observed that variation in yield level per site (farmer's field) was partly explained by stand loss during the first season. The behaviour of the larvae inside the maize determines the nature and extent of damage they cause. The noctuid species S. calamistis, breed throughout the year while B. fusca is trivoltine, with the third generation dispausing at the end of the second season (Usua, unpub.). During the early season, new fields are infested by the adults that survive the dry season. The emphasis during this period is on increase in number of the next generation. The significant positive correlations between percentage length damage and numbers of S. calamistis, A. ignefusalis and B. fusca across the seasons show that these species put more stress on the plant, but only S. calamistis significantly reduced cob weight, accounting for 17.7% of the variance. This is probably due to the fact that it produces two generations, the first feeding mainly on the vegetative parts (leaves and stems) and the second on the vegetative (stem) and reproductive part (cob).

Therefore, stemborers not only significantly cause stand loss during the early and late seasons, but also reduce cob weight as a result of damage to the stalk or nodes. Factors affecting ovipositional preference, survival and growth of the species as well as larval behaviour within the stem need to be investigated.

ACKNOWLEDGEMENT

The first author thanks the Ford Foundation for a Grant through H.J.W.M with which this study was conducted.

REFERENCES

Adeyemi, S.A.O. 1969. The survival of stemborer populations in maize stubble. Bulletin of Entomological Society of Nigeria 2:16-12.

Adeyemi, S.A.O., Donelly, J. and Odetoyinbo, J.A. 1966. Studies on chemical control of the stemborer of maize. Nigerian Agricultural Journal 3:61-66.

Bosque-Perez, N.A. and Mareck,J.H. 1990. Distribution and species composition of lepi-dopterous maize borers in southern Nigeria. Bulletin of Entomological Research 81:243-247.

Bowden, J. 1954. The stemborer problem in tropical cereal crops. Report 6th Common-wealth Entomological Conference. pp. 104-107.

Daramola, A.M. 1985. Field evaluation of the resistance of nine maize cultivars to stem-borer infestation in southwestern Nigeria. Nigeria Journal of Science 19:28-30.

Harris, K.M. 1962. Lepidopterous stemborers of cereals in Nigeria. Bulletin of Entomological Research 53:130-171.

International Institute of Tropical Agriculture (IITA), 1986. Maize Research Program. Annual Report for 1986. IITA, Ibadan.

Leyennar, P. and Hunter, R.B. 1977. Effect of stemborer damage on maize yield in the coastal savanna zone in Ghana. Ghana Journal of Agricultural Science 10:67-70.

Macfarlane, J.H. 1990. Damage assessment and yield losses in sorghum due to the stemborer Busseola fusca Fuller (Lepidoptera: Noctuidae) in Northern Nigeria. Tropical Pest Management 36:131-137.

Martin, R.C., Anarson, J.T., Lambert, J.D.H., Isabelle, P., Voldeng, H.D. and Smith, D.L. 1989. Reduction of European Corn Borer (Lepidoptera: Pyralide) damage by intercropping corn with soybean. Journal of Economic Entomology 82:1455-1459.

Moyal, P. 1988. Les foreurs du maiz en zones des savenes de Cote d'Ivoire. Collection Etudes et Theses, Paris, ORSTOM, Institut Francais de Recherche Scientifique Pour le Development en Cooperation. 367 pp.

Mutsaers, H.J.W. 1991a. Opportunities for second cropping in southwestern Nigeria. RCMP Research Monograph No. 4. Resource and Crop Management Program. International Institute of Tropical Agriculture, Ibadan. 28pp.

Mutsaers, H.J.W., 1991b. Farmer-related variables in on-farm trials:Their measurements and use in statistical analysis. In: On-Farm Research in Theory and Practice. H.J.W. Mutsaers & Walker, P. (Eds.), pp. 46-52. International Institute of Tropical Agriculture, Ibadan, Nigeria.

Mutsaers, H.J.W. & Walker, P. 1990. Farmers maize yields in S.W. Nigeria and the effect of variety and fertilizer: an analysis of variability in on-farm trials. Field Crops Research 23:265-278.

Usua, E.J. 1968. The biology and ecology of Busseola fusca and Sesamia species in southwestern Nigeria: Distribution and population studies. Journal of Economic Entomology 61:830-833.

Steel, R.D.G. and Torrie, J.H. 1980. Principles and Procedures of Statistics. 2nd ed. McGraw-Hill, New York.

Copyright 1997 The African Crop Science Society


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