African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 7, Num. 4, 1999, pp. 539-548

African Crop Science Journal, Vol. 7. No. 4,  pp. 539-548, 1999                                                              

Influence of Farmer Production Goals on Cowpea Pest Management in Eastern Uganda: Implications for Developing IPM Programmes

P. Isubikalu, J.M. Erbaugh,¹ A.R. Semana and E. Adipala²*
 Department of Agricultural Extension/Education, Makerere University,
P. O. Box 7062, Kampala, Uganda
¹International Programs in Agriculture, Ohio State University, Columbus Ohio 53210, USA 
²Department of Crop Science, Makerere University, P. O. Box. 7062, Kampala, Uganda

* Corresponding author; E-mail acss@starcom.co.ug

Code Number: CS99045

ABSTRACT

We investigated using a case study the influence of differing  production goals on cowpea production and pest management practices.  The cases (farmers) were characterised as commercial, dual purpose and subsistence depending on the primary goal of production.  Production goal influenced cowpea acreage, varietal choice, seasonal planting, perception of problematic pests, and stage and frequency of pesticide application. Farmers preferred to use pesticides, as the primary method of pest control, because they insured a marketable crop, were associated with yield increases, permitted two season cropping, and reduced demand for labour at labour peaks during the cropping season.  Pesticides  were used by the majority of farmers in the area. The only limitations to pesticide use were local availability and cost.  Besides the use of pesticides farmers had local knowledge on alternative methods for controlling pests such as early planting, variety choice, weeding, leaf picking and intercropping.  Generally, farmers were unknowledgeable (or uniformed) about cowpea diseases.  Future research should seek to introduce resistant varieties; investigate efficacy, timing and rate of pesticide application; and, educate farmers regarding proper pesticide use and safety.

Key Words:  Pesticides, resistant varieties, Vigna unguiculata

RÉSUMÉ

Nous avons examiné en utilisant une étude de cas, l’influence des différents objectifs de production du niébé et les pratiques de gestion des pestes.  Les cas (agriculteurs) étaient caractérisés comme commerciaux, double objectifs et  subsistance dépendant de l’objectif primaire de production.  L’objectif de production influençait la superficie emblavée par le niébé, le choix variétal, la plantation saisonnière, la perception du problématique des pestes, le stade et la fréquence d’application des pesticides.  Les agriculteurs préférraient l’utilisation des pesticides comme méthodes primaires de gestion de pestes parce qu’ils assurent une culture commercialisable, étaient assocées à l’augmentation des rendements, permettent deux saisons culturales, et réduisent la main d’oeuvre aux périodes de pointe des travaux durant la saison culturale.  Les pesticides étaient utilisés par la majorité des agriculteurs dans la région. Les seules limitations d’usage des pesticides étaient la disponibilité locale et le coét.  En plus de l’utilisation des pesticides les agriculteurs avaient une connaissance locale sur les méthodes alternatives de contrôle des pestes telles que la plantation précoce, le choix variétal, le sarclage, le ramassage de feuille et l’association des cultures. Générallement les agriculteurs n’étaient pas au courant des maladies du niébé.  La recherche future devra chercher à introduire des variétés résistantes, étudier l’efficacité, le temps et le taux d’application des pesticides, et éduquer les agriculteurs sur l’utilisation propre et la sécurité de pesticides.

Mots Clés:  Pesticides, variétiés résistantes, Vigna unguiculata

Introduction

Cowpea is an important food crop in many parts of the semi arid tropics (Jackai et al., 1985).  In eastern Uganda, where nearly 90% of the country’s crop is produced (Adipala et al., 1997), cowpea production is in transition. It was traditionally grown almost exclusively as a food crop for domestic consumption, however, with the demise of cotton as the main cash crop and the emergence of important external markets, many farmers in the region now grow cowpea for cash markets (Sabiti et al., 1994).    

Despite its importance, cowpea yields are relatively low, averaging <500 kg ha^-1 (Adipala et al., 1997).  The primary production constrain is a diverse and destructive pest complex that sometimes results in  total crop failure in the field and considerable losses in storage (Sabiti et al., 1994; Adipala et al., 1997;  Omongo et al., 1997; Omongo et al., 1998).  The major field insect pests are aphids (Aphis craccivora Koch), leaf beetles (Ootheca spp.), flower thrips (Megalurothrips sjostedti Trybom), pod borer (Maruca vitrata Fab.) and a complex of pod sucking bugs (Hemiptera) (Omongo et al., 1997). 

In order to control insect pests, cowpea growers in eastern Uganda are increasingly using  chemical pesticides (Erbaugh et al., 1995; Omongo et al., 1997).  The increased use of chemical pesticides may be an adaptation by farmers to changing  production goals.  It is generally agreed that cowpea cannot be successfully grown commercially without the use of insecticides (Jackai et al., 1985).  Nevertheless, questions of economic and environmental sustainability and negative impacts on public health have been raised in regard to pesticide use (Jackai and Adalla, 1997).

 Thus, there is a pressing need to develop suitable alternatives to pesticides that combine various control components into appropriate integrated pest management (IPM) packages for farmers with different production orientations (Kristen, 1994; Palis, 1998). IPM employs several techniques such as pest monitoring, biological control agents, insecticide sprays, cultural practices and host plant resistance. These techniques are then combined to form a pest management system that is both user and environment friendly (Brader, 1979).  However, the development of IPM packages hinges upon  knowledge of farmer production goals and associated production practices (Croxton, 1994).  To date in Uganda, this knowledge is lacking and has impeded the development of viable pest management alternatives.

Integrated pest management (IPM) is often promoted as an approach for controlling destructive pest populations while simultaneously eliminating or reducing the use of chemical pesticides (Jackai and Adalla, 1997).  However, its limited adoption by small-scale farmers in developing countries has been noted (Kiss and Meerman, 1991; Morse and Buhler, 1997).  Since farmers co-evolved with cropping systems, their cumulative knowledge and experience with crop production represents a potential source of valuable information upon which successful IPM interventions can be designed and constructed.

The use of cowpea production goals as a concept for differentiating farmers is suggested by the transition in market relations from primarily production for subsistence, to production for cash markets.  Production goals can be arranged on a continuum ranging from subsistence, where all the crop produced is consumed domestically leaving no surplus for sale; to a transition or dual purpose phase, where  portions of the crop are both consumed and  sold in markets; to a commercial goal, when all or most of the crop is marketed (Palis, 1998). 

There is substantial evidence that links production goals with production practices,  such as  pest management (Seckler, 1993, Ruthenberg, 1980).   In fact, mode of production is profoundly influenced by market relations (Barker, 1989). Subsistence production is commonly associated with production practices such as multi-cropping, reliance on family labour, and other inputs endogenous to the farming system.  Commercial crop production is associated with mono-cropping, use of hired labour, and increased use of externally purchased inputs, including seed fertilisers and pesticides. 

The objectives of this study  were to examine the influence of different production goals on the production practices (pest management in particular) of cowpea in eastern Uganda and to ascertain the implications of farmer knowledge in the development of  IPM strategies for different producer groups.

 Methodology

A multiple case study that included cases (farmers) from the districts of Pallisa, Kumi and Katakwi was initiated in 1997 and ran for a period of 2 years.  These three districts represent some of the major cowpea growing areas of the country (Sabiti et al., 1994).  “How and why” questions pertaining to cowpea production and pest management dictated the use of a case study approach in order to provide an in-depth understanding from the farmers perspective of the relationship between production goals and practices.

Three categories of cowpea farmers were designated.  The categories involved those (i) growing the crop mainly for cash  (commercial);  (ii) growing primarily for home consumption (subsistence); and, (iii) those growing for cash and home consumption (dual purpose).  Farmers in each category were selected based on previous surveys (Adipala et al., 1997; Adipala et al. 1999) and interviewed with knowledgeable local extension agents, and other local informants.  The main criterion used for  farmers’ selection was their “representativeness”  of a particular production category.  Selection of farmers, therefore, was based on purposive sampling. Meetings were held with selected farmers to explain study objectives, and to obtain their consent and participation in fieldwork.  A total of 18 cases were eventually selected. 

Theoretical propositions and a case study protocol were developed prior to fieldwork.  Data were collected using interviews, direct observation and participant observation.  This was done over  four growing seasons (March-June, 1997;  August-November, 1997; March-June, 1998 and August-November, 1998).

Findings

Land use and cowpea production. Although analysing the relationship between production goal and socio-economic background was not an objective of this study, the summary descriptive data presented in Table 1 appear to indicate a relationship between land resource base and commercial goal orientation of cowpea growers.

Table 1.   Production goals and cowpea land use in eastern Uganda¹
                                                                                                            

¹All figures represent averages for farmer sample sizes; n = 6 farmers for each production goal category

On average, the commercial cases in the study had the largest land holdings.  Interestingly, however, the subsistence cases had larger land holdings than the dual purpose cases.  The commercial category had more acreage  under crop production, followed by the subsistence cases; the dual purpose category had the least total crop acreage on average.  This order changed when it came to land under cowpea production.  On average, the commercial category  had more land under cowpea production (2.4 ha), followed by the dual purpose (0.9 ha), and subsistence category (0.5 ha).  This rank order may be explained by the shift  towards commercialisation of the crop, due to  better profit margins.  This is supported further by the observation that cases who could afford to buy pesticides cultivated more land for cowpea production than those who could not afford. 

Available land to farmers appeared not to be an issue with regard to size of cowpea fields.  For instance, subsistence farmers in Katakwi had more land than most of the cases but cultivated smaller portions.  However, lack of capital and inadequate labour seemed to be the main factor restricting cultivation of larger acreage (Isubikalu, 1998).

Variety selection. Choice of variety appears to depend on production goal and locality. The cowpea varieties  grown in the study region are Icirikukwai (semi-spreading, indeterminate), Ebelat (erect, determinate) and a black seeded variety called Kenyan. No improved cowpea cultivars were observed to be grown among all the cases.  Icirikukwai was grown solely for local consumption of leaves and grain.  The Kenyan variety was grown solely for sale in Kenya.  Local farmers do not consume the leaves nor grain  produced by this variety because of the higher market value when sold in Kenya. Ebelat was grown by both subsistence, dual purpose (transition) and commercial farmers.  Three of the farmers   grew both Ebelat and Kenyan varieties.  The market value for Icirikukwai was less than for the other two varieties (Icirikukwai, 800 Uganda shillings (Ug. Shs.) per kg; Ebelat = 1350 Ug.Shs./kg; and, Kenyan = 2500 Ug. Shs./kg). Explanations for the low market value of Icirikukwai were that it produced a small seed, took longer to cook and had low yield potential.  As one farmer commented, "In order for one to get better and more profits, it is better to sell fewer things and get more, than selling more and getting less".

Farmers indicated that they needed to spray both Ebelat and Kenyan varieties in order to obtain a crop.  According to commercial farmers who produced Kenyan, this variety required frequent spraying.  Farmers indicated that they did not spray Icirikukwai, thus  indicating that this variety may exhibit some level of resistance to local pests and diseases. The additional costs for purchasing and applying insecticides, coupled with the transportation costs for selling the Kenyan variety in external markets probably explain why this variety was only grown by commercial farmers.

Seed acquisition. All cases, except two commercial and two subsistence farmers,  purchased seed for planting.  Reliance on purchased seed was attributed to the rapid destruction of stored grain by the cowpea bruchid (Callosobruchus spp.).  Most farmers reported inability to store cowpea - in the pod or threshed for longer than three months.  Local practices for storing grain such as in pots or traditional granaries were considered to be ineffective, inconvenient and labour intensive.  Thus, in many cases, the incapacity to store cowpea generally leads to its rapid consumption or sale following harvest.    The only exceptions to these commonly held perceptions were two commercial farmers who treated cowpea with malathion or actelic in order to reduce damage in storage, and two subsistence farmers who grew the variety Icirikukwai.  Subsistence farmers indicated that stored Icirikukwai was less affected by the cowpea bruchid.

Seasonal planting. Traditionally, cowpea is only grown during the second season (short rains).  In the traditional rotation it follows the harvest of first season finger millet (Isubikalu, 1998).  All farmers in this study grew cowpea during the second season.  While, 13 of 18 farmers grew cowpea during both seasons.  Therefore, only 5  farmers in this study grew cowpea during the first season (long rains).  The reasons farmers gave for preferring the second season were: heavier pest pressure during the first season; constrained labour supply during the first season due to production of finger millet (Eleusine coracana L. Gaertn), groundnuts (Arachis hypogea), cassava (Manihot esculenta) and sorghum (Sorghum bicolor); and, heavier first season rains leading to additional vegetative growth, delayed seed ripening and reduced grain yields.  

Commercial and dual purpose growers were more likely than subsistence producers to grow  cowpeas during both seasons because they had the resources to purchase seed, insecticides, and pay for additional labour.   They were also more dependent on the cash flow generated by the crop. These farmers advanced several reasons as to why the crop should be grown during both growing seasons of the year round.  These reasons include:  to insure a varied and constant supply of food (leaves and grain); to insure cash flow; to provide seed for the second season; and, according to several farmers “cowpea can now be grown anytime as long as it is sprayed”. 

The five subsistence farmers  who grew cowpea only during the second season reported that pest pressure and labour demands for other crops were less, and that they could not afford to purchase seed and pesticides.  With reference to pest pressure, subsistence farmers specifically mentioned that there were fewer foliage beetles during the second season.  Since subsistence farmers were more dependent on cowpea leaves as a food source and were less able to afford pesticide purchases their concern with leaf defoliation by foliage beetles appears to be justified.

Planting date. Early planting is recognised by most farmers as a key factor in moderating aphid damage on cowpea. However, several factors impeded the capacity to plant early.  First, weather patterns were reported to be more erratic than in the past, and thus reliance on traditional planting dates less dependable.  Second, lack of labour, particularly during the first season, makes early planting more difficult. In order to stretch labour supplies, several farmers relied on relay planting of cowpea.  In addition, farmers reported  that using relay planting prolongs leaf availability and reduces the risk of total crop loss due to unpredictable climatic conditions (Isubikalu, 1998).

 For the first growing season, April-June, planting in April is considered early planting.  For the second growing season, June-September, planting in June is considered early planting.  Commercial and dual purpose farmers were more likely to pracatice early planting.  However, commercial growers indicated that cowpea performed well irrespective of planting date, as long as insecticides are applied throughout the growing season.

Leaf harvesting. Cowpea leaves are harvested prior to flowering to make a "spinach" sauce.   After flowering, leaves lose desired texture and palatability. The local varieties Ebelat and Icirikukwai were considered to have the most palatable leaves.  Most of the farmers harvested leaves for home consumption. However, only  two farmers (one commercial and one dual purpose) harvested leaves and sold them in local markets. 

Farmers believed that leaf picking also increased yields and reduced pests.  According to farmers, foliage beetles and pod borers were attracted to dense leaf canopies, and reducing the leaf canopy through leaf picking, exposed pests to sunlight and improved the performance of pesticide applications. Thus, in addition to food diversification, leaf picking was used as a pest control practice.

Most farmers waited for 3-5 days, to pick leaves,  following pesticide application. Although farmers preferred picking  leaves  before spraying, some women growers indicated that they picked leaves immediately after spraying because of “hunger and poverty”.

Weeding. All farmers in the study reported weeding their cowpea fields only once per season. The commercial farmers weeded one to two weeks earlier than dual purpose and subsistence farmers.  Late weeding of cowpea was attributed to labour  demand for activities in other crop enterprises such as harvesting finger millet, weeding casava, and seed bed preparation for sweetpotatoes.  In addition to recognising the beneficial effects of weeding on plant health and yield, four commercial farmers preferred earlier weeding because they thought that weeds created an environment that harbored pests, particularly foliage beetles, and that weeds wasted pesticides.

Cowpea cropping system. Most farmers commonly grew cowpea as an intercrop with cassava or maize during first season.  Three commercial farmers and one dual purpose grower sole cropped cowpea indicating potential association  of production goal with cropping system.  The main reasons provided by farmers for intercropping was to diversify food supply; to keep fields in continuous production, and to maximize labour inputs.  Only one farmer expressed  awareness that intercropping reduced pest infestation, particularly of Maruca and thrips.   Commercial farmers were less interested in intercropping because they believed that  it lowered cowpea plant population and cash returns.  Subsquently sole cropping was more pronounced during the second season in which all commercial cases sole cropped their cowpea.  Among the subsistence and dual cases  who intercropped during the second season, cowpea/greengram and cowpea/cassava intercrops were the most common cropping systems.

Perception of priority pests. Farmers indicated that aphids (Aphis craccivora), pod borers (Maruca  vitrata) and different pod sucking bugs (Hemiptera) were the most important pests (Table 2).  Other insect pests mentioned by cases were foliage beetles (Ootheca mutabilis), flower beetles (Mylabris spp.), and thrips (Megalurothrips sjostedti).

Table 2.  Farmer perception of priority cowpea pests (eastern Uganda)

Aphids were considered by most farmers to be the most important pest of cowpea particularly at the vegetative stage prior to flowering.  Subsistence farmers, who grew cowpea primarily for leaf harvest, also ranked foliage beetles as very important pests. 

In general, commercial farmers were more concerned with seed eating insects (pod borers and suckers), while subsistence cases considered leaf eating pests to be more important, reflecting the differing production priorities of the two different categories of producers.  However, for dual purpose farmers, both pod and leaf insects were of equal importance.

Pest management. Most farmers with the exception of two subsistence farmers in Katakwi relied on pesticide sprays as the primary pest control strategy. Farmer perception that cowpea yields are enhanced by pesticide application is clearly demonstrated  based on results presented in  Tables 3 and 4.  Commercial farmers, who sprayed more frequently, had higher yields than did the other two production categories.  Farmers’ stated belief was that frequent sprays resulted in  increased yields.  

Table 3.   Average yields by production goal categories in eastern Uganda

All figures represent averages for farmers (n = 6) by production goal categories.

Table 4. Cowpea stage at first spraying and frequency of application in eatern Uganda

Commercial cowpea growers  sprayed earlier and they also sprayed more frequently than did transition and subsistence growers (Table 4). Commercial growers were more interested in the grain than leaves, thus, they viewed spraying as a form of crop insurance.  Additionally, several commercial growers commented that reliance on sprays permitted cowpea to be planted later.  This allowed them to divert labour for planting cowpea to other farming activities.

Most commercial growers began spraying 2 - 3 weeks after germination to prevent the build up of pest populations. The frequency of sprays (chemical application)  ranged between  6 - 10 times per season.  Transition farmers tended to commence their spray programmes 1 - 2 weeks later after the commercial farmers; they sprayed less frequently, generally 4 - 6 times  per season; and their rationale for spraying was to control pests that had already accumulated in their cowpea fields. Both commercial and transition growers indicated that spraying after the sixth week was not as effective as spraying earlier because of their belief that leaf canopy protected the insects from the spray.

Farmers who delayed spraying until after the 6th - 7th week after germination did so in order to allow cowpea leaves to be harvested before spraying or because they could not afford to purchase pesticides.  Farmers indicated awareness of the health hazards from eating leaves that had been recently sprayed. 

Among the commecial cases the interval between spraying was longest (10 days) during the vegetative stage; it was reduced to 5-7 days during flowering; and further reduced to 3-5 days during podding.  Again, this appears to indicate the interest of commercial farmers in protecting grain production.  It also indicates an awareness of different pests species that may be present at different stages of plant growth.

Cowpea farmers used 10 different commercial pesticides.  The most commonly used pesticides were Super-Ambush and Dimethoate.  There was a high degree of variability in farmer perception of pesticide efficacy; pesticide efficacy at different growth stages; pesticide efficacy on different pests; pesticide formulation (concentration); and perceptions of pesticide impact on plant health and pollinators.  In general, three perceptual criteria emerged that impacted farmer choice of pesticide: pest control efficacy, minimising impact on plant health and pesticides  availability  in local markets.

Discussion

Different production goals appear to influence the production practices and pest management of cowpea in eastern Uganda.  Farmer production goal influenced cowpea acreage, variety choice, seasonal planting, perceptions of problematic pests, and stage and frequency of pesticide application. 

The increasing commercialisation of cowpea has led to changes in the production system including the intensified use of land, labour and capital inputs.  Cowpea is now regularly planted during both cropping seasons;  seed is generally purchased from markets and not saved from previous season harvests; and, pesticides are relied upon as the primary form of pest control.  

Increasing commercialisation of cowpea production and increased use of pesticides appear to be mutually reinforcing.  Increased use of pesticides associated with commercialisation is a trend noted before in Uganda with other crops (Erbaugh, 1997). Pesticides are the main means currently available for controlling the pest complex found on cowpea, and cash is required for  pesticide purchases.   Application frequency appears to be increasing and this might lead to pesticide resistance (Brader, 1979).   Several farmers in this study associated the increase in aphid populations with the increased use of pesticides.  This is an  indication that excessive use of pesticides is resulting in a “pesticide treadmill”, where indiscriminate pesticide use reduces beneficial insect populations, engendering more frequent use of pesticides.  These conditions appear to indicate a favourable environment for developing IPM strategies that seek to reduce the use of chemical pesticides (Jackai and Adalla, 1997).

IPM strategies  that reflect different production goals and perceptions of problematic pests  need to be developed.  Two pest management trends associated with production goals are revealed by the case study.  First, earliness and frequency of pesticide application increased moving across the production goal continuum from subsistence to commercial production.  Second, interest in grain  over leaves moved in the same direction, from subsistence to commercial production.  These two trends appear to explain the association between grain production and intensive pesticide use, and can be merged to suggest IPM strategies for the two polar types of production systems.

Commercial and some dual purpose cowpea growers producing more susceptible varieties for lucrative niche markets used pesticides more intensively.  They sprayed earlier and more often  to ensure high quality grain harvests.  As a result,  these same farmers were more concerned with insects that damage or destroy pods and grains.  The IPM package for this group of farmers should include the development and dissemination of economic thresholds and crop scouting procedures to encourage farmers to apply pesticides only when needed. These two practices will help rationalise and reduce the use of pesticides through the use of combining compartible control strategies (IPM) as opposed to sole use of calendar based spray programmes.  Research work at Makerere University has clearly demonstrated that early season spraying to reduce grain yield losses is unnecessary and that 1-2 spray applications at bud initiation/flowering and at podding is more economical (Karungi et al., 1999; 2000).

For subsistence and some dual purpose farmers more interested in leaf harvests, the primary concern was with insects that cause defoliation.  For this group, pesticide use should be discouraged to protect consumers from exposure to pesticide poisoning.  Instead, the efficacy of cultural, locally available bio-rationale products or biodegradable pesticides should be investigated.  Additional research should also investigate the level and impact of defoliation caused by leaf eating insects and identify specialised varieties for leaf production that could be harvested throughout the year.

Finally, all farmers prioritised aphids and the cowpea bruchid as important pests.  Farmers were aware and research has demonstrated that aphids can be effectively controlled by early season planting, higher plant population, intercropping  and seed dressing, making it possible for farmers to eat leaves without fear of poisoning (Karungi et al., 1999; Nampala et al., 1999).  The fact that these practices are not limited to farmers without economic capacity  is recognised.

Future research direction. Clearly, the findings of this study indicate a need for follow-up studies.  Pesticide management research, including timing, application rate and efficacy of different pesticides should be emphasised along with the development of relatively simple action thresholds.  The concept of field scouting has already been introduced to the farmers (Erbaugh et al., 1995).  However, this practice in combination with action thresholds needs to be disseminated to more growers.

Strategies to control all the pests and diseases which attack cowpea in eastern Uganda may not be viable.  Efforts must therefore focus on determining which pests are the most damaging and the critical stage(s) of plant growth at which damage occurs.   For instance, farmers perceive aphids as the most important pest, however, other studies (Omongo et al., 1997; Karungi et al., unpubl.) indicate that Maruca and thrips are the most important.  Farmers are generally unaware of thrips and their damage.

The germplasm base appears to be limited.  Thus, the introduction and field testing of new genetic cultivars with resistance to pests and diseases should be considered.  Currently, improved germplasm developed at the International Institute of Tropical Agriculture (IITA) are being field tested by Makerere University Cowpea Improvement Program.  The existing sources of resistance should be fully exploited.  As indicated by several farmers, the possibility that the land race, Icirikukwai, is resistant to field  and storage pests  requires more investigation.

The impact of certain agronomic practices on various pests needs to be evaluated.  Practices such as early planting, plant spacing, earlier and multiple weedings, leaf harvesting and intercropping have demonstrated effects on lowering pest populations.

All farmers in this study planted cowpea by broadcasting the seed by hand. As a result, field plant densities were uneven resulting in reduced land use efficiency, low yields and potentially providing a favourable habitat for pests and weeds.  Farmers preferred to broadcast seed because this method of sowing was perceived to be faster and saved labour.  Despite farmer reluctance to row plant cowpea, this practice should be introduced on a trial basis for several reasons.  First, row planting will facilitate the evaluation of different plant densities on pests and disease occurrence.  Higher plant populations are expected to reduce aphid infestations with a concomitant reduction in aphid-borne diseases (Ogenga-Latigo et al., 1992; Edema et al., 1997).  Second,  row planting might reduce seed wastage that occurs with broadcasting and save farmers money.  Third, row planting may facilitate easier weeding, a critical labour and yield constraint.  Fourth, row planting may lead to higher per hectare yields. 

Farmers’ lack a well developed concept of natural enemies, pesticide resistance, and pesticide safety including handling and potential negative impacts on human health.  This area warrants further investigations.

Acknowledgement

This study is part of a broader Makerere University project to develop integrated pest management system for cowpea farmers in Uganda which is funded by the Rockefeller Foundation Forum on Agricultural Resource Husbandary Grant RF 95007 # 77. The second author is supported by  the Integrated Pest Management Collaborative Research Support Program USAID Grant No. LAG-4196-G- 00-3053-00.

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©1999, African Crop Science Society