African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 8, Num. 3, 2000, pp. 317-325

African Crop Science Journal, Vol. 8. No. 3, pp. 317-325

The influence of farmer perception on pesticide usage for management of cowpea field pests in Eastern Uganda

P. Isubikalu, J.M. Erbaugh¹, 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

(Received 14 April, 1999; accepted 30 September, 2000)

Code Number: CS00034

INTRODUCTION

Cowpea (Vigna unguiculata (L.) Walp) is a legume of considerable importance in arid and semi-arid tropics, being an integral part of traditional cropping systems throughout Africa (Jackai and Adalla, 1997). The crop maintains soil fertility, establishes rapidly thereby reducing soil erosion and soil temperature, and also lowers weed pressure (Zuofa et al., 1990). In eastern and northern Uganda, the crop is of critical importance as its leaves provide vegetable sauce to off-set early season famine. In many parts of the world, its leaves and grains are sold for income (Singh and Jackai, 1985; Ahenkora et al., 1997) and stalks fed to livestock (Steele et al., 1985).

Despite its importance, cowpea yields are relatively low in Uganda, averaging <500 kg ha^-1 (Adipala et al., 1997). These low yields are due to ravages of a multitude of pests (Omongo et al., 1997). Field and storage pests sometimes cause yield losses of up to 100% (Singh and Jackai, 1985; Omongo et al., 1997; Omongo et al., 1998).

In order to avert the pest problem, cowpea growers in eastern Uganda have resorted to frequent and indiscriminant use of pesticides (Omongo et al., 1997). It is believed by some farmers that pesticide application leads to reduced pest infestations and, consequently, increased cowpea yields (Isubikalu et al., 1999). In most cases, however, local sources of pesticides, farmers’ method of application and dosage are inconsistent, and the basis for their decision on which pesticide to use, when to spray, e.t.c., are largely unknown.

Although use of chemicals appears to be the most effective pest control method for cowpea production (Alghali, 1992; Edema and Adipala, 1996), chemicals are not used judiciously, leading to ineffective pest control (Omongo et al., 1997). Moreover, because of economic concerns and public sensitivity to environmental destruction, insecticide use is currently considered socially unacceptable (Giliomee, 1994; Jackai and Adalla, 1997). Nevertheless, it is generally agreed that commercial cowpea production can not be successful without insecticide sprays (Jackai et al., 1985; Nampala et al., 1999; Karungi et al., 2000a,b). Thus, attempts should be made to devise methods that reduce pesticide use. Integrated pest management (IPM) is a promising alternative.

For development of a suitable IPM package, farmer knowledge and perception of pesticide use, and rationales, need to be explored. This knowledge would assist scientists to advise farmers on what pesticides to apply at a given stage of the crop, dosage, frequency of application, and target pests. The purpose of this study was to establish and document farmer knowledge and perception with regard to pest control in cowpea production. The theoretical proposition that guided the study was that, farmers growing cowpea for market are likely to be using pesticides as their primary pest control measure. The possibility that commercial cowpea growers used more pesticide sprays than either subsistence or dual purpose cases for the purpose of achieving greater profit from higher grain yields was also investigated. The study also aimed at establishing whether there were differences in types of pesticide used among the commercial, dual purpose and subsistence cases.

METHODOLOGY

To answer "How" and "Why" questions regarding pesticide use and perceived efficacy on pests, a case study approach was adopted. The study was conducted in eastern Uganda covering the districts of Pallisa, Kumi and Katakwi, the major cowpea growing areas of the country (Sabiti et al., 1994; Adipala et al., 1997). A multiple cases study design was used to collect more compelling data and to make the overall study more robust (Yin, 1989). Cases (farmers) were categorised as subsistence, dual purpose and commercial, basing on their cowpea production goals. A total of 18 cases were studied. Of the three districts, Kumi was represented by two sites because cowpea production is most commercialised in the area compared to Pallisa and Katakwi which had one site each. Qualitative and quantitative data were collected for two consecutive years (1997 and 1998) using open-ended questioning (interviews) guided by a checklist, and direct participant observation. The checklist, developed basing on the objectives of the study, included site selection, land preparation, planting method and time, weeding time and frequency, pest control practices used, use of leaves and grains, harvesting and post harvest handling of cowpea. Generally, data were collected throughout the cowpea growing season. Information was gathered on activities involved at each stage of cowpea production and the rationale behind the choosen activity. The data were subjected to an analytic progression: from describing to explaining (Miles and Huberman, 1994). Information from the field (farmers’ words and actions) was transcribed. Appropriate data were selected, focussed, simplified and organised to satisfy the set objectives. General themes were identified and an explanatory framework made. This was also referred to as a natural progression (Rein and Scion, 1977), "Ladder of abstractions" (Carney, 1990) and data transformation (Geradii and Turner, 1987).

FINDINGS

Pesticides were used in Pallisa and Kumi, as the main pest control strategy because the varieties cultivated, Ebelat and black type ("Kenyan"), were susceptible to field and storage pests. Katakwi had only the subsistence category which did not use pesticides. The cases in Katakwi grew Icirikukwai, a variety considered to be resistant to pests. This variety was cultivated primarily for home consumption.

A number of pesticides were used by the cases (farmers in the study) to control cowpea pests. These included Ripcord, Super-ambush, Agrothoate, Dimecron, Agrocythrin, Sumithion, Thionnex, Dursban, Decis and Dimethoate (Table 1 ). Reasons as to why the cases used pesticides in the production of cowpea varied from farmer to farmer, but were generally used to kill pests and obtain clean seeds (Table 2). Farmers tended to spray irrespective of the presence or absence of pests. "Once a crop is sprayed 2 weeks from emergence, the chemical keeps within the plant, killing any insect that attempts to attack the crop", observed one subsistence case in Pallisa.

Choice of pesticides used in controlling cowpea pests. The choice of pesticide appeared to depend on its popularity, perceived efficacy, type and intensity of pests, crop growth stage, availability and harmlessness to the flora and fauna. In Pallisa, Super-ambush and Ripcord were the most commonly used pesticides by farmers because they were readily available on the market. Most cases in Kumi used more than one pesticide, throughout the growing season. However, one commercial case solely used Sumthion while Super-ambush and Agrocythrin were solely used by two different dual purpose cases. Among the pesticides used, some were perceived to be more effective at the vegetative stage (Table 3) while others were preferred for the podding stage (Table 4).

Vegetative pests and perceived effectiveness of pesticides in their control. Before flowering, target pests were mainly aphids (Aphis craccivora Koch). Other pests included Ootheca beetles (Ootheca mutabilis Walp), flower beetles (Mylabris sp.) and, to some extent, legume pod borers (Maruca vitrata Fabricius). Sumithion was generally perceived to be most effective pesticide at the vegetative stage (Table 3). However, one commercial case in Kumi (Abata) indicated that when cowpea seedlings were attacked by low populations of aphids, Agrothoate was the best pesticide. "Although Agrothoate is not very effective, it gives sufficient protection to the young seedlings," he said. This was supported by one commercial case in Pallisa who said that Agrothoate was the best for the young cowpea crop. However, since Agrothoate was not very effective, a higher concentration of 40-50 ml in 20 litres of water (depending on aphid intensity) instead of the normal 30 ml in 20 l of water, was used by this case. As the crop developed, Dimethoate was a better choice of pesticide for protection since infestation of several pests increased with crop growth. "Dimethoate is very effective against aphids and all other pests," the commercial case in Kumi added. According to him, Dimethoate had adverse effects on seedlings making them dry-out, and was therefore not good at flowering as it scorched the plants. On the contrary, one commercial case in Kumi (Abata) preferred Dimethoate on cowpea seedlings infested with aphids. His application rate was 30-40 ml depending on the pest intensity.

One commercial farmer in Kumi (Malera) preferred Dursban for controlling aphids and leaf eaters. However, "Dursban spoils cowpea flowers," he said. Sumithion was preferred by one dual and two subsistence cases in Kumi (Malera) for controlling vegetative pests. However, aphids did not respond to Sumithion during dry periods, observed one subsistence case. He preferred Dimecron which he applied at a rate of 40 ml in 20 litres of water. "Dimecron is the best pesticide against aphids but it is not effective against other pests," he said. On the contrary, one dual purpose case in Kumi (Abata) indicated that dimecron was only effective against low aphid infestations. He preferred super-ambush, but because his cowpea was still young (3.5 weeks), he mixed Dimecron (10 ml) with super-ambush (20 ml) in one spray tank (20 l). "I feared my crop to be spoilt by the "strong" ambush yet the aphids were many and they did not respond to Dimecron (30 ml/20l)," he explained.

Pesticides perceived as best for controlling flowering and podding pests. Among the chemical pesticides used by the cases, some were mentioned to be most effective at controlling flower and pod pests (Table 4). However, choice of pesticide for use at flowering and podding stages also varied from farmer to farmer. For instance, one commercial farmer in Kumi (Abata) used Super-ambush because it was considered more effective than Dimethoate (which he used during the vegetative stage) at controlling flower thrips (Megalurothrips sjostedti Trybom), and pod pests (legume pod borers and pod sucking bugs). He applied Super-ambush at 30 - 40 ml in 16 l of water depending on pest intensity. Another commercial case in Abata discontinued use of Dimethoate in favour of Sumithion and Thionnex, because Dimethoate scotched flowers and destroyed non-target insects. He mixed Sumithion (20 ml) withThionnex (20 ml) and applied the mixture at flowering."Sumithion kills insects while Thionnex promotes flowering," he said. He at times mixed Sumithion with Agrocythrin "to avoid development of pest resistance to the chemicals". During the podding stage, he resumed using Dimethoate. According to him, Dimethoate was the most effective pesticide against pod pests.

All the opinions about pesticides efficacy were based on actual experiences. One commercial case in Kumi (Malera) mentioned that Super-ambush or Decis were the most effective after the vegetative stage. However, he commonly used Super-ambush because Decis was not readily available on the market. One dual purpose and one subsistence case used Agrocythrin or Super-ambush depending on their availability in the market. They also indicated that Agrocythrin was better at podding stage. Sumithion, commonly used in Malera (Kumi), was discontinued at flowering for the reasons indicated in Table 5.

Timing and frequency of spray applications. Stage at which first spraying was administered and frequency of application varied across the three categories (Table 6). Most of the commercial cases (5) started spraying within the first three weeks from planting so as to protect the crop from early season pests, especially aphids and leaf beetles. "By that time, there are only a few aphids but we spray to prevent further infestation build-up" indicated the commercial cases. According to these cases, early spraying ensured effective crop protection against pest ravages. Another commercial case sprayed as early as 2 weeks from planting to minimise legume pod borer infestation. She said that legume pod borers folded cowpea leaves, making it difficult for the chemical (spray) to reach the cacoon. According to this case, the earlier the spray, the less chances of the pest hiding among cowpea leaves because the pesticide would destroy it before it hid in a cocoon. Hill and Waller (1988) also indicated that legume pod borers frequently web flowers, pods, and leaves together with trass.

One commercial case monitored his field for pests and began spraying after three weeks. He sprayed at 4.5 weeks from planting to eradicate aphids, Ootheca beetles and legume pod borers. None of the commercial cases applied chemical sprays after the fifth week from planting because to them pest populations would have reached high levels, caused irreversible damage and that control at this point in time would not be economically jusfified.

Some dual purpose cases commenced spraying 1-3 weeks after planting, but an equal proportion commenced spraying 3.5-5 weeks after planting. This reflected a transition towards commercia-lisation. The three dual purpose cases who commenced spraying 1-3 weeks after planting mentioned that they wanted to protect the crop from aphids and pod borers. "The legume pod borer infestation starts at leaf development stage and when the newly formed cowpea leaves begin folding. The insect hides in the leaves and cannot be reached by pesticides if you spray later than that," the cases explained. According to these three dual purpose cases,"first spraying requires a lot of pesticide to ensure that all cowpea plants in the field are properly covered with the chemical". They indicated that aphids were among the most serious pests of cowpea. According to the cases aphids damage cowpea seedlings causing leaf distortion and stunted growth, hence the need to control them early enough. The other three dual purpose cases who commenced spraying 3 - 3.5 weeks after planting did so to eradicate pests that were already in the cowpea fields. According to these cases, aphids, legume pod borers and Ootheca beetles had already invaded their cowpea fields. This reflected a curative measure since they sprayed purposely to kill the pests present. The delay to begin spraying was mainly attributed to the need to harvest "spinach" for early season vegetable.

Among the subsistence category, one case commenced spraying during the first three weeks after planting because one of his neighbours, a commercial farmer, did it that way. "I want to get as much cowpea yields as my neighbour. If my harvest is better, I intend to expand my cowpea production for money," he emphasised. He sprayed to protect his crop mainly from aphids and had the desire to shift towards dual purpose cowpea production. Two subsistence cases who commenced spraying 3.5-5 weeks after planting mentioned that it was the best time to eradicate cowpea pests (curative and protective strategy) in order to induce early flower production. "That is the period when insects get attracted to the leaves, feed and hide in the cowpea", the two subsistence cases said. Delayed spraying by the subsistence cases was mainly attributed to the expense incurred in using pesticides and the need for leaves. Thus, the more commercial oriented cowpea production became, the earlier first spraying was administered since "it led to better grain harvests". The subsistence cases commenced spraying late partly because of being unable to purchase insecticides but also because they were interested in eating the leaves, and so wanted to avoid pesticide poisoning.

The frequency of pesticide application varied depending on farmer category. The commercial category applied chemicals more frequently than the subsistence farmers. This reflected reduced interests in leaves and increased interests in grains among the subsistence and commercial categories, respetively. At flowering, chemical sprays were applied at an interval of 5-7 days depending on the intensity of pests in the field. During the podding stage, the interval was further reduced to 3-5 days. These sprays were aimed at controlling pod borers and pod sucking bugs (Clavigralla spp. especially Clavigralla tomentosicollis Stal). According to one commercial case, frequent spraying was very necessary during the rainy season. "When it rains during the flowering stage, I spray twice a week," she said. Her argument was that rain favoured extensive leaf formation and, as a result, led to increased legume pod borer incidence.

According to another commercial case, at podding stage the leaves were rough and could not be picked for consumption and as a result, the canopy attracted pests thus requiring more frequent sprays at podding. One commercial case (male) indicated that his shortest spraying interval was at flowering because it was the period when flower thrips invaded and destroyed flowers, and the time when pod sucking bugs (which he called ‘cotton stainers’) began invading cowpeas. One commercial case sprayed only 2 times. He was discouraged from spraying because his cowpea was heavily infected by aphids due to late planting. He predicted a long dry spell and a heavy aphid infestation later in the season. All the dual purpose cases sprayed 4-6 times. They sprayed every 10-15 days with or without pests. To them, that was the best interval since pesticides reduced in efficacy if applied at more than 2 weeks interval. "It is better and relatively cheap and more effective to provide fresh pesticides following a fortnights’ interval", explained one dual purpose case.

One subsistence case sprayed at an interval of 14-16 days to minimise pest damage and at the same time achieve better grain yields for consumption. Among the 3 subsistence cases who sprayed 1-3 times a season, one case could not afford the chemical. "My cowpea got a chance to be sprayed when I requested a neighbour who was spraying his sweetpotato garden to help me too," she said. Her cowpea was sprayed during the 8th week after aphids had already attacked and damaged the crop. Another subsistence case sprayed twice at an interval of about 20 days to secure some grains for seed.

IMPLICATIONS OF THE FINDINGS

The higher market value of the black cowpea variety which is susceptible to pest infestation has encouraged many farmers to cultivate it. This implies that commercial oriented farmers are prepared to grow susceptible varieties as long as they have high market value. Thus, they are ready to invest heavily on pesticide application to ensure high and quality harvest. For this category of farmers, scientists should; a) sensitise them on the safe use of insecticides and, b)develop a spray package that is cost-effective. The package should include threshold levels for the different pests, identify pesticides for a particular pest or crop growth stage, and cultural practices that compliment pesticide use.

Certainly, the high frequency of pesticide application by the commercial oriented cowpea growers to achieve better yields and profits, coupled with choice of a variety of pesticides depending on perceived efficacy has negative side effects on human health and the environment (Brader, 1979). It is therefore, important for scientists to educate farmers about the hazardous effects of pesticides and how to minimise pesticide poisoning.

Farmers’ interest in cowpea leaves for "spinach" to off-set early season hunger has a number of implications: a) dual purpose cowpea varieties are needed and/or leafy (vegetable) cowpea varieties should be identified for harvest of "spinach" throughout the year; b) leaf consumers are likely to be exposed to pesticide poisoning. It is, therefore, important that non-pesticide control measures and biodegradable pesticides be identified and recommended to farmers in this category.

For all the categories, farmers who used the highest frequencies of pesticides and sprayed earliest were in Malera (Kumi), an area where the crop was most commercialised. Choice of pesticide depended on farmers’ perception of its efficacy, pest pressure and non injuryness to the crop, but the commercial and dual purpose cases exhibited similar perception about pesticide efficacy. While use of Agrothoate against seedling pests was preferred by two commercial cases other cases (dual and subsistence) did not like it because it was perceived to be ineffective. The contradicting ideas from the farmers could be due to the relativity in establishing pesticide effectiveness and differences in the rates used. Also, while one comercial case used Sumithion without any complaint, one dual purpose case mentioned that it killed non-target insects. According to one subsistence case, Sumithion was not effective against flowering and pod pests. These contradicting perceptions about pesticide efficacy need scientific investigations to establish right dosages, time and frequency of application, and threshold levels for each economic pest.

The frequency of pesticide application in cowpea fields varied depending on farmer category. Also, commercial cases started spraying early (1-3 weeks after planting) while the dual and subsistence cases delayed spraying until 4-5 weeks after planting, to enable them eat cowpea leaves. This reflected reduced interests in leaves and increasing interests in grains with regard to commercialised cowpea production. For the commercial category, there is need to encourage judicious use of pesticides, i.e., based on economic injury levels and thresholds, rather than using calender sprays. For example, on cotton in Uganda, Sekamatte and Heneidy (1997) were able to reduce the number of sprays against cotton pests from 10 to 3, based on action thresholds. Also, although commercial and dual purpose cases indicated the need for early season sprays, and more frequent sprays at flowering and podding. Other studies at Makerere University have demonstrated that early season spraying is uneconomical, and that only 1-2 sprays is/are needed at bud initiation/flowering and at podding (Karungi et al., 1999a,b; Karungi et al., 2000b). Moreover, both Karungi et al. (2000a) and Nampala et al. (1999) have shown that early season pests, i.e., aphids, can be controlled by cultural practices (early planting and close spacing), and seed dressing making it possible for the subsistence and dual purpose cases to eat the cowpea leaves.

The findings also indicated that farmers perception of pesticide efficacies differed considerably, but demonstrated a clear understanding about the target pests for each pesticide and when to use or stop using each pesticide, and the hazardous effects of the pesticides to the cowpea plant and beneficial flora and fauna. Thus, farmer knowledge should be included in developing IPM and other programmes. Additionally, farmers seemed ignorant about the potential danger of pesticides in the process of application since most of them did not wear protective clothing. Therefore, the importance of wearing protective clothing should be demonstrated to the farmers as well as informing them about the dangers and reduced cost effectiveness due to frequent pesticide application.

ACKNOWLEDGEMENTS

This paper is a joint output of the Rockefeller Foundation Forum Project on Development of an Integrated Pest Management package for cowpea farmers in Uganda (Grant RF 95007 # 77) and IPM/CRSP USAID Grant No. LAG-4196-G- 00-3053-00.

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