Fabrication and Evaluation of a Probe Trap for Monitoring Cowpea Weevil (Callosobruchus Maculatus) Infesting Stored Cowpea
CHAPTER ONE
Objectives of the Study:
- To fabricate an insect probe trap for monitoring C. maculatus in stored cowpea.
- To evaluate the performance of the modified probe trap on C. maculatus infesting stored cowpea.
- To assess the cost benefit analysis of the fabricated probe trap.
CHAPTER TWO
LITERATURE REVIEW
Black Eyed Pea – Vigna unguiculata (L.) Walp
Cowpea, Vigna unguiculata L. Walp is one of several species of the widely cultivated genus Vigna, and one of the most important food legume crops in the semi-arid tropics covering Africa, Asia, Southern Europe, Central and South America (IAR, 2012). Cowpeas are drought-tolerant and warm-weather crop, well-adapted to the drier regions of the tropics, where other food legumes do not perform well (Singh et al., 2003). The major cowpea producing countries are Nigeria, Burkina Faso, Uganda, Niger, Senegal and Tanzania. According to Peace (2015), the global annual production of cowpea was about
5.4 million tons of which Africa accounts for about 5.2 million tons. Similarly, it was reported that Nigeria, being the largest producer of cowpea in the world accounts for more than two million metric tons (Adeola et al., 2011) which represents about 58 % of the total world cowpea production annually (Peace, 2015).
Like many other grain crops grown in the semi-arid tropics, cowpea post-production system in developing countries is an important constraint; in particular, bruchids can destroy a granary full of cowpea in less than one year (Carlos, 2004). Even if the cowpeas are not completely consumed, consumers demand a substantial price discount before they will buy bruchid damaged cowpea (Carlos, 2004). Over the years, the difficulty faced by many developing countries is satisfying the nutritive food requirement of their teaming population amidst world population increase thus further adding to global food security concerns (FAO, 2013). The global population increase according to FAO (2013) translates into 33 % more human mouths to be fed by the year 2050, with the greatest demand growth in the poor communities of the world (e.g. Africa). According to Alexandratos and Bruinsma (2012), food supplies would need to be increased by 60% in order to meet the global food demand by the year 2050. Thus, reduction of post-harvest losses is a critical component of ensuring future global food security (FAO, 2013).
While cowpea play a key role in subsistence farming and livestock fodder, the cowpea is also seen as a major cash crop by Central and West African farmers, with an estimated two hundred million (200,000,000) people consuming cowpea on a daily basis (Langyintuo et al., 2003). According to Langyintuo et al. (2003), at least two hundred and eighty five thousand (285,000) tons of cowpea is shipped among countries in the African region each year. Cowpea trade in West and Central Africa is clustered around Senegal and Nigeria. In Nigeria, cowpea passes from farmers to consumers through various marketing channels; farmers usually sell their surpluses to rural assemblers, who in turn sell to urban wholesalers directly or through commission agents (Carlos, 2004). Large wholesalers hold large stocks for sale to retailers when prices are high enough to pay for cost of procurement, storage, handling and a margin for profit. Factors influencing price setting are: grain quality, selling time, transport, storage, market tolls, and taxes (Carlos, 2004).
Storage losses in West Africa are substantial in spite of the use of storage insecticides by merchants, coupled with chemical hazards. Selling early in the storage season results in a loss of income because prices rise as grain legumes become increasingly scarce. However, deterioration in grain quality is not just a problem faced by farmers alone because traders at all levels within the system also suffer storage losses (Carlos, 2004).
CHAPTER THREE
MATERIALS AND METHODS
Research Location
Fabrication and evaluation of the performance of the modified probe trap on C. maculatus infesting stored cowpea was conducted in the Entomology Laboratory of Nigerian Stored Products Research Institute (NSPRI), Kano Sub-Station (Coordinate 11o30’N, 8o30’E) Nigeria, between March 2016, to October 2016, at average temperatures of 29 ± 3 oC and 52 to 75 % relative humidity.
Trap Development
Materials for fabrication of probe trap
Materials used to fabricate the trap included; Anvil, Bench-vise, work/vise bench, 1 mm plumbing sockets; threaded male, threaded female and plain respectively (Conex, 2017), plastic cone (cosmetic container), sand paper, scissors, saw-blade, plastic gum, glue gum, screw driver, measuring tape, transparent ruler, coloured plastic materials (2.5 mm thick), plastic funnel, hammer, chisel, steel pipe (1 mm), perforated steel plate (from obsolete automobile silencers and heavy duty equipment casings), needle/office pins, knife, iron sponge, wood-ash, soap and water.
Fabrication and coupling procedure
Perforated steel material got from obsolete automobile parts were first de-coupled using chisel, hammer and anvil, and were straightened back into a flat plate, washed with wood- ash, iron sponge, soap and water to remove rusts.
CHAPTER FOUR
RESULTS
Fabricated Trap and its Components
The newly fabricated probe trap has a transparent light lure window cap (figure 2), perforated body made of steel from obsolete automobile silencers, and other body parts made from locally sourced plastic materials as shown in plate XIV and XV.
The probe body of the trap has a pointed end made from cosmetic containers, beneath which is the trapping chamber made of plastic materials. The plastic funnel is lengthy, appearing as tunnel inside, and the reservoir which is 12.5 cm deep, is also detachable (plate XV).
CHAPTER FIVE
DISCUSSIONS
Fabricated Trap and its Components
The insect probe trap was fabricated from locally sourced materials. Different light sources on the cap were evaluated on how to trap C. maculatus in stored cowpea (Arnold et al., 2016). The 4 mm holes on the traps body could permit entry of C. maculatus (3 mm) and other pulse insects of 4 mm and below in size, while precluding entry of cowpea grains into the trap (Neethirajan et al., 2007). Which means the trap can be used to detect other pests of cowpea like C. subinotatus. Improvised plastic materials and other components used in fabricating the traps were of the desired dimension and shape, and as such fitted well.
Summary
With the major aim of developing an improved probe trap for monitoring/detecting C. maculatus in stored cowpea, the incorporation of light source into the probe trap revealed some level of improvement in detecting cowpea bruchids within 24 hours trapping duration, and was also economically profitable (cheaper) due to locally sourced materials. The best light which detected the bruchids most among the selected light sources was the natural (ambient) light source because it had the least light intensity. However, the effect of light colour was insignificant in the study. Four millimeter (4 mm) holes on the modified trap permits entry of C. maculatus (3 mm) and could permit other larger cowpea bruchids like C. subinotatus.
Conclusions
Based on the result obtained from the study, the following conclusions were made:
- The modified probe trap was fabricated using locally sourced
- Natural (ambient) light trapped 42 % of bruchids infested into samples and was the best light source to improve the performance of the probe trap among the selected light sources which means that the cost of trap production (i.e. artificial light source) as well as use-maintenance (i.e. battery) is reduced for fabricators
- The modified probe trap catch of 13 bruchids and above within 24 hours trapping period, at average temperature of 29 ± 3 oC and 52 to 75 % relative humidity has reached the economic injury level (EIL) and should be fumigated. Catches between 12 and 5 brchids is within the action threshold (AT) and control measures must be applied to prevent pest populations from reaching the economic injury level. While catches of 2 or < 5 bruchids is below the action threshold (AT) and sampling must be done again before a growing insect population can cause economic losses.
- The modified probe trap was N75 cheaper compared to the standard probe trap and had higher return per naira invested in the study area.
Recommendations
From studies carried out in this work, recommendations are that:
Ambient light source should be incorporated into probe traps made for detecting cowpea beetles infesting stored cowpea.
It is advisable for the people concerned (grain handlers) to use the modified and locally fabricated probe trap because the cost compared to the standard (imported) is less, it is locally available and does not depend on foreign currency.
The new improved design of probe trap should be adopted for commercialization in order to make it readily available to users.
Another modified trap of this design (i.e. with ambient lighted cap) can have a pheromone in order to increase its trapping ability.
It is also desirable to extend the study to different types of stored products under various climatic conditions on other stored grain pests to determine how to best control stored grain insects using probe traps.
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