The Effect Of Sunflower Oil On Black-Eyed Beans

The data from this experiment seemed to show Callosobruchus maculatus oviposition occurred less on black-eyed beans when the legumes were covered with sunflower oil. In all trials, the least number of eggs were laid on the beans coated with 15 mL/kg sunflower oil, an intermediate number of eggs were laid on the ones coated with 5 mL/kg, and the most were laid on the cowpea without sunflower oil (Figure 4, Figure 5). No eggs were laid in quadrant C, which reinforces the idea that bean beetles will only lay their eggs on legumes (Table 1, Figure 5). The relative amounts of beetle eggs to concentration of sunflower oil, consistent throughout the experiment, seem to indicate that bean beetles oviposit less on beans coated in more sunflower oil.
These results support the hypothesis that sunflower oil could be used to reduce the number of eggs bean beetles lay on eggs, and indicate that sunflower oil could potentially be used to protect African cowpea stores from the bean beetle in the future.
Results similar to the ones found in this experiment have been recorded in previous attempts to use sunflower oil to prevent C. maculatus oviposition on cowpea. One study recorded that 5 mL/kg of sunflower oil resulted in slightly less than half the control number of eggs being laid on cowpea and that 10 mL/kg of sunflower oil resulted in only a fourth of the control number of eggs getting laid on cowpea (Rajapakse & Emden, 1997). The sunflower oil in this experiment seemed slightly less effective at preventing oviposition, with 5 mL/kg only preventing around a fourth of the control number of eggs from being laid and 15 mL/kg resulting in half the control number of eggs from being oviposited. However, sunflower oil does not seem as effective the oil made from its botanical relative, safflower. While the study that used safflower oil to protect cowpea from compared the effects of the oil at different dilutions, at the lowest dilution of .25% safflower oil, less than half of the number of control eggs were laid, whereas at the highest dilution of 1.00% safflower oil, only around a third of the number of control eggs were laid (Rahman & Talukder, 2006). The results of the safflower oil are comparable to the results of the sunflower oil, but the safflower oil seems to be more potent because the concentrations used in the cited study are only a small percent actual oil (Rahman & Talukder, 2006). This implies that pure safflower oil would be much more effective at preventing C. maculatus oviposition than pure sunflower oil. There were several possible sources of error in this experiment that could have impacted the results.
The age of the C. maculatus specimens used is unknown, and if the beetles used were near the end of their lifespan, they would likely be less fertile and produce less eggs. Less eggs oviposited could exaggerate the apparent effect of the sunflower oil on the beans since less eggs could be produced in general. In addition, the population measured in this study was relatively small, so any variation in egg number for each quadrant would significantly affect the average. This can be seen in the slight overlap between error bars in Figure 5. The overlap between error bars implies that the difference between the categories may not be statistically significant, so further testing of the impact of sunflower oil on bean beetle oviposition should be conducted to clarify these results. However, since C. maculatus eggs seem to occur less on beans covered in higher concentrations of sunflower oil, greater concentrations of sunflower oil should also be tested to see if this effect becomes any more prevalent. In addition, due to the potential promise sunflower oil has as a cowpea protectant, the long term effects of sunflower oil on black-eyed beans should be examined to assess whether or not it could cause damage to the
beans. In conclusion, the data supports the idea that sunflower oil inhibits C. maculatus oviposition on Vigna unguiculata to some extent, and that effect increases when the concentration of sunflower oil is increased. These results suggest that sunflower oil could potentially be used as an affordable and accessible method for African farmers to protect their cowpea stores and reduce losses from bean beetle infestations. In turn, widespread protection of cowpea stores could eventually aid in reducing malnutrition and starvation in Africa as this highly nutritious legume becomes more and more available to the populations that need it.