Assessment of pesticides used to control insect pests and their effects on storage of cabbage (Brassica oleracea var capitata) -A case study in Ejisu-Juaben Municipal Area.
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Date
January, 2010.
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Abstract
One of the setbacks to cabbage production in Ejisu-Juaben Municipal Area is insect pests. These
insect pests are controlled in various ways; prominent among them is the use of pesticides.
However, the use of pesticides in cabbage production comes with various health issues such as
residual effects. The objective of this research was therefore, to find out the various pesticides
used by farmers to control insect pests in cabbage production, the mode of the application of
pesticides and their effects on the quality and safety of cabbage produced. The results of the study
showed that majority of cabbage producers were men (representing 88%) and the remaining 12%
were female. Eighteen percent (18%) of the farmers had no formal education; eighty percent
(80%) of them had basic education and the remaining two percent (2%) with post secondary
education. The result showed that about twenty seven (27) different pesticides were used by
farmers to control insect pests on cabbage in the municipality. Sixty-one percent (61%) of the
farmers mixed two or more pesticides together without considering their compatibility or active
ingredients but just relied on trade names on the containers.It was also revealed from the results,
that some banned chemicals like Lindane, Endosulfans, and DDT and those not recommended for
vegetables like Akate master, Confidor and Cocostar were also being used. This suggested that
some farmers misused pesticides which affected the quality and safety of cabbage heads for
consumption. Even though, the results revealed that 51% of the farmers did routine (calendar)
spraying which was usually done between 3-4 days interval, the rest did it when they noticed the
presence of insect pests. The survey results showed that 80% of the farmers interviewed continued
spraying pesticides during harvesting period; hence no waiting period was adopted. Only 21% of
the farmers adopted one week waiting period on the average, which in many cases was not
enough, considering the kinds of pesticides used.
Laboratory analysis confirmed that pesticide residues were indeed present in the cabbage heads
and further analysis quantified the amounts present. Analysis of organochlorine residue levels in
the cabbage heads at harvest indicated that Alpha BHC, Gamma BHC (Lindane), Beta BHC,
Delta BHC, Beta Endosulfan and Heptachlor, had residue levels of 0.321 mg/kg, 0.908 mg/kg,
0.883 mg/kg, 0.394 mg/kg, 0.207 mg/kg and 0.140 mg/kg respectively, which were all higher than
the FAO/WHO Guideline value of 0.05 mg/kg. The DDT and DDE had the same residue levels of
0.017mg/kg which is below the FAO/WHO Guideline value of 0.02mg/kg for them. The rest of
the organochlorine pesticide residue levels indicated that Endrin, Dieldrin and Endosulfan
Sulphate, had residue levels of 0.022 mg/kg, 0.010 mg/kg and 0.005 mg/kg respectively, which
are all below the FAO/WHO Guideline value of 0.05 mg/kg for Endrin, Dieldrin and Endosulfan
Sulphate, respectively. Analysis of residue levels of the organochlorines, after 14 days storage in a
refrigerator at 5oC showed significant (P < 0.05) reductions in pesticide residues in the cabbage
heads. All the pesticide levels fell below the FAO/WHO recommended levels except Gamma
BHC (Lindane) and Beta BHC whose levels although dropped significantly (P < 0.05), were still
higher than the FAO/WHO levels. The analysis showed that storing cabbage for 14 days could
remove all traces of Aldrin, Dieldrin and Endosulfan Sulphate. The organochlorine pesticides are
banned for vegetable production in Ghana; therefore the detection of these residues in cabbage
samples indicates misuse of agrochemicals among cabbage producers in Ejisu-Juaben
Municipality. This poses health hazards for consumers, particularly, if the cabbages are consumed
soon after harvest.
Description
A thesis submitted to the School of Research and graduate Studies, Kwame Nkrumah University of Science and Technology,Kumasi, in partial fulfilment of the requirements for the award of Master of Science (MSC.Postharvest Physiology) degree on