Fareed R, Ansari A, Seecharran D, Munroe L. 2017. Investigating the degrading properties of three different strains of fungi on commonly used pesticides in Guyana. Biofarmasi (Rumphius J Nat Prod Biochem) 15: 5-14. Bioremediation is the use of microbes to remove various contaminants from the environment. The present research work was carried out during 2014-15. Aspergillus niger, Aspergillus flavus and Penicillium spp. were employed for biodegradation of pesticides commonly used in Guyana. Initially, the fungi were screened for ligninolytic potential by observing decolorization/degradation of a synthetic dye (Remazol Brilliant blue) in PDA agar. The degradation of dyes was noted by the change in original colour of the dye and visual disappearance of colour from the fungustreated Petri plates. In addition, accumulation of the dye by the fungal mycelium was also noticed. The fungi were then tested for their tolerance to the pesticides Diuron, Malathion and Diazinon respectively. This was done on solid media using PDA agar with amoxillin to prevent bacterial growth. The pesticides were introduced to the fungi by way of disc diffusion. Discs of a known diameter were infused with the respective pesticides at different concentrations and placed at strategic points around the inoculated fungal mycelium. The extent of inhibition was measured by comparing the growth diameter in the sample verses growth in the control. The pesticide diazinon was found to have inhibited the fungi more when compared to Malathion and Diuron. Finally, the fungi were used to degrade the pesticides in a liquid culture-Peptone Broth. The pesticide Diuron was selected because the fungi thrived best in all concentrations of this pesticide. A concentration of the pesticide Diuron was place in flasks containing the peptone broth with mycelia discs of the respective fungal strain. The final concentration of the pesticide was determined by using High Performance Liquid Chromatography (HPLC). The concentration of the pesticide in each strain of fungi was decreased. Aspergillus niger was found to have the highest rate of pesticide degradation followed by Aspergillus flavus and Penicillium.

The aphid, Doralis symphyti (Homoptera: Aphididae), a harmful pest of many crops, causes direct damage by consuming all plant parts, reducing plant vigour, and indirect damage by honeydew secretion and transmission of several viruses. Due to the problem of pesticide resistance, alternative techniques for chemical control, such as the use of natural insecticides with minimal effects on the environment and natural enemies also coincide with organic agriculture have been the objective of this research. The effects of Mammea (Mammey americana) leaf extracts on the mortality of aphids were evaluated. The mammey extracts (Crude and refined) were tested in the laboratory (bioassays) at 100%, 90%, 80%, 70% and 60% dilution. The 80% was determined to be the most efficient dilution. The refined extract resulted in 100% mortality at 84 hours while the dry leaf and green leaf extracts gave 100% mortality in 96 hours. In the field, the refined extract resulted in 65% mortality, dry leaf crude extract obtained in 43% mortality and the green leaf crude extract gave 25% mortality. The mamey leaf extracts were efficient against the aphid in the laboratory since 100% mortality was obtained for all treatments. The field study found that the green leaf extract obtained 29% mortality, dry leaf extract achieved 47% mortality and the refined extract attained 63% mortality of aphids.

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