Repelling insects with plants

Done by Low Zihao Davis

Research Question

What plant parts can be used to repel insects?


Many people often apply citrus-based products to repel insects. Lemongrass products has also shown to be effective at repelling insects. Therefore, we hypothesise that lemongrass will be able to repel fruit flies.


  1. The variables (5 g of lemongrass, garlic, and pandan) were crushed and placed onto the centre of Chamber A. The negative setup contained no samples while the positive control contained of 5 ml of neem oil.
  2. Subjects (10 D. melanogaster flies) were placed into each chamber and two chambers were fitted together and sealed with cling wrap.
  3. The number of flies in each chamber was recorded at intervals of one minute for five minutes.
  4. The percentage repellency was recorded as the number of D. melanogaster in Chamber B against the total number of flies in each setup.
  5. To assess for repellency of the culinary herb, the percentage of flies in Chamber B in each setup was compared to the negative control.


We reject our hypothesis as lemongrass has shown to not repel fruit flies. This was different from what we've found from literature. However, one unexpected finding was that fruit flies were repelled by garlic. The study was also limited to fruit flies only, and may not apply to other common pests. Garlic can be used as a repellent but the smell is very strong and not many people may like it. Perhaps further studies can test if rubbing garlic onto surfaces is sufficient to repel fruit flies.

Group 5

Right-hand corner of the classroom