What it shows
Grain stores lose food to weevils and beetles. Comparing traditional protectants in sealed jars shows how farmers can protect stored pulses without chemical sprays.
The science
Storage pests lay eggs in grain, and the larvae eat the seed from inside. Neem repels and disrupts feeding, ash fills the gaps between grains and blocks movement, and turmeric gives a smell and a coating pests dislike. Dry, sealed jars also limit oxygen and moisture.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Four glass jars with lids
- Pulses such as moong or gram from a store (not treated)
- Dried neem leaves, wood ash, turmeric powder
- A pinch of weevil-infested grain from an old store bag (from home or a shop)
- A hand lens
- A kitchen scale
- Labels and a notebook
Safety
For this project: Wash hands after handling grain and powders. Wear gloves and a dust mask when mixing ash and turmeric, because ash irritates skin and eyes. Do not eat pulses used in the experiment, and keep jars away from food and children.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Weigh 200 g of the same pulses into each of four jars.
Mix in 10 g dried neem leaves in jar 1, 20 g ash in jar 2 and 5 g turmeric in jar 3.
Leave jar 4 with plain pulses as the control, then add the same small pinch of weevil-infested grain to every jar so each starts with pests.
Close the lids tightly and store the jars in the same shaded place.
Every week look through the jars with a lens and count live insects and holed grains.
Record the counts and note any smell or change in colour.
After four weeks, weigh the grain and count damaged seeds in a handful.
Make a chart comparing damage in each jar.
What you should see
The control jar shows the most damage, and the protected jars show less. The chart shows which protectant is best over four weeks.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01What is a weevil?
A beetle whose larvae eat stored grain.
02Why does ash help?
It fills gaps and blocks insects from moving.
03Why seal the jars?
To keep out new pests and moisture.
04Why not use chemicals?
Residues can be harmful to health.
Take it further
Compare grain dried in the sun with grain that has not been dried before storage.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
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