One effective and natural deterrent for beetles, including those that might be eating the leaves of your coffee plant, is a combination of essential oils mixed with water and soap. Here’s an easy-to-make recipe:

### Natural Beetle Deterrent Spray

**Ingredients:**
1. 1 cup of water
2. 1 tablespoon of vegetable oil (to help the mixture stick to leaves)
3. 1 teaspoon of dish soap (preferably natural, like castile soap)
4. 10-15 drops of essential oils (choose from the following options):
– Peppermint oil (strong scent that beetles dislike)
– Eucalyptus oil
– Tea tree oil
– Citrus oils (like lemon or orange)

**Instructions:**
1. Mix all ingredients in a spray bottle.
2. Shake well before each use to ensure the mixture is properly blended.
3. Spray the solution on both sides of the leaves and the stem of your coffee plant.
4. Apply every 3-5 days, or after rain, until the beetle problem is under control.

### Tips:
– **Test a Small Area First:** Before spraying the entire plant, test a small area to ensure the mixture doesn’t harm your coffee plant.
– **Reapply Regularly:** Beetles can be persistent, so regular application is important.

Yes, a homemade spray using garlic and onion can act as an effective natural deterrent for beetles and other pests. The strong scent of garlic and onions can repel many insects, including beetles.

Here’s how you can make a DIY garlic and onion insect repellent:

### Garlic and Onion Insect Repellent Spray

**Ingredients:**
1. 1 small bulb of garlic
2. 1 small onion
3. 1 tablespoon of hot pepper flakes (optional, for added deterrent power)
4. 1 liter of water
5. 1 teaspoon of dish soap (to help the solution stick to leaves)

**Instructions:**
1. Peel and roughly chop the garlic and onion.
2. Place the chopped garlic and onion in a blender or food processor with enough water to make a smooth puree.
3. Strain the mixture through a fine-mesh sieve or cheesecloth into a bowl, pressing to extract as much liquid as possible.
4. Add the strained liquid to a large container or spray bottle.
5. Stir in the hot pepper flakes (if using) and dish soap.
6. Fill the rest of the spray bottle with water.
7. Shake well before each use.

**Application:**
– Spray the mixture on both sides of the leaves, as well as on the stem of your coffee plant.
– Apply the solution every 3-5 days or after rain to maintain its effectiveness.

### Tips:
– **Test a Small Area First:** Before spraying the entire plant, test a small area to ensure the mixture doesn’t harm your coffee plant. Some plants can be sensitive to garlic and onion sprays.
– **Store Properly:** Keep any unused mixture in the refrigerator if you plan to use it within a few days. Otherwise, make fresh batches as needed.

This natural spray should help deter beetles from eating the leaves of your coffee plant without resorting to chemical pesticides.