Updated: May 5, 2022

Cosmos plants are beautiful flowers that add a touch of color to any garden. Unfortunately, caterpillars can wreak havoc on these plants, eating away at the leaves and flowers. If you’re dealing with a caterpillar infestation on your cosmos plants, don’t worry – there are several solutions that can help you get rid of these pests and keep your flowers healthy.

1. Handpicking

If you only have a few caterpillars on your cosmos plant, one solution is to simply pick them off by hand. Wear gloves to protect your hands and carefully inspect each leaf and stem for caterpillars. Remove any caterpillars you find and dispose of them in a sealed plastic bag.

2. Insecticidal Soap

Insecticidal soap is a safe and effective way to get rid of caterpillars on your cosmos plants. Look for a product specifically labeled for caterpillar control and follow the instructions carefully. In general, you’ll need to spray the soap directly onto the affected areas of your plant, making sure to cover both the tops and undersides of the leaves.

3. Bacillus thuringiensis (Bt)

Bacillus thuringiensis (Bt) is a natural bacteria that targets caterpillars. It’s available in powder or liquid form and can be applied directly to your cosmos plants using a spray bottle or watering can. Bt works by infecting caterpillars with a toxin that causes them to stop eating and eventually die.

4. Neem Oil

Neem oil is another natural solution that can help control caterpillars on your cosmos plants. Mix neem oil with water according to the instructions on the label and spray it directly onto your plants. Neem oil works by disrupting the feeding habits of caterpillars, causing them to stop eating and eventually die.

5. Companion Planting

Companion planting involves planting certain plants together to help repel pests. In the case of cosmos plants, planting them alongside herbs like parsley or cilantro can help deter caterpillars. The strong scent of these herbs can confuse and repel caterpillars, making them less likely to target your cosmos plants.


How do I know if my cosmos plant has a caterpillar infestation?

Look for signs of damage on the leaves and flowers of your cosmos plant. Caterpillars will eat away at the foliage, leaving behind holes or ragged edges. You may also see small black droppings (frass) on the leaves.

Are caterpillars harmful to my cosmos plant?

Yes, caterpillars can cause significant damage to your cosmos plant if left unchecked. They can eat away at the leaves and flowers, weakening the plant and making it more susceptible to disease.

Are insecticidal soaps safe for my cosmos plant?

Yes, insecticidal soaps are generally safe for use on cosmos plants. However, be sure to follow the instructions carefully and avoid using too much soap, as this can damage the plant.

Can I use more than one method to get rid of caterpillars on my cosmos plant?

Yes, it’s often recommended to use a combination of methods for best results. For example, you could start by handpicking any visible caterpillars, then follow up with an application of insecticidal soap or neem oil.

How often should I check my cosmos plants for caterpillars?

It’s a good idea to check your plants regularly throughout the growing season, especially during warm weather when caterpillars are most active. Inspect both the tops and undersides of the leaves, as caterpillars often hide on the undersides.