Florida Fern Caterpillar

Asked September 20, 2014, 2:14 PM EDT

I bought a sm. Boston fern and brought it into the house where I have two huge beautiful (3ft.) Boston ferns. The other day I noticed they had worms and looked them up on the internet. They are the Florida Fern Caterpillar. I am not familiar with the insecticides listed and am afraid to use anything in fear of loosing them. Can you suggest something to use on them that is sold in normal stores?

Thank you!!

Cindy Wright

Isabella County Michigan master gardener program fern florida fern caterpillar

1 Response


Florida fern caterpillars (Callopistria floridensis) are a very common culprit. These pests lay eggs on plants while they're still at growers' facilities in Florida; ferns infested with Florida fern caterpillars may carry the eggs to greenhouses and garden centers in other states. The eggs are laid on the fern by a moth while the fern was being grown. The eggs are difficult to spot but the caterpillars can quickly strip the foliage off of a Boston fern.

Hand-picking is the usually the best solution to many caterpillar species infestations, but you might have too many, even on a single plant, to pick off. Bacillus thuringiensis, a natural, soil borne bacteria, is among the most effective treatments for these caterpillars, and is readily found in many big box stores in their garden centers. If not found there, try different nurseries or garden supply stores. Pesticides containing the insecticidal proteins of Bacillus thuringiensis are safe to use on ferns, though they may leave a harmless white residue on your plant's foliage.

To use a Bt spray, dilute the concentrate in water, usually at a rate of 4 teaspoons of the produce in 1 gallon of water. Check the label because rates may vary. Pour the mixture into a spray bottle and spray all leaf surfaces on the ferns. Spray every 14 days until the caterpillars are gone. You will still see some feeding damage as the caterpillars need to feed on the insecticide in order to be effective. Wear long sleeves and long pants when spraying and avoid breathing in the spray or getting it in your eyes.

The Florida fern caterpillar has been found to be resistant to a number of insecticides including the pyrethroid group. You may need to rotate insecticide groups to avoid resistance developing. Materials that are known to be effective include products that contain Bacillus thuringiensis like DiPel 2X or Javelin, Carbamates like Sevin, or Spinosyns like Conserve. There are a number of other products that contain Bt, so be sure to read the labels. You may need to make multiple applications to achieve good control. Be sure to get a thorough spray coverage.

Always read and follow the label instructions of each product before using.

This is an interesting site: http://msue.anr.msu.edu/news/florida_fern_caterpillar_a_pest_of_boston_fern

Hope this was helpful. Feel free to contact us again if you have further questions.