Hi Basilio,

Thank you for contacting the helpline and providing an excellent photo of the insect damage. Those small holes are being caused by flea beetles. Numerous tiny feeding holes can injure leaves and stunt or kill plants, especially seedlings. The beetles emerge in early spring when temperatures reach about 50 degrees and feed on weeds or crops. Unfortunately, one of their favorite plants is the radish.

One approach to prevent the beetles from causing damage is to use row covers. The row covers protect plants from egg-laying adults. Flea beetles are small and persistent so row covers will only protect crops if there is no way for them to get under them. They must be well secured with soil or bags of rocks or other heavy material around all edges. When you need to weed under the row cover, it needs to be replaced soon as possible. If beetles do get under the covers, control them with insecticide, then re-cover. Row covers work best when used immediately after seeding or transplanting.

It appears from your photo that the radishes are past the transplant stage so it may be too late to use row covers. You can treat your crop with organic insecticide sprays containing kaolin clay (Surround) or pyrethrins (Pyganic). Please carefully read and follow the directions exactly as specified on the label and remember that they must be reapplied after a rainfall.

Additionally, you should weed around your plants to limit food sources for flea beetles. Many common weeds in the vegetable garden can attract flea beetles from surrounding areas in the landscape. In fall, remove old crop debris so that the flea beetles will not be able to find protection in the winter.

Additional information on the flea beetle can be found on these websites.

https://extension.psu.edu/flea-beetle-in-spring-brassica-plantings#:~:text=Flea%20beetle%20larvae%20feed%20under,inspection%20works%20just%20as%20well.

https://extension.umn.edu/yard-and-garden-insects/flea-beetles#using-insecticides-3089113

In the future, you may see another possible pest that affects your radishes - the cutworm. You will know because the seedling or transplant is cut off at the soil line. I’ve included a website just in case this happens:

https://extension.umd.edu/resource/cutworm-vegetables

I hope this helps and happy gardening!