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White spots on baby kale #750007

Asked May 14, 2021, 7:12 PM EDT

I planted some kale and about 2 weeks afterwards they started getting white spots. See photos. I have heard four different theories: sunburn, herbicide drift, fungus, or white fly. There don't seem to be any eggs--just the white spots which were just on two plants now it is more.

Benton County Oregon

Expert Response

Dear Leah,

Thank you for the kale photos.  Even though your pictures are very clear when I try to enlarge they do not go far enough.  So, I think you may have leaf miner damage where you see the white spots.  If you rub your fingers on the spot, part of the upper leaf should come off.  

If it is powdery mildew, which I doubt, you should see a white powdery substance.  

And then since these are baby plants, it could be sunburn (the large white spots).

The small white spots on one of the leaves actually looks like dried hard water spots.  They should rub off with your fingers if they are.  The rest of the white spots blur when I tried to enlarge the picture.  

Kale is subject, especially this time of year, to leaf miners and they are difficult to remove.  

A small fly lays eggs in the leaf not on it. The larva eats inside the leaf and makes what are called mines, hence the name leaf miner. The larva changes into a pupae and emerges from the leaf and drops to the soil where it creates a cocoon and then emerges as an adult fly. I am attaching a video that shows their life cycle: youtube.com/watch?v=lmu1G30Nltg Life cycle of a leaf miner by Koppert Biologicals.

They are difficult to get rid of. You can look for a tiny usually black worm in the leaves but it may have left already. Bag the damaged leaves and put in the garbage. Disturb the soil around the plants if you find the cocoons, destroy them as well.  Disturb means with gloved hands mix up the soil.  I see you have wood chips around the plants, which is fine but get into the soil.

Use pure Neem oil (find it online) and follow the directions. You can drench the soil around the plants that are affected and it will kill most everything in the soil. Spray it on the leaves both sides to kill the adults as they will open holes in the leaves and suck the juices out. You use as little as a teaspoon for complete effectiveness. Follow the directions on the container.

If the large spots are powdery mildew the Neem oil will kill that as well.  It is an organic fungicide and insecticide so it will kill all bugs which is not a good thing.  You want lady bugs and there instars.

Often there are only a few worms in the leaves. You follow the directions above and your plants should come back. 

Disturbing the soil with your hands, drenching it with Neem and removing the leaves that are damaged are about all you can do unless you want to remove the plants as well.

After doing all of that, you can cover the plants with row cover sold in most nurseries. Bury the cover in the soil or make sure that there are not tiny holes for the flies to get through. That will stop them from depositing the eggs in the plant leaves. Here is a brief outline on the Leaf Miner. https://extension.umn.edu/yard-and-garden-insects/leafminers

The pesticides mentioned with exception of Spinosad in the above link are not for organic use. Since your plants are grown to be eaten, I would only use Neem or Spinosad.

Hard water is not bad for the plants but it can leave residue on the leaves.  You can stop that by watering only the soil around the plant.  Otherwise, if it is hard water spots, there is not much to worry about.

I am also adding a link on lady bugs.  This shows pictures of immature lady bugs that many people have never seen.  http://oregonstate.edu/dept/nurspest/Lady_beetles.html

Scroll down to the bottom on the right and you will see pictures of the instars of lady bugs as well as several different types of lady bug adults.

If you have further questions, please contact us again.

Sheryl Casteen Replied May 14, 2021, 10:05 PM EDT

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