My baby lemon tree is getting sick

Question

I planted a couple of lemon seeds in a pot in June 2021 and a baby lemon sprouted. She grew up in a really healthy way. Since then, I have changed the soil and the pot only once. I used regular soil that I got from the supermarket. Unfortunately, lately, I've been having a problem with my baby lemon tree. Since I am not very knowledgeable with botany, I don't know the reason for this and I don't want to do anything wrong.

There are various white and brown spots on her stem. Two of her leaves are starting to turn brown. Also, when I pour water, somethings that look like tiny tiny bugs jump up, but when I don't pour water, there is no movement in the soil. I live in the south of Germany, the sunniest city. No matter how sunny I say, there are many dark, cloudy and gloomy days. I try not to water her too much. She stands in front of the sunniest window. You can see the photos attached.

My baby lemon tree is very precious to me. When I planted her, I wasn't feeling well mentally, I was going through stressful and unhappy days. I don't want to lose her. I hope someone can help me figure it out.

I am looking forward to hearing from you soon.

Best wishes,

Pinar

Answer 1

Your lemon tree is infested with Coccus mealybugs. They are insects that sucks the sap of the stem/leaf. Contrary to other mealybugs such as obscure mealybugs, this genus is difficult to get rid because the last stages are protected by a shell.

The earliest (and smallest) stages move on the plant until they find a permanent and appropriate location. Then they make a shell that will protect them from extreme environmental conditions, predators (and insecticide!). The smallest stages (the one which moves) are too small to spot, but all the other stages can be seen easily on your pictures. The sticky drops are the scale droppings.

Treatment based on diluted soap+oil+alcool can be sprayed on the plant, but my personal experience is that manual removal is the most efficient, especially on plants that does not have many leaves like yours:

1. Learn how to spot them: tiny green to large brown scales are the different permanent stages.
2. Use a teeth brush to remove all of the visible scales. Don't forget in between leaves and the stems.
3. With some soap and water, rrush carefully all the leaves (both sides) and the stem to get rid of the smallest stages, including the eggs, as well as the sticky drops that could feed fungus later
4. You may want to remove the plant from the pot to clean the pot and change the soil, in order to be sure to get rid of any scales which has fallen. But removing the soil may also stress the plant.
5. Repeat the leaf/stem washing up (stage 2, and stage 3 if motivated) every week for ~2 months
6. Keep checking carefully for scales for a few additional months, every week, and proceed stage 2 if any.

Be careful not to contaminate other plants by touching the lemon tree and then touching other plants.

Answer 2

welcome to the Gardening Stackexchange! :)

I would say you are taking appropriate care of your lemon tree by giving it plenty of sunlight and not too much water. I would particularly stress that you should water your citrus very conservatively, too much water can be fatal for your plants (in general). Always be conservative and wait for the soil to go dry before adding any water.

Keep in mind that you are dealing with a tree here, which you have in a pot. Its natural medium would be in the soil, so it's normal that it's not completely comfortable in such a constrained medium. That said, it can survive, as long as you give her fertilizer once in a while (maybe once a month) and plenty of sun light.

Good luck with your friend there!