HELP!! My Mayer lemon tree is about to bite it!

Asked July 21, 2020, 5:53 PM EDT

Hello! I was gifted a dwarf Mayer lemon tree in a whiskey barrel. A few weeks ago I noticed it started looking unwell. There were scales all over it. Three days ago I sprayed it with the Dawn dishwashing liquid and water, and then took a soft cloth and rubbed down all of the branches to remove the scales. But it is looking worse than ever. I SO suck at gardening, but I really love this tree. What can I do?!

Lane County Oregon

4 Responses

For the scale, you can use rubbing alcohol or try squishing them with your hand. You can prune off heavily infested twigs and branches, if they are limited to only a few small parts of the tree. A horticultural oil (also called narrow range oil) can also be used to control scale in late spring or summer. Don't spray if temperatures are above 75-80 degrees F (or under 32F) or you may burn the tree. Neem oil and soap sprays are also effective. Chemical treatments are most effective when the crawlers are just emerging in the spring. Making homemade soap sprays with dishwashing soap can be risky since the products tend to contain many other ingredients or chemicals, some of which may burn or damage the plant. Natural based soaps are generally better for homemade sprays, but there isn’t a lot of research on homemade products. Whatever you spray, you will need to get good coverage and make sure all parts of the tree are sprayed, including the underside of leaves where the scale often hang out. Always read and follow the label instructions.

Having a well-cared for and healthy tree will also make the tree less susceptible to pest infestations. Are you watering the tree? Is it kept in a greenhouse or indoors/warm spot over winter? Do you fertilize? You may have some frost damage. The yellowing could be due to many issues, but if you have not been fertilizing it is possible you have a nutrient deficiency. Watering the tree and fertilizing it every year will help it to stay healthy. For more information on caring for lemon trees in Oregon, see: https://today.oregonstate.edu/news/pucker-it%E2%80%99s-time-talk-lemons and https://portlandnursery.com/docs/fruits/Citrus.pdf. I suggest following the management tips recommended in these articles to see if you can bring the tree back to good health. Don’t give up, it may take some time to develop a green thumb, and it will be worth the reward once you start harvesting lemons!

Hello. Erica. Thank you so much for a timely and in depth response. So I pruned all of the dead branches, of which, sadly, there were many. I had used a soft cloth to rub down all the branches of the tree to rid it of the scales. I also gave it a good watering, so some of the leaves have now come back to life.
The Neem oil is on order, but is there anything else I can do to help it along? Some nutrients? Fertiliser?
The tree is an outdoor tree and when winter comes we cover it entirely with plastic, move it closer to the house, put blankets about the base and put two clamp lights in there with it to keep it from freezing. By the way, I have never put any nutrients or fertiliser on this plant since I received it, about two years ago. Up until a month ago there were so many little buds on it, and now...
I'm a terrible, terrible plant mum, but it is so out of my ken.

Yes, I would definitely give it some fertilizer! Spring and summer are the best time to fertilizer citrus. You can look for a citrus, rhododendron or blueberry fertilizer blend at garden retail stores or online. Check the label for amounts. Cut back or discontinue feeding during winter. One other thing to consider is testing the soil pH. The cheapest and easiest way to do this would be to use some soil pH test strips to get a general idea of the pH of the soil. Meyer Lemons like a pH between 5.5 and 6.5. If the soil pH is too high or low it can impede the plants ability to take up nutrients out of the soil. Lemons also need a well drained soil, so make sure you have holes in the bottom of the pot to ensure good drainage. Hopefully with some fertilizer and a little TLC your tree will rebound!

Hello, Erica. Thank you again for your response. I've purchased a pH soil test kit; the lemon tree is just where you suggested: 6.0. I have also purchased fertilizer and neem oil, which I shall wait until the sun goes down (it is currently 97 degrees where I am) and apply both.
I had cut off all of the dead bits as well. SO far its holding its own-- there are a couple of remaining branches with happy leaves on them.
Fingers crossed!!
Thank you again, Erica.
Best, Thalia