Q.Can Indoor Lemon Tree Have Huanglonbing?
Hello, I have been growing my indoor lemon tree from seed since October of 2020. I started noticing about 2 months ago yellowing of the leaves and curling. So I did some research on it and found some say it can be from not enough nutrients, under or over watering. So I ended up getting some citrus fertilizer and a moisture meter to help me to fix this problem. Then is started noticing little bugs in my soil about a week after, found out they were predator mites so I left them alone. Then noticed things flying around and in the soil. So I’m thinking fugus gnats, so I ended up spraying my plants with neem oil routinely and I haven’t seen them since. But just last week I saw them again and the yellowing of my plants are getting worst. They are still growing. I see new growth each week but they don’t look healthy. I research citrus diseases and came to this website and saw Huanglongbing. The pictures match how my trees look and I research some more about the disease and the psyllid is the pest that causes it, I’m still a little frustrated. They are found in tropical areas and warmer climates. I live in Maryland and grow these trees indoors. How am I getting this disease, if this is what it is? I don’t see any sign of the psyllid on the branches, under or on top of the leaves, or on the root. What should I do, I need some help please. Is it coming from the soil? I use Miracle Gro Catcus, Citrus and Succulent Potting Soil. This I my first time at planting food so I’m excited but nervous. My plants are in a green house right now because of how cold it can get at night, with full spectrum grow lights and fertilized with Espoma Organic Citrus and Avocado Fertilizer. I will post some pictures. Can I save my plants?

Certified GKH Gardening Expert
You probably did have fungus gnats; they like moist soil. Lemon trees need their soil consistently watered, but not constantly wet. Are you following the package instructions for the fertilizer? Lack of nutrients can cause yellowing. I've included more information on yellowing leaves as well. I don't think your citrus has Huanglongbing disease. Your problems are probably nutritional or environmental. I've also included information on growing lemon in containers.
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaves-turn-yellow.htm
https://www.gardeningknowhow.com/edible/fruits/citrus/curling-citrus-leaves.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/growing-lemon-trees-containers.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/pests-of-lemon-trees.htm