My citron tree is an indoor one, several years old. It lost 75% of its leaves before I was told it is scale. I sprayed with soapy water and also diluted white oil. I fetilized it as well. The pot is about 35 gallons in volume, and the tree stands about 7-8' high. I keep up with the scale, put cannot rid it entirely. Many leaves are yellowing, also curling. Some to have brown patches. I misted the tree heavily with water to rinse off any dilute soap residuer. New leaves are forming, and some flowers, but some of the new leaves just dry up. HOW CAN I SAVE MY TREE?!! Treat the soil? Keep spending 45" a day picking off scale insects? Would an overwater cause a sudden massive leaf drop, or a change to hotter weather? The tree cannot be taken outdoors and is in a northern exposure (not good, I know). Should I buy lights? Please help.

Yes, the pot looks small and the plant looks underfed. You are giving it only about a quarter of its nutrient needs: Citrus Focus instructions say "Add 10ml of Citrus Focus in every litre of clean water, weekly. If leaves are pale or yellow, increase frequency of application."

You do not have to remove the fruit off the tree. The tree will probably abort the fruit on it's own during what is considered June drop which is normal. I have older trees than yours and a lot of fruit has dropped. Most trees on the retail market are at least 2 years old and still a bit juvenile to produce fruit. You may get lucky and get at least 1 if you don't stress it by the lack of water. Your tree is going through the bloom cycle so until that is over, you may not get new leaves.

I'm going to try and stay general. Pots shouldn't be left on floor if it can be helped, coldest spot in room - leading to cold roots. Are you attempting a holding action or want winter growth. You give no temperature numbers and no pictures. Do you use lights? Leaves should be well lit but not necessarily hot, or you'll get leaf drop. Air temperatures for indoor growing should be in a 72 to 85 degree tops range indoors, your soil temperature should be above 70 at all times. there should NOT be a huge differential but there generally is some. You need a thermometer for air and soil. You won't be watering as often indoors as outdoors in wind and sun, possibly only once a week in winter but pot should be flooded when you water to get lower pot moist - encourage root growth and flush out any fertilizer salts. Soil i supposed to hold moisture for a while and then dry out from the top down - just like the garden. You need to test - I use cheap wood BBQ skewers and poke in the soil all the way down to bottom to watch for wetness depth. Small pots dry out quicker than big ones. lots of variables. You can shine a cheap clip on spot light on roots/top of pot to warm them so they can supply needed water to leaves if needed. Some people here successfully keep their trees in a very cool state - probably in the 50 degree range (I'm not one of them - someone will chime in), without too much light, and not too much differential between air and soil temps as a holding action - little to no growth and hopefully no leaf drop .