Thanks to the Garden Information Center at the University of Maryland!
I emailed them my questions and in less than a week they replied with some solutions for my winter weary lemon tree.
I have a dwarf Meyer Lemon Tree. It produced over 15 lemons this fall. We brought the plant indoors and recently we noticed that the leaves started to turn yellow. Prior to that, some of the green leaves looked puckered and munched on. Do you know what causes this?
The Garden Information Center’s answer :
The yellowing may be due to low light levels, nutrient deficiencies, and possible insect problems. During the winter the plant is dealing with low light levels and not actively growing. It is going through a rest period and older leaves may yellow and fall. You should also check for spider mites and scale insects(sucking insects) .
You should also check the root system and make sure the plant is not pot bound. You may see surface roots or roots coming from the bottom of the container hole. Repot with new potting mixture or top dress the mixture with fresh potting soil.
Do not feed the plant until the lighting improves in the late winter-spring (usually sometime in March). Provide at least four hours a day of direct sunlight. Place outdoors in bright light during the summer. Give an actively growing citrus a high potash, tomato type fertilizer every two weeks. Shorten overlong shoots of citruses by two thirds in early spring.
Looks like I need to let it rest in a sunny spot, spray it with Captain Jack organic insecticide, top dress it with more potting soil and feed it at the end of winter.
Thanks University of Maryland Agriculture Extension!