Is there a way to correct a plants crop so it doesn't alternate between good years and bad years?

Diving into the phone lines, Dan hears from callers covering a variety of topics such as what is wrong with my Meyer lemons being small, if you can put cloth bags over your plants during the winter but should you take them off whenever it warms back up to the 50's and 60's, and some questions regarding sudden drops in crop production in citrus trees.