Malathion will eliminate them. Use a fertilizer that contains all of the trace elements. Most people apply fertilizer around the trunk of the tree but the correct area for application is six feet beyond the drip line of the tree. Manganese and magnesium deficiencies may occur on citrus leaves. These two problems are similar but can easily be separated.
Magnesium deficiency appears as a yellowing of the tip of the leaf.
There will be wide dark inverted V-shaped green veins near the base of the leaf. Manganese will have dark green veins along the midrib of the leaf but the major part of the leaf will be green, not yellow. Citrus trees with a lot of yellow leaves may be in need of nitrogen. Dry weather may also cause yellowing of mature leaves as well as excessive leaf fall. Many times the pH of the soil is too acid and the tree cannot take up the needed fertilizer.