Pests

• Avocado trees may become infested with pests that feed on the foliage, fruit and trunk of the tree. Pests that affect leaf growth, development and coloration include mites, thrips, lace flies, loopers, borers and beetles. These insects use sucking mouth-parts to extract fluids from inside of leaves or to eat away at the leaf itself. The result is a pale greenish-yellow leaf that may show only patches of discoloration at first. Treat pests as soon as they are discovered using a pesticide formulated specifically for the pests you are treating and labeled as safe for avocado trees. Always follow the label instructions on the pesticide closely. Organic pesticides are available.
  
  

Disease

• Disease is a common culprit in avocado leaf discoloration. Fungal, viral and bacterial diseases infect trees and spread by wind, water and pests. These diseases cause an array of symptoms, including pale or otherwise discolored leaves, rotting of roots, trunk, branches, leaves and fruit, leaf drop and wilt of young trees. Treat disease using an appropriate anti-bacterial, anti-fungal or anti-viral agent. Use a treatment formulated specifically for which your tree is infected and that is labeled safe for avocado trees. Follow directions for use closely and do regular inspections of your trees to look for signs of further infection or that further treatment is necessary.
  
  

Watering

• Water is essential for avocado tree health and well-being. However the very water that keeps the tree hydrated and strong may actually cause problems for the tree if proper amounts are not used. Both under-watering and over-watering your avocado tree may result in pale leaf discoloration. Though water is necessary, avocado trees may develop root rot if they are given too much water. Provide the plant with well-drained soil and keep the soil moist, never damp, soggy or muddy. Allow the tree to dry out slightly between watering, never allowing the soil to dry completely. During warm weather, water daily. In cooler, damp months, water less frequently to avoid moisture problems.
  
  

Fertilization

• Lack of proper fertilization often leads to a loss of full, vibrant color in avocado tree leaves. When an avocado tree does not receive enough nitrogen, iron or zinc, often the end result is leaf discoloration making the leaves pale green or pale greenish yellow. Combat this problem by providing mature plants with a well-balanced citrus fertilizer during the spring and summer growing seasons. Doing so replaces nutrients lost from the soil as the tree feeds and grows, allowing the tree to continue to feed and produce healthy foliage.