Scales and Citrus Trees

• Numerous species of scale are known to infest citrus trees, including purple scale, snow scale, red scale, Caribbean black scale and cottony cushion scale. Depending on your geographic area, some of these species may be more likely to attack your citrus trees than others -- and other species in addition to these may be a threat as well.
  
  

Damage Caused

• There are two kinds of scales. Armored scales cause direct feeding damage by bursting plant cells and sucking on plant juices with their mouthparts. Soft scales cause plant damage in a rather different way; by secreting a sugar-rich excrement called honeydew as they travel across the plant, soft scales provide an ideal growing medium for a fungus that covers plant cells in a black, sooty mold. Both types of scales are a threat to citrus trees, and both need to be controlled for a successful citrus fruit harvest.
  
  

Natural Management

• As is the case with most insect pests, preventative- and natural-control methods are often more effective and are always preferable to chemical control methods. Inspect citrus trees when you buy them from nurseries for any signs of the presence of scales. Small scale infestations can be managed by simply picking the insects off by hand or washing them off with a garden hose. Similarly, black, sooty mold infections can be controlled by removing infected parts of the plant and by removing the insect that is depositing honeydew on the plant. Fruits with black, sooty mold are still safe to eat so long as the mold is washed off prior to harvesting the fruit.
  
  

Chemical Controls

• Sometimes, a scale infestation will be so severe that using a chemical insecticide will be warranted. To the best of your ability, try to time pesticide applications to coincide with the "crawler" stage of the scale's life cycle, as this is well before the scales have developed a hard, armory covering that protects them from contact insecticides. Use only approved insecticides labeled for outdoor scale control on citrus trees, and always follow the manufacturer's application instructions meticulously.