In California various types of scale insects infest citrus trees. For several years I tried spraying or using systemic pesticides (and then having to destroy a crop) before I started thinking about the scale bugs habits. Scale insects are flat, ovalbugs that suck sap from the leaves and branches of a number of different plants including grapes, mock orange, citrus, and ornamental shrubs such as eunoymus. Some scale insects are covered with cottony white tufts that look like lint.
Often the first sign that a plant is infested is a trail of ants. The ants are harvesting “honeydew” which is sap that leaks from the plant as the insects drink. Ants carry fungus on their mouth that often produces a sticky sooty residue on the fruit and plants. The sooty black residue is another sign of scale infestation. When scale insect infestation becomes severe, leaves will begin to show yellow mottled regions and small branches may die.
In the spring, the scale insects mainly attack young tender growth, but move to the branches just before winter. Often eggs will be laid on the branches and when they hatch in the spring, the larvae will seek out the young growth.
This summer I began to paint the scale insects on my citrus trees with dish detergent – the cheapest brand I could find. Everywhere I saw scale, I coated it with dish detergent. Within two weeks my plants had very little scale insect problems. I attached a jet sprayer nozzle to my hose and literally sprayed off the sticky scale bugs. Not only did the detergent make the insects come off the leaves and branches easily, they were also dead. It seems that the detergent suffocated them. After everything dried off, I re-coated the trees with more dish detergent.
Even the most stunted tress have doubled in size this year and they are full of fruit. I also used old spice jars to make ant bait traps (attach them in the trees out of reach of children), with mixture of boric acid and sugar to reduce the ant population.
I can do this in California because we seldom have rain in the summer which would wash away the detergent. This winter I will be closely watching the trees to see whether or not they are re-infested. I anticipate needing to use the detergent on a regular basis as this is controlling, and not eradicating the scale insects. If you live in an area where the weather permits you to try this, please do so and let me know how it works for you. JRodgers
For more information and to identify scale insect pests, check on these websites:
Photo Credit: WSU.Edu