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The Red Gum Eucalyptus tree is probably the most planted Eucalyptus species in Central California. Since about 2000 they have been under severe attack by an insect called Red Gum Lerp Psyllid. This insect creates a huge quantity of sugary capsules on the surface of the leaf. Under the capsules, live the nymphal stage of this insect, which when adult is the size of a very small gnat. These insects, over time, will suck out the life blood of the tree, putting it under great stress and lessening its resistance to other hazards such as cold, heat, disease and other insects. In the process of destroying the tree, it creates a gigantic mess.
The hoped-for biological control provided by a parasitic wasp has not materialized. If you have many of these trees, the cost to treat them on an ongoing basis would be prohibitive, and you may need to replace them with a less beleaguered species. If you have one or a few of these trees that are important to you, make sure to water them thoroughly. This is helpful. Do not fertilize them very much and do not trim them back, because this just promotes more succulent growth for the bugs to suck on and destroy. Your best bet is an annual treatment with a nicotine-like injection that will control the insects for about twelve months. Please call us if you have any questions or would like to schedule a treatment.