Photograph by Shari Kaplan

Statice, also known as sea lavender, is a perennial often found growing wild along the California coast. It can also be cultivated in gardens.

Eucalyptus trees in danger, but pest management helps

By Tony Tomeo

Various species of eucalyptus have been popular in California for at least the past century. Some have been useful for screens, windbreaks or shade trees. Others have been plantation-grown for wood pulp, railroad ties or cut foliage. Most grow well on their own and will even naturalize. They are often planted where other trees will not grow, or outside landscaped areas. Their performance has always been reliable because they were not susceptible to disease or insect infestation. Unfortunately, their carefree lifestyle is not as secure as it once was.

In the last few years, several of their natural pathogens from Australia have mysteriously appeared in California. What is worse is that the new pests did not arrive with their natural predators. They are proliferating at an alarming rate with nothing to stop them. Eucalyptus in California are now much more susceptible to infestation than they would be in Australia.

The effectiveness of chemical control has not yet been determined for most of these newly arrived insects. Even if chemicals are found to be effective, many trees are too large to be sprayed thoroughly. Large groves would be even more difficult. Systemic insecticides are being tested on some of the new pathogens. Biological agents will likely be the most effective control. Research continues on finding, producing and releasing the parasites and predators specific to each species of pest in their natural habitats.

The main pests are the eucalyptus longhorn borer, eucalyptus gall wasp, various leaf-eating beetles and at least six species of psyllids. Each pest attacks specific species of eucalyptus. Some are limited to only a few potential hosts, but others are not as discriminating. For example, the eucalyptus longhorn borer will infest any of at least six species. Although some eucalyptus are not attacked by any pests, many may be attacked by more than one. Because there is no practical treatment for most of these new pathogens, preventing infestation is important.

Stressed trees are most susceptible. It is therefore important to keep trees healthy. Eucalyptus that normally do well without irrigation might appreciate occasional deep irrigation through summer. Damage to roots should be avoided. When choosing new trees, resistant species should be considered.

If the species of eucalyptus in the landscape is known, it is easy to determine which insects may be a problem and for which symptoms to watch. Identification of potential pests is also useful when trying to protect trees. For example, redgum lerp psyllid is attracted to fresh new growth. Therefore, fertilizing should not be done because it would promote such growth.

More information may be obtained from the University of California Cooperative Extension and the U.C. Division of Agriculture and Natural Resources. Hort Script, published by the U.C. Cooperative Extension, is a collection of continually updated articles specific to each pathogen.

The U.C. Division publishes Pest Notes , which serves the same purpose. (See Hort Script August 1994 No. 8 and August 1996 No. 20; and Pest Notes No. 7425 and No. 7460.) This and other information may be found online. Pest Notes is at www.ipm.ucdavis.edu.

It is important when researching gardening concerns online to limit the geographical area from which information is retrieved.

Flower of the Week: Sea Lavender

This is one of many perennials I miss from college. Sea lavender, Limonium perezii, more commonly known as statice, grew like a weed in San Luis Obispo. More impressively, it grew just as well in gardens near the beach in Los Osos. Once established, it is tolerant of heat, sun, drought and poor soil as long as it is well drained. If too shaded, foliage will be sparse and blooms stunted. It may be planted from seed, but more commonly from No. 1 cans.

Statice often seeds itself, but is not normally invasive. The thick leaves are usually low, but can reach up to one foot from the ground. Plants grow quickly to produce dense clusters of very small bluish purple flowers with white specs. Each white spec is actually a corolla (petal cluster) surrounded by a large purple calyx, which is the bulk of the bloom.

Healthy plants may produce clusters up to two feet wide, supported three feet off the ground. Now that is high statice! Flowers last a long time and may be cut and dried. (The statice more commonly grown as a cut flower is actually Limonium latifolium.)

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Horticulturist Tony Tomeo can be contacted at 408.358.2574.

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