by Fred Hoffman
As if the local eucalyptus trees don't have enough problems. Now entering the valley is another pest problem for this widely planted tree, the eucalyptus tortoise beetle, first discovered in Riverside County five years ago.
While the red gum lerp psyllids are sucking away along the undersides of eucalyptus leaves and the longhorned eucalyptus borer is tunneling its way into the tree's branches and trunk, the eucalyptus tortoise beetle is chewing semicircular or irregular notches along the leaf margins, leaving only the mid-vein when its done dining.
Although beneficial insects have been introduced to battle both the red gum lerp psyllid and the eucalyptus tortoise beetle, it may be years before the beneficials population is large enough to control these pests. In the meantime, homeowners can help out their suffering eucalyptus trees with a few simple steps:
* Water eucalyptus trees, once a month, during the summer. Soak the area beneath the outer canopy of the tree. Don't flood the area near the trunk, though; eucalyptus are susceptible to root rots.
* Don't fertilize these trees. Nitrogen-induced tender, new growth is especially susceptible to these pests.
* Clean up any dead branches on the ground. This could be a breeding area, especially for the eucalyptus longhorned beetle.
* Don't plant pest-susceptible eucalyptus species. The varieties most susceptible to damage by these critters include the blue gum (Eucalyptus globulus), manna (E. viminalis) and the widely planted river red, E. camaldulensis.
* Choose eucalyptus varieties that have shown some resistance to these pests. This list would include the Australian beech (E. polanthemos), lemon eucalyptus (E. citriodora) and the red ironbark (E. sideroxylon).
* Read and follow all label directions if using a soil drench systemic insecticide whose active ingredient is imidacloprid, which may control the red gum lerp psyllid; studies aren't in yet if it is effective on the tortoise beetle. The University of California reports mixed results on the efficiency of imidacloprid in controlling the red gum lerp psyllid; for best results apply this soil drench in early spring.
For more Information:
The Eucalyptus Tortoise Beetle:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74104.html
Red Gum Lerp Psyllids:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7460.ht
Eucalyptus Longhorned Borers:
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7425.html