My wife and I built two large raised mounds and planted five birch trees on each one. Each tree has a drip sprinkler on a timer set for 30 minutes a day and seems to stay damp.

The trees have grown and filled out nicely, but we lost one tree on each mound recently. They seemed to go from healthy to dead leaves almost over night. Help.

– Garry and Diane Emond, Orangevale

According to UC Master Gardener Bill Pierce, the following are some of the things to consider in determining why your tree died.

Birches have root systems that are close to the surface. Did you use "Weed and Feed" fertilizer on your lawn? These trees can pick this up through their roots and the herbicide in the fertilizer is enough to kill them, especially young trees.

Do you see any evidence of gophers in the lawn area or adjacent flower beds? Dig around the dead tree to find a gopher run, examine the roots of the tree to see if they have been eaten. Trapping and poison baits are effective against gophers.

Carefully examine the trunk of the tree for small holes that would be the entry points for bronze birch borers. European white birch are highly susceptible to these insects.

Proper cultural care is vital to prevent borer infestation in the remaining trees. Well-timed insecticide application may reduce borer attacks, but are not a substitute for proper cultural care or trees are still likely to die. The insecticides permethrin and imidacloprid are registered for borers.

Evaluate your irrigation methods. Depending on the output, one emitter per plant may not be sufficient and cause death.

However, watering every day is excessive and may cause root rot. Dig down and verify that water is reaching the root zone and the roots are healthy.

We hope you can help! We have a variegated hydrangea and the leaves are getting eaten by something. We're hoping that you could help us stop whatever that critter is.

It seems that it eats toward the ends of the leaves and to the stem, but not the stem itself. The leaves end up looking like a skeleton.

– Peggy Sue and John Foley, Sacramento

Two possibilities come to mind, said UC Master Gardener Bill Pierce.

Finches – those little birds will make lace out of sunflower leaves and probably go after hydrangeas as well.

Nurseries sell "bird scare" products such as flashing vinyl tape that should keep them away.

Foliage-feeding caterpillars – the larval stage of moths or butterflies – also skeletonize foliage. To preserve the butterflies, no management is recommended. The munched leaves are a tradeoff.

A sample of the plant leaves would help with identification of your problem.

If possible, bring a sample to the UC Cooperative Extension office located at 4145 Branch Center Road, Sacramento.

Call the office at (916) 875-6913 for hours or to make an appointment.

GARDEN QUESTIONS?

Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA. 95852. Send e-mail to h&g@sacbee.com. Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:

• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays

• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email ceamador.ucdavis.edu

• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays

• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays

• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned

• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message

• Shasta, Tehama, Trinity: (530) 225-4605

• Solano: (707) 784-1322; leave a message and calls will be returned

• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

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