Needs tips on identifying what’s killing azaleas? Ask an expert

We’re deep into fall and gardening is winding down, but there are still things you’re wondering about. If you’ve got questions, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website and type in a question and the county where you live. Here are some questions asked by other gardeners. What’s yours?

Q: Is it safe to put dead and dying azalea in the yard trash bin? I’ve lost six bushes so far and another is in trouble. I know they need to come out.

Is there any word yet on how to stop it? When I trim out the dead branches or take them out completely can I safely plant new ones in their place in the spring? – Benton County

A: Sorry to hear you are having problems with your azaleas. To answer your first question: Yes, you can throw it in the trash. You could also put it in a commercial compost bin because these will be processed with a high-temperature method that kills most diseases.

There are several directions you could go to determine the problem and determine if you can plant new ones in the same location.

The first hint is that you have lost six bushes. So, the problem will most probably continue in any new plantings. Here are questions to ask yourself as you determine what to plant in this area:

Is it the environment (too much/little sun, moisture, competition from the roots of surrounding plants, etc.) or the soil (too much/little acid, diseases in the soil, moles eating roots…) or insects or plant diseases?

I have had all these issues with a row of azaleas that I planted, so I know your pain!

Here and here are lists of what to look for, possible diseases or pests, and best environment for growing azaleas.

I hope this helps you to make a good decision regarding what to plant in this area next spring. – Ann Kinkley, OSU Extension Master Gardener

Q: We have about 20 conifers in our backyard and many of them have dead limbs toward the bottom of the trunks. They are not next to houses and we are not bothered by the aesthetics of the dead branches. Is there any reason to take out these dead limbs? Or to let them be? – Washington County

A: In general, it’s recommended to remove dead, diseased, or damaged branches on conifers. If the branches are in your way they can also be removed.

If you don’t see obvious disease or oozing sap, it’s likely OK to leave the branches as long as they are not a safety hazard. The dead branches will eventually fall off as they would in a forest setting.

If you choose to prune, here and here are pruning guides for conifers. – Weston Miller, OSU Extension horticulturist

Q: We have a hibiscus that has small egg sacks all over the leaves and branches. Can you tell me what they are and the best way to get rid of them? The hibiscus was on our back porch, but we brought it inside a few weeks ago. We just noticed the insects today. I have an insect killing soap and oil, but haven’t tried either choice yet, as I’m new at this. We’ve had the plant for 1.5 years. It lost a lot of leaves a few weeks ago in the cold, but it’s inside now recovering from the cold. – Washington County

A: Your shrub is a hardy hibiscus which, if planted in the ground would be fine outdoors throughout the winter. Hardy hibiscus is a deciduous plant; thus, the leaf loss is normal at this time of year.

However, because the shrub is growing in a pot, it is at risk of dying during one or more of the frosts that are yet to come. Frankly, that might be a good thing because then, you could start over with a healthy, fresh, plant next spring.

Do you see all those small bumps, both white and dark, on the backs of the leaves, also on all the branches? They are scales, small sucking insect pests which will gradually weaken the shrub and may kill it.

Then, too, the sticky stuff on the leaves and branches is honeydew, the excrement shed by scales as they feed on fluids they suck out of the plant.

Scale is very difficult to eradicate, especially on an indoor plant. You could start by hosing off the shrub to get rid of the sticky stuff. Then, continue by physically removing the scales from the leaves and stems. Use gloves and/or a paper towel or cloth to rub them off.

The bottom line is that it’s extremely difficult to get rid of all the scale because they hide in cracks and crevices you can’t get to. Applying a superior horticultural oil will help to eradicate the scale but will need to be used several times, according to label directions.

Frankly, I encourage you to chalk this up to a learning experience, then save yourself a lot of grief by getting rid of the plant now. Then, if you’ve enjoyed having this plant, you could start over with a healthy, fresh, plant next spring and plant it in a sunny spot in the garden where you can enjoy it.

This article on scales offers images and information about several different kinds of these small sucking insect pests. – Jean Natter, OSU Master Gardener Diagnostician