Unhappy Chionoides Rhododendron

[Jenny]

We planted two of these last spring as part of our foundation planting in an northwest facing area that gets about 4 hours of afternoon sun but is otherwise shaded. They've fallen prey to all kinds of insects which seem to just laugh off the systemic insecticide that the knowledgeable lady at the garden center suggested. I think they have root weevils, plus various caterpillars and other bugs. All the other plants we put in at the same time are doing fine (a burkwood viburnum, pyramidal yews, rosebud azaleas and Blaaw's Pink azaleas.)

My question is this: if I pull out theses miserable plants, what do I have to do to the soil to make sure that replacements don't have the same problems (root weevils in particular).

I'm thinking of putting in more pyramidal yews where these were.

Thanks for your ideas!

Also, any suggestions for

[bamboo]

Insufficient information. Location / zone Soil ph Moisture

[Jenny]

Location: Western Massachusetts, close to VT/NH border. Zone 5 but barely. Soil Ph slightly acid. In addition, I mulched with coffee grounds last year. Moisture: It rained all last summer and fall and we had snow cover all winter. However, the drainage is very good where these were planted since it is the foundation and there are curtain drains underneath.

[Stephen Henning]

Most rhododendrons including chionoides are acid loving plants. Your soil may be slightly acidic, but near a foundation it will be alkaline due to the lime in the foundation. Wet conditions on an unhappy plant will make it susceptible to most anything. The plant should thrive if given more sun and acidic soil. When healthy they transplant very easily. They have very shallow roots.

The bugs were in the soil already, either in the soil from the garden center or your soil. Weevils live in the ground but come out at night and chew on the edges of the leaves. This is a very common problem in many areas.

[Jenny]

Stephen,

I put a lot of coffee grounds around these plants all last summer, hoping that would help acidify the soil. What else would help?

More sun isn't an option here. There are about 4 hours in the afternoon and that's it.

Any suggestions as to what to do about eliminating those weevils? I'm assuming they came from the garden center (which grows its own plants) as none of my 4 other azaleas or 2 yews show any signs of damage. I've been spraying once a month with a systemic insecticide as directed by the "expert" at the locally owned Farmers Ag coop. After 2 sprayings, I'm not seeing much progress. I've also hit them with "rose spray" to take care of the caterpillars which also showed up this spring.

The rhodos did put out big clumps of leaves this past week, so they're still alive.

Any detailed suggesti> Jenny wrote:

[Stephen Henning]

Powdered sulfur is best. If there are signs of chlorosis (Yellowing of a leaf between green veins) then acidity may be increased by adding flowers of sulfur (powdered sulfur) or iron sulfate. I add 1 tablespoon of sulfur powder around the base of any plant showing signs of chlorosis.

That will reduce the number of flower buds but is not a big problem.

Leaves chewed on edges is a symptom of chewing insects. Most are nocturnal feeders and can be found at night with a flashlight. The most prominent chewing insects on rhododendron and azaleas are the Black Vine Weevil and Strawberry Root Weevil. Feeding is done at night. Specimens may be collected at night for identification. The major damage is caused by weevil larvae which girdle the roots and kill the plant. Larvacidal drenches may be used to kill them but are of limited effectiveness. A more effective approach is to use nematodes. They are very effective against weevils. Foliar sprays are very effective at controlling adult weevils when leaf notching starts. Foliar sprays must be repeated until no adults emerge. Since weevils feed at night, you can hand pick adult weevils at night using a flashlight. Since weevils spend the daytime in the soil and come out at night to feed, you can paint the trunk with Tanglefoot to stop them, but make sure no branches are touching the ground. Other chewing insects include caterpillars, cut worms and loopers.

This is a very good sign. Resist the temptation to fertilize. I good fertilizer like Hollytone now is OK but none later.

Good Luck!