Spider Mites on Dwarf Alberta Spruce - Knowledgebase Question

Duncannon, PA
Question by wwwgemberli
November 29, 1998
My topiary have brown needles and are defoliating. I have been treating them once every two weeks for spider mites with a pesticide I purchased from a local nursery. I have also been treating the soil with Miracid every two weeks. They are still withering away.

One tree is completely defoliated and a few days ago I noticed that the tree next to it has started to defoliate.

What can be done to save these trees?

What is an appropriate maintenance/preventive regimen for these conifers?



Image
Answer from NGA
November 29, 1998

0

In other words, thorough spray coverage is absolutely critical. In addition, you must be careful to follow the label instructions.

Horticultural oil is used when the mites are active, and dormant oil is used to kill the overwintering mite eggs. It would be applied when the weather turns cold -- in late fall after there have been several light frosts or in late winter or early spring (before bud break).

When the infestation has been so severe it is worthwhile to continue to monitor the plants closely even after applying the dormant oil. Unfortunately, you might also consider removing or at least isolating the worst-affected plant(s) to cut back on possible sources of infestation next year.

Finally, healthy plants have a better chance of resisting infestation. These dwarf trees prefer a moist yet well drained, sandy, acid soil. They resent winds, reflected heat (such as that from a driveway or building), hot/dry weather and crowding. As a general guideline, you might also wish to perform some basic soil tests to determine which, if any, soil amendments or fertilization might be needed. Your County Extension can help you with the tests and with interpreting the results.

Good luck with your topiaries!
In other words, thorough spray coverage is absolutely critical. In addition, you must be careful to follow the label instructions.

Horticultural oil is used when the mites are active, and dormant oil is used to kill the overwintering mite eggs. It would be applied when the weather turns cold -- in late fall after there have been several light frosts or in late winter or early spring (before bud break).

When the infestation has been so severe it is worthwhile to continue to monitor the plants closely even after applying the dormant oil. Unfortunately, you might also consider removing or at least isolating the worst-affected plant(s) to cut back on possible sources of infestation next year.

Finally, healthy plants have a better chance of resisting infestation. These dwarf trees prefer a moist yet well drained, sandy, acid soil. They resent winds, reflected heat (such as that from a driveway or building), hot/dry weather and crowding. As a general guideline, you might also wish to perform some basic soil tests to determine which, if any, soil amendments or fertilization might be needed. Your County Extension can help you with the tests and with interpreting the results.

Good luck with your topiaries!

You must be signed in before you can post questions or answers. Click here to join!

« Return to the Garden Knowledgebase Homepage

Member Login:

Username:

Password:

[ Join now ]

Today's site banner is by Fleur569 and is called "Working with Purple & White"