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These little pests love hot, dusty, dry conditions


Spider mites can quickly turn a green leaf into a speckled mess. Fight them with water! (Photos courtesy UC Integrated
Pest Management)

To fight spider mites, use water, not pesticides



These itsy-bitsy spider cousins are making a mess.

Recent hot weather has brought out the spider mites, tiny arachnids that attack a wide range of edible and ornamental plants. Right now, they’re really going after roses, covering the underside of leaves with white webs and sucking the life out of foliage.

According to the UC Cooperative Extension master gardeners, spider mites also attack many fruit trees, vines, berries, vegetables and other ornamental plants. Look for the telltale webbing.

The spider mites themselves are teeny-tiny, no bigger than the period at the end of this sentence. When shaken from a leaf onto a sheet of paper, they look like fast-moving dots.

They love hot, dry, dusty conditions. May’s early heat wave brought them out in force. They can multiply quickly, producing a whole generation in a week. If left undisturbed, they can overwhelm plants. They’re especially bad during drought conditions and can do the most harm to water-stressed plants.

The key to their control? Water. By keeping plants well hydrated and dust down, spider mites are a lot more manageable. In addition, they have many natural predators in the garden. By August, the good guys usually can keep the spider mite population in check.

Unless you apply a broad spectrum pesticide. That kills the good bugs while leaving the spider mites free to weave their webs of destruction.
This is an advanced case of spider mite damage.

Besides attacking roses, spider mites can cause fruit trees to lose their leaves in spring and early summer. The damage at first looks a little like peach leaf curl with foliage developing stipples and turning yellow or red before falling off. Except spider mites attack a lot more than peaches and the fallen leaves usually show signs of that white webbing.

In the vegetable garden, they attack the leaves of squash and melons, potentially leading to sunburn. They also like beans, munching the pods as well as leaves.

Early signs of spider mite damage are stippling and yellowing of leaves. Turn a suspect leaf over and look for the white webbing. Remove and dispose of that infested leaf. Then, spray the bush with water, washing dust off leaves (along with some spider mites, too).

Insecticidal soap also can be effective in nipping a spider mite infestation in the bud. Make sure to spray the underside of leaves.

For more tips and details, see the UC IPM pest notes on spider mites:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7405.html

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Garden Checklist for week of Jan. 19

Dress warmly in layers – and get to work:

* Apply horticultural oil to fruit trees to control scale, mites and aphids. Oils need 24 hours of dry weather after application to be effective.

* This is also the time to spray a copper-based oil to peach and nectarine trees to fight leaf curl. The safest effective fungicides available for backyard trees are copper soap -- aka copper octanoate -- or copper ammonium, a fixed copper fungicide. Apply either of these copper products with 1% horticultural oil to increase effectiveness.

* Prune, prune, prune. Now is the time to cut back most deciduous trees and shrubs. The exceptions are spring-flowering shrubs such as lilacs.

* Now is the time to prune fruit trees. Clean up leaves and debris around the trees to prevent the spread of disease. (The exceptions are apricot and cherry trees, which are susceptible to a fungus that causes dieback if pruned now. Save those until summer.)

* Prune roses, even if they’re still trying to bloom. Strip off any remaining leaves, so the bush will be able to put out new growth in early spring.

* Clean up leaves and debris around your newly pruned roses and shrubs. Put down fresh mulch or bark to keep roots cozy.

* When forced bulbs sprout, move them to a cool, bright window. Give them a quarter turn each day so the stems will grow straight.

* Browse through seed catalogs and start making plans for spring and summer.

* Divide daylilies, Shasta daisies and other perennials.

* Cut back and divide chrysanthemums.

* Plant bare-root roses, trees and shrubs.

* Transplant pansies, violas, calendulas, English daisies, snapdragons and fairy primroses.

* In the vegetable garden, plant fava beans, head lettuce, mustard, onion sets, radicchio and radishes.

* Plant bare-root asparagus and root divisions of rhubarb.

* In the bulb department, plant callas, anemones, ranunculus and gladioli for bloom from late spring into summer.

* Plant blooming azaleas, camellias and rhododendrons. If you’re shopping for these beautiful landscape plants, you can now find them in full flower at local nurseries.

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