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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:


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Dig In: Garden Checklist

For week of March 19:

Spring will start a bit soggy, but there’s still plenty to do between showers:

* Fertilize roses, annual flowers and berries as spring growth begins to appear.

* Watch out for aphids. Wash off plants with strong blast from the hose.

* Pull weeds now! Don’t let them get started. Take a hoe and whack them as soon as they sprout.

* Prepare summer vegetable beds. Spade in compost and other amendments.

* Prune and fertilize spring-flowering shrubs after bloom.

* Feed camellias at the end of their bloom cycle. Pick up browned and fallen flowers to fight blossom blight.

* Feed citrus trees as they start to blossom.

* Cut back and fertilize perennial herbs to encourage new growth.

* Seed and renovate the lawn (if you still have one). Feed cool-season grasses such as bent, blue, rye and fescue with a slow-release fertilizer. Check the irrigation system and perform maintenance. Make sure sprinkler heads are turned toward the lawn, not the sidewalk.

* In the vegetable garden, transplant lettuce and kale.

* Seed chard and beets directly into the ground.

* Plant summer bulbs, including gladiolus, tuberous begonias and callas. Also plant dahlia tubers.

* Shop for perennials. Many varieties are available in local nurseries and at plant events. They can be transplanted now while the weather remains relatively cool.

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