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Is there a cure for spider mites?

Grab the hose to fight these dust-loving pests

Multicolored oval tomatoes with mite damage
Look closely to spot the mite damage on this Brad's Atomic Grape tomato plant. It's especially evident around the sepals (green "caps") of the tomatoes. Water is your best weapon against spider mites. (Photo: Kathy Morrison)



Hot weather, smoky skies, dusty plants and no rain in sight: That’s paradise for spider mites.

With prolonged dry heat, this summer has seen a spider mite explosion. The itty-bitty arachnids seem to be spinning their webs over everything: Tomatoes, roses, camellias, berries, fruit trees, you name it.

A cousin of spiders, spider mites have built up massive populations in local community gardens as well as backyards. Usually, natural enemies can keep these voracious critters under control. But right now, spider mites are having a baby boom.

Spider mites can produce a whole generation in five to 10 days. Each mama mite can lay 100 eggs. No wonder their numbers can overwhelm a plant in a short time.

Spider mites are so tiny – smaller than the period at the end of this sentence – gardeners usually don’t notice them until they’re mature; that’s when they start spinning their telltale webs.

As they grow, they tend to hide out on the underside of foliage, practically invisible to even the most observant gardeners. Spider mite feeding may cause polka-dot stippling to appear on leaves.

According to the UC Cooperative Extension master gardeners, spider mites attack many fruit trees, shrubs, vines, berries, vegetables and other ornamental plants. Besides tomatoes and roses, they also love beans, grapevines, squash and melons.

The damage at first looks a little like peach leaf curl with foliage developing stipples and turning yellow or red before falling off. Then the webs start appearing, coating leaves and stems.

If left undisturbed, spider mites can overwhelm plants. They’re especially bad during drought conditions (like right now) and can do the most harm to water-stressed plants.

Spider mites can’t be controlled by insecticides – they’re not an insect, they’re a mite. But miticides are not recommended either, since they kill many beneficial insects in addition to the mites, which often manage to evade pesticide sprays.

Neem oil applied in the early stages of an infestation may smother the mites, but also kills beneficial insects including those that eat mites. In addition, neem oil sprayed on hot days can cook the plant’s foliage – eliminating any benefit.

Instead of neem oil or miticides, grab a hose and make it “rain.” Spider mites are proliferating because of lack of rain and resulting dusty, dry conditions on plants. Washing down foliage mimics a summer storm and disrupts the mites’ happy homes.

Insecticidal soap also can be helpful if applied at the first signs of trouble. Make sure to spray the underside of leaves, too.

The good news? Spider mites usually die out in September when their natural enemies can keep their numbers in check. Until then, keep giving plants a gentle morning shower as needed to wash dust and mites away.

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

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Flowers in My Back Yard Series

Aug. 25: Crape myrtles, Sacramento's unofficial tree of summer

Aug. 18: Pollinators adore scabiosa, aka pincushion flower

Aug. 11: Hardy hibiscus adds big tropical impact

Aug. 4: Dianthus a deceptively hardy flower

July 28: Naked Ladies put on summer show

July 21: Thank Luther Burbank for these long-lasting beauties (Shasta daisies)

July 14: How to keep hydrangeas happy

July 7: Grow these bright cosmos for bees and butterflies

June 30: Agapanthus adds blue fireworks to the garden

June 23: Easy-care gazanias fill those hot corners

June 16: Daylilies are perfect for water-wise gardens (and a lot more)

June 9: Grow coneflowers for pollinators -- and yourself

June 2: Sunflowers capture Sacramento's summer attitude

May 29: Are your roses going 'blind'?

May 26: Zinnias are the summer flowers every garden needs

May 19: Plant dahlias now for late-summer flower power

May 12: Know your coreopsis from your bidens

May 5: Mums the word on Mother's Day weekend

April 28: Majestic Matilija poppy is worth a look

April 21: Celebrate roses, America's favorite flower

April 14: Small flowers with outsized impact

April 7: Calendulas do double duty

April 3: Make Easter lilies last for years to come

March 31: In praise of a pollinator magnet (small-leaf salvias)

March 24: Azaleas brighten shady spots

March 17: The perfect flower for beginners? Try zonal geraniums

March 10: Keep camellias happy for years to come

March 3: Fruit tree blossoms are a fleeting joy

Feb. 27: Are your roses looking rusty?

Feb. 24: Treasure spring daffodils now and for years to come

Feb. 17: How and why to grow wildflowers

Feb. 10: Let's talk Valentine's Day roses

Feb. 3: Why grow flowers?

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Taste Summer! E-cookbook

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Find our summer recipes here!

Garden checklist for week of Aug. 30

Enjoy this mild late-summer weather – and get to work!

* September starts another season in the vegetable garden. Now is the time to plant for fall. The warm soil will get these veggies off to a fast start.

* Keep harvesting tomatoes, peppers, squash, melons and eggplant.

* Compost annuals and vegetable crops that have finished producing.

* Cultivate and add compost to the soil to replenish its nutrients for fall and winter vegetables and flowers.

* Fertilize deciduous fruit trees.

* Plant onions, lettuce, peas, radishes, turnips, beets, carrots, bok choy, spinach and potatoes directly into the vegetable beds.

* Transplant cabbage, broccoli, kale, Brussels sprouts and cauliflower as well as lettuce seedlings.

* Sow seeds of California poppies, clarkia and African daisies. Transplant cool-weather annuals such as pansies, violas, fairy primroses, calendulas, stocks and snapdragons.

* Divide and replant bulbs, rhizomes and perennials.

* Dig up and divide daylilies as they complete their bloom cycle.

* Divide and transplant peonies that have become overcrowded. Replant with “eyes” about an inch below the soil surface.

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Taste Spring! E-cookbook

Strawberries

Find our spring recipes here!

Taste Fall! E-cookbook

Muffins and pumpkin

Find our fall recipes here!

Taste Winter! E-cookbook

Lemon coconut pancakes

Find our winter recipes here!

Food in My Back Yard (FIMBY) Series

Lessons learned during a year of edible gardening

WINTER

Is edible gardening possible indoors?

Hints for choosing tomato seeds

Starting in seed starting

Why winter is the perfect time to plant fruit trees

When to plant? Consider staggering your transplants

How to squeeze more food into less space

Potatoes from the garden

Plant a fruit tree now -- for later

Win the weed war by tackling them in winter

Tips for planting bare-root trees, shrubs and vegetables

Time to give vegetable seedlings some more space

Ways to win the fight against weeds

FALL

Add asparagus to your edible garden

Soggy soil and what to do about it

Plant artichokes now; enjoy for years to come

It's late November, and your peach tree needs spraying

What to do with all those fallen leaves?

Prepare now for colder weather in the edible garden

Plant a pea patch for you and your garden

As citrus season begins, advice for backyard growers

Change is in the autumn air 

We don't talk (enough) about beets

Fava beans do double duty

Seeds or transplants for cool-season veggies?

How to prolong the fall tomato harvest 

SUMMER

Time to shut it down? 

How to get the most out of your pumpkin patch

Summer-to-fall transition time for evaluation, planning

To pick or not to pick those tomatoes?

: Put worms to work for you

Grow food while saving water

Enhance your food with edible flowers

Why won't my tomatoes turn red?

A squash plant has mosaic virus, and it's not pretty

Does this plant need water?

 Tear out that sad plant or baby it? Midsummer decisions

How to grow summer salad greens

 Weird stuff that's perfectly normal

SPRING

Help pollinators help your garden

Battling early-season tomato pests

Make your own compost

Where are the bees when you need them?

How to help tomatoes thrive on hot days

Your plants can tell you more than any calendar can

Maintain soil moisture with mulch for garden success

What's (already) wrong with my tomato plants?

Should you stock up on fertilizer? (Yes!)

Grow culinary herbs in containers

When to plant summer vegetables

Don't be fooled by these garden myths

Fertilizer tips: How to 'feed' your vegetables for healthy growth