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Hot weather brings out spider mites, mosquitoes

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED JUL 13, 2020

Telltale webbing of spider mites covers this spirea. The cure? Water. (Photo: Debbie Arrington)

Watch out for sunburned plants, too

Recent blazing hot weather has brought out heat-related pest and garden issues – while making other problems disappear.

First the good news: Gone is powdery mildew. It can’t survive in this heat. We shouldn’t see another outbreak of this fungal disease until October or later.

Also unable to cope with triple-digit temperatures are immature brown marmorated stink bugs and leaf-footed bugs. This heat wave likely toasted a whole generation of these destructive pests. That also means fewer bad bugs in August.

But some pests like it hot.

These tomato leaves show stippling by spider mites.
(Photo: Kathy Morrison)

With no rain for weeks, it’s also dry and dusty – perfect conditions for spider mites. If you see their telltale webs or stippling on leaves, get out the hose. Wash the plant down, removing the dust and likely many mites.

Spider mites attack a wide range of plants including roses, fruit trees, berries, grapevines, beans, squash, melons, tomatoes and more. Miticides are not recommended; they kill many beneficial insects in addition to the mites, which often manage to evade pesticide sprays.

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

Also out in force now are mosquitoes, which are a threat to people and pets as well as wildlife. According to the state’s West Nile Virus website, five dead birds found in Sacramento County last week tested positive for WNV. That brings the 2020 county total to 12. Four more Sacramento County mosquito samples last week tested positive, too, bringing that total to six.

County officials urge residents to be alert for dead birds and report them to the WNV bird hotline, 1-877-WNV-BIRD (1-877-968-2473).

Protect yourself, too. Wear mosquito repellent when working outdoors. At dawn and dusk when mosquitoes are most active, wear long sleeves and long pants.

For more info and the latest WNV statistics, visit https://westnile.ca.gov .

While most plants need full sun, too much sun (and heat) can cause problems, too.

A plastic plant flat serves as shade for a Patio Yellow potted tomato plant.

(Photo: Kathy Morrison)

Just like people, plants can get sunburned. If you notice crispy edges to leaves or pale patches on ripening tomatoes and peppers, that plant may need some shade. Construct a temporary shade structure to give plants some relief. It can be as simple as cardboard pieces on top of a tomato cage or burlap loosely draped over stakes.

Sunburn also can damage bark, especially on young trees or shrubs, opening up the plant to wood-boring pests and premature death. It tends to be worse on the west- and south-facing sides of plants. Painting the trunk and exposed lower limbs with diluted interior white latex paint (1:1 dilution with water) can protect a young tree's bark.

Besides a little shade, consistent irrigation can help plants survive too much sun.

For more tips on helping your garden deal with sunburn, see the advice of UC Cooperative Extension experts at http://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/sunburn.html .

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Keywords:

Sacramento spider mites pests heat wave heat stress heat pest irrigation mosquitoes gardening summer garden heat high heat summer

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Garden checklist for week of April 19

After this midweek storm, start getting serious about spring gardening. Flowers are blooming about three weeks ahead of schedule. That includes weeds!

* Get ready to swing into action in the vegetable garden – if you haven’t already. As nights warm up over 50 degrees, set out tomato, pepper and eggplant transplants.

* From seed, plant beans, beets, cantaloupes, carrots, corn, cucumbers, melons, radishes and squash; wait on pumpkins until May. Plant onion sets.

* In the flower garden, plant seeds for asters, cosmos, celosia, marigolds, salvia, sunflowers and zinnias. Transplant petunias, zinnias, geraniums and other summer bloomers.

* Plant perennials and dahlia tubers for summer bloom. Late April is about the last chance to plant summer bulbs, such as gladiolus and tuberous begonias.

* Transplant lettuce and cabbage seedlings.

* April is the last chance to plant citrus trees such as dwarf orange, lemon and kumquat. These trees also look good in landscaping and provide fresh fruit in winter.

* Smell orange blossoms? Give citrus trees a low dose of balanced fertilizer (such as 10-10-10) during bloom to help set fruit. Keep an eye out for ants. If leaves look yellow, your tree may need an iron boost -- apply some chelated iron fertilizer.

* Apply slow-release fertilizer to the lawn.

* Thoroughly clean debris from the bottom of outdoor ponds or fountains.

* Spring brings a flush of rapid growth, and that means your garden needs nutrition. Give shrubs and trees a slow-release fertilizer. Mulch with a 1-inch layer of compost, which helps the soil, but keep it a few inches away from trunks and stems.

* Azaleas and camellias looking a little yellow? If leaves are turning yellow between the veins, give them a boost with chelated iron.

* Trim dead flowers but not leaves from spring-flowering bulbs such as daffodils and tulips. Those leaves gather energy to create next year's flowers. Also, give the bulbs a fertilizer boost after bloom.

* Pinch chrysanthemums back to 12 inches for fall flowers. Cut old stems to the ground.

* Mulch around plants to conserve moisture and control weeds.

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