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As temperatures warm, watch out for aphids

Hungry pests can devour tender new growth

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED FEB 22, 2021

Aphids are munching away on this tender rosebud. Don't let them get ahead of you, or they will destroy all the almost-spring growth. (Photo: Kathy Morrison)

Spring arrived early in Sacramento. So did aphid season.

Warmer temperatures bring an explosion of green growth in our gardens – and possibly masses of hungry aphids, too. These voracious insects love temperatures in the 65- to 80-degree range, and our current forecast is for several days in the high 60s and low 70s.

Just as your favorite spring flowers are opening, aphids seem to burst on the scene to spoil the show. They can overwhelm new shoots and buds on rose bushes and other plants now pushing out spring growth. They can eat up your whole cabbage patch as well as attack almost everything in the vegetable garden from beans to potatoes. They’re particularly destructive to seedlings and tender shoots. (They like fruit trees, too.)

Aphids can seem to come out of nowhere, in part because they never really go away. Our winter temperatures are mild enough that aphids can survive our cold months. Then, when temperatures start to rise, they “reappear.”

Their numbers can rise so rapidly because the adult females can produce a dozen live offspring a day without mating. And they’re ready to start birthing in about a week.

“When the weather is warm, many species of aphids can develop from newborn nymph to reproducing adult in seven to eight days,” explains the UC Cooperative Extension pest notes. “Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.”

What can a gardener do to stop this onslaught? Get out the hose.

On sturdy plants, a strong blast of water can knock off aphids. They can’t fly and their soft bodies can’t survive the fall to the ground.

“Using water sprays early in the day allows plants to dry off rapidly in the sun and be less susceptible to fungal diseases,” advise the master gardeners.

For more tender plants, try adding a teaspoon or two of liquid soap to a quart of water and spray the aphids directly. Or use insecticidal soap, specifically made for this purpose.

Use of insecticides is not recommended; chemical sprays will wipe out the beneficial insects (and there are many species of these) that prey on aphids and help keep them under control.

Instead, monitor for aphids regularly, checking the underside of leaves as well as shoots. Also, remove weeds (especially mustard) that can serve as aphid nurseries.

To cut down on aphid problems, watch how much you feed your plants. Too much nitrogen (which prompts rapid growth) can invite an aphid army.

“High levels of nitrogen fertilizer favor aphid reproduction, so never use more nitrogen than necessary. Instead, use a less soluble form of nitrogen and apply it in small portions throughout the season rather than all at once,” say the master gardeners. “Slow-release fertilizers such as organic fertilizers or urea-based time-release formulations are best.”

Sometimes the best solution is to cover tender seedlings.

“Because many vegetables are susceptible to serious aphid damage primarily during the seedling stage, reduce losses by growing seedlings under protective covers in the garden, in a greenhouse, or inside and then transplanting them when the seedlings are older and more tolerant of aphid feeding,” added the master gardeners. “Protective covers will also prevent transmission of aphid-borne viruses.”

And don’t forget lady beetles, especially the nymphs. They LOVE aphids. But the adults usually leave your garden after they’ve had their fill.

For more on aphids and possible controls: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html

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Keywords:

natural predators gardening Sacramento integrated pest management February pests spring beneficial insects aphids weather

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Garden Checklist for week of Nov. 3

November still offers good weather for fall planting:

* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.

* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.

* Set out cool-weather annuals such as pansies and snapdragons.

* Lettuce, cabbage and broccoli also can be planted now.

* Plant garlic and onions.

* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.

* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.

* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.

* Give your azaleas, gardenias and camellias a boost with chelated iron.

* For larger blooms, pinch off some camellia buds.

* Prune non-flowering trees and shrubs while dormant.

* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.

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