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Aphids, with ant assistance, go for what they like

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED AUG 3, 2020

Look hard: Ants are on the leaves, carrying honeydew down to their nest. (Photo: Debbie Arrington)

Chrysanthemum aphids one of 5,000 species

One day, my mums were fine, growing happily and rapidly.

The next day I checked, the tips and upper stems were covered with tiny black bugs. The insects looked like aphids, but instead of the familiar lime green or light pink aphids that attack my roses and other plants, these were quite dark.

Also odd was their grouping; the bugs were lined up almost in straight rows.

Then, I noticed the ants – tiny little black ants that were moving up and down the mum stem. They were carrying something down from the rows of little bugs.

Like itsy bitsy dairy farmers, the ants were “milking” the critters for honeydew and carrying it back to their nest. The ants are how these bugs probably got there in the first place.

What to do? First, identify the invader. I turned to the best pest expert I know.

“Most likely this aphid is the chrysanthemum aphid but there are other aphids that also feed on mums,” said retired state entomologist Baldo Villegas, Sacramento’s Bug Man.

Aphids with an appetite for mums? Of course, they’re chrysanthemum aphids.

One of the most common summer pests in our gardens, aphids come in many, many variations, named for what they like to eat. At last count, there are about 5,000 species of aphids with at least 400 that attack food and fiber crops. Hundreds of others (such as the chrysanthemum aphid) go for ornamental plants.

Aphids come in all colors. Yellow-gold oleander aphids crowd

the stem of a milkweed plant. (Photo: Kathy Morrison)

The UC Integrated Pest Management website lists 1,430 articles on aphids. There’s advice for control of citrus aphids, peach aphids, bean aphids, cabbage aphids, corn aphids, potato aphids, walnut aphids and scads of other aphids.

“Almost every plant has one or more aphid species that occasionally feed on it,” say the UC experts. “Many aphid species are difficult to distinguish from one another; however, management of most aphid species is similar.”

Villegas shared advice on chrysanthemum aphids from Clemson University:

“Chrysanthemum aphids ( Macrosiphoniella sanborni ) and other aphid species are pests on chrysanthemums. The chrysanthemum aphids are brown to black, which other species range in color from green to pink. Aphids feed by piercing plant tissue and sucking plant sap. They prefer feeding on new growth in such areas as shoots, the undersides of leaves, buds and flowers. Their feeding can result in distorted growth, stunting and sometimes death of the entire plant.

“As they feed on plant sap, they excrete honeydew (a sugary material). The sooty mold fungus feeds on the honeydew, resulting in unsightly, dark fungal growth. In addition to damage caused by their feeding, chrysanthemum aphids can transmit various plant viruses.”

Whether aphids are eating mums, roses, beans or whatever, control methods are the same. Here are more Clemson tips:

“Aphids can be removed from plants by applying a forceful spray of water to the plants every two days, especially to the undersides of leaves. Continue as needed, but at least three times.

“Several naturally occurring enemies feed on aphids. As much as possible, these predators should be allowed to reduce aphid populations.

“As a result of their phenomenal ability to reproduce, aphids are very difficult to control with insecticides. Leaving one aphid alive can result in the production of a new colony very quickly. In addition, the use of insecticides kills the beneficial insects that normally keep aphid populations under control.”

If natural predators do not keep aphids under control and serious damage is occurring, spray plant with insecticidal soap or horticultural oil, Clemson recommends. Follow label directions.

Since discovering this outbreak, I’ve been blasting the mums with the hose; the plants appreciate the extra water. The aphids? They can’t swim – and they don’t survive the fall.

As for the ants, I’m sure they’re looking for a new spot to set up their next dairy farm.

For more on aphids, check out the UC IPM main aphid page: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html

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Keywords:

gardening Sacramento integrated pest management pests roses pest control garden pests chrysanthemums UC IPM aphids flowers

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Garden Checklist for week of May 19

Temperatures will be a bit higher than normal in the afternoons this week. Take care of chores early in the day – then enjoy the afternoon. It’s time to smell the roses.

* Plant, plant, plant! It’s prime planting season in the Sacramento area. If you haven’t already, it’s time to set out those tomato transplants along with peppers and eggplants. Pinch off any flowers on new transplants to make them concentrate on establishing roots instead of setting premature fruit.

* Direct-seed melons, cucumbers, summer squash, corn, radishes, pumpkins and annual herbs such as basil.

* Harvest cabbage, lettuce, peas and green onions.

* In the flower garden, direct-seed sunflowers, cosmos, salvia, zinnias, marigolds, celosia and asters.

* Plant dahlia tubers. Other perennials to set out include verbena, coreopsis, coneflower and astilbe.

* Transplant petunias, marigolds and perennial flowers such as astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia and verbena.

* Keep an eye out for slugs, snails, earwigs and aphids that want to dine on tender new growth.

* Feed summer bloomers with a balanced fertilizer.

* For continued bloom, cut off spent flowers on roses as well as other flowering plants.

* Don’t forget to water. Seedlings need moisture. Deep watering will help build strong roots and healthy plants.

* Add mulch to the garden to help keep that precious water from evaporating. Mulch also cuts down on weeds. But don’t let it mound around the stems or trunks of trees or shrubs. Leave about a 6-inch to 1-foot circle to avoid crown rot or other problems.

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