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Aphids, with ant assistance, go for what they like


Mum stem and leaves with ants
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.

Oleander aphids on milkweed
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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Garden Checklist for week of Jan. 19

Dress warmly in layers – and get to work:

* Apply horticultural oil to fruit trees to control scale, mites and aphids. Oils need 24 hours of dry weather after application to be effective.

* This is also the time to spray a copper-based oil to peach and nectarine trees to fight leaf curl. The safest effective fungicides available for backyard trees are copper soap -- aka copper octanoate -- or copper ammonium, a fixed copper fungicide. Apply either of these copper products with 1% horticultural oil to increase effectiveness.

* Prune, prune, prune. Now is the time to cut back most deciduous trees and shrubs. The exceptions are spring-flowering shrubs such as lilacs.

* Now is the time to prune fruit trees. Clean up leaves and debris around the trees to prevent the spread of disease. (The exceptions are apricot and cherry trees, which are susceptible to a fungus that causes dieback if pruned now. Save those until summer.)

* Prune roses, even if they’re still trying to bloom. Strip off any remaining leaves, so the bush will be able to put out new growth in early spring.

* Clean up leaves and debris around your newly pruned roses and shrubs. Put down fresh mulch or bark to keep roots cozy.

* When forced bulbs sprout, move them to a cool, bright window. Give them a quarter turn each day so the stems will grow straight.

* Browse through seed catalogs and start making plans for spring and summer.

* Divide daylilies, Shasta daisies and other perennials.

* Cut back and divide chrysanthemums.

* Plant bare-root roses, trees and shrubs.

* Transplant pansies, violas, calendulas, English daisies, snapdragons and fairy primroses.

* In the vegetable garden, plant fava beans, head lettuce, mustard, onion sets, radicchio and radishes.

* Plant bare-root asparagus and root divisions of rhubarb.

* In the bulb department, plant callas, anemones, ranunculus and gladioli for bloom from late spring into summer.

* Plant blooming azaleas, camellias and rhododendrons. If you’re shopping for these beautiful landscape plants, you can now find them in full flower at local nurseries.

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