Mulch on, and don’t fear the aphids

Mulch on, and don’t fear the aphids  by Rhonda Nowak for the Mail Tribune Published Sunday, November 22nd 2020
( In response to a question posed by AGC member Donna R.)

“Listen
With faint dry sound,
Like steps of passing ghosts,
The leaves, frost-crisp’d, break from the trees
And fall.”
— Adelaide Crapsey, “November Night” in “Verses,” 1915

American poet Adelaide Crapsey (1878-1914) did not enjoy a long life — she died in New York at the age of 36 from tuberculosis. Although her poetry is not widely remembered today, Crapsey left an important legacy in the form of her unrhymed, five-line, 22-syllable poems, inspired by her love of Japanese haiku.

Her style has become known as the American cinquain, adopted and modified by many poets of the 20th and 21st centuries. In his 1918 collection of poems “Cornhuskers” (for which he won a Pulitzer Prize), Carl Sandburg published a tribute to Adelaide Crapsey in a section of the book called “Persons Half Known.”

Speaking of the “half known,” I received an email from a reader who wanted to know more about using fall leaves for mulch in the garden (the topic of my column Nov. 8). Donna wrote, “I appreciate the benefits of mulching. However, no one seems to include aphids in these discussions, only beneficial insects. What is the life cycle for aphids and does mulching encourage their overwintering?”

I replied to Donna that aphids do, indeed, overwinter in our garden, usually in the egg phase of their development. Although leaf litter provides shelter for aphids, most of the approximately 5,000 known species of aphids lay eggs on the leaves and stems of specific host plants. For example, Donna’s aphid nemesis is the lupine aphid (Macrosiphum albifrons), and my roses are sometimes plagued by a different species called rose aphids (Macrosiphum rosae).

Other aphids prefer vegetable crops for their host plants, such as cabbage aphids (Brevicoryne brassicae) and turnip aphids (Lipaphis erysimi).

In the spring, only female aphids hatch from overwintered eggs, and they begin reproducing one week later. During most of the year, female aphids reproduce asexually through a process called parthenogenesis, whereby they give birth to miniature replicas of themselves rather than laying eggs. During one season, some aphid species can produce up to 41 generations of offspring, each insect living 20 to 40 days and producing between 50 and 100 babies.

Most aphids live out their lives on their host plants. Later in the summer, some adults will develop wings and fly off to visit other plant species, but subsequent generations of females will return to their host plant species in the fall. By then, some aphids have developed into males, so females find a mate and then lay their fertilized eggs on the host plant, or in leaf litter, to start the process all over again.

By layering garden beds with leaf mulch, it seems like gardeners are practically ensuring aphids will not only survive but remain comfortable all winter. However, scientists have found that 70% to 80% of overwintering aphids die before spring due to predation or cell damage. (Keep in mind that leaf mulch also provides shelter to aphid predators.)

Aphids that do survive the winter are an excellent source of nutrition for hungry birds, as well as many kinds of beneficial insects: parasitic wasps, ladybugs, lacewings, hover flies and soldier beetles.

In fact, aphids are not just sap-sucking, disease-spreading garden pests; they’re also an important part of the food chain in a balanced ecosystem. In order to attract our pollinator friends to the garden, we must provide food for them, and aphids and other insects we consider pests fit that bill quite nicely.

Aphid infestations occur when the garden doesn’t have enough aphid predators or when weakened plants are unable to ward off insect pests; thus, aphid invasions tell us that the garden ecosystem is off-balance in some way. We might say aphids are “food for thought” for gardeners just as they are food for wildlife.

Leaf mulch is an efficient use of fall leaves to provide habitat for overwintering wildlife, including aphids. When we see overwintering birds foraging in the garden, we may even be thankful the aphids are there!

Rhonda Nowak is a Rogue Valley gardener, teacher and writer. For more about gardening, check out her podcasts at https://mailtribune.com/podcasts/the-literary-gardener and her website at www.literarygardener.com.

Home Remedy

Aphid Control

Pour 2 tablespoons liquid dish soap into 1 gallon water. Stir the dish soap into the water and transfer the contents into a plastic spray bottle.

Spray the affected plant’s leaves on both sides with the soapy mixture. Pay attention to coat the underside of the leaves with the mixture, as this is where you’ll find the highest concentration of aphids.

Spray the soapy mixture directly onto any aphids you notice falling from the leaves. The aphids are small, and it’s necessary to shoot them with the soapy water to kill the unwanted pests.

Rinse away the soapy residue after one to two hours. Allowing the soap to remain on the leaves for longer than a few hours can cause damage and burning. Use a garden hose or spray bottle filled with plain water to remove the residue.

Reapply the mixture every few days, or as necessary, to keep the aphid infestation under control.

Tip:  Add 1 teaspoon vegetable oil to the mixture to increase the mixture’s density and make it stickier, helping it attach to and kill the aphids more effectively.

Warning: Test the soapy mixture on a small leaf before a larger application. If the plant shows sign of wilting or damage, don’t use this mixture.

Reprinted from SFgate online:   http://www.sfgate.com/homeandgarden

DIY: Aphid Spray

Make your own insecticidal soap: Aphids attacking a rode bud and stopping it from opening

Mix 5 tablespoons of all-natural liquid soap with 1 gallon water. 

Using a hand sprayer apply soap mixture directly on the aphids. Wait an hour then spray the roses with a garden hose to remove any soap residue and the dead aphids.

Repeat as needed.