Dear Miss Floribunda,
I hope you can help me. My irises are crawling with aphids this year (so is my kale, but that’s another story). I’ve never seen aphids on my irises before. I have had them on some of my roses, and rose dust has helped. But the aphids seem to be damaging the flowers and leaves. What can I do? And why are they here this year? Is it because it’s been so cold and wet? I’ve heard ladybugs would help. Where would I get them?
Iris Lover on Ingraham Street
Dear Iris Lover,
You are right. There is a correlation between the cool, wet weather and the aphid infestation. Now, wet springs actually deter some insect populations: cutworm larvae drown; grasshopper eggs rot before hatching; spider mites are discouraged. That’s good. On the other hand, wet weather can have bad effects, too. Important pollinators, such as bees, don’t like to go out in chilly rain, and that can be a delaying factor for the development of apples and other fruit. The lush green growth that results from spring rain attracts crop-eating TPBs (tarnished plant bugs) and, as you noticed, aphids. This is particularly serious for irises because aphids are a vector for iris mosaic virus, which is much more serious than the usually transitory aphid attack. For a quick, nontoxic way to get rid of aphids, strongly spray them with your garden hose or just pick them off if you have a strong stomach. Overwintered kale is known to attract aphids, so you might want to hose it, pull it up, wash it, and cook it if still tender.
You are also right that ladybugs provide a long-term solution. I don’t know what you used as “rose dust,” but if you don’t have ladybugs around then it was probably poisonous to beneficial insects and did more harm than good. You can order ladybugs from online sources, but they won’t stay if your garden isn’t poison-free. I turned to my visiting cousin, Cozy (Mlle. Cosette Compagnon from Millefleurs, France), for advice on how to attract and keep ladybugs and other beneficial insects. A devoted practitioner of companion planting and organic gardening in general, she asserts that organic farming never really died out in France, burgeoned in the 1970s, and — thanks to government subsidies for the last seven years — has doubled and now leads the rest of Europe.
The ladybug, called affectionately and reverently “la poulette de la Madone” (the Madonna’s little chicken) and “la vache de Dieux” (God’s cow), is a favorite beneficial insect there as here. I asked her if it was true that both dill and cosmos attract ladybugs, and she answered that they do, but, because they are both annuals, they are unlikely to be much help in the spring, though they both self-seed. She suggested planting yarrow and fennel, which are perennial. She also mentioned tansy, but you have to be careful because it can become invasive. She plants hers where the soil is poor so it doesn’t spread too much. She dries the striking and fragrant golden flower heads for autumn bouquets. And, being French, she loves the dandelion. In France, the tender new leaves of dandelions are sold as a delicacy in markets in the spring and are highly prized in salads, not only for their flavor, but for their high vitamin and mineral content and various medicinal qualities. (They may be contraindicated if you are taking certain medications, so be careful.) Dandelions not only attract ladybugs, lacewings and other aphid-eating insects, but their long roots fertilize and condition the soil. However, to keep from getting in trouble with your neighbors, you would have to vigilantly pick the flowers before they go to seed and invade the gardens of the lawn-loving. I’d advise Hyattsvillians to choose instead clover and Queen Anne’s Lace. Although they also are considered weeds by some, they are lovely and they attract beneficial insects and improve the soil.
Cousin Cozy also recommends nasturtiums, for an interesting reason. This is a trap plant, which attracts aphids and draws them away from your irises and roses. Mint attracts them away from your irises, while at the same time repelling ants, who are the greatest enablers of aphids. In fact, ants appear to actively farm them, herding them in little flocks, because they like the “honeydew” they can “milk” from them. In addition, if you have peonies you will want to plant mint just to discourage the ants from crawling all over them. While mint can be considered invasive, it can easily be controlled by picking it for use in teas, mojitos, juleps and other drinks.
To discuss the complexities of companion planting and other gardening topics, please come to the next meeting of the Hyattsville Horticultural Society on Saturday, June 18, from 10 a.m. to noon. Our hosts will be Jeff and Marsha Moulton at 6122 42nd Avenue.