It's been a buggy spring and summer in my new garden, where I've encountered varieties of scale, aphids and flies I hadn't experienced before. About 18 months ago we moved to a new house in a new neighborhood. With some exceptions, the general goal for our new, smaller garden was to plant drought-tolerant, pollinator-friendly plants, use California natives whenever possible, and encourage beneficial insects.
This spring I planted milkweed seeds obtained from the La Loma Native Garden in Modesto. In May, I discovered the now 6-inch-tall plants were covered from top to bottom with orange-yellow aphids! I learned they are called oleander aphids which are a common pest of milkweed. The leaves of the milkweed looked as if they had white spots all over them.
According to UC Integrated Pest Management (UC IPM), aphids are small, soft pear-shaped bodied insects with long legs and antennae, with slender mouthparts used to pierce stems, leaves and other tender plant parts to suck out plant fluids. The site recommends first attempting to control aphids by washing them off with a gentle stream of water. I did this over several mornings and evenings, with my hose set on fine spray, washing both the top and underside of the leaves. After about a week, I still had quite a few aphids, so I sprayed an insecticidal soap, making sure I covered both the top and bottom of leaves. Aphids produce many offspring, so they required an additional treatment.
I brought with me from the old house three pots of cyclamen plants given to me by former students. These plants were the source of my first insect attack during the spring, which was soft scale. I've had these plants for 15-20 years have never had a bug problem. One pot was particularly hard hit with leaf tips appearing browned and wilted, often dropping off. A sticky honeydew also appeared. Unlike hard scale, which I've experienced with olive trees, where the insect is underneath an armored cover and do not produce honeydew, the soft scale surface is the actual body wall of the insect and cannot be removed.
Soft scale is a sucking insect, appearing as tiny dots on the leaves or stems of a plant. They can grow up to ¼ inch long and have a smooth, cottony or waxy surface. They feed on the sap of the plant and excrete sticky honeydew, which can attract ants. Mine were brownish-yellow with a waxy color, usually appearing on the underside of the leaves.
I removed badly damaged leaves, checked undersides of the leaves for the scale and scraped off any scale I found using a wet Q-tip. I also checked my other two plants and occasionally found a scale or two on them, scraping them off also. I repotted the infested plant with potting mix. Over time I was able to completely get rid of the soft scale.
My final insect encounter was with whiteflies. I've been planting bulbs the past few years, planting dahlias for the first time this spring, which started to bloom in June. The whiteflies showed up in July, particularly infesting the two large white dinner-plate dahlias. The leaves on the plant became mottled yellow. Another sap-sucking insect, whiteflies are not true flies, but are related to aphids, scales, and mealybugs. Adults are tiny insects with a white wax covering on their wings and body. I spent a week trying to wash the whiteflies off with a heavy mist spray of water both on the top and bottom of leaves twice a day, but, it didn't manage them well enough. I switched to spraying on a weekly basis with an insecticidal soap, thoroughly covering both the top and bottoms of the leaves, which has reduced the infestation to a manageable level. Since these dahlias are annuals, not being able to completely eliminate the whiteflies is acceptable in my view.
My Buggy Summer Summary
It has been an educational summer learning about these insect pests and dealing with their infestations. I'm gratified I've been able to manage them using less toxic pesticides that are less harmful to beneficial insects and the environment. You can learn more about less toxic pesticides such as insecticidal soaps and oils by visiting the UC IPM website or by watching this video.