From homemade soap sprays to armies of lady bugs, local landscapers, biologists and nursery owners said it will take a committed effort in the next month to prevent outbreaks of the small, sap-sucking insects from causing holes and yellow spots to form on plants and vegetable crops.
The recommended treatment is homemade soap sprays, which are created by diluting one to two tablespoons of liquid soap in a quart of water, but the mixtures have no residual effect for later kills.
Because February’s ice storm pushed back the insects’ late-April breeding schedule by two weeks, some experts said gardeners might want to consider covering plant leaves with a pesticide poison to knock off any feeding populations of aphids and whiteflies.
“If you don’t get ahead, you’ll find yourself battling these insects throughout the spring and summer,” said Milledge Peterson, the owner of Bedford Greenhouses near Lake Olmstead. “If you get them under control by early May, however, you’ll be pest-free through August.”
Based on the frequency of the insects’ mating cycles and their ability to produce thousands, maybe even billions, of offspring, experts said the urgency to treat plants for whiteflies and aphids is particularly high before temperatures get into the 80s and 90s.
Dr. Cathy Tugmon, a biology professor at Georgia Regents University, said aphids propagate through parthenogenesis, meaning they don’t require males to reproduce. A single aphid can produce 600 billion offspring in one season, according to research journals.
Whiteflies also don’t require mating to reproduce, and though females usually only lay up to 200 eggs at a time, they can spread just as quickly, said Marc Mayer, a regional technical manager for TruGreen, the nation’s largest lawn care company.
Though the life cycle for whiteflies typically is two months, Mayer said, it takes only half that long for new generations to mature and lay new eggs on the undersides of a plant’s upper leaves, where they’re protected from wind and rain and can thrive in hot and humid environments.
“They have so many generations per year that it is very difficult to control them because there are new ones popping up constantly,” Mayer said. “Once one generation gets on a plant and it’s not treated, they’ll rapidly multiply under the right conditions.”
Conditions have been ripe for whiteflies and aphids the past three years.
Since 2010, Mayer said, his region, which includes Augusta; Macon, Ga.; and Charleston, S.C., has reported increasing populations of the two insects, mostly silverleaf whiteflies, migrating north from Florida greenhouses.
Though Peterson said he has not seen any problems with aphids Tugmon said that does not mean the green, wingless insects are not as prevalent or destructive.
Both aphids and whiteflies insert parts of their mouth into a plant’s phloem, the tube that carries sugar water. They suck plants dry of nutrients, causing leaves to turn yellow and sometimes killing the plants. The insects also secrete a honeydew material that attracts ants.
Gardenias, ligustrum and hibiscus are popular for whiteflies. Crepe myrtles and azaleas are common for aphids.
“It will take a lot to ruin a garden, but they definitely will wreak havoc,” Peterson said.
For treatment, experts recommended first scouting plants for tiny white eggs or shaking leaves to gauge the level of infestation.
“If it looks like it’s snowing, then you know you need to treat,” Peterson said.
At that point, Mayer said, gardeners should remove all affected leaves, while keeping plants pruned and watered appropriately. He suggested using sticky traps, neem oil and homemade soap sprays, which kills the insects by penetrating their outer skin and dehydrating protective membranes.
Mayer said gardeners who do not get results from these tactics should spray underneath leaves or drench a plant’s soil with insecticides. Mayer recommended using Bayer synthetic insecticides or Espoma organic pesticides on plants in the late evening, when whiteflies and aphids usually congregate.
Tugmon said another trick, often used on farms, is to buy lady bugs, which feed on aphids and whitefly eggs.
“The downside of that is they are not always going to be there,” she said of the ladybugs. “So if you buy some lady bugs, encourage them to hang around for a while.”