Aphids Attack Gardens in Wake of Medfly Spraying
A campaign of malathion spraying for Mediterranean fruit flies has created havoc for back-yard gardeners throughout Southern California, allowing aphids to flourish by destroying other bugs that normally keep the blossom-devouring pests in check.
The aphids have attacked carefully nurtured flower beds, disfigured rosebuds, wilted orchids and coated leaves with sticky dew that soon turns black with mold.
Grim damage reports are available from amateur and professional gardeners alike. For instance, Clair G. Martin III, curator of roses at the Huntington Library, Art Collections and Botanical Gardens in San Marino, said the aphids are “the worse I’ve seen in the eight years I’ve been here.”
Distressed gardeners can be found in swarms at commercial nurseries, stocking up on containers of aphid-killing pesticides (which experts recommend against) or vials of aphid-eating ladybugs (which will work only after the malathion campaign has ended).
“It’s hard to describe how bad I feel; gardening is part of my life,” said Marty Asolas, 42, of Bellflower. “There are aphids on my violets, aphids covering my herbs. It’s horrifying. I have just decided not to plant anything else because I can’t bear to see my flowers attacked.”
Entomologists blame the infestations of aphids and other bothersome but less destructive garden pests on the absence of ladybugs, lacewings and tiny wasps, which have been all but eliminated within the nearly 400 square miles of spray zones.
They say the outbreaks demonstrate anew that even back-yard gardens support delicate ecosystems, a balance of nature that has been knocked askew by widespread pesticide spraying.
“Seven to eight malathion sprays in an urban area is enough to kill off beneficial insects and cause a massive infestation,” said Lester Ehler, a UC Davis entomologist and one of several university scientists who have studied the effects of malathion on plant life. “When you think about damage to an ecosystem you usually think of forests and rangelands, but there is an ecological balance in back yards too. Malathion spraying causes an imbalance.”
The aphid outbreaks were not unexpected, state agricultural officials said. They described the resulting garden destruction as a necessary sacrifice in the greater campaign to eradicate Medflies, which ravage fruit trees and other crops.
“We knew this was going to happen,” said Robert Dowell, senior economic entomologist for the state Department of Food and Agriculture. “But it is infinitely preferable to what the Medfly can do to the state. This is not something that causes the kind of damage that we would seriously reconsider the Medfly eradication program.”
In the current campaign, malathion has taken a toll on a variety of bugs beyond Medflies. Wild honeybees, which pollinate fruit trees, have been either killed by the pesticide or become sick and lethargic--”as if they have a hangover,” one scientist said. One state-funded study reports that the Medfly campaign also has robbed spring of one of its traditional sounds: the chirping of crickets.
Aphids, leaf-scales and annoying whiteflies survive the sprayings because they live close to petals or beneath leaves, shielding them from the poison droplets. Ladybugs and bees, however, are highly sensitive to malathion. They also are active airborne travelers, which increases their exposure to the pesticide.
The pest invasions support conclusions of several state-funded studies conducted during the 1980-82 Medfly infestation in Northern California. Those studies showed that gardens in spray areas were more heavily infested with aphids and scales than were gardens outside the spray zones.
It could take anywhere from several months to a year or longer after malathion spraying ends for gardens to become populated again with beneficial insects, the studies indicate.
“We don’t know what the long-terms effects are on plant life,” said Ehler, whose 1982 study of the native vegetation in the Northern California town of Woodside only covered one year. “Some of the vegetation there was so badly ravaged by insects that we could no longer take samples.
“I would say that the effects in Los Angeles will not be permanent, but it is hard to say how long it will last.”
Other entomologists said that because Southland gardens received far fewer sprays than those in Northern California, gardens should bounce back by the end of summer. Said one: “Your plant might not look very pretty and it may not grow very well, but it probably won’t die.”
Some frustrated gardeners, however, are not waiting for helicopters to be grounded. At the San Gabriel Nursery, one of the largest in the San Gabriel Valley, manager Henrick Mar reports a run on $3.95 tubes of a thousand ladybugs.
“We have people calling us up asking to reserve ladybugs.”
Other gardeners are eager for quick fixes, he said, and head for the pesticide shelves.
Peggy Watson in San Gabriel said she is considering using a mild pesticide because “the aphids in my garden are solid and relentless. My orange trees are so covered the leaves just curled under. It’s gross. It’s sickening.”
She said the morning after a malathion spray she finds dead bees on her outside furniture and patio.
“It’s as if they drop dead in mid-flight. I am preparing for a light orange crop, if any,” she said.
Thomas Cairns, a biochemist and editor of the American Rose magazine, said “a mass infestation” of aphids is attacking his 1,000 rose bushes. “This year I could not believe it,” said Cairns, who lives in a spray zone in Studio City. He said he uses both pesticides and natural predator releases to control his garden aphids.
The aphid infestation has become the hottest topic of conversation among members of the Pacific Rose Society, said Bartje Miller, president of the organization and chairwoman of Wrigley Gardens of Pasadena’s Tournament of Roses. She said society gardeners debate whether the infestations are caused more by malathion or prime aphid breeding weather.
“It’s a whole combination of factors,” Miller said. “I think Mother Nature is just throwing us a curve.”
Indeed, battling aphids has always been a traditional part of back-yard gardening, and this spring aphids have been helped by the weather as well as malathion.
The dry winter provided ideal breeding conditions for aphids that pass the cold season beneath evergreen leaves. Recent warm, spring showers have moistened plants, further improving breeding conditions.
When the aphids die down, as they normally do during hot summer weather, gardeners can expect to see more scales and whiteflies, tiny bugs that stick to leaves like crust, sucking out plant juices.
Entomologists advise gardeners to control aphids and other pests by hand-washing leaves with soap and water. Increased pesticide use in the garden will only prolong the time it takes beneficial bugs to return and could burn and damage leaves. When malathion spraying stops, good bugs can be purchased at nurseries and set loose.
BACKGROUND
The state has been applying droplets of malathion-laced molasses across a rapidly expanding swath of Southern California since last August. The Medfly battlers, while warily watching for signs that the infestation remains entrenched in portions of the region, nonetheless intend to end malathion applications over most spray zones by May 9. At that time, millions of sterile fruit flies will be released in an attempt to breed their fertile counterparts out of existence.
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