Pesticide technicians are in the midst of treating as many as 100 properties in The Arbors residential community of San Luis Obispo in an attempt to protect nearby vineyards from a potentially devastating disease.
In October, county agricultural inspectors found an infestation of the glassy-winged sharpshooter in the neighborhood near Islay Hill. The insect spreads a bacterium that causes Pierce’s disease, which is fatal to wine grapes, the county’s highest-value crop.
State and county farm officials determined that the infestation was restricted to The Arbors neighborhood, which is adjacent to 36,000 acres of wine grapes in the Edna Valley. They then began planning an eradication effort to eliminate the pest before it could damage grape crops.
The effort consists of technicians treating ornamental yard plants with a common flea and tick pesticide, imidacloprid. Sharpshooters are poisoned when they feed on the treated plants.
“Hopefully, we can do this right and do it effectively,” said Marc Lea, the county agricultural biologist in charge of the effort.
Citrus trees are a favorite host for the sharpshooter, so those receive the highest priority. However, most common ornamental yard plants are potential hosts.
On the hunt
During the treatment, technician James Moore used a piece of rebar to drive a hole into the ground beneath a small lemon tree in a backyard on Arbor Street. Jennifer Steele, another technician, dropped a round tablet the size of a small marble into the hole and covered it up.
The soil beneath this small tree will receive 10 tablets. Large trees can receive 50 or more. The next time it rains or the tree is watered, the tablets will release the pesticide, which will then be absorbed into the tree’s foliage.
The pesticide moves into trees’ growth tips, and not into the fruit, said Karen Lowerison, deputy county agriculture commissioner.
The tablets release the pesticide slowly and will last all summer, making them the preferred treatment for citrus. For other, less-preferred plants, technicians with Pestmaster Services use applicators that inject a liquid form of the pesticide into the soil, which is effective for about two weeks.
“We get down into the root zone on all sides of the tree so there will be good uptake,” explained Tim Sharpe, Pestmaster field supervisor, as he treated a manzanita bush.
The pesticide is also sprayed directly onto the leaves of a limited number of shrubs. The technicians passed up redwoods and the handful of other trees that the sharpshooters don’t like.Lea said he is encouraged by the reception he and his crews have gotten from homeowners.
Only two have refused to give them permission to enter their property.
“So far the response from the public has been positive rather than antagonistic,” he said.
The field eradication work will wrap up by April and is timed to coincide with the sharpshooter’s most active feeding time. Then it will just be a matter of waiting to see whether more of the insects turn up in any of the 300 traps in the surrounding area.
Lea is optimistic that won’t be the case. The Arbors neighborhood has plenty of citrus trees, so the sharpshooters should have little reason to migrate elsewhere.
Agricultural officials believe this intensive effort is warranted in order to prevent a serious infestation such as the one that occurred in 1999 in Temecula in Riverside County. Two- thousand acres of vineyards there were struck by Pierce’s disease and 300 acres were destroyed.
Since then, the insect has spread throughout Southern California and is starting to spread northward. So far, no sharpshooters have been found in any vineyards in San Luis Obispo County.
Lea said he should know by the end of the summer if the eradication effort has been a success.