Pests of the Season

Weed of the season: Dandelion,Taraxacum officinale

Chill weather slows down grass growth in our lawns and we can notice the bright yellow flowers of Taraxacum officinale,

the common dandelion.  In our mild climate, dandelions bloom nearly year-round.  Even as they bloom, these weeds seldom rise above their basal rosette at the lawn surface.  The leaves are strongly serrate, a “lion's tooth,” or dent de lion in French, hence the common name. The taproot penetrates 6 to 18 inches below the soil, and this root can regrow the entire plant even when all the leaves have been removed at the soil level.  The plant and root should be removed before the yellow flowers mature to white seed heads to be spread miles by the wind.

To remove the plant and taproot with a minimum soil disturbance, many special tools including “dandelion knives” have been developed for hand weeding.  The UCIPM video “How to Remove Dandelions” demonstrates several of these special tools.

 

Pest of the Season: Goldspotted Oak Borer

During these cold winter months, most insects go through diapause, quietly buried or hidden, unmoving and with minimal metabolic processes.  Most of the pests will not reappear in the garden until warm spring temperatures bring them back to activity.  In the meantime, we humans remain active and spend our evenings huddled around a warm fireplace.  We burn oak wood in the fireplace since oaks are common native trees in California.

Previously few of the insects found in oak firewood harmed our forests.  Yes, Prionus californica beetles and the giant (stingless) wasp, Megarhyssa sp., frighten homeowners by flying out of unburned firewood, hurting neither trees nor people.

In the past decade, a new beetle species has invaded southern California from Northern Mexico and Arizona.  Agrilus auroguttatus, has killed oak trees in San Diego County since 2008.  Adults females are about ½ inch long and 1/5 inch wide and males are slightly shorter, but both have a bullet-shaped body. They are black or iridescent green with six gold-colored pubescent spots on the forewings and two gold-colored spots on the edge of the thorax.

Please, buy your firewood locally.  Make sure you do not bring firewood from southern California.  Our beautiful oak woodlands are at risk.

 

Disease of the Season: Peach Leaf Curl 

By the beginning of January, if you have not already addressed the problem, it is time to treat your peach and nectarine 

trees for peach leaf curl, a fungal disease. The fungus distorts the leaf with reddish areas which become thickened and puckered as the leaves grow in early spring.  The affected leaves soon turn yellow and brown before they drop off the tree. Young shoots can become infected and stunted. Massive leaf loss weakens the tree, slowing its growth and decreasing its fruit production. If the disease is untreated, the tree may weaken and die within a few years.

Although some varieties of peach are resistant to this disease, even the resistant varieties need to have fungicides applied for the first few years. Few nectarine varieties are resistant.

Treatment with fungicide should begin soon after the leaves fall in November, but this may occur as late as early January. Historically, fungicides used for this purpose were copper-containing products. The higher the “metallic copper equivalent,” (MCE) on the label, the more effective against fungus. Fixed copper products (such as copper sulfate and cupric hydroxide) can be effective, but few of these are available to the backyard gardener. Bordeaux Mixture, requires mixing and a search for chemical ingredients, but we are aided by a special UCIPM Pest Note: Bordeaux Mixture.