California's bustling international trade and tourism combined with its moderate climate and diversity of crops create opportunities for exotic pests to invade the state and take up residence. In this issue of California Agriculture, scientists from the U.S. Department of Agriculture, California Department of Food and Agriculture, and University of California report on the threats posed by imported plants and insects, and how these pests can be controlled.
A new sharpshooter threatens plants. An insect that has recently invaded California is creating serious problems for both agricultural and ornamental plants. The glassy-winged sharpshooter's greatest threat is its ability to spread the bacterium Xylella fastidiosa, which induces Pierce's disease in grapevines, almond leaf scorch disease, and a new disease known as oleander leaf scorch. If oleander leaf scorch were to kill all the oleanders along the state's freeways, Caltrans would suffer a $52 million setback.
Because the glassy-winged sharpshooter feeds on a broader variety of plants than other insects that carry X. fastidiosa, UC scientists say other diseases caused by different strains of the bacterium may hurt even greater numbers of crops and ornamental plants.
Sticking it to starthistle. Yellow starthistle now infests 22% of the state, covering about 22 million acres. This fast-spreading weed replaces desirable vegetation. In natural settings, its prickly thorns can make hiking paths unpassable and its density can help carry wild fires. Within the agricultural community, yellow starthistle most severely affects ranchers. While young shoots can be grazed by cattle, the sharp spines of older starthistle plants deter cows from feeding. Yellow starthistle also can be toxic to horses that eat it.
To control the invasive weed, scientists are attacking it with a variety of methods -- biological, chemical and mechanical.
USDA scientists have released overseas ins
Contact: Pam Kan-Rice
University of California - Division of Agriculture & Natural Resources