CTV (citrus tristeza virus) is a virus transmitted by aphids, and it infects most types of citrus. It exists in several strains and is found throughout the world, including California. Most strains cause trees growing on sour rootstock to die within months of infection. Approximately 10 to 20 percent of the citrus trees in the San Joaquin Valley are on sour rootstock. The remaining trees are grown on hybrid rootstock and are more tolerant to the effects of the disease. Adverse consequences of CTV infection on tolerant trees include stem-pitting, chlorosis, loss of productivity, and reduced fruit size. Trees infected with CTV may serve as a source of infection for other healthy trees, and removal is the only effective virus eradication strategy currently available. Central California Tristeza Eradication Agency: The Government Code provides a procedure that allows public agencies to enter into agreements which jointly exercise their powers on a regional basis. (See Gov. Code, 6500 et seq.) In 1963, the West Fresno County Red Scale District, the Central Valley Pest Control District, the Tulare County Pest Control District, the Southern Tulare County Citrus Pest Control District, and the District, entered into an "Agreement for Joint Operations of the Tristeza Eradication Program." Thus was born the Central California Tristeza Eradication Agency (the Agency). The Agency's purpose is to: 1) identify and eradicate CTV in a timely and cost-effective manner, and 2) encourage and support research programs to assist in eliminating the threat of CTV. Since 1963, the joint powers agreement has been amended. In July 1995, the latter four districts signed another agreement that extended the Agency's operation for an additional three-year term. Pursuant to the 1995 joint powers agreement, each participating district appointed one representative to the Agency's board. In addition, each district with a citrus acreage in excess of 15,000 acres appointed one additional representative for every 15,000 acres of citrus trees in the district. In July 1995, based on the conclusions of several plant pathologists and virologists that suppression of CTV was feasible in the Central Valley, the Agency prepared a three-year plan on how best to do so. The plan called for the identification and removal of CTV-infected citrus trees. Monitoring would occur through an annual systematic sub-sampling of 10 percent of total acreage to be randomly selected. The Agency collected samples from every commercial citrus grove within its jurisdiction and tested for CTV. If a sample tested positive, the Agency performed additional testing to locate all infected trees within a grove. the infected trees were then removed by the grower voluntarily or, if the grower chose not to comply, by the Agency through court action. The Agency was authorized, but not required, by statute to pay compensation up to $ 25 per tree removed as part of the pest eradication program, with a $ 3,000 cap per acre. ( 8553, 8555.) The Agency provided the following compensation and removal expense scale for tree removal: for trees with an infection level between 0 and 5 percent, $ 0 compensation, and $ 35 per tree removal expense; for an infection level between 5 and 10 percent, $ 25 per tree compensation, and $ 35 per tree removal expense; for an infection level between 10 and 20 percent, $ 25 per tree compensation, and $ 50 per tree removal expense; and for an infection level between 20 and 100 percent, $ 25 per tree compensation, and $ 55 per tree removal expense. In the event the infection level was 20 percent or higher, the Agency allowed the grower to elect whole grove removal with compensation of $ 5,500 per net citrus production acre.