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CDFA Plant Health

Curly Top Virus: General Program

The CTVCP represents an overall strategy for the control of the BLH statewide where the infection of susceptible crops and backyard gardens is likely. Control is performed within rangeland habitats on both public and private lands and along ditch banks, roadsides and fallow fields in cultivation adjacent to rangeland.

The total acres treated in any given year vary depending on rainfall patterns and BLH density and may occur at any location within the potential treatment areas mapped.

Throughout California, the BLH population builds up at various times of the year carrying BCTV from weed hosts to cultivated crops. Control is a year round effort. As with most insect pests control is linked to the life cycle and directed at disrupting its continuity. Aerial treatments are employed to control BLH populations in rangeland habitat and in large cultivated fallow fields.

San Joaquin Valley
In the San Joaquin Valley, the CTVCP usually conducts three aerial campaigns annually which closely coincide with the reproductive biology of BLH. The winter, spring and fall control periods in the San Joaquin Valley are performed on the west side and southern end of the Valley and are generally performed within three separate geographical areas. A single treatment per calendar year for any given area is generally sufficient to control BLH populations. A second San Joaquin Valley treatment per calendar year over the same geographic area may be necessary to control BLH populations if:

  1. Fall populations of BLH are developing in Russian thistle on rangelands previously treated in the spring, or
  2. Late spring rains rejuvenate drying rangeland vegetation and a second generation of BLH develops on rangeland treated earlier in the spring. Late spring rains have historically developed a second spring generation of BLH in the San Joaquin Valley every five or six years involving an estimated 1,000 to 10,000 acres of rangeland.

Imperial Valley
In the Imperial Valley, the CTVCP conducts a single aerial treatment when necessary, in the winter or spring, depending on weather patterns. Historically, treatments in the Imperial Valley are necessary one out of every three years. The treatment acreage varies form 100 to several thousand acres and the specific locations receiving treatments vary from treatment period to another . Many years may pass between treatments to any specific location. A second treatment per calendar year over the same geographical area, due to additional rain in the Imperial Valley, has never been necessary and is not anticipated in the future.

Salinas Valley
Historically, aerial treatments in the Salinas Valley are infrequent, but have been performed, as needed, during the spring (about once every 7-10 years). The last aerial treatment performed in the Salinas Valley was during the spring of 2001.

While aerial treatments are employed to control BLH populations in rangeland habitat and large fallow fields, ground-rigs are used to control BLH populations along ditch banks within cultivated areas adjacent to rangeland breeding grounds. On rare occasions, ground-rigs are used to treat BLH populations in small, cultivated fallow fields too small or isolated to be economically treated by aircraft.

A ground-rig is typically a four-wheel drive pickup truck with an engine-powered blower in the bed. Insecticide is injected into the air stream of the blower nozzle that is movable. The blower is equipped with dripless nozzles and electric cutoff for precise control of spray. All controls are inside the cab where the operator can start and stop the blower engine, turn the spray off and on and control the direction of the blower. The malathion is mixed in a 100-gallon tank mounted in the bed of the truck and applied at the same rate as an aerial application. The ground-rig vehicles are driven on roads accessed by agricultural vehicles and equipment.

The size and locations of ground-rig treatments in cultivated areas are related to the size and location of BLH populations in adjacent rangeland habitats. One treatment per year is generally sufficient to control to BLH populations on roadsides and ditch bank weed hosts.

Ground-rig Only
The CTVCP employees use ground-rigs to control BLH populations in three distinct control areas. These areas are designated "ground-rig only" and include the Cuyama Valley, Blythe and a portion of western San Joaquin, Stanislaus and Merced Counties.

Parasite Release Only
Previously designated as ground-rig only areas, the Hemet and Palmdale/Lancaster regions have been designated as parasite release areas. Since 1997, parasites have been released in these two areas to establish BLH egg parasites outside the San Joaquin Valley.