Despite a threat of rain and a peaking navel orange harvest, growers in Tulare County, the nation’s top citrus producer, could start a concerted spraying program in mid-December as they seek to eradicate a pest that could carry a deadly disease into their trees.

Officials with the California Department of Food and Agriculture told hundreds of growers who gathered in Tulare for an update on the pest that they will not face an immediate quarantine because of the discovery of a single Asian citrus psyllid in two different locations in Tulare County in November.

But they will have to use sprays in an 800 meter radius – about a half mile – of each of those finds in an effort to eradicate the pest. And there will be restrictions on movement of citrus in a five mile radius around each of the finds near Strathmore/Lindsay and Terra Bella.

(For more, see: California citrus growers schooling on Florida for coming HLB war)

The areas cover a total of about 163 square miles.

CDFA stopped short of a quarantine declaration, something that has been done in Southern California, because the Tulare County finds do not amount to an infestation.

But Robert Leavitt, CDFA’s director of plant protection and plant health, made it clear that further finds – additional adults or other stages of the insect such as eggs or nymphs – could change that picture.

“If there are a lot of adults, nymphs or eggs or the presence of HLB (huanglongbing, the tree-killing disease the pest can carry), then we would go to a standard quarantine.”

That could mean a 20 mile radius, he said, “by default, all of Tulare County.”

Ted Batkin, president of the California Citrus Research Board, said before the meeting that drew 400 people, “We hope this is a far as we have to go.”

Leavitt and others said the restricted and eradication zones could be in place for two years, but in six months their presence will be re-evaluated based on what is – or is not – found. The approach is being put into place, CDFA officials said, “Because there is a potential pathway for ‘hitchhiking’ ACP from Southern California quarantine areas along the Highway 65 corridor.”

Organic marketing may take hit

Regulators said one effect of the required treatments in the eradication zone is a likely blow to marketing of organic citrus. Because organic treatments have proven ineffective on the pest, Leavitt said, conventional sprays would be needed.

That, he said, would mean that the sprayed crop could not sold as organic. But, he said, it would not mean loss of certification for future crops because the spraying is mandated.

While CDFA is paying for spraying of residential trees in the zones, growers must pick up the tab for treating commercially grown citrus.

Leavitt said the Tulare County agricultural commissioner can use “abatement authority” for groves where treatment is not occurring, basically ordering that it be done at the expense of the landowner.

Beth Grafton-Cardwell, a University of California authority on treatment for the pest, said it is important that treatment be coordinated, swift and complete “to knock down outbreaks.” She said growers in Ventura County had to do additional spraying and faced other challenges because they “didn’t get control” and sprayed at different times.

Grafton-Cardwell, UC integrated pest management specialist and research entomologist, said different materials should be used depending on the timing of sprays. That’s because adults are most likely to be around in the winter, and the nymphs and eggs appear at other times.

A pyrethroid is recommended for the winter. It can also be used in the spring, followed by a soft insecticide. In summer, Grafton-Caldwell said, uptake of neonicotonoids is good and those should be combined with the pyrethroid.

Grafton-Caldwell also recommended sampling for the insect pest by using a white clipboard with a grid and knocking at branches of trees. She recommends sampling 10 trees on each of the borders of a grove and in 10 the middle. The psyllid prefers borders, she said.

She said it’s not best to rely solely on yellow sticky traps. While research is under way to improve traps, the insect is more likely to be drawn to volatile organic compounds from foliage than to the yellow traps.

Grafton-Caldwell said sprays that combat the pest can be timed with sprays that target others including thrips, katydids, peelminer, leafminer and scale.

Brian Taylor, director of field operations for the California Citrus Research Board, explained that the board is seeking to amass contact information for growers, pest control applicators, pest control operators, packinghouses and field operators in the restricted zones. He asks that they contact [email protected].

HLB, the disease itself, has been found in only one tree in Hacienda Heights in Southern California. But it has been found elsewhere in places that include Florida, Texas, Louisiana, Georgia and South Carolina.

 Also called citrus greening, the disease kills citrus trees and there is no cure. Diseased trees produce lopsided, bitter fruit and eventually die.

Field cleaning machines

Melinda Mochel, senior environmental scientist with CDFA, spelled out the regulations put in place in the restricted zones in Tulare County. She said bulk citrus with leaves and stems attached cannot be moved out of the restricted area.

One step in harvest may involve use of field cleaning machines, something that is done is Southern California’s quarantine zones where equipment and personnel are brought into the grove to run fruit across belts and to use systems of brushes and rollers to make sure the citrus is free of leaves and stems.

There is no restriction on movement of bulk fruit within restricted areas, and commercially cleaned, graded and packed fruit or field-cleaned fruit can leave those areas. A “field cleaning verification form” would be required.

Mochel said growers in the restricted areas should be sure harvesting and transport equipment is kept clear of all stem and leaf debris.

Information on CDFA efforts is available at http://cdfa.ca.gov/plant/acp/.