Fallbrook growers face both a Mediterranean fruit fly quarantine and an Asian citrus psyllid quarantine following finds made in monitoring traps.
An Asian citrus psyllid was found in a trap on a tangelo tree October 30 in northwest Valley Center.
A Fallbrook trap in the 400 block of Puerta Loma Drive that day found two male Mediterranean fruit flies, and over the weekend a mated female Medfly was discovered in a Fallbrook trap in the 5000 block of Hill Ranch Road.
A quarantine area is based on the range a pest can travel during its lifetime while the length of a quarantine is a factor of the pest’s lifecycle.
Exact quarantine lines have not yet been drawn, but the Asian citrus psyllid quarantine area will have a 20-mile radius and the quarantine is expected to last for 24 months.
The Medfly quarantine area will cover approximately four and a half miles from the finds.
In warm weather the lifecycle of a Medfly is between three and four weeks, but all lifecycle stages are longer during colder months and expectations of the quarantine lasting only 90 days if no additional Medflies are discovered is unlikely.
“It’s going to be a lot longer than that. We’re heading into the cool months,” said Bob Atkins, the Commissioner of the county’s Department of Agriculture, Weights and Measures. “Three generations is going to take us into July.”
The location of the Medfly finds translate into a quarantine which will encompass most of Fallbrook.
“It clobbers pretty much all of it. It’s down into Sleeping Indian and down across 76,” Atkins said. “It doesn’t quite get to the 15.”
The Department of Agriculture, Weights and Measures will work with the California Department of Food and Agriculture and the U.S. Department of Agriculture to set exact quarantine boundaries.
When feasible quarantine boundaries are based on streets rather than imaginary lines and seek not to split groves.
The southeastern boundary of the quarantine area is expected to be approximately at Gird Road or Monserate Hill Road.
The quarantine area will also depend on whether additional Medflies are found.
Normally traps are placed at a density of five per square mile, but after the first find the trapping is intensified.
The density is 50 traps per square mile within a one-mile radius of each find, 25 traps per square mile between one and two miles of the find, 20 traps per square mile between the second and third miles, and 10 traps per square mile between the third and fourth miles.
A female Medfly lays eggs inside a fruit. The eggs hatch into maggots which tunnel through the flesh of the fruit and thus make the fruit unsuitable for human consumption.
A Medfly can infest more than 260 different fruits and vegetables including apricots, avocados, grapes, grapefruit, guava, lemons, limes, loquats, nectarines, oranges, peaches, pears, plums, pomegranates, tangerines, and walnuts.
“It covers a lot of plants,” Atkins said of the quarantine.
Past experience with Mexican fruit fly infestations have shown that Hass avocado fruit still on the tree and not split to allow an opening is not a host for a Mexfly. Healthy Hass avocados have no such protection against Medflies. “Med is actually worse for the avocado growers,” Atkins said.
In an effort to eliminate any eggs and maggots which could be carried out of the area to spread the infestation, all fruit from trees within 100 meters of the Medfly finds is being stripped.
Properties within 200 meters of each find will be treated with the organically certified Naturalyte, which contains the naturally-occurring bacterial extract Spinosad.
The use of natural treatments will not jeopardize organic certification of farms within the area.
The release of sterile male Medflies will not take place until AWM, CDFA, and USDA officials can determine the most appropriate target areas.
“We have the steriles readily available,” Atkins said.
Medfly quarantines surrounding El Cajon, Imperial Beach, and the Mira Mesa area of San Diego have recently been lifted.
A Medfly quarantine in Escondido is already in effect, and the detection of three additional Medflies in Escondido is expected to expand that quarantine area.
“This has just kind of been a nagging problem this year,” Atkins said.
Growers in the Medfly quarantine area will need to treat their crops weekly and have those treatments certified before the fruit can leave the quarantine area.
“They will be able to harvest if they’re not right in the core square mile,” Atkins said. “We’re working with the growers so they know when they have to begin treatments.”
Citrus fruit within the Asian citrus psyllid area must be commercially cleaned or sent to a packing house within the quarantine area.
Citrus nurseries will be able to sell within the quarantine area, but trees will require expensive screening and certification of freedom from disease before they can leave the quarantine area.
The Asian citrus psyllid feeds on leaf tissues, which causes distortion and leaf curling. Psyllid residue can be conducive to sooty mold which can damage a plant.
The Asian citrus psyllid is also a carrier of a bacteria which causes huanglongbing, which stunts and defoliates infected trees and also causes twigs to die, leaves and fruit to drop, and fruit which is bitter and inedible.
There is no known cure for huanglongbing, and infected trees must be removed as quickly as possible to prevent the spread of the disease.
Often nearby citrus trees are removed along with the infected tree. “That creates a market for the nurseries,” Atkins said. “It greatly reduces the number of nurseries, but those nurseries have a ready market.”
The 20-mile radius area reaches De Luz Road. “I’m hoping to keep De Luz out of it,” Atkins said of the quarantine.
Including one in northwest De Luz which is likely to be excluded from the quarantine area, the Fallbrook/De Luz area has four citrus-producing nurseries.
“They can sell within the quarantine area, but they’re going to have to meet restrictions even there,” Atkins said.
Atkins expects to hold community meetings regarding the quarantines.
CDFA has a San Marcos office which is being used for the Valley Center and Escondido quarantines, and there are currently no plans for a Fallbrook office as was the case during the 1999-2000 Mexican fruit fly quarantine.
According to San Diego County’s 2008 Crop Statistics and Annual Report, commercial farmers in the county produced 59,805 tons of avocados in 2008 with a crop value of $144,694,905 and 216,092 tons of citrus last year with a crop value of $64,586,235.