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County, 19 in SanBernardinoCounty and one in SanDiegoCounty. There have also been recent detec- tions of another citrus threat—sweet or- ange scab—in Imperial, Riverside, San Bernardino andOrange counties. Within the same psyllid bulk citrus re- gional quarantine zone, tarping or use of a fully enclosed vehicle is required. To transport to a different zone or within the HLB quarantine area, fruit must also be field cleaned by machine or treated, and transportersmust completeanpsyllid-free declaration form. There are required spray and harvest products. None are organic. Field cleaning must be done by a ma- chine that uses rollers. An alternative is
grate cleaning powered by gravity to re- move stems and leaves. Users of the latter must seekapproval fromtheir local county agricultural commissioner. Okasaki saidthe reviewprocesscantake some time. He said detection of an HLB-positive tree triggers a mandatory response. The grower is required to treat the tree with a University of California- recommended foliar insecticide within 72 hours of notification. The grower must remove and destroy thediseasedtree.CDFAsurveysall treeson theperimeterof thegroveandgroveswith- in 250meters (820.2 feet) of the detection. All growers within 250meters from the detectionare required to apply one or two ganic trial, the lownavel orangewormlev- els in the organic block are encouraging,” Edstrom said. “The plan is to use mating disruption in 2021.” Weeds are another difficult matter. Researchers have struggled to find an organic system that is both effective and economical. “While propane flaming in the tree row hasbeenmostlyeffective, it is slowandex- pensive,” Edstromsaid. Some of the organic trees benefitted from installation of a 6-foot-wide cloth at planting, which prevented most weed growthwithin the tree line. This practice, however, costs $1,500 an acre at the beginning, with additional re- pair costs annually. It presented the chal- lengeof trying tocontrolweeds justoutside the6-footareawithoutdamaging thecloth. “Weeds were hard to control along the edges of the clothwheremowers couldn’t operate without catching or pulling the cloth,” Edstromsaid. “Theweed clothwas removed at the end of 2011 after annual maintenance became too expensive and
UC-recommended insecticides. The in- secticidemustbeonthe list recommended for bulk citrus quarantine requirements. “Be sure green waste is removed from field bins before sending them back to groves,” Okasaki said. “Sending dirty bins back to groves is a pathway for spreading ACP.” Binsinwhichfruitwithsweetorangescab hasbeencollectedmust bedisinfected. Okasaki said culls and rotted fruit are regulated, and fruit juice and cattle feed must be safeguarded in transit. Online resources may be found at cdfa. ca.gov/citrus/ and citrusinsider.org. (Denni s Pol lock i s a repor t er in F r e s no . He ma y b e c on t a c t e d a t agcompollock@yahoo.com.) time-consuming to continue.” With theweed cloth experiment aban- doned, researchers went back to the drawing board and came up with mod- ifications of the irrigation system that made propane flaming within the tree line more economical. “The surface drip systemwas replaced in October 2007 with a dual line subsur- facedripsystem, primarily to reduceweed growth, seed emergence and associated weed-control costs,” Edstrom said. “This hasreducedpropaneflamingexpensessig- nificantly compared toprevious seasons.” Thecombinationofburieddripirrigation and propane flaming largely worked, but the systemhad tobe redone to account for clogged lines invisiblebelowthe surface. “The subsurface drip lines were re- placed in spring 2016 due to plugging issues,” Edstrom said. “Vented end- caps for each line were installed with the new hoses.” ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.)
So far, Southern California has taken thebrunt of damage fromthepsyllid, with over 2,400 trees turning up with the HLB disease.MosthavebeeninOrangeCounty. Quarantine areas include both man- datory and nonmandatory treatment re- quirements based on the extent of risk. Control efforts include detection, sur- vey, treatment and biocontrol. That in- cludes detection trapping in residential areas with five to 16 traps per squaremile andservicing those trapsmonthly. Incom- mercial areas, it’sone trapper 40acres and trap servicing every twoweeks. Delimitationsurveys aredone if there is a psyllid detection of all properties within 50 meters. If HLB is detected, the survey extends to a 250-meter radius. Biocontrols, includingreleasesof awasp predator of the psyllid, are used around HLBlocations. The focus isonbordersand trade routes, newly infested areas, and in buffer zonesbetweenurbanandcommer- cial citrus. KeithOkasaki, anenvironmental scien- tist with CDFA, said there have been 116 psyllid detections in Kern County since January 2020. Eight were reported in San LuisObispoCountyandoneeachinKings, Madera and Tulare counties. Meanwhile, there have been 439 HLB detections at sites in Los Angeles County, 1,255 in Orange County, 44 in Riverside
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The Fritz pollinator variety, which har- vests later and is more susceptible to na- vel orangewormdamage, suffered 16.1% damage in the 2017 season. But it also dropped from 2% to 0.5% in the first year of the pheromone program. “While 2020 was generally a light navel orangeworm damage year and an adja- cent hard-shell block was removed the year before, reducing pressure in the or-
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GOPHER
VOLE
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8 Ag Alert September 8, 2021
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