Continued exports of California citrus to South Korea are in jeopardy due to the Fuller rose beetle (FRB). Growers are urged to immediately develop aggressive management protocols ahead of trade talks between South Korea and the U.S..
At the heart of the issue is South Korea’s desire to keep the pest out of its country. A bilateral agreement between the U.S. and South Korea will likely require specific management protocols by California producers, including skirt pruning, weed control, and chemical treatments.
Korea is California’s largest orange export market, so any disruptions caused by FRB could have serious consequences. South Korea’s new policy on methyl bromide fumigation makes the issue that more critical for growers to eradicate the pest from groves, according to James Cranney, Jr., president of the California Citrus Quality Council.
According to the University of California’s Integrated Pest Management website, the beetle does not generally cause economic damage to citrus, but the presence of viable eggs on fruit exported to countries like South Korea present a quarantine concern as South Korea does not have the pest and wants to keep it that way.
While methyl bromide fumigation procedures will kill the pest, Cranney says South Korea wants to move away from the fumigant this season. As a result, California must demonstrate full control of the Fuller rose beetle prior to this year’s harvest.
Other control measures to remove adult populations and their resulting egg masses from groves are also under investigation.
Required control measures include skirt pruning of trees so that FRB cannot climb on low hanging tree branches. Weed management is another issue growers must implement since weeds can provide another pathway into the tree.
The point is to reduce pathways that allow the crawling insect access to the tree.
Fuller rose beetles do not fly. They only crawl. A foliar insecticide application and packinghouse agreements could also be part of the trade agreement, Cranney says.
Joe Morse, entomology professor at the University of California, Riverside, said FRB populations appear at the highest numbers from July through September in the San Joaquin Valley (SJV) and August through October in southern California regions due to weather conditions.
The beetle tends to have a long lifespan – about 111 days in the lab on average.
“What works in our favor is they don’t lay a lot of eggs,” Morse said.
As a result, aggressive treatment programs can provide good control of the beetle if they are sustained.
Morse suggests a two-year treatment and management program could be necessary to gain significant control of FRB populations.
Morse offered management tips to growers, PCAs, and consultants during a jam-packed meeting in Tulare, Calif.
Growers shipping to South Korea should first select groves with FRB populations at the lowest level. This requires an extensive survey of trees to search for leaf damage inside the tree canopy. Leaf damage is quite obvious by the appearance of eating marks on the leaves.
Skirt prune trees approximately two feet from the ground, Morse recommends. In trials at Lindcove Research Center, Morse says skirt-pruning alone showed a 53-percent effectiveness in FBR control in trees.
Weed control is vital to eliminate the “bridge” between the soil and the tree. Ensure products used to create an adequate barrier are used properly and get to the base of the trunk. He says be careful with sprays under the trees since California has a zero tolerance for spray residue on hanging fruit, he said.
A two-spray program studied by Elizabeth Grafton-Cardwell at Lindcove Research Center near Visalia, Calif. showed 91-98 percent effectiveness in FRB reductions, Morse said. This number was 86 percent in similar studies conducted in San Diego, Calif.
Pyrethroids were not as effective in FRB control as other products, Morse explained.
Establishing specific groves designated as “Korean fruit” is also recommended for more efficient management purposes.
Morse recommends that SJV growers harvest Navel oranges between February and April and apply three sprays to be the most effective. An early June foliar application is important, but not mandatory if growers elect to go with a two-spray treatment program.
As for other spray programs, Morse advises growers to apply an early August ground spray of Brigade and an early October foliar treatment.
Crucial in control efforts is eliminating egg masses from the button of the fruit. Morse says Koreans inspect about 600 pieces of fruit in surveys of imported fruit.
“This kind of inspection is very efficient at finding egg masses,” he said.
FRB populations are more active at night.