YAKIMA, Wash. — Southcentral Washington cherry growers are ripping out cherry trees and ramping up post-harvest sprays to combat the Western X strain of Little Cherry Disease that a scientist warns could be as damaging as citrus greening disease has been in Florida.
“In Florida, the reaction was too little too late, and I fear that could happen here,” says Scott Harper, virologist and director of Clean Plant Center Northwest at the WSU Irrigated Agriculture Research and Extension Center in Prosser.
Harper worked in Florida citrus before coming to Washington State University in 2017 and says Western X and citrus greening are both bacterial diseases that can be spread quickly by insects.
Since the greening epidemic started in Florida almost one-third of the acreage has been infected, removed and not replaced with citrus trees, Harper said.
Little Cherry Disease causes small, bitter-tasting fruit that is unmarketable. It all but wiped out the British Columbia cherry industry in 1933 where 90% of trees were removed, WSU scientists have said. British Columbia experienced another serious episode in the 1970s as did California.
LCD was detected in Washington in the 1930s but was dormant until wet, cool springs may have contributed to an initial rise in the Wenatchee area around 2009.
A year ago, Harper said LCD was “well into epidemic levels,” meaning it cannot be not easily controlled.
This year, Harper says Western X is at 60% to 90% infection rates in Yakima Valley orchards versus 5% to 10% last year.
Growers are pulling out entire blocks of 40 to 50 acres at a time to try to get ahead of it, but it will probably be worse next year because there is a lot of pathogen that vectors can easily spread, he said.
While Little Cherry Virus 1 and 2 are viruses that spread slowly by apple and grape mealybugs and roots, Western X is a phytoplasma that spreads slowly by roots or quickly by leafhoppers that fly.
All three strains are found throughout Central Washington but Western X had dominated south of Interstate 90 and Mattawa while the other two have been more prevalent to the north.
Now Western X is gaining ground in the north, which is a real concern, Harper said.
B.J. Thurlby, president of Cherry Institute and Northwest Cherry Growers, said the extent of the problem is hard to quantify. New orchards have replaced ones torn out so production volume has not declined, he said.
The industry is nearing the end of a 22.3 million, 20-pound box season, one of the largest just under the record 26.4 million-box crop of 2017.
The Cherry Institute is urging growers to combat the disease aggressively by spraying for leafhoppers every 21 days or less until November dormancy instead of just once after harvest.
“It is imperative that all cherry growers take notice. Western X is on the rampage throughout the Yakima Valley, Mid and Upper Valley and the Tri-Cities area,” the Institute said in a memo to growers.
“This disease is responsible for wiping out the California cherry industry in the 1970s and 1980s. We are at a critical stage right now as many blocks in the above mentioned areas have been significantly impacted or removed from production. If immediate actions are not taken our Washington industry will suffer the same fate as our neighbors to the south,” the memo states.
Growers are talking about getting the state involved to create tree removal requirements, Thurlby said.
Rob Valicoff, president of Valicoff Fruit Co., Wapato., said he has been pulling out cherry trees and that many other growers are as well to combat Western X.