Avocado thrips resurfacing in North County groves

By: MARK WALKER - Staff Writer | Tuesday, March 30, 2004 11:33 PM PST ∞

FALLBROOK ---- The damage they cause is cosmetic, but an outbreak of avocado thrips last spring is now showing up on mature fruit, sending up to 20 percent of the state crop to the processed food market and resulting in lower earnings for growers.

The damage from the thrip, a tiny winged pest, varies from location to location. One 30-acre Valley Center grove had as much as 65 percent of its fruit scarred from the insect that showed up in California in Ventura County in 1996.

"Across the board we are looking at about 20 percent of the crop being affected," said Gary Bender, an avocado and citrus fruit adviser for the University of California cooperative extension office in San Diego.

Undamaged avocados retail for $1 or more per pound. Damaged fruit sent to the processed food market results in returns to growers that range from 40 to 80 cents less per pound than premium fruit commands. The damaged fruit is fine to eat but is not acceptable for the retail market and is instead made into guacamole or other food products.

At Del Rey Avocado Co. in Fallbrook, co-owner Bob Lucy said Tuesday that the damage caused by avocado thrips on the current crop mirrors the damage caused to the state's avocado crop three years ago.

"It leaves a blemish on the fruit and downgrades it considerably so that fruit goes to the food service industry to be made into another product," Lucy said. "With the amount of scarred fruit, our job now is to convince a typical food service company that may buy a pallet or two twice a week to agree to buy more."

California growers this year are predicting they will have harvested 385 million pounds of all varieties of avocados when the industry's crop year ends Oct. 31. Last year, state growers took in $363 million for their avocado crop, with Hass the dominant variety. California harvested 359 million pounds of all varieties, with San Diego's 26,000 producing acres accounting for 44 percent of the overall state crop. Ventura, Riverside, Santa Barbara and San Luis Obispo counties are the other major production areas.

Avocado thrips spread rapidly after they were first discovered in Ventura County, showing up in San Diego and Riverside county groves by spring 1997.

Bender and Lucy said that last year's outbreak of Mexican fruit fly in Valley Center is in part to blame for the problem seen this year. Many growers who needed to rent helicopters to spray their groves to control thrips were unable to do so because the crop dusters were booked by growers spraying for fruit fly outbreak.

"That's the part that is really frustrating ---- growers simply didn't have access to the helicopters," Lucy said.

Bender, who has been working with a Valley Center grower where the damage to one block of trees is particularly heavy, said that when thrips were discovered the industry believed it was a cool-weather pest that would thrive in the cooler and wetter weather like that in Ventura County. Researchers did not believe the insect would gain a strong foothold farther south, but that belief has been shattered.

"In the last couple of years it seems to have really blown up and moved out to places like the Pauma Valley," Bender said. "It looks like what we now have is a heat-resistant strain and I think we are looking at a long-term problem."

Past attempts to control the pest with biological methods using predator insects appear to have failed. About the only way to control it is to spray one of three chemicals ---- Abamectin, Sabadilla or Spinosad, Bender said. The cost ranges from about $100 to $250 per acre to apply one of those chemicals.

Growers need to spray during bloom, which is when the thrips build up their populations on the succulent new leaves, Bender said. The fruit that is damaged is less than three-quarters of an inch in length with the damage not clearly visible until the fruit matures.

Fallbrook's Charley Wolk, an avocado industry leader and chairman of the Hass Avocado Board that oversees the industry's promotion and research efforts, said he does not necessarily support chemical applications to control thrips.

"In my case, when I went out looking for thrip last year, I didn't see any, but then later on I saw damage on the fruit and I don't really know what happened other than somehow the population exploded. I saw far more damage than I saw actual thrip.

"Over the years I have chosen not to spray because I believe it will come back in to biological balance and the problem will be reduced," Wolk said.

Wolk had particular praise for packinghouses such as Del Rey Avocado that he said have developed the processed food market for thrips-damaged fruit.

"The handlers have done a tremendous job of marketing that fruit into food service chains and they should be complimented for doing a really good job since we first got it," he said.

Jerome Stehly, a grower with groves in Valley Center and Fallbrook and chairman of the Santa Ana-based California Avocado Commission, said the thrips problem will be around for months.

"It will go through the whole season as we pick and it will be a challenge to market all that damaged fruit," he said.

Contact staff writer Mark Walker at (760) 731-5794 or mlwalker@nctimes.com.