California's 1,500 olive producers are on the ropes in their fight against the ravenous olive fruit fly that in just five years has spread to all olive-producing areas of the state.
The $66 million per year industry has only one tool to battle the fruit fly in 36,000 acres of oil and table olive orchards, but a European company wants to add an attract and kill product to the arsenal this fall that has proven effective in Europe.
Unless the fruit fly can be brought under control, California's economically struggling table olive industry is doomed and the olive oil business may not be far behind, said Nick Sciabica of Modesto, Calif. He is a third generation California olive producer who has seen the olive fruit fly literally envelope the state's olive industry like a cloak of darkness.
The first fruit fly was trapped in 1998. Three months later state officials declared it impossible to eradicate and today 39 counties have the pest in residence in commercial olives.
Canneries are demanding zero tolerance for olive fruit fly worms in grower deliveries. Sciabica said unless growers can bring the pest under control, that zero could spell the end for commercial California table olives.
“In Europe where olives are grown primarily for oil, there is a 10 percent tolerance level so the California olive oil industry may be able to withstand the fruit fly if we can get reasonable control if it,” said Sciabica.
“However, in some coastal areas infestation levels were 100 percent last year — some growers had two worms per olives and did not harvest any olives,” he said.
“I have seen three worms in a single olive. That is an amazing level of infestation for such a small fruit,” echoed University of California entomologist Dick Rice. “When I tell the Europeans about the kind of infestations we are seeing, they cannot believe it and they have had the olive fruit fly for a long time.”
“We are really in the dark about the full impact of the olive fruit fly on the Central valley,” said Sciabica, who only began trapping for it in his Calavaras County orchard this year.
“We learned very quickly that is can be devastating in the coastal areas,” said Sciabica. “Weather is a big factor in dealing with the olive fruit fly. It gets hotter and colder in the valley than coastal areas and that may make a difference.
“However, make no mistake the California olive industry is in a desperate situation from this insect pest,” he added.
“We went from one fly in one trap in Los Angeles to statewide infestation in five years,” said Dan Dreyer, Tulare County olive producer and chairman of the California Olive Committee. He estimates he now spends $100 per acre to control the olive fruit fly with the only product he has available, Spinosa (GF-120), a bait/pesticide from Dow AgroSciences available via a Section 18 emergency registration. In high infestation areas, the recommendation is to spray every seven days until pit hardening and then as a post harvest treatment. It is approved for as many as 19 applications per season.
“We definitely need something as an alternative or in conjunction with to Spinosa,” said Dreyer.
That something may be an “Olive Fruit Fly Attract and Kill” product from a United Kingdom company, AgriSense. The product will be marketed by Certis in the U.S.
Toby Narin of Porterville, Certis regional sales manager for California's Southern Central Valley, said the company has applied for an emergency product registration from the California Department of Pesticide Regulation, and he is hopeful that it will be granted this fall.
That will not be too soon, according to Rice, who is now researching the product under California conditions. However, he is encouraged by the performance of the product in Europe under fairly high populations.
Entomologist Owen Jones, director of technology for AgriSense in the UK, told a group of growers and pest control advisers at an impromptu field day near Lemon Cove, Calif., recently that his company's product has proven effective in controlling the olive fruit fly in Europe for six months with a single orchard application, especially at low populations.
Jones said both female and male olive fruit flies are easily attracted by lures, pheromones for the males and an ammonia lure for females. The male is also attracted to the ammonia lure.
AgriSense has attached both lure types to a piece of flat cardboard impregnated with the pyrethroid pesticide, lambda cyhalothrin, the same active ingredient as in Karate and Warrior.
These traps are wrapped around an inner branch of a tree at about eye level. The olive fruit flies are attracted to the trap and as soon as they touch it, they get a dose of the pesticide. Jones said they die within 10 minutes after flying away.
“It is not a sticky stick trap so you don't have to worry about the trap becoming covered with insects,” he said.
The traps attract olive fruit flies from a distance of 12 to 15 yards.
Jones said European olive oil producer place one trap per tree where orchards typically are about 40 trees per acre. In California, olive plantings are denser, up to 120 trees per acre. More typically California groves are 75 to 80 trees per acre.
“I don't think it would be necessary to place one trap per tree in denser plantings,” said Jones.
Jones reiterated the importance of using the traps where populations are low.
“If you do not keep populations down, the insect will get away from you very quickly,” he said, citing incidents in Spain last year when infestation levels reached 80 percent to 90 percent because producers did not actively control the fruit fly. “The only thing they could do was harvest early. They could not afford to treat at those infestation levels.”
Asked why that happened, Jones said Spaniards typically vacation in August and when the olive growers returned to the orchards, the olive fruit fly had taken over because there had been no control measures.
Rice said the traps would likely be most effective in California in spring at emergence and late fall before they lay eggs in non-harvested fruit.
“One of the big problems with this insect is that a significant amount of fruit goes unharvested both on the tree and on the ground since the crop is almost all hand harvested. This provides ideal conditions for females to lay eggs that will hatch in the spring,” Rice said.
Trap in fall
“If we can put these traps in trees in October or November, we could provide control for six months or until spring,” said Rice. Olive fruit fly remains active year around except under very hot or below freezing temperatures. Some of the highest trap counts in the state have been recorded in those months.
The traps would be used with the GF-120 Spinosa bait, which can be sprayed once every 7 to 14 days.
“Last year Dow indicated the 10-ounce rate recommended every 14 days may not be high enough for good control to achieve zero tolerance,” Rice said. “This year what is being recommended is a 14-ounce per acre rate with half the acreage treated every seven days. Your are talking about treating every other row every seven days.”
“If we can reduce those GF-120 sprays by using the traps it would hopefully reduce control costs to producers and reduce the resistance buildup pressure on Spinosa (the pesticide in the bait spray),” said Rice.
There is little doubt producers are eager to try the attract and kill product, but cost is a major factor in how widely they will be used. California's table olive industry is struggling economically, burdened by oversupplies domestically and highly subsidized European imports of oil and table olives. Spain can deliver table olives to the U.S. east coast $10 per case less than California producers.
Prices are not expected to improve this year, even though the year's crop is projected to be significantly smaller than last year (85,000 tons vs. 130,000 tons in 2001), but prices are expected to be lower.
Certis representatives would not say exactly how much the traps would cost. Only that they would be “competitive.” However, the price range is reportedly in the $1.35 to $1.75 range.
With a $10 to $12 per acre labor cost to apply the traps at a spacing of one trap for every two trees in an 80-tree orchard, the cost would nudge $90 per acre.
Whether struggling olive producers can afford that, remains to be seen.
“Growers would like to have available a pesticide cover spray,” said Rice.
Dimethoate is widely used in Europe as a spray and in bait, but it is highly unlikely the organophosphate could win approval for use against the olive fruit fly in the U.S. Other commercial products like Sevin may offer olive fruit fly control, but olive growers are finding chemical companies unwilling to spend the money to expand product labels for such a small and economically struggling crop as olives.
Rice said, however, UC entomologists and others will be examining products in the IR-4 pipeline to see if there is something there that may look promising as a cover spray.
Even if the traps proved effective and economical, there remains a huge reservoir of uncontrolled olive fruit flies in urban areas of the state to re-infest commercial orchards.
“I have been monitoring an abandoned olive orchard on the outskirts of Fresno that will eventually become a subdivision. Until the trees are taken out, it is acting as a huge reservoir for fruit flies for a commercial orchard just 100 yards away,” said Rice.
Olive trees are attractive ornamentals and where subdivisions are built in former orchards, developers often preserve the trees for landscaping. Plus, many people plant olives in their yards to harvest and can olives for home use. Large olive trees also are often salvaged from older orchards to be sold for commercial and high-end residential landscaping.
These olives are being decimated by the olive fruit fly, but there is little incentive for homeowners and commercial properties to control the fruit flies.
“If we could get places like Home Depot and Lowe's to sell some of these attract and kill traps maybe it could make a difference not only on the number of fruit flies moving to commercial plantings but in controlling the fruit flies in urban areas,” said Rice.