On a 10-acre test plot with Diamonte variety strawberries, he compared the foliar-applied Messenger to a standard fungicide program in adjacent strawberries.
He reported a 15 percent increase in volume of trays, or an increase of 190 more trays than the standard program.
Kohatsu said he was impressed that there were no quality adjustments (discounts for more than 2 percent decay) on fruit grown in the Messenger plot. His fruit under the standard treatment had a 1 percent adjustment.
Messenger, recently registered in California, is produced by Eden Biosciences of Bothell, Wash. The company says it is effective on an array of other crops from cotton to citrus and tomatoes.
During the gathering at Kohatsu’s Misha Berry Farm, Robin Ross, Eden field development scientist at Santa Maria, said Messenger operates on the principle that plants produce compounds to protect themselves against disease. These constitute the resistance which plant breeders traditionally have sought to improve.
When a plant is attacked by a pathogen, genes producing these compounds are "turned on" for a defense, but often plants are overwhelmed within the three days it takes for them to mount a defense.
The solution was to find a way to induce the natural plant defense, and Cornell University scientists isolated a natural protein, harpin, derived from the Erwinia amylovora bacterium that causes fireblight in fruit trees.
When harpin is applied, one effect is activation in the plant of oxygen which kills the invading pathogen immediately and thickens plant cell walls to exclude other pathogens. Full response occurs in three to five days, and the protection may last for several weeks.
Ross said Messenger, while it generates plant resistance, enhances growth giving potential making for reduced use of fungicides and at the same time produces fruit with greater shelf life.
Marie Ocafrain, Eden technical sales representative at Grover Beach, Calif., gave results of an Oxnard trial gauging Messenger against a standard program of Captan and Thiram treatments on strawberries.
In a May picking, the test yielded 411 trays per acre from the standard treatment and 425 trays per acre from the Messenger portion. In the June picking, the yields were 121 trays and 109 trays, respectively.
The label for the wettable dry granule product calls for a use rate of 4.5 ounces per 75 to 100 gallons of water per acre. It is foliar applied at a 14- to 17-day interval.
It should not be used with chlorinated water, and if a surfactant is used, it should be a non-ionic type. The pH in the spray tank should be between 5.0 and 10.0. It should be used within 24 hours after bags are opened and applied within four hours after the spray mixture has been prepared.
"Optimal timing is early in the season," said Ocafrain, "so you have season-long control for botrytis. The first application should be at early flowering, following up with a 13- to 17-day interval."
She stressed that Messenger is not a curative, and three to four sprays must be made for season-long protection and post-harvest quality of the fruit. A vigorously growing plant is essential for the proper uptake of the product, as is close attention to water and nutrient management