Project Update
Artichokes
An affordable, biorational pest management program for artichokes on the Northern Central California coast

Artichoke growers on the Northern Central Coast of California in Santa Cruz and San Mateo counties and growers in San Benito County face many challenges: poor soil fertility, irrigation water salinity and shortages, infestations of vertebrate pests such as rodents, rabbits, and deer, and the very big problem of the artichoke plume moth, the crop’s primary insect pest. The average yields of artichokes from these farms is typically less than a quarter of the yields expected from farms in the Central Coast region, which includes the Castroville area.

With these issues in mind, Sean Swezey, then associate director of the Center for Agroecology and Sustainable Food Systems at UC Santa Cruz, Mohammad Bari, entomologist at the Artichoke Research Association, Reggie Knox, outreach coordinator for the Community Alliance with Family Farmers, and Northern Central Coast artichoke growers received funds from SAREP in 1998 to design and demonstrate a biorational management program for artichokes that they hoped would be economically feasible for the area.

Artichoke plume moth (APM) is a major limiting factor for perennial artichoke production. In the mild weather of the Northern Central Coast, APM never becomes dormant; instead it reproduces throughout the year. Conventional growers have relied heavily on chemical insecticides to control APM; without control measures the infestation rate can reach as high as 70 percent.

Other control methods such as biological control, use of sex pheromone in mating disruption, and mass trapping of APM have been studied during the last 20 years. Though many of these studies demonstrated success, the techniques did not gain acceptance among Central Coast artichoke growers because of the higher material and/or labor costs compared to conventional chemical control.

Northern Central Coast artichoke growers with smaller farms expect yields of 100 cartons/acre compared to an average of 450 cartons/acre on Central Coast farms. With the low cash flow resulting from these yields, these farmers have little incentive to use any APM management program requiring a major capital investment. It is estimated that for these growers, the contracted cost of one insecticidal spray aimed at APM is approximately $40/acre. Several applications would be needed to achieve optimum control of this persistent pest. It is also likely that use of chemical control against APM would disrupt the delicate balance of naturally occurring predators and parasitoids and secondary pests such as aphids, leaf miners, lygus bug, and proba bug, possibly resulting in increased loss.

Project phases

The first phase of this project focused on two components of a potential biorational management program: release of an egg parasitoid (Trichogramma thalense) and the use of mating disruption (APM Rope). During this time a group of ten growers met with project researchers to share research information and farming experiences.

“These meetings were a great opportunity for growers to hear about the latest research and for researchers to hear what was actually happening on the farm,” said Knox.

Bari stepped in as principal investigator in 1999 for the second phase of this project after Swezey was appointed director of SAREP; Swezey became the project adviser.

By the beginning of Phase Two in early 2000, it had become apparent that the egg parasitoid and the APM Rope dispensers that were studied in Phase One were prohibitively expensive and no longer available to Northern Central Coast growers. The focus of the project shifted to evaluate the effectiveness and economic feasibility of a mass trapping technique to control APM.

Mass trapping uses a pheromone lure to attract APM to a water-oil trap. The trap, developed by the Artichoke Research Association, is easy to assemble from locally available materials and has proved to be both durable and inexpensive.

Various types of pheromone lures were first tested in field trails to determine their effectiveness and longevity. The Trece lure, a red rubber septum containing APM pheromone Z-11 Hexadecenal, was determined to be most effective in attracting APM to the trap and highly stable in maintaining its attractiveness for more than two months.

To test the use of a mass trapping system in the Northern Central Coast, four experiment fields were selected on grower Tim Hudson’s Coastways Ranch in Pescadero. In October 2000, mass trapping was established in two fields. Traps were stationed in a grid pattern with 100 X 100 foot spacing to achieve a density of 4.3 traps per acre. At six to eight week intervals the lures were renewed and the traps were replenished with fresh water and oil. In the two control fields, no attempts were made to control APM.

Throughout the growing season, researchers monitored the level of APM larval infestation of vegetative shoots in all four fields. By the end of August 2001, the two fields using mass trapping had significantly lower rates of APM infestation (approximately 2% and 4%) than the two control fields (approximately 7% and 20%). Hudson was satisfied with the APM control maintained in the fields using mass trapping.

The total cost of parts and labor for assembling the traps is estimated to be $100 for a five-acre field; depreciated over five years, the total hardware cost can be estimated at $20 per year. Including the recurring costs (lures, miscellaneous supplies, and trap maintenance), the total annual cost for a five-acre field is estimated to be $358 ($72 per acre).

These study results show that mass trapping is an economically feasible method of APM control for Northern Central California artichoke growers. Although this method is not currently compatible with organic culture because of the petroleum-based oil used in the traps, future studies could be done to determine if sticky traps may be a viable alternative for organic systems. Hudson has expanded the use of mass trapping to control APM on all 28 acres of his artichoke crop.

“The material and labor costs of mass trapping probably don’t quite equal the cost of one pesticide spraying,” Hudson said. He continues to find it economically beneficial to avoid spraying by keeping his APM populations under control with mass trapping.

For more information, contact Mohammad A. Bari, Artichoke Research Association, (831)-755-2871; mohdabari@aol.com. The full report of this project is available on SAREP’s Web site at: www.sarep.ucdavis.edu/Grants/Reports/Bari/bari.htm