CONTROL OF ASPARAGUS RUST IN THE SACRAMENTO-SAN JOAQUIN DELTA REGION OF CALIFORNIA

Asparagus Rust (Puccinia asparagi) is a recurring foliar disease problem on some asparagus fields in the Sacramento-San Joaquin Delta Region of California, as well as on the Central California coast. Severe infection can defoliate asparagus fern during late summer and early fall, resulting in reduced carbohydrate storage in the crowns for the following harvest season. Foliar fungicide sprays of currently registered materials in California have been somewhat ineffective, or erratic in their performance on this pathogen. Evaluation of new candidate chemical materials, as well as standard compounds, for control of asparagus rust was begun in 1991. Thirteen individual or combination treatments have been studied for disease control efficacy over the three year study period. To date, the most effective fungicide has been Sandoz 619F, sprayed alone, on a 14 day repeated schedule at 0.12 kg/ha active ingredient once pustule and uredinospore development begins to occur, followed by Bayleton (triadimefon) alone, and a standard combination treatment of Funginex (triforine) plus Dithane (mancozeb). Rally (myclobutanil), tested in 1993 alone, shows excellent promise. Cultural practices such as long interval furrow irrigation, wide-row spacings, orientation of rows with the prevailing wind, and mechanical soil incorporation of fern at the end of the season can greatly reduce disease incidence.