Earlier this week, the California Citrus Quality Council (CCQC) contacted the industry to provide information on complying with the Chinese and Korean export protocols. The table below summarizes the accumulated hours of temperatures of less than -1° C and total precipitation and the resulting risk levels for copper reduction, Septoria spot, and Phytophthora syringae for the fall season until January 24, 2025.
This data, in combination with local rain events and weather forecasts, will provide a good estimate of when future treatments will be needed.
China
Growers in San Luis Obispo (District 2) and Fresno Counties (District 1) are currently at-risk level of 4 and 3 for copper reduction and level 3 for P. syringae risk and should have made a second application of either copper or approved alternative to acreage destined for export to China by January 21, 2025, as described in the Dec. 27 advisory. Based on the Phytophthora-forecasting model, Tulare and Kern Counties risk levels are currently at level 2 for copper reduction, whereas W. Riverside Co. is at level 3. Based on the P. syringae risk model, Tulare County is at level 3, while Kern and W. Riverside Counties are at level 2. With total precipitation of >55.5 mm, copper reduction is >54.5 percent for Kern County and W. Riverside using the copper reduction model. The 14-day forecast shows a 20% to 30% chance of rain the first week of February in Tulare, Kern, and W. Riverside Counties. Therefore, a second application of either copper or an approved alternative should be made for these three counties by Feb. 17, 2025.
The P. syringae risk levels for Imperial, E. Riverside, Ventura, Santa Barbara, and San Diego Counties are at 0 or 1, and copper reduction is currently 43.6 percent or less for these counties, indicating that these counties are not at risk at this time.
For all counties or regions, copper applications are required for the first preharvest foliar application between October 15 and November 30 to meet the China protocol, but the second treatment may be applied using copper, phosphite (ProPhyt and other products), oxathiapiprolin (Orondis older label), mandipropamid (Revus), or the premixture of oxathiapiprolin + mandipropamid (Orondis Ultra) based on environmental conditions. Oxathiapiprolin is the most active fungicide, providing long-lasting residual protection against Phytophthora brown rot. Additional advisories will be announced if additional fungicide applications are needed.
Korea
Due to the accumulated hours of temperatures of less than -1°C and moderate precipitation levels in Tulare and Kern Counties, the risk for Septoria spot is currently at level 3. Growers should plan on applying copper or approved alternative fungicides (e.g., Quadris Top, Luna Sensation, Priaxor, Cevya) for acreage destined for export to Korea in the next three weeks by February 17, 2025. Growers in other counties are at a low risk level of 1 or 0 (Table 1) and should wait for additional rainfall and the next advisory. Levels of Septoria spot were low last season (winter and spring of 2024), therefore, high rainfall will be required in winter of 2025 to increase inoculum levels.
The extended forecast shows a low chance of rain in the next 14 days in the Central Valley and coastal areas and low rainfall for all inland desert citrus-producing counties. In general, additional precipitation is needed before the risk for Septoria spot reaches an actionable level.
The GAPs for Septoria and Phytophthora management include more detailed information. Follow-up advisories will be distributed in the coming weeks if additional fungicide applications are needed for Septoria and Phytophthora brown rot.
China and Korea Acreage
If citrus groves are being managed jointly to meet the China and Korean protocols, an application of copper or a copper alternative is needed to maintain eligibility for both export markets for Fresno, San Luis Obispo, Kern, and Tulare Counties. Fungicides listed for Phytophthora brown rot can be mixed with fungicides listed for Septoria Spot.
If you have questions or need additional information, please contact CCQC at (530) 885-1894 or via e-mail at jcranney@ccqc.org.
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