jan-feb-2021

IN YOUR ORCHARD avoided at bloom. In addition, adjuvants, particularly organosilicones, can harm bees and should be left out of bloom sprays. Foliar nutrients may also harm bees. Protect your bee investment, just put fungicides in the spray tank at bloom. The key to good hive health is keeping sprays off the daily pollen load that goes back to the hive. In an orchard with good bee activity, pollen released that day should be gone from flowers (until more is released the next day) and hauled to the hive by early afternoon. Fungicide spraying shouldn’t start until that time when all or most pollen available for the day has been collected. How can someone tell if the pollen is gone from the orchard for the day ? If the pollen gathering bees (the ones with yellow lumps of pollen on their hind legs) are just doing touch-n-go landing on flowers, those flowers don’t have pollen left and it’s okay to spray. Bloom Protection (Fungicides) Given the stakes (the success of your crop!) and the risk of rain/dew in February, at least one good fungicide spray should go on an orchard at bloom. Fungicides work best as protectants and should be applied ahead of rain. For the best results for bloom protection, see the table on this page for the three main spray programs/considerations at bloom (clear skies, warm rain, and cold rain) and the Fungicide Timing and Efficacy tables at the end of this column. Information in all these tables is from Dr. Jim Adaskaveg, UC Riverside. Crop damage from bacterial blast was severe in many orchards in 2018 and 2019. The primary risk indicator is frost. The most effective bactericide is kasugamycin (Kasumin ® ), which received a Section 18 in 2020 for use on almonds that expired last March (it has a full registration on walnuts, apples, and cherries). Section 18’s must be renewed each year and I have not heard if one has been approved for 2021. If frost is in the forecast as bloom approaches, check with your PCA about the availability of Kasumin ® . Multiple strains of the bacteria responsible for bacterial blast, Pseudomonas syringae , pv syringae , are resistant to copper, the only registered option. Limited/sporatic benefit from a copper spray targeting bacterial blast should be expected. Biological materials such as Actinovate AG and Botector reduced blast damage in Dr. Adaskaveg’s research in cherry, but not as consistently and effectively as kasugamycin. Consider calibrating your sprayer(s) for bloom to work differently than for spring and summer foliar sprays. Sprayers delivering good coverage at hull split in a particular orchard at two miles per hour should deliver good coverage at faster ground speeds during bloom. Faster ground speeds save time and money. It should also be possible to reduce PTO or engine speeds (10 to 20 percent less) to reduce fan output and drift as well, saving diesel and reducing drift. Bloom Weather Forecast Spray Timing(s) Elevated Disease Risks/ and Fungicide Selection Primary Considerations Clear Skies 1x; 30-40% bloom FRAC 3,9, and/or 11 (locally systemic fungicides) Warm Rain 2x; pink bud and full bloom Brown rot and anthracnose Cold Rain 2x; pink bud and full bloom Jacket rot, blossom blast. [FRAC 3 fungicides ineffective on jacket rot.] 5 0 A L M O N D F A C T S