Almond bloom is approaching fast. Based on local conditions and projected warm weather next week, bloom will probably be within 7-10 days. Conditions this year are wetter than they have been in the past which will be conducive to many almond diseases, including brown rot, shot-hole, anthracnose, and jacket rot. Furthermore, orchard access may be limited, reducing the ability to apply fungicides by ground rigs reducing coverage. Below are a few points to consider as we begin the 2017 season.
Be prepared for several fungicide sprays. If wet conditions persist, a more conventional bloom spray program should be considered with an application around pink bud to 20% bloom, an application at 80% bloom, and a petal fall spray. These regular sprays ensure coverage of the expanding floral tissues. Sprays should be made every 10 to 14 days in consistent rain, and every seven to ten days if heavy rains are experienced.
Fungicide rotation is critical. With multiple fungicide applications, each successive spray should be a different fungicide mode of action. This is represented by the FRAC number. If using multi-mode of action fungicides, the fungicide used in the follow up spray needs to be different than both modes of actions utilized in the previous spray. Please review the modes of action for the various diseases and timings by using the Fungicide Efficacy tables outlined here. Almond relevant information is on page 31.
Often wet winters are followed by wet springs. With the potential need of fungicides through the spring, it may be useful to mix in a broad spectrum fungicide at petal fall. This would provide the ability to apply the same mode of action twice in the same season. A spray program with this type of rotation could look like this: Pink bud: FRAC 9; Full Bloom: FRAC 3/11; Petal Fall: M5 (Chlorothalinil); 2 weeks post petal fall: FRAC 7/11; 5 weeks post petal fall FRAC 3, Summer: FRAC 11. Please see the link above for potential trade names.
Recent research has identified a new modes of action to manage bloom time diseases. This class is known as the hydroxyanilides or FRAC 17. Effiacy has only been determined for brown rot and jacket rot. If wanting to use these products, consider applying them during the early part of bloom.
Research into the use of adjuvants has found that the organosilicone adjuvant Sylgard 309 can negatively impact honey bee health. Exposure to this adjuvant was shown to increase bee susceptibility to the common bee pathogen Black Queen Cell Virus, leading to hive decline. At this time, it is suggested that organosilicone adjuvants be avoided during bloom. The findings of this study can be found here.