Q. What disease pressure can I expect this spring?
A. Trees stressed from the drought coupled with this winter’s wet weather may be more susceptible to the diseases that prevail in wet years. Growers and PCAs need to be diligent in their scouting and be on top of their fungicide programs. Input from county extension and universities can help keep you informed about disease pressures occurring throughout the region.
The weather conditions each year and the orchard history of disease need to be considered in your disease management program. Timing of your fungicide sprays is critical for optimal disease management. As almonds enter their bloom season, infection of some diseases (like brown rot) will be favored by rainy weather. Brown rot spores are airborne or rain splashed, so your first timing may be at pink bud during a wet year. The frequency of spraying will also be important in disease management, especially if there are frequent rains during the bloom period. Pistachios begin their bloom in April and a fungicide program for Botrytis and Botryosphaeria needs to start at bloom.
Anti-resistance strategies should be in place for all your tree nuts. If the wet weather brings on more disease this year, it will be especially important to practice fungicide stewardship. After your dormant Kocide + oil sprays, start your fungicide program with Double Nickel 55 biofungicide, with its five multi-site modes of action. Then continue in rotation with or in tank mixes with fungicides of different modes of action.
Q. When should I start my disease program for tree nuts?
A. This year I’m suggesting you consider using Double Nickel 55 biofungicide and Cueva, a low-load copper octanoate fungicide/bactericide, as the cornerstones of your fungicide program. Here’s why. Both Double Nickel and Cueva are contact and systemic materials, which maximizes your flexibility. You can use both in combination with a systemic fungicide or use them alone as a contact material. Both have a short 4-hour reentry and can be used on organic or conventionally grown nuts.
For bacterial canker, you can apply Cueva as a dormant spray when buds begin to swell, repeating at the bud burst stage and weekly thereafter as needed, up to six sprays. For brown rot blossom blight, start and repeat with Cueva or Double Nickel at the bud swell, popcorn, full bloom and petal fall stages. For walnut blight, make your first applications when leaflets start to unfold, prior to, but no later than 1% pistillate bloom.