sept-oct-2020

Plan and prep for orchard sanitation. It is a critical step in managing navel orangeworm (NOW) and maximizing crop quality and nut price to grower in 2021. Mummy nuts left over from the 2020 crop are food and shelter for NOW in your orchard and a significant risk to next years’ crop. They should be removed and destroyed before March 1. While the actual shaking may not happen until December or January, make sure the equipment and operators are ready ahead of time. There may be only a short window for orchard access between rains. Start with blocks that have the highest damage history. Monitoring mummies before and after sanitation helps keep costs and NOW pressure down. Once leaves drop, count the mummies in 20 trees per block. The target is two mummies or less per tree by February 1, with very low numbers (0.2 mummies per tree and less than four “grounder” mummies under each tree) suggested in high pressure areas. Keep final mummy counts under these thresholds for best results. If shaking doesn’t do it, consider polling with hand crews — especially in areas with a high damage history. Reducing mummy numbers also reduces two-year-old, moldy nuts in the crop next year, which further reduces rejects. Don’t talk yourself out of orchard sanitation. If the fall mummy counts show a need, not doing this key practice means you could be taking a chance with your returns for next year. Weed management is another important task in the late fall and into winter. A careful weed survey after the first winter rains is the first step in effective weed management. Talk with your PCA about cost-effective weed control practices. Once target weeds have been identified, consider timing and materials for pre-emergent control for the coming season. Post- emergent sprays can be used with pre-emergents as well as applied next year once rains have passed. One cost-effective strategy for long-term weed control is sequential applications of pre- emergent herbicides. This is where a combination of winter and spring treatments is used to extend control into the summer instead of a single tankmix spray of heavy winter rates. March applications of pre-emergent materials require sprinklers or rain for incorporation, so such a program may not be for all growers in all years, but worth a look. Make sure all pre-emergent sprays are applied to clean, bare soil, not over the top of leaf litter. The herbicide can attach to the leaf litter and not end up on the soil. Talk with your PCA about pre-emergent materials/programs in young orchards. Water, nutrients and sunlight make for “great” weed growing, and repeated post-emergent “burndown” applications can be expensive. Also, check with your PCA about possible unintended tree damage with certain herbicides (pre- and post-emergents), especially at the row ends where extra material may be applied as the sprayer slows down or speeds up. Certain effective 3 7 S E P T E M B E R – O C T O B E R 2 0 2 0