In recent years, California growers have experienced a lot of variation in seasonal weather patterns. Warmer winters, earlier springs, sporadic rain, and periods of prolonged heat seem to be the new normal. These conditions have an impact on pest pressure, with growers alarmed at high trap counts early in the season.
Unfortunately, the industry may have to adjust to these erratic weather conditions. Going forward, growers should monitor their fields carefully and keep an eye on local weather in order to adjust pest management tactics as needed.
For more on how temperature affects pest development, and how growers can proactively protect their crops using mating disruption, continue reading.
Warmer Winters Do Not Allow Pest Populations to Reset
California winters have been mild the past few years, with few (if any) significant freezes or cold weather events. Environmental conditions help naturally suppress pest populations until trees break dormancy in the spring. But without a significant drop in temperature, pests do not have a chance to “reset,” meaning that more insects are able to survive and carry out reproduction.
Temperature directly impacts how pests develop throughout the growing season. A sustained period of warmth means that pests will begin developing sooner. With that in mind, crops are vulnerable for longer periods, specific milestones are sped up, reproduction potential is higher, and generational turnover occurs faster.
Management Updates for California Nut Crops
Same as every growing season, the nut crop industry is carefully tracking navel orangeworm development. Those active in the industry , such as Joe Coelho, have used degree day models to anticipate flight timing for pests like navel orangeworm. To calculate degree days for navel orangeworm in your area, growers can pull data from local Cimis stations and use predictive models like UC IPM’s Degree Day model. Some growers may also use in-orchard weather stations equipped with localized sensors to help with degree day tracking.
Growers hoping to precisely time navel orangeworm insecticide treatments during the growing season should begin monitoring late February to early March by placing traps baited with their preferred lure in orchards. It is good practice to use at least one large plastic delta trap for every 5-40 acres. For up to date population numbers, liners should be changed and counted at a bi-weekly cadence. Growers using NOW BioLures should replace them every 4-5 weeks. Growers may use trap numbers, along with degree day models to make treatment decisions in fluctuating weather conditions.
How Mating Disruption Can Help Reduce Damage in Difficult Growing Years
As growers do their best to work with fluctuating weather conditions, proactive integrated pest management tactics matter more than ever. With pest pressure increasing at a rate higher than what is historically expected, growers should employ a combination of reliable tools to help control pest pressure.
For season-long, continuous protection against navel orangeworm, growers should deploy Puffer® NOW Ace. It has an internal temperature gauge that allows the aerosol to release pheromone only when the pest is active. For growers looking for a flexible approach aligned with crop phenology and NOW flights, choose CheckMate® NOW-F sprayable pheromone. It can be applied in April as a spring mummy spray, at hull split, at harvest, or post-harvest depending on pest pressure and grower preference.
For help determining which of these two mating disruption solutions work better for your orchard or to hear about our special grower rebates for Puffer® and NOW-F contact a member of our technical team here. Don’t wait too long; in a year like this waiting doesn’t just reduce control, it also builds pressure throughout the rest of the season.