Navel orangeworm (NOW) is a highly damaging and challenging pest to manage for California almond and pistachio growers.
In this guide, we'll be sharing the latest updates and tools to help growers better manage NOW. This includes reports on data gathered from the expansive Semios network of in-canopy sensors, and insights from the Semios in-house research team of PCAs, agronomists, entomologists, and irrigation specialists.
Use the list below to quickly jump to different sections:
Using data from our in-canopy weather station network and the regional full bloom model, we've created the following regional map of forecasted 1% hull split dates for nonpareil almonds.
We're expecting to see about a 2-week span across the Central Valley for nonpareils to reach 1% hull split.
Note that these predicted hull split dates do not account for the impact of plant water status leading up to split. Moderate amounts of water stress can lead to nuts splitting earlier, whereas severe stress has been shown to delay hull split.
Semios started monitoring navel orangeworm (NOW) activity for the 2022 season throughout the Central Valley in late February this year, and it did not take long for us to catch our first moths.
Here are our average year-to-date trap catches for the 2022 season so far, from late February to mid-April.
Some general observations of NOW trap catch patterns include:
In the two charts below, we took a look at how NOW trap catches varied over time in almonds and pistachios in Fresno, Kern, Kings, and Madera counties.
Traps set in almonds have been consistently active since February, whereas we recorded peak activity in pistachios during the last week of March in Fresno and Kings counties.
Traps may not provide a clear picture of NOW flights for those of you using mating disruption. By placing egg traps in your NOW hot spots, you can set a biofix to track NOW development.
Stay on top of key degree days thresholds to ensure your spray timing is well aligned with NOW activity on your farm with the help of the following Semios tools:
All of the tools above use in-canopy degree day readings for the most accurate reporting.
For those with a lot of area to cover, the per-acre degree days heatmap helps identify where to start spraying first. Target the warmer, more vulnerable areas first to boost the efficacy of your sprays.
After narrowing down the dates, how do you know precisely when you should spray for maximum impact? Semios provides a daily and hourly spray conditions forecast that factors in wind, rain, environmental temperatures, and inversion data.
Look for time slots highlighted in green since those will have ideal conditions for spraying:
When hull split is around the corner, it means it’s time to review your spray strategy for the season.
While percent damage in previous seasons can give you a sense of how successful your NOW management program was, it can be hard to find the answers when things don’t go according to plan. Looking at how your sprays were timed, relative to the industry may give an indication if something is amiss in your spray program.
After orchard sanitation, spray timings are critical for a successful NOW management strategy. New almond crop becomes susceptible to NOW at hull split; as nuts begin to split, volatiles are released that attract females looking for that perfect food source for their young.
This is why UC Extension recommends that NOW sprays are applied at 1% hull split, followed by a second application two weeks later. This second application coincides with pollinizer hull split, as well as when some products lose their residual effect.
Finally, when populations are high, a third spray, or sometimes even a fourth may be recommended.
While the guidelines seem simple to follow, material application decisions are not as straightforward as just spraying at hull split. Many factors come into play including logistics, the speed of hull split progression, and pest development. It’s also important to keep in mind that, earlier spray applications may be needed if NOW peak flight occurs early or if rainfall is predicted around hull split.
Example of a California almond orchard per acre hull split forecast heatmap
These factors all impact effective spray timing. For example, 2017 was a year of heavy NOW damage partially because of poor sanitation due to heavy winter rainfall but spray timing may also have played a part. The chart below shows when growers applied sprays relative to hull split in 2017 and 2018; two hull split sprays and the third if applied.
State-wide hull split spray timings relative to non-pareil hull split for the sprays 1 - 3
Many growers were unable to make timely hull split sprays in 2017 due to the high amount of rainfall which prevented equipment from entering the fields. In 2017, growers applied the first hull split spray on average 4.6 days after hull split. In contrast, in 2018, most growers applied their NOW sprays before hull split, with growers applying hull split sprays on average 2.5 days before hull split. 2018 was reported as having less NOW damage compared to 2017.
Semios' hull split model provides a 90 day hull split prediction so you can get a head start on planning logistics and better time your NOW sprays. The hull split model provides:
Semios' Per-Acre Hull Split Forecast
Water management is important for NOW management at hull split.
Well-timed deficit irrigation helps advance splitting and dry your nuts out more quickly and the regulated stress can reduce the window of time that your orchard is vulnerable to damage. You can read our guide on deficit irrigation around hull split for more tips.
By using Semios water management tools, you can make more informed decisions and maintain your trees' stress at the desired level:
Based on the MAD (Management Allowable Depletion) target you set and using data collected from soil moisture probes, the Semios Available Water Content Graph provides clear color-coded regions for different water deficit levels. You can use the ranges to stay within the desired deficit level and adjust your irrigation plans accordingly.
To prevent causing long-term damage to your trees from the induced water deficit, you can refer to the Plant Stress Graph. This graph shows your trees' stress levels based on maximum daily shrinkage (MDS) data collected from dendrometers.
This is a good way to double-check that your deficit irrigation strategy is working properly and not causing excessive stress for your trees.
However, not all dendrometer-based plant stress tools are the same, and you can read more about the science behind the Water Stress Index that powers Semios' plant stress insights.
Using the Semios Almond Management Tool, you can check your spray timing and see how it compares with other almond growers:
The Semios almond management tool helps you check your spray timing by showing: (1) Block specific hull split (2) Trap captures (3) Average hull split application times (4) Hull split application times relative to hull split
Here are some questions you can use to guide your evaluation of your hull split spray program:
If you have any questions, our entomologists, PCAs, and Irrigation Specialists can help. Leave us a comment below or check out the blog posts below for more management tips:
Comparing Degree Day Sources For Tracking NOW Generation Flight Prediction
References:
How Much Does Navel Orangeworm Damage Cost?