The work is quite feasible, and it is the only thing in our power . . . Let go the past. We must only begin. Believe me and you will see.” -Epictetus, Discourse, 2.19.29-34

Insects and mites unfortunately do not celebrate the holidays, nor do they take vacations. And as a consequence, neither do we! Ventura and Santa Barbara County growers and PCAs were busy dealing with mites given these dry, windy, and warm conditions. A trial I had planned to start at the end of January was forced to start in mid-December because Lewis mites showed up to the Christmas party. The Strawberry Center entomology lab is in the thick of it.

I want to share the work we plan to do for 2025. We have 7 different project buckets for 2025. Each bucket contains several different experiments or trials. Our goals and projects for 2025 are the following.

1. Pesticide efficacy testing

This is very straightforward. Spray the compounds; see how many perish. We are planning to dive into the effects of increasing acidity and spray volume to see if we can replicate claims we have heard over the past year. We are currently preparing for a Lewis mite trial in a grower field in this month of February to generate important product efficacy data on pest that is still somehow rare in the larger agricultural sphere but occasionally a real pain in the neck for strawberry growers. Most miticide efficacy trials are conducted against twospotted spider mite (TSSM) and not Lewis mite, mainly because of the time of year and unreliability of Lewis mite outbreaks.

2. Pesticide resistance monitoring

This is our most ambitious project that brings together collaborators from the USDA and UC Extension. The goal is to examine 22 sites over the strawberry growing season to detect differences in pesticide efficacy between each district within season and over seasons. We have selected our 10 sites over the Santa Maria region and are now selecting sites in Oxnard and Salinas.

3. UV-C application for mites and Lygus

This project has luckily been relatively inexpensive to conduct because the majority of the pieces were already in place. Colin Koubek has taken up UVC as part of his master’s thesis. The goal is to confirm efficacy of UVC against TSSM in the lab and the field. In addition, Colin is examining the effects of UVC at varying doses on the life stages of Lygus, which had its challenges. We now have the appropriate caging materials to contain the Lygus nymphs and adults and still allow UVC to penetrate.

4. Predatory mite bottle quality

Another challenging project has been performing predatory mite bottle quality checks. After about 8 bottles we quickly realized problems with the method. We were only retrieving 30-40% of the mites that were said to be in the bottle. One of the manufacturers claimed that the old Cal Poly method had issues, and I went down to their facility to observe their bottle procedures. Taylor Hibino, another of my master’s students, is tasked with testing a reverse Berlese method. It will be necessary to use a combination of the industry standard method and the reverse Berlese method to satisfy both industry and grower needs for transparency and provide a quantitative and qualitative assessment of the bottled Phytoseiulus persimilis.

5. Beneficial insects

We have projects in progress with Biobee examining their line of P. persimilis and Neoseiulus californicus in field and small plot trials. With Bioline we will be conducting outdoor caged trials with Podisus maculaventris (a potential Lygus predator) to examine their efficacy against Lygus on the plant. We are also hoping to finally start a quantitative assessment of Drone vs. Hand application predatory mites to have data that confirms the seemingly universal idea held by some in the industry that uniform application over a field is preferable to the haphazard pepper shaker method.

6. Fungicide lethal effects on predatory mites

Building off of previous research, Colin Koubek is finding some surprising results that are forcing us to think more about spray and droplet structure. We have completed testing on Captan 80WDG and Switch mixed with the adjuvants Broadspred, Widespread, Kinetic, Silwet, and Dyne-amic. We should complete this battery of testing with Thiram, Luna Sensation, and Sulfur by the end of March 2025. Colin will present his data at the California Strawberry Commission meeting in April 2025. We will repeat this study with the same compounds on N. californicus in the fourth quarter of 2025.

7. Host plant resistance to mites, Lygus, and spotted wing drosophila

The host plant resistance trial was planted in early November 2024. The first phase of the trial will focus on twospotted spider mite which will be infested this month. We will allow the mites to build up to an intolerable level to examine differences between genotypes/cultivars and measure the mite population growth. Once the mite population hits 100 -150 per leaflet, we will aggressively spray the trial to finish it. Yields will be collected over a two-month period from April to May.

The Lygus and spotted wing drosophila (SWD) testing will be pilot studies to see if we can see differences between the genotypes/cultivars. The Lygus method will involve caging 5th instar nymphs directly on flowers with controls to examine the severity of catfacing between genotypes/cultivars. The SWD testing will be the most challenging because of the following risks: a) we detect no differences; or b) we detect differences, but they cannot be replicated in a grower’s field. One problem with SWD testing is that differences detected across a gradient do not translate into the grower’s field because when faced with no choice, an SWD female will just lay her eggs, regardless of preference.

Conclusion

Is this ambitious? Yes. Will we succeed? Are these a lot of projects? Depends on who you ask. The proof will be in the delicious strawberry pudding. We have a good team in place. We will find that upper limit and adjust accordingly. In the meantime, enjoy these nice rainstorms that are boosting plant growth out of the filthy claws of the mites.