Presentations
North American Strawberry Symposium (NASS) 2023: Presentations
Ahmadi, M., Atefi, A., Kraemer, W., Fink, C., Mendez, M. and Lin, J. 2023. Demonstration and Implementation of Cost-Effective UV-C Technology for California Strawberry Pest Management John Lin, Ph.D. Director of Automation Engineering March. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Strawberries in California are susceptible to two-spotted spider mite and powdery mildew. These foliar problems can often be difficult to control due to resistance to many chemical treatments. One promising alternative to conventional chemical management is the use of short wavelength ultraviolet light (UV-C). When UV-C is applied for a few minutes at night, it significantly damages genetic components and processes of foliar pests and disease but does not affect the strawberry plants. However, the technology has not been widely adopted due to minimal outreach and economic barriers. Therefore, this project aims to educate growers about UV-C technology. This includes a cost analysis of current integrated pest management practices and UV-C platform operations, and methods of integrating UVC technology into existing IPM strategies.
Alvarado Rojas, J. L. and Zukoff, S. 2023. Assessing UV-C as a potential tool for arthropod control in California strawberry. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
California strawberry growers utilize integrated pest management tactics to control western tarnished plant bugs, Lygus Hesperus, two-spotted spider mite, Tetranychus urticae, spotted wing drosophila, Drosophila suzukii, and whitefly species, Trialeurodes spp. These tactics include Lygus vacuuming, crop rotation, and the use of beneficial arthropods. Additionally, growers utilize short re-entry interval pesticides to aid them in controlling pests without restricting their ability to harvest fruit adequately. Chemical control has become less effective as their targeted pests have acquired resistance. New Non-chemical control methods, such as autonomous UV-C, are needed to address this issue. The field efficacy of UV-C was tested by conducting studies on two farms and comparing leaf samples between a UV-C-treated plot and a plot treated with the grower’s standard treatment. Lab bioassays helped quantify the UV-C exposure required to impact pest populations by directly exposing them to UV-C and assessing mortality for each pest.
Atefi, A., Ahmadi, M. and Lin, J. 2023. Lygus bug detection using machine learning for pest management. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Lygus bugs (Lygus spp.) are significant pests for California strawberries. They cause substantial reduction in the yield due to mis-shappen fruit. Tractor-mounted bug vacuums are used to mechanically control the Lygus population in the field. Traditional methods to evaluate the performance of bug vacuums are tedious and time consuming. Automated insect detection using machine learning is an effective approach for pest monitoring tasks and can overcome the drawbacks of conventional manual techniques. The objective of this research was to detect adult and nymph Lygus in images using deep learning in lab settings. A monochrome camera, an optical filter, and a light were used to capture videos from moving Lygus inside of a chamber. Deep learning was applied to recognize adult and nymph Lygus in images. The results showed that the deep neural network could accurately identify both Lygus classes. This can be useful to assess the performance of bug vacuums and monitor Lygus population.
Atefi, A., Ahmadi, M. and Lin, J. 2023. An IoT-based operator aid system for the Lygus bug vacuum. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March. In California, bug vacuums are widely used to mechanically control Lygus bugs in the field. The efficacy of the vacuums to remove Lygus is dependent upon operating parameters such as tractor speed, vacuum height, and the air speed of the vacuum’s fan. Drivers usually use their experience to maintain these parameters, which is an imprecise and tedious process. This research introduced an IoT-based (Internet of Things) system that could automatically collect and save tractor/vacuum parameters on both a local memory storage and a remote cloud-based system. The saved data was used to track changes in the parameters and display them as heatmaps. The proposed system also included LED indicator lights installed on a tractor to help drivers maintain the recommended operating parameters. The performance of the system was evaluated through field trials.
Blauer K. and Holmes, G. 2023. Effects of plastic mulch color and number of drip irrigation lines on incidence of Macrophomina root rot. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Incidence of Macrophomina root rot on ‘Sweet Ann’ strawberry plants was evaluated with respect to environmental influences of temperature and irrigation water distribution during the California fall planted season (Nov 2021 to Aug 2022). Treatments consisted of white or black plastic mulch and 2 or 3 subsurface drip lines in a randomized design with four replications. Plants were inoculated at the soil-crown interface by adding 5 g of Macrophomina phaseolina cornmeal-sand inoculum two weeks after transplanting (16 Nov). On 2 Aug, black mulch with 2 drip lines had significantly more mortality at 72.2% than the white mulch with 3 drips at 39.5%. Black mulch with 3 drip lines and white mulch with 2 drip lines had statistically similar morality at 62.8% and 61.0%, respectively. Results indicate that mulch color and the number of drip lines can greatly influence plant mortality caused by Macrophomina root rot.
Blauer K. and Holmes, G. 2023. Multi-year summary of fungicide efficacy on botrytis fruit rot and powdery mildew. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
This poster contains efficacy ratings for 59 different fungicides for use on strawberries in California and 2 pending registration. Results are compiled from 28 trials over an 8-year period conducted at the Cal Poly Strawberry Center. Efficacy trials for Botrytis fruit rot consisted of five weekly applications followed by at-harvest and post-harvest evaluations. Efficacy trials for powdery mildew were conducted in the greenhouse on raised tabletop benches and consisted of five weekly applications with weekly severity and incidence ratings on the foliage. Each trial included a non-treated control and grower standard as a positive control. Fungicide efficacy was averaged across multiple trials and given a relative fungicide efficacy score. Fungicide efficacy scores range from 5 (excellent and consistent) to 0 (ineffective). There are 15 products that are excellent and consistent against powdery mildew and 9 that are excellent and consistent against Botrytis fruit rot.
Fink, C., Mendez, M., Rodriguez, J., Lobo, C., Molinar, A. and Lin, J. 2023. Recommended spray rig designs for California strawberries. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Spray rig coverage is important to pest management efficacy. It depends on multiple factors including weather, operating parameters, and sprayer design. This work compared 30 spray rig designs used in California strawberry production. Field evaluations were conducted in beds with 4 canopy lines in Santa Maria, CA on 162 cm beds and in Oxnard, CA on 172 cm beds as well as in beds with 2 canopy lines in Watsonville, CA on 122 cm beds and 132 cm beds. Pressure, number of nozzles, nozzle type, and nozzle spacing were evaluated with water-sensitive spray cards (n=2,000). Spray rigs were properly maintained and calibrated before each evaluation. Cards were placed both horizontally and vertically on plant canopies near the middle and edge of the beds. The results indicated that increasing nozzle pressure and positioning the nozzle closer to the canopy level could potentially increase coverage by 30%.
Holmes, G. J. 2023. The California strawberry industry: current trends and future prospects. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
California grew 16,187 hectares of strawberries in 2022 in three growing districts located along California’s Central Coast: Oxnard, Santa Maria, and Watsonville-Salinas. Transplants are grown on approximately 2,023 hectares at high and low elevation nurseries located hundreds of miles from fruit growing districts. In 2022, there were 13 public cultivars grown, with the most popular being Monterey, Portola, Fronteras, Cabrillo, and San Andreas, grown on 28%, 11%, 10%, 5%, and 3% of the planted acres, respectively. Proprietary cultivars made up 38% of the planted acres. The most important diseases are Macrophomina root rot, Fusarium wilt, Verticillium wilt, Phytophthora root rot, Botrytis fruit rot, and powdery mildew. The most important arthropod pests are twospotted spider mites and Lygus bug. Labor issues, loss of fumigants, and water quality (nitrates and saltwater intrusion) are current challenges. Increased regulation, increased urbanization and drought magnify these concerns.
Jensen, K. and Zukoff, S. 2023. Resistance status of two-spotted spider mite and Lygus bugs in California strawberries. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Management of the arthropod pests the two-spotted spider mite (Tetranychus urticae Koch) and Lygus bug (Lygus hesperus Knight) in California strawberries is highly reliant on chemical control measures. Intensive use of pesticides has led to continuously decreasing efficacy and exacerbated levels of resistance. Current resistance status of arthropod pests in California strawberries is not well understood. Laboratory bioassays were conducted to determine the toxicity of different miticides and insecticides to the two-spotted spider mite and Lygus bug. LC50 values were generated from our susceptible laboratory population of two-spotted spider mite after a series of discriminating dose trials. The susceptibility of an insecticide native population of Lygus was also determined at the maximum field label rate. Field populations from each major strawberry growing region in California were obtained and subjected to the discriminated dose and maximum field rate of each chemical tested. Factors affecting insect resistance management and future use in strawberries are discussed.
Kraemer, W., Lin, J., Wells, J. and Fink, C. 2023. Optimized Lygus bug vacuum. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Lygus spp. are major pests of the California strawberry industry and have prompted growers to purchase and use machines called “bug vacuums” to mitigate damage throughout the production season. Field tests of the two new vacuum models were conducted in Guadalupe, California and Watsonville, California on raised strawberry beds with fully developed canopies. Results indicated that the vacuum significantly increased removal of Lygus spp. compared with a conventional vacuum. The average number of Lygus spp. removed on each pass by the Double Barrel Bug Vacuum was 2.2 times greater than that of the conventional vacuum, and the Single Barrel Bug Vacuum was 3.0 times greater. The elimination baffle located at the outlet of the conventional vacuum was observed to significantly reduce air speed, and raising it 30.2 cm above the outlet increased air speed by 17% (3.0 m/s) at the vacuum inlet.
Kraemer, W., Lin, J. and Ahmadi, M. 2023. Plastic mulch hole burning and cutting for strawberry planting. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Creating wide holes in plastic mulch on strawberry beds in preparation for planting helps with preventing plants from growing under the plastic and increases the amount of water and sunlight available. Currently, this process is performed by hand, either using a knife to cut open the plastic mulch or burning it with a handheld burner, which makes it a labor-intensive operation in strawberry production. To assist growers in reducing the effect of labor shortages, two new mechanical hole-cutting systems have been developed. The first device was designed to be retrofitted on conventional hole punchers, which would make perpendicular cuts on the plastic mulch. The second device was developed as a new implement to automate the hole-burning process. The first and second apparatuses have been tested successfully to cut holes in the plastic for around 5 and 35 acres (about 46 football fields) of strawberry beds, respectively.
Schaap, G., Speth, G., Kraemer, W., Wells, J., Fink, C. and Lin, J. 2023. Automated hoop house arch removal. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
Hoop houses have been proven to protect strawberries from extreme weather conditions. Currently, the process of implementing and removing hoop houses is done by hand, resulting in high labor costs for growers and a mildly unsafe work environment. A solution to this problem is to design an agricultural implement that can safely and efficiently remove hoop houses from the ground to ensure optimal harvest timing, reduced labor costs, and a safe work environment. Three iterations were tested in grower and research fields. During final testing, the implement produced a 98% success rate in removing the hoop from the stake and a 68% success rate in racking the hoops after removal. The economic analysis revealed that the payback period of the implement would be roughly 100 acres of hoops.
Simard, S. Z., Blauer, K. A., Serpa, B. R. and Holmes, G. J. 2023. Farm-scale evaluation of UV-C for control of powdery mildew in strawberries. Annual NASGA Meeting & North American Strawberry Symposium, San Luis Obispo, CA. 7-10 March.
This study compared the efficacy of UV-C and a conventional fungicide program against strawberry powdery mildew within commercial strawberry production fields. A field of summer planted Portola in Nipomo, CA was used. Strawberry beds (73, 400 linear ft.) were divided into two treatments: grower standard and UV-C. The grower standard consisted of conventional fungicides applied via tractor-mounted sprayer at the grower’s discretion. UV-C treatment was applied twice-weekly between 9:00 PM and 1:00 AM using an autonomous robot. Weekly powdery mildew assessments occurred from 7 Jul through 15 Sep. Assessments consisted of leaf counts, disease incidence and severity. UV-C treated plants had significantly less powdery mildew incidence at five of the nine evaluation dates. Disease incidence peaked 26 Jul, reaching 16.1% and 37.8% for the UV-C treatment and grower standard treatment. These findings suggest that UV-C treatment, applied twice-weekly, significantly reduces powdery mildew incidence compared to the growers’ fungicide program.
2020 — 2025
2019 and earlier
Ivors, K. 2018. Host resistance for managing soilborne diseases. Ventura County, CA. May
Ivors, K. 2018. Fall of Phytophthora. Santa Maria Field Day, CA. May
Ivors K. 2017. Anaerobic soil disinfestation for managing Verticillium wilt. Annual Santa Maria Strawberry Field Day. Santa Maria, CA. 10 May
Holmes, G.J. 2017. The California Strawberry Industry in a post-methyl bromide era: Apathological perspective. APS Pacific Division meeting, Riverside, CA.
Annual Santa Maria Strawberry and Vegetable Meeting. 2017. Santa Maria, CA. 28 Nov
Holmes, G. 2016. Strawberry Center Goals and Projects. Cal Poly Crops Club biweekly BBQ. San Luis Obispo, CA., 27 Jan
Holmes, G., Ivors, K., and Brantley, R. 2016. Efficacy of Dominus fumigant and performance of four UC cultivars in Verticillium-infested soils. Annual Central Coast Strawberry Meeting, Watsonville, CA., 4 Feb
Biology and Management of Anthracnose. 2016. CAPCA, San Luis Obispo, CA
Anthracnose Nursery Survey and Plant Dipping Research Update. 2016.
5th Annual Strawberry Production Meeting. 2016. Ventura, CA. Sept
Holmes, G. 2015: Keynote address at 8th North American Strawberry Symposium at the Crowne Plaza Hotel in Ventura, CA. Title: The California Strawberry Industry: An outsider’s view from the inside. 3 Feb.
Ivors, K. 2015. Genetic resistance to Fusarium wilt. Farming Without Fumigants Field Day Demonstration. Monterey Bay Academy, Watsonville, CA. August 13
Holmes, G. 2015. The Strawberry Center kicks off at Cal Poly. CA Strawberry Society, Santa Maria, CA. 22 Apr.
