The Lower Rio Grande Valley farmers traditionally irrigate vegetable crops with furrow irrigation systems. To conserve water and mitigate the effects of droughts, there is a need to adopt more efficient irrigation and fertilization methods and practices in vegetable crops to increase crop production quality and profitability. Farmers that use furrow irrigation systems apply from 4 to 6 inches per irrigation depending on their furrow length and apply more than five irrigations during the vegetable growing season, and using between 20 inches (1.7 ac-ft) and 40 inches (3.3 ac-ft) of irrigation water in their fields. Vegetables have a shallow root system, so farmers must irrigate frequently to maintain good moisture levels during the growing season for optimum growth, possibly wasting water. We use image analysis derived from Unmanned Aerial Systems (UAS) and irrigation soil water sensors to provide management recommendations to schedule drip and surface irrigation to conserve additional amounts of water. We established replicated research experiments using subsurface drip irrigation and soil water sensors (watermark sensors) to irrigate watermelons and other vegetable crops. We grew plants under three different water levels to trigger irrigation (50, 75, and 100 cb). A drip irrigation system with plastic mulch was placed in the field, as well as soil-water sensors, to measure and monitor the soil moisture. After calculating the water used in the three water level treatments, the 50 cb treatment used 0.27 ac-ft, the 75 cb treatment used 0.24 cb and 0.22 ac-ft was used by the 100 cb treatment. According to our results, we could conserve up to 3.0 ac-ft with our recommendations. We concluded that watermelons could be managed when the soil-water sensor readings range between 50 and 75 CB and approximately 0.3 ac-ft of water using subsurface drip irrigation. We obtained an average yield of 53,536 lb/ac, when irrigated under the 50 cb treatment, 42,059 lb/ac at 75 cb, and 36,719 lb/ac at 100 cb.
Not only are Phytophthora, Pythium, and interesting Phytopythium species potentially devastating horticultural pathogens, they regularly present challenges in vitro. In this study, multiple established and novel methodologies were built upon to bolster researchers’ ability to quickly isolate, differentiate, and promote virulence of multiple oomycetes principally collected from symptomatic conifers and nearby water sources. These methods allow greater flexibility in generating clean mycelial cultures for genetic characterization, varying pathogen structures for use in novel bioassays (such as synchronized production of sporangia or zoospores), and ultimately inoculations to evaluate oomycide efficacy or make headway towards completion of Koch’s postulates for previously uncharacterized host: pathogen pairings. Phytopythium vexans (Pp. vexans) (n=8 isolates), three Phytophthora species / species complexes including P. cinnamomi (n=10), P. cryptogea / drechsleri complex (n=4) and P. humicola (n=2), as well as 5 tentative species of Pythium, were evaluated. Isolations took two forms, standard root sampling onto Phytophthora selective media (PARPH), or water-based sampling through a modified ‘baiting/trapping’ technique that utilized on-site collected water samples in the laboratory. The ‘baits’ were Cannabis sativa seed, Vigna radiata beans, and Rhododendron maximum leaves suspended in aerated water samples or slurry of silt/soil. Samples were evaluated on V8-agar (V8A), pea agar (PA), pea broth (PB), potato dextrose agar (PDA), cornmeal agar (CMA), and water agar (WA), each of which provided distinct morphological indicators and structures useful in diagnostic guides and in bioassays or inoculations. As is typical with all plant pathogens, the longer they remain in culture, the less virulent they may become. With oomycetes, this is compounded as the pathogen will often go into chlamydospore or oospore formation (long lived survival structures) which are not ideal for experimentation. Inclusion of germinated then surface sterilized (70% ethanol for 30s) Vigna radiata and Lupinus perennis sprouts into recently poured (still liquid) 1/8 clarified V8 juice agar (1/8 clV8A) provided a media capable of rejuvenating the pathogen due to presence of living roots and dynamic plant nutrients. This allows for more predictability of zoospore formation, especially if they are intended to be used with a time sensitive trials. In numerous incidences multiple species of Phytophthora and Phytopythium vexans isolates went into zoospore release simultaneously by utilizing these approaches in combination with resource starvation and culture washing with sterile distilled water. Taken together these approaches will greatly aid any researcher working with root disease oomycetes in culture.
Optimizing planting date for strawberry in California production is a sustainable measure to maximize yield and maintain plant health. The goal of this project is to assess the optimal planting date for two predominant cultivars: 'Monterey' and 'Fronteras'. The trial was conducted in field 25 at Cal Poly, San Luis Obispo. The experimental area consisted of 3 beds, each 53.5 ft. long. Standard 64-inch beds with 4 rows of plants per bed and 3 lines of drip tape were used. Beds were planted at two-week intervals: 26 Oct, 9 Nov, 23 Nov 2022. Each bed was planted with four plots of ‘Monterey’ and four plots of ‘Fronteras’ (20 plants/plot). Plug plants were produced at North Carolina State University’s nursery and shipped overnight to Cal Poly and planted in the field the next day. First harvest was 13 Apr 2023 when the first fully red fruit were observed. Fruit were harvested, counted, and weighed twice weekly. The trial was completed 8 Aug 2023 and replicated in the 2024 growing season.
