Diagnosing problems in the field is never an easy task, but it is one of the most interesting aspects of my job because I usually never encounter the same set of circumstances twice. This summer, I have been called out on a few interesting diagnostics calls, and I wanted to share some observations.
I visited a blackeye bean field that was planted at the end of June. Since June was unusually cool this year, the grower's planting was delayed. Blackeyes shouldn't be planted until the soil temperature reaches at least 65 degrees F, and the cool spring conditions kept the soil cool. About six days after planting, the beans were only sporadically emerged. The plants that had emerged looked healthy, but the overall stand was poor. The grower said that soil moisture was good at the time of planting. I scratched down and found the seed about three inches deep, which is perhaps a little bit deep for blackeyes. Seed had germinated, and the germinated seed looked healthy with no apparent seedling diseases. Seedling diseases include Pythium and Rhizoctonia. Pythium symptoms appear as water-soaked lesions, and the hypocotyl eventually ‘dampens off'. Rhizoctonia symptoms appear as reddish-brown lesions that can girdle the stem. We felt better that it didn't appear to be a disease problem. I reached out to my farm advisor colleague, Rachael Long, to get her take on the situation, and she agreed that this was likely delayed emergence due to cool soil and a deeper planting depth. In the end, we decided to test our patience, wait a few more days, and see what would happen. After another five days, the grower let me know that the plants had emerged, and the stand looked good!
The UCCE network has a breadth of experience to help identify problems and provide potential management solutions. Please don't hesitate to contact me if you'd like help with diagnosing problems in the field.
UC Cooperative Extension will host the annual Delta field meeting on Thursday, September 30th from 10:00-11:30am, on Tyler Island in Sacramento County. The agenda is pasted below and attached. In addition to providing information on the annual field corn variety trial, this year's agenda includes presentations on nitrogen management in corn and wheat. The attached version of the agenda includes a map and directions to the field site. We have applied for CCA and CDFA INMP continuing education credits. The University is attentive to the ongoing Covid-19 pandemic. Please monitor yourself for Covid-19 symptoms before coming to the event, and do not come if you are experiencing symptoms. While this meeting is outdoors, we will be following University safety precautions for in-person events. Please practice social distancing, or wear a mask if within 6 feet of another person. Thanks for your interest in UC Cooperative Extension programming, and we hope to see you in the field!
10:00am Field corn variety evaluation – preliminary results, Michelle Leinfelder-Miles, UCCE, SJC/Delta
10:15am Variety traits for the Delta, Seed company representatives
10:30am In-season nitrogen management in wheat, Michelle Leinfelder-Miles, UCCE, SJC/Delta
10:45am Development of site-specific nitrogen fertilization recommendations for annual crops, Suzette Turner and Daniel Geisseler, UC Davis
11:00am Viewing of field plots
I am pleased to announce the following meetings and webinars.
1. The Rice Experiment Station (RES) Annual Field Day will takes place next Wednesday, August 25, 2021 from 7:30am to 12:00pm, followed by lunch. The RES is located at 955 Butte City Highway (Hwy. 162), approximately two and one half miles west of Highway 99, north of Biggs, California. The field day is an opportunity to learn about the research being done at the RES, including variety development. It is sponsored by the California Cooperative Rice Research Foundation (CCRRF) and University of California (UC). For more information, please visit the RES website.
2. Farmers' Rice Cooperative and Wetlands Preservation Foundation will host a Delta Rice Field Day next Thursday, August 26, 2021 from 8:30am to 1:45pm. The event will start at Canal Ranch (23011 Blossom Road, Thornton, CA 95686), followed by a bus tour of nearby Delta rice production. I will be present to answer questions about my rice research and extension program, including the Delta variety trial, armyworm monitoring, herbicide trials, and weedy rice outreach. Space is limited, so please see this flyer to reserve space.
3. The UC Dry Bean Field Day will take place on Tuesday, August 31, 2021 from 9:00am to 11:30am. The field day will begin at Honey Bee Haven, Bee Biology Road, on the UC Davis campus. Due to Covid-19 safety precautions, preregistration for this event is required. There is no registration fee. I invite you to view the agenda and register here. CCA continuing education credits (2.0) are available (0.5 of NM; 0.5 of PM; 1.0 of CM).
4. The UC Alfalfa and Forage Field Day will take place on Thursday, September 23, 2021 from 8:00am to 12:15pm, followed by lunch. The field day will take place at the Kearney Research and Extension Center, 9240 S. Riverbend Ave., Parlier, CA 93648. Due to Covid-19 safety precautions, preregistration for this event is required. There is no registration fee. I invite you to view the agenda and register here. We have applied for DPR, CCA, and N management (ILRP program) continuing education credits.
5. The Vertebrate Pest Council is hosting vertebrate pest webinars on September 28 (field rodents), September 29 (use of rodenticides), and September 30 (managing commensal rodents). The webinars run from 8:00am to 10:00am each day, and registration is required. Please see this flyer for more information.
Finally, the Covid-19 pandemic is a fluid situation. At this time, I plan to hold an in-person field meeting at the Delta field corn variety trial, as I have done in the past. The date is TBD but will take place in late-September or early-October. I will send a separate blog announcement when the date has been set.
Thank you for your interest in our programs. Stay healthy, and hope to see you soon at one of these events.
The 2020 UCCE Delta field corn variety trial, located on Tyler Island, was planted on April 21st by air planter and consisted of three replicate blocks of seventeen varieties. The seventeen varieties included fourteen varieties submitted by seed companies and three submitted by the grower. All varieties were glyphosate tolerant. Over the course of the season, we evaluated stand count, bloom, disease incidence (Fusarium ear rot, head smut, common smut; Fig. 1), lodging, and yield. The field was harvested on September 25th.
Table 1 presents mean values for the three replicates. The statistical method used to compare the means is called the Tukey's range test. Varieties were considered statistically different if their P value was less than 0.05, or 5 percent. Twelve varieties have a letter “a” following their mean yield, which means that those twelve varieties all yielded similarly in the trial.
In addition to yield, there were also statistical differences among varieties in Fusarium ear rot, head smut, common smut, ear height, grain moisture, and bushelweight. The CV, or coefficient of variation, is the standard deviation divided by the mean, or a measure of variability in relation to the mean. For the diseases, the variability among the three replicates was very high.
For a printable report with more description of the trial, please visit my website. Special thanks go to the cooperating growers, Gary and Steve Mello, and the participating seed companies.
Figure 1. Diseases monitored in the UCCE Delta field corn variety trial: A) Fusarium ear rot, B) head smut, and C) common smut. These three diseases are generally managed by variety selection.
Table 1. 2020 UCCE Delta field corn variety trial results. Results for each variety are expressed as the average across three replications.
* Data were transformed for analysis. Arithmetic means are presented.
‡ Yield adjusted to 15% moisture.
Stand counts were made approximately two weeks after planting. The stand was assessed in the center two rows of each four-row plot, counting the plants along a 10-foot length. Bloom was assessed over the week of July 15th. We monitored disease incidence and plant lodging in late September. Disease incidence, particularly Fusarium ear rot, was lower in 2019 compared to 2018. A sign of Fusarium ear rot is white fungal mycelium around the kernels. The disease is usually introduced to the ears by corn earworm or by thrips that travel down the corn silks at pollination. Incidence may be reduced in varieties with longer or tighter husks that prevent insect infestations. Planting earlier in the season may also reduce incidence, as the crop may reach pollination before insect pests are prevalent. Head smut, a disease that replaces ears with dark brown spores, had low incidence this year. These two diseases are generally managed by variety selection.
The table presents mean values for the three replicates. The statistical method used to compare the means is called the Tukey's range test. Varieties were considered statistically different if their P value was less than 0.05, or 5 percent. What this means is that when differences between varieties exist, we are 95% certain that the two varieties are actually different; the results are not due to random chance. Differences between varieties are indicated by different letters following the mean. For example, a variety that has only the letter “a” after the mean yield value is different from a variety that is followed by only the letter “b”, but it is not different from a variety whose mean value is followed by both letters (“ab”). Similarly, a variety whose mean yield is followed by the letters “ab” is not different from a variety whose mean yield is followed by the letters “bc”. Eight varieties have a letter “a” following their mean yield, which means that those eight varieties all performed similarly in the trial. In other words, based on this research, we cannot attribute numerical differences to varietal differences.
In addition to yield, there were also statistical differences among varieties in days to bloom, Fusarium ear rot, head smut, ear height, grain moisture, and bushelweight. The CV, or coefficient of variation, is the standard deviation divided by the mean, or a measure of variability in relation to the mean. For the diseases, the variability among the three replicates was very high.
For a printable version of this report, please see: https://ucanr.edu/sites/deltacrops/Corn/. Special thanks go to the cooperating growers, Gary and Steve Mello, and the participating seed companies.