- Author: Michelle Leinfelder-Miles
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 16th. While planting occurred on the same day as in 2017, the days to bloom was 68 in 2018, averaged across varieties, compared to 65 in 2017. This amounts to an approximate accumulation of 1230 growing degree days (GDD) in both years. In general, the temperatures were lower in 2018 compared to 2017. Over the course of the season, there were four days above 100⁰F, compared to a total of 14 days over 100⁰F during the 2017 season. (Temperature data is from the neighboring Staten Island CIMIS station.)
We monitored disease incidence and plant lodging in late September. Disease incidence, particularly Fusarium ear rot, was higher in 2018 compared to the two previous years. 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 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. Seed company representatives have indicated that Fusarium ear rot incidence was high in other parts of the state as well.
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”. Eleven varieties have a letter “a” following their mean yield, which means that those eleven varieties all performed similarly in the trial. In other words, based on this research, we cannot attribute numerical differences to varietal differences. The variety that had the lowest yield in the trial also had the lowest stand count. This may have been the result of the planter settings. Seed inventory records indicate that a standard bag of this variety weighed 54 pounds for 80,000 seeds; whereas, bags of other varieties weighed 39 to 44 pounds for 80,000 seeds. This larger-sized seed may not have dropped consistently from the planter in order to achieve the desired plant stand. Growers should contact the seed company with further questions.
Across varieties, there were also statistical differences in stand count, days to bloom, Fusarium ear rot, head smut, ear height, grain moisture, and bushel weight. 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.
Special thanks go to the cooperating growers, Steve and Gary Mello, and the participating seed companies. A printable version of these results is available from my website.
Table 1. 2018 UCCE 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.
† Larger seed size and planter settings may have caused lower stand and yield. Contact company representative for more information.
I have received a couple inquiries from Pest Control Advisors about wheat that is showing leaf tip yellowing and burning (Fig. 1). Their suspicion is frost injury, and with the weather we have experienced over the last several weeks, their suspicion is likely true.
There isn't a hard-fast rule of when frost injury will occur because several factors influence its occurrence and severity. The factors include the temperature but also the duration of cold exposure, the plant growth stage, and the growing conditions. The UC Small Grains Production Manual (see page 101) states that injury may occur with temperatures at or below 35⁰F and that even just a couple hours of exposure is enough to cause injury.
Below (Fig. 2), I present temperature data from the last month from a few local CIMIS stations. Remember that in early-February, daytime highs were getting above 70⁰F. By mid-February, however, minimum temperatures were low enough to cause frost injury, and hourly data (which I am not showing but is available from the CIMIS website) shows that temperatures below 30⁰F often spanned several hours over many nights in late-February.
The plant stage of development is critically important to how a crop may be injured from frost and how it may overcome injury. At tillering, leaf yellowing and tip burning will be the obvious symptoms. At this stage, however, yield impact will likely be slight, if any. That is because the growing point of the tillers is close to the soil and protected from the cold. When warmer weather resumes, the plants may be able to continue tillering, particularly in thin stands where there is space to fill, and overcome the injury. In the jointing stages, in addition to the leaf yellowing and tip burning, some leaf or stem lesions may be apparent. There could be moderate impacts on yield if the growing points of the tillers have been injured. Look for a chlorotic or dead leaf in the whorl. Also, try splitting the stem with a razor blade at the growing point. This picture from Texas A&M University shows how to do this. If the growing point (at the arrow) appears white, brown, or water-soaked, then there has been frost injury. Once the crop gets into the reproductive stages of growth, it becomes more sensitive to injury with bigger repercussions for yield, but luckily, I think most of the fields in our region aren't yet to these later stages of development.
Keep in mind that there are field and other growth conditions that may lessen or worsen the severity of frost. Low parts of the field where cold air settles will likely show more injury. Fields that were planted earlier in the fall, or earlier-maturing varieties, that are in a later stage of growth will likely show more injury. Crops that have had good moisture and nutrient conditions may also show more injury. With one of the inquiries I received, the field had been fertilized about a month ago, and given the warm daytime temperatures we had at that time, those plants were likely resuming growth and probably got hit by the frost all-the-more. Crops that have been moisture stressed, however, may have been hardened and not show as much injury.
So, what now? Again, growers and consultants with crops in the jointing stages who are seeing leaf tip yellowing may wish to split some stems to observe whether there has been injury to the growing points. If this has occurred, there is nothing that can be done to “save” those tillers, but it might provide some insight into potential yield impact. If stem lesions appear, be on the look-out for disease infections but also lodging later in the season. Unfortunately, the most telling symptom will appear after heading when grain doesn't fill. Don't hesitate to reach out to me or your local farm advisor if you have questions about frost injury.
- Author: Michelle Leinfelder-Miles
The results of the 2017 UCCE Delta field corn variety trial, located on Tyler Island, are shown in Table 1 (below). Three replicate blocks of fifteen varieties were planted on May 9th by air planter. The trial was planted almost two weeks later than the 2016 trial, due to the wet winter and spring. The fifteen varieties included 14 varieties submitted by seed companies and one submitted by the grower. Glyphosate-tolerant and conventional varieties were tested; conventional varieties are indicated in Table 1 as (Conv.). Each plot consisted of four 30-inch beds on an average row length of 1218 feet. Seed was planted approximately two inches deep and six inches apart down the row. The soil is a Rindge mucky silt loam with approximately 20 percent organic matter in the top 15 inches of soil. The Rindge series is a mucky peat soil down to about 60 inches, and approximately 55,600 acres in the Delta are described by the Rindge classification. The previous crop in the field was corn. Subsurface irrigation by “spud ditch” was employed three times. Nitrogen was applied pre-plant (125 units/acre as NH3), and 34 gallons/acre of 8-24-6 with ½% of zinc (additional 31 units/acre of N) was knifed in at planting. Weed control was by cultivation and herbicide program (Laudis, Crosshair, Super Spread MSO, UAN 32%). Onager miticide was applied. The field was harvested on October 18th.
Stand counts were made approximately two weeks after planting, and bloom was assessed over the week of July 10th. While bloom occurred later this year due to the later planting, the number of days to bloom was less than in 2016. Across all varieties, the average number of days to bloom was 65, compared to 70 in 2016. This is likely due to warmer temperatures in 2017 compared to 2016. The average high temperature between planting and bloom was 86⁰F, and the average low temperature was 52⁰F. There were three days above 100⁰F during the time from planting to bloom, and a total of 11 days over 100⁰F for the season. Whereas, between planting and bloom in 2016, the average high temperature was 84⁰F, the average low temperature was 50⁰F, and there was one day above 100⁰F, (six total for the season). (Temperature data is from the neighboring Staten Island CIMIS station.)
We monitored disease incidence and plant lodging in late September. At that time, very little lodging was observed, as indicated by the data. Heavy winds occurred in early October, however, between rating lodging and harvesting the crop. At harvest, we observed more lodging but did not collect additional data. Based on observations, varieties MY 2D848, ES 7622VT3P, and DKC 63-07RIB experienced more lodging than other varieties from the early-October winds.
The table presents mean values for the three replicates. The statistical method used to compare the means is called 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”. Twelve varieties have a letter “a” following their mean yield, which means that those twelve varieties all performed similarly in the trial. In other words, based on this research, we cannot attribute numerical differences to variety differences. Among varieties, there were also statistical differences in bloom date, 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.
Special thanks go to the cooperating growers and seed companies. This report is available from my website.