Sunflower Chronicles: Part 2 – "Progress and Problems"

Welcome back! Previously we looked at the preparation and planting stages of Penn State Extension's Western Pennsylvania Sunflower Trial. This week, we will be looking into current progress and problems encountered within the trial. There are several factors that are currently most prominent in observation and impact on the trial including: Plant Growth, Herbicide Program, and Weather.

Plant growth is currently proceeding as projected with the plants having reached the R-2 stage of growth, which is, flower buds have appeared and are prominent. Plants are healthy with little disease showing and with only minor insect and vertebrate damage. There are some leaves with burned areas from an unknown source, but it does not appear to be impacting plant growth. However, variability in height is very widespread across the field. Some plants stand at around 18 inches while others have passed 4 feet. Buds are still appearing on shorter plants and there is little variability in growth stage. This will impact yield as the smaller plants will have smaller flowers. Finally, the population is far below expected levels. While the initial planting targeted a final population of 18,000 plants per acre the loss percentage across the entire field puts the actual living population within the range of 12,000-15,000 plants per acre. Overall, the field is light on population but the plants that are standing appear to be of decent quality.

The herbicide program is currently presenting the most issues for the trial. While the application of Beyond (Imazamox) in early July caught most of the existing weed populations including both grasses and broadleaves, it either allowed for Smooth Pigweed to drastically expand in population due to lack of competition or it failed to control it at all. Redroot Pigweed, a similar plant, is listed as a weed that Beyond has Excellent control over. As such, there is the possibility that weather had an impact on the effects of the herbicide and may be responsible for this escape. Outside of an extremely large Smooth Pigweed population there are very few weeds presenting themselves and none in large enough populations to be considered an issue.

Weather-wise, the Sunflowers have had stable growing conditions. They have received approximately six inches of rain during the month of July, stable heat for growing degree days, and relatively consistent sunshine. However, while heat and sunshine were relatively consistent, they were not ideal. This may have put the growing stages behind schedule which may impact yield, but other stressors will still have more impact this year.

Closing notes from this observation period:

• Population is currently the biggest issue facing the trial. Due to an unexpected loss percentage, the canopy did not develop to shade out weeds. For future trials, populations will be adjusted to better manage this issue.
• Variability in size and population may have a variety of factors feeding into them. This ranges from soil type to weather conditions, to herbicide program, and more. Without further evaluation, it will be difficult to determine which one may have had the biggest impact at this location.

This article series will continue with progress throughout the growing and harvest season. In the next article we will review Harvest Practices, Trial Evaluation, Budgeting and more!