Friday, April 18, 2008

Seedhead Suppression

One of the biggest challenges in maintaining high quality Bentgrass/ Poa Putting greens is having the two different grass type’s acting as one. Each grass type has its own growth habit and growth rate, and to top it off the Poa Annua is a prolific seedhead producer.

Here at CCCP we have relatively low populations (10%-20%) of Poa Annua on our greens which says a lot for greens that are 23 years old. We have been extremely committed over the years in trying to manage the Poa infestation and have actually reduced the total populations over time.

One of the methods of managing the Poa populations comes through applications of PGR’s (plant growth regulators) for seedhead suppression. These applications are made just before the actual seedheads are visible and if timed right the production of seedheads will not occur. There are several methods for determining the timing such as Degree days and phenological indicators.

Degree -Days
The weather plays a major role in determining the rate of plant growth and development and influences development of insect life cycles and plant disease cycles, which is why trying to make pesticide applications by calendar dates, is not very effective. Degree-day accumulations are a measurement of air temperatures above a predetermined base temperature. Insect development is often tracked according to the accumulation of a specific number of temperature units called growing degree days (GDD), a simple, temperature-derived index. Growth and development of many insects and plants depend upon the amount of heat present in or around the organism. Most plants and animals develop when temperatures fall within a specific range.

Phenological Indicators

While degree days are dependent solely on air temperature, the use of plant phenological indicators takes into account the influence of other climatic factors. They provide an accurate, low-cost predictive tool where weather data is not available or practical to track. Soil and air temperatures, rainfall, humidity and exposure are all contributing factors. Plant phenological indicators reflect the development of insects and plants within the many microclimates in a landscape.
I have found tracking Forsythia bloom to be the most effective tool for timing the applications of PGR’s to our location.