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Primo Maxx Technical Update

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Primo Maxx has been in use in the Canadian turf market for 15 seasons as a unique chemistry
that provides turf managers with a way to limit vertical growth, improve the overall health of the
turf, and pre-condition the turf to withstand abiotic stresses while conserving valuable resources.

The Product

Primo Maxx is a Class A plant growth regulator that works by inhibiting the synthesis of
Gibberellic Acid 1(GA1), which is responsible for cell elongation in turf. By inhibiting GA1 vertical
shoot growth slows and the energy is redirected into the production of lateral growth- rhizomes,
stolons, tillers and roots.

The Benefits

1. Plant Health and Playability
Increased Density
When vertical growth is inhibited the density and the tensile strength of the turf stand is
enhanced by the increased lateral growth while clipping yield is reduced. The result is a stronger
surface, less prone to ball marks, spike marks or scalping.

Improved Shade Tolerance
The natural response of turf that is growing in the shade is to increase the GA production in
order to become taller in an effort to find sunlight. This creates a thin, spindly weak stand. Primo
Maxx will inhibit GA production helping to increase the density of turf grown in the shade.

Increased Fertilizer Efficiency
Increasing the nitrogen rate increases the growth rate and health of turf. Unfortunately, a high
nitrogen rate can also have detrimental effects on playability through decreased density and
turgidity and a detrimental effect on plant health through increased succulence of the plant. By
inhibiting the vertical growth of the plant a higher nitrogen rate can be realized without the
detrimental effects, increasing both plant health and playability (Kussow, et al., 2012).

2. Conserve Valuable Resources
Enhanced Fungicide Performance

Reduced vertical growth means less of the plant is removed with each mowing. Therefore,
contact and systemic fungicide can potentially remain active longer by being present in or on the
plant longer without being removed through mowing.

More Efficient Use of Water
Turf that has been treated with Primo Maxx is able to retain water longer through reduced transpiration rates (Huang 2014). Under consistent Primo Maxx growth regulation the water utilization of a plant can be increased by up to 20%. This is accomplished by:

  • Smaller leaves with less surface area for transpiration
  • Improved rooting creating a larger reservoir to draw from
  • Increased turf density, reducing the water loss directly from the soil
  • Reduced GA production, which aides in stomatal regulation

Reduced Mowing
Inhibiting vertical growth can reduce the growth by up to 50%. This reduces the time required for mowing, clipping cleanup and disposal with reduced consumption of fuel required for mowing while preserving a very valuable resource in mowing equipment and labour.

Optimal Application Strategies
Excellent work has been done to show that growth regulation effect of Primo Maxx is directly influenced by the growth rate of the turf as the product is depleted through metabolic processes of the individual plants (Kreuser, Soldat 2011). The rate of the metabolic process can be determined by tracking the Growing Degree Days (GDD) using the average daily temperatures with a base temperature of 0 Celsius for each day. Research has shown that as the GDD model nears 200 then the effect of Primo Maxx is depleted and the turf enters a ‘rebound effect’ where vertical growth is actually increased for a period of time. To avoid this rebound effect and realize consistent growth regulation re-applications of Primo Maxx should be made at 200 GDD.

Bacterial Etiolation
Primo Maxx has been used safely and effectively for 15 years and for much longer around the world. In 2012 a Michigan State study identified bacterial etiolation, Acidovorax aenae subsp.avenae as a disease of turf (Giordano et al., 2012). Further research has shown that turf infected with Acidovorax aenae subsp.avenae experienced increased etiolation when treated with Primo Maxx (Roberts et al., 2013, 2014). However, there was no loss of turf reported and the turf treated with Primo Maxx had the highest visual turf quality in the study.


A consistent program of growth regulation produces significant return for the turfgrass manager. The individual turf plants benefit from an improvement in their overall health and performance while the turf manger is able to deploy the resources available with an increased efficiency.


Giordano, P. R., G. Sundin, M., Chilvers, B. Day, K. Frank, N. Mitkowski, et al. 2012. Acidovorax
subsp. avenae: An emerging bacterial pathogen on creeping bentgrass. Phytopathology. 102

Huang, B 2014. Improving drought performance of creeping bentgrass. Golf Course Management 2014.

Roberts, J. A., J. P. Kerns, and D.Ritchie. 2014a. Plant growth regulator effects on etiolation development in creeping bentgrass putting green turf caused by Acidovorax avenae. Agron.Abr. p. 88373.

Kreuser, W. C., and D. J. Soldat. 2011. A growing degree-day model to schedule trinexapac-ethyl applications on Agrostis stolonifera golf putting greens. Crop Sci. 51:2228-2236.

Kussow W., Soldat, D., Kreauser W., Houlihan, S. Evidence, regulation and consequences of nitrogen-driven demand by turfgrass. ISRN Agronomy 2012.

Roberts, J. A., J. P. Kerns, and D.Ritchie. 2014a. Plant growth regulator effects on etiolation development in creeping bentgrass putting green turf caused by Acidovorax avenae. Agron.Abr. p. 88373.