While some golf course managers are opting to cultivate annual bluegrass (AB) on their greens, others continue to treat the grass as a weed and attempt control. Researchers at the University of Illinois at Urbana seek to prevent the invasion of AB at renovation by reducing the population of AB seed. Their study looked at the use of various rates of dazomet, a soil sterilant, prior to seeding creeping bentgrass (CB), along with a variety of soil preparation methods and time of seeding CB. Their studies took place in both fall and spring of 2000 and 2001 at two locations. The amount of dazomet and soil preparation method had very little influence on the success of spring (May) seedings and control. The population of AB seed was so heavy and the weather so unfriendly to the efficacy of dazomet that researchers recommend spring seeding of CB should not be attempted in AB infested soils.

The results from fall treatments were much more favorable. More than 80 percent of AB seed are found within the top 1 centimeter of soil/thatch and these seeds germinate readily all spring and summer, thereby providing an environmental reduction in seed population. In addition, CB seeds are extremely tolerant of dazomet and could be successfully seeded as soon as one day after dazomet soil treatment. Dazomet only worked at the highest applications rates, those greater than 420 kg-ha-1. Soil preparation method did not greatly influence the success of control, whether the soil was aerified and the cores replaced before or after dazomet was applied or if there was no preparation at all. Because the AB seeds are primarily in the top thatch layer, dazomet does not have to travel far to contact them. After reducing the AB seed population, establish CB as quickly as possible using known cultural techniques. For more on control methods, see “Code Blue” on page G1.

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