Researchers test the limits of biological Pythium control

A research trial established in the summer of 2022 aimed to evaluate the impact of biological product applications on Pythium root rot development in Penn A1 creeping bentgrass maintained on a sand-based root zone as a golf course putting green.

Researchers mowed the experimental site five times a week at a cutting height of 0.125 inches, and reduced frequency to three times a week in July and August during excessive heat. Fertilizer applications totaled 1 lb. Nitrogen (N) (46-0-0) through foliar applications (0.25 lbs. N/1000 sq. ft.) every 14 days. Researchers applied Harrell’s Fleet (polyoxyalkylene polymers) at 4 fl. oz./1000 sq. ft. every 28 days to maintain water infiltration and uniformity in the root zone.

The research team applied Syngenta’s Primo Maxx (trinexapac-ethyl) every two weeks at 0.138 fl. oz./1000 sq. ft. to limit vertical growth following standard management practices in the region. Researchers applied Prostar WG (i.e., flutolanil) at 3 oz./1000 sq. ft. on June 7 and Daconil Weatherstik (chlorothalonil) at 3.5 fl. oz./1000 sq. ft. on July 26 as curative applications for brown patch and algae.

Treatment plots measured 3-by-10 feet and were arranged in a randomized complete block design with four replications. The team applied treatments as a foliar spray in water equivalent to 2.1 gal/1000 sq. ft. using a CO2-powered walk-behind sprayer equipped with dual TeeJet 8002 nozzles.

Pythium root rot developed naturally across the experimental site in early July. Researchers observed some variation initially, but continued disease progression resulted in more uniform symptom development. Across all rating dates, Zelto + Select Phite 3 fl. oz. did not significantly impact Pythium root rot when compared to the non-treated control. Except for Zelto + Select Phite 3 fl. oz., all remaining treatments significantly reduced Pythium root rot compared to the non-treated control on July 7 when disease pressure was low.

Continued disease progression in mid-July showed Azoxy Bio 0.9 fl. oz., Zelto + Select Phite 6 fl. oz., and Segway 0.45 fl. oz. treated plots had significantly less Pythium root rot than the non-treated control on July 19, and only Zelto + Select Phite 6 fl. oz. and Segway 0.45 fl. oz. were able to significantly reduce disease compared to the non-treated control on July 29. On the final date, Segway 0.45 fl. oz. was the only treatment able to significantly reduce Pythium root rot compared to the nontreated control.

These results show that biological products tested offer some benefit to reducing Pythium root rot under low disease pressure, but may break down under severe pressure experienced on creeping bentgrass.



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