Turfgrass Scouting Report: July 14, 2019

I hope everyone is doing well out there on your respective courses. I think it is fair to say we’re well and truly in summer mode now. The 14-day forecast is looking good with only a few days of rain on the books. It looks like we’ll be seeing a 13-day stretch of highs in 80’s. This past week Dr. Ed Nangle dropped by the Golf House to say hello, so if you saw him out and about I hope you pointed and shouted things at him!!

The maximum temperatures have been fluctuating between ~80–90°F, while the minimum temperatures have been fluctuating between ~60–75°F over the last 2 weeks. Soil temperatures have remained around ~70°F for the past two weeks. We had a couple of rain days at the start of last week, but nothing to bad. Looking forward to the next two weeks, the weather is steadily getting warmer with only a few rain days forecast.

This past week Ron Townsend and I got to spend the day at the Purdue Turfgrass Research Field Day. There was a number of different research projects being demonstrated, all round a great day of learning.

This past week I got sent a picture of bacterial etiolation on creeping bentgrass. Below I have highlighted a number of research articles from the past few years looking at this disorder. One important factor when dealing with bacterial etiolation on your course is the identification of the species of the bacteria infecting the bentgrass. Based on the research summarized below the species of the bacteria dictates the management strategy you need to impose.

Roberts, J.A., Kerns, J.P. and Ritchie, D.F., 2015. Bacterial etiolation of creeping bentgrass as influenced by biostimulants and trinexapac-ethyl. Crop Protection, 72, pp.119–126.

Abstract: “Bacterial etiolation, caused by Acidovorax avenae and Xanthomonas translucens, has become a widespread problem in turfgrass throughout the U.S. Various management tactics are used in managing this disease and differ among turfgrass managers. The use of biostimulants and trinexapac-ethyl (TE) has become a staple in putting green management and many products have been associated with etiolation outbreaks. Experiments performed in field and controlled environments evaluated the impact of commercial biostimulants and TE on etiolation of creeping bentgrass (Agrostis stolonifera L. c.v. ‘Penn A-1’) caused by both A. avenae and X. translucens. In the field, a factorial study was arranged as a split-plot randomized complete block design with 4 replications. The main plot consisted of biostimulants (Knife Plus, CytoGro, Astron, Nitrozyme, PerkUp, BioMax, and none) applied at label rates while the subplot treatments consisted of TE application frequency (0.049 kg ha−1 applied at 7 d, 14 d, and none). For controlled environment experiments, biostimulant and TE treatments were arranged in a randomized complete block design with 4 replications. Bacterial etiolation was measured regularly when present using a grid count to determine the percent area exhibiting etiolation in the field while etiolated turfgrass plants were counted individually in controlled environments. Turf quality was also rated using a scale of 1–9 with 1 = completely dead, 9 = best, and 5 = minimum acceptable turf quality for all experiments. Biostimulant treatments did not have a significant effect on etiolation caused by either bacterium. Trinexapac-ethyl decreased etiolation caused by X. translucens and increased etiolation caused by A. avenae. These results support the necessity of identifying bacteria associated with etiolation as variable effects were observed with TE treatments. These factors should be considered when developing plant growth regulator programs if etiolation is problematic. Future research to evaluate phytohormone production in these bacteria may improve our understanding of etiolation development while improving methods for control.”

Liu, S., Vargas, J. and Merewitz, E., 2017. Phytohormones associated with bacterial etiolation disease in creeping bentgrass. Environmental and Experimental Botany, 133, pp.35–49.

Abstract: “Acidovorax avenae subsp. avenae (Aaa) is a pathogen that can cause bacterial etiolation of creeping bentgrass (Agrostis stolonifera). In vitro and in vivo studies of this pathosystem for phytohormone analysis were performed. Aaa and a non-pathogenic, negative control Pseudomonas aureofaciens (Pa) were cultured at room temperature (20–22 °C) for 14 days. For in vivo studies, Aaa infected and uninfected creeping bentgrass ‘Tyee’ and ‘Penn-A4’ were grown in hydroponics under optimal 23/20 °C day/night temperatures and heat stress 35/30 °C conditions in growth chambers. Bacterial culture or plant samples were taken for analysis of phytohormones: gibberellic acid isoforms (GA1, GA3, GA4, and GA20), jasmonic acid (JA), salicylic acid (SA), indole-3-acetic acid (IAA), zeatin riboside (ZR), and abscisic acid (ABA). GA1, GA3, GA4 and IAA were detected in some Aaa cultures but not in Pa. ‘Penn-A4’ was more Aaa sensitive under high temperature than ‘Tyee’. ‘Tyee’ infected with Aaa at high temperatures showed higher JA content in all plant tissues, higher SA in stolons and roots, and less GA3 and GA20 in leaf and stolon tissues than ‘Penn-A4’ in the same conditions. Differential GA isoform accumulation produced by Aaa could contribute to disease severity and JA and SA accumulation may contribute to disease tolerance.”

Roberts, J.A., Ma, B., Tredway, L.P., Ritchie, D.F. and Kerns, J.P., 2017. Identification and pathogenicity of bacteria associated with etiolation and decline of creeping bentgrass golf course putting greens. Phytopathology, 108(1), pp.23–30.

Abstract: “Bacterial etiolation and decline has developed into a widespread issue with creeping bentgrass (CBG) (Agrostis stolonifera) putting green turf. The condition is characterized by an abnormal elongation of turfgrass stems and leaves that in rare cases progresses into a rapid and widespread necrosis and decline. Recent reports have cited bacteria, Acidovorax avenae and Xanthomonas translucens, as causal agents; however, few cases exist where either bacterium were isolated in conjunction with turf exhibiting bacterial disease symptoms. From 2010 to 2014, turfgrass from 62 locations submitted to the NC State Turf Diagnostic Clinic exhibiting bacterial etiolation and/or decline symptoms were sampled for the presence of bacterial pathogens. Isolated bacteria were identified using rRNA sequencing of the 16S subunit and internal transcribed spacer region (16S-23S or ITS). Results showed diverse bacteria isolated from symptomatic turf and A. avenae and X. translucens were only isolated in 26% of samples. Frequently isolated bacterial species were examined for pathogenicity to 4-week-old ‘G2’ CBG seedlings and 8-week-old ‘A-1’ CBG turfgrass stands in the greenhouse. While results confirmed pathogenicity of A. avenae and X. translucens, Pantoea ananatis was also shown to infect CBG turf; although pathogenicity varied among isolated strains. These results illustrate that multiple bacteria are associated with bacterial disease and shed new light on culturable bacteria living in CBG turfgrass putting greens. Future research to evaluate additional microorganisms (i.e., bacteria and fungi) could provide new information on host-microbe interactions and possibly develop ideas for management tactics to reduce turfgrass pests.”

I visited a course last week that was experiencing area in the rough that were thinning out and dying. So I collected some samples and brought them back to the lab. We found dollar spot, summer patch and “leaf spot” (we narrowed it down to either bipolaris or Drechslera).

There is some silvery thread moss activity right now, carfentrazone-ethyl is the best chemical control option. In the past I’ve carried out spot treatments with baking soda, which essentially desiccates the moss.

The first sighting of Japanese beetles in the area has also occurred this week. If your looking for information regarding the life cycle and control options please follow the link to the University of Minnesota extension website. https://extension.umn.edu/yard-and-garden-insects/japanese-beetles#life-cycle-1057360

For anyone interested Dr. Lee Miller’s most recent disease report can be found at https://turfpath.missouri.edu/reports/2019/07_11_19/.

Well, we’ve came to another abrupt end to the scouting report!!!!

Please don’t hesitate to call or email and I will ensure you get a rapid response.

Thanks,

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Bobby Kerr, Ph.D. Director of Turfgrass Programs. Chicago District Golf Association, 11855 Archer Ave, Lemont, IL 60439. C: (312)-519–7940. W: (630)-685–2307.

Dedicated researchers and turf pathologists working for golf course superintendents in the Chicago area.