June? Cool/Wet Returns, Pythium Root Dysfunction, Bipolaris Leaf Spot, Cyst Nematode and KBG Divot Research

Image 1. A Pure Distinction creeping bentgrass green isn’t covered with disease (dollar spot). No, its just the day that a lot of tree seed was released and landed everywhere — cottonwood trees (Populus deltoides) grow along the edge of the Bob Berry Sunshine Course in Lemont, IL. Settle, Jun 7, 2022

Weather Recap (June’s first 10 days) by Shehbaz Singh, MS

Air Temperature. The weather for first 10-days of June in Chicago was pretty mild. The air temperature ranged mostly from 58 to 78°F. The highest temperature of 81°F was recorded on June 3rd. This is actually in the normal range at this point of the month for Chicago. Last year in 2021, the air temperature at this time was on the higher-end and ranged from 70 to 89°F.

Figure 1. Current Chicago air temperatures (blue bars) versus normal range (brown band) in June, 2022.
Figure 2. Accumulated rainfall in Chicago (green line) versus normal (brown line) in June, 2022.

Pythium Root Dysfunction Arrives

One of the chronic issues that creeping bentgrass greens can suffer from is a disease called Pythium root dysfunction. More than one Pythium species can be the causal agent. The problem occurs when conditions are wet (Chicago’s spring in 2022) and then when conditions become hot which drives up plant water use via evapotranspiration rates or ET (Memorial Day weekend in 2022). It is most associated with golf greens. They are necessarily maintained at low mowing heights. That is enough additional stress to make this a problematic disease of golf greens that is becoming more and more common.

Image 1. In creeping bentgrass, Pythium root dysfunction is associated with darkened roots that appear damaged (layers of root cells slough off). Root hairs either disappear entirely or are reduced. Roots are short. Settle, Jun 8, 2022
Image 2. Presence of oospores (Pythium resting spores) are used to help confirm Pythium root dysfunction. Settle, Jun 8, 2022

Bipolaris Leaf Spot of Creeping Bentgrass

Bipolaris leaf spot (B. sorokiniana) on creeping bentgrass greens at two locations in the Chicago District was another early arrival. Again due, in part, to the HOT Memorial Day weekend. This is an interesting foliar fungal disease because it is closely associated with certain creeping bentgrass varieties. For example, Penncross is highly susceptible as are probably some others. We just don’t know which varieties are more prone to it until we run into it. This isn’t a common disease of creeping bentgrass, but when it does occur it is problematic.

Image 1. Bipolaris leaf spot of creeping bentgrass. The infection appears to be localized on a clone (dark green patch) of what is likely Penncross. Note: It was raining = ideal conditions for this disease! Settle, Jun 8, 2022
Image 2. Presence of multi-celled conidia/spores is used for positive diagnosis of Bipolaris leaf spot. To see this you must incubate a sample for 24–48 hours. Settle, Jun 8, 2022

Turfgrass Cyst Nematode (Heterodera iri)

Occasionally we find something out of the ordinary. Recently, we identifed the presence of cyst nematodes (likely Heterodera iri) from a root zone sample that represented an unhealthy area of a creeping bentgrass/Poa annua green. A healthy root zone sample (a check) from the same green did not contain cyst nematodes. It suggests that this endoparastic nematode may be part the story. For example, a different Heterodera species is a major nematode problem in soybeans. It’s part of an ongoing survey of golf course nematodes in the Chicago District area that uses a sucrose floatation with centrifugation to extract nematodes from soil samples. Historically (c. 2005), Dr. Randy Kane found cyst nematodes were associated with patches of wilt in sand-based greens during midsummer in Chicago. The occurrence of cyst nematodes in golf green is thought to be relatively rare. More to come.

Image 1. A juvenile (J2) cyst nematode from the root zone of a creeping bentgrass/Poa annua sand-based green. Settle Jun 1, 2022
Image 2. An enlarged female cyst nematode containing eggs from the root zone of a creeping bentgrass/Poa annua sand-based green. Settle Jun 1, 2022

Divot Research on a Kentucky Bluegrass Tee by Shehbaz Singh

A second divot study in collaboration with Zach Nicoludis, USGA, is yielding similar results as we are finding in the creeping bentgrass tee. This study is on an HGT Kentucky bluegrass tee at the Bob Berry Sunshine Course in Lemont, IL. The divot mix treatments have now seen seven weeks of turfgrass recovery.

  1. If a golfer is able to use an intact sod piece they should. But the success of this divot repair method may be influenced by time-of-year.
  2. Adding Leeward chewings fescue seed as a ‘nurse grass’ is improving divot recovery versus a divot mix alone.
  3. The two best treatments so far are: Compost + chewings fescue seed & 8:1:1 mix + chewings fescue seed.
Fig 1. Visual recovery (%) of HGT Kentucky bluegrass given 8 different divot treatments in 2022, Bob Berry Sunshine Course, Lemont, IL. Fig 2. Visual quality (1–9, with 6 acceptable and 9 best) of HGT Kentucky bluegrass given 8 different divot treatments in 2022, Bob Berry Sunshine Course, Lemont, IL.
Fig 3. Normalize Difference Vegetation Index (NDVI) of HGT Kentucky bluegrass divot treatments in 2022, Bob Berry Sunshine Course, Lemont, IL. Fig 4. Images taken 7 weeks after initial divots were made to a HGT Kentucky bluegrass tee at the Bob Berry Sunshine Course, Lemont, IL. Singh, Jun 9, 2022

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CDGATurfgrassProgram

CDGATurfgrassProgram

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