Eagle Ops Scheduler

What it is

Anthracnose is a debilitating disease of putting-green turf caused by Colletotrichum graminicola (also referenced in modern taxonomy as C. cereale). On UK / IE cool-season greens it is almost exclusively a disease of annual meadow-grass (Poa annua): per STRI, "it would be quite rare to find activity on grasses other than annual meadow-grass" [stri:diseases-itm-2022]. Greens can be "destroyed in a short period of time if disease pressure is high" [stri:diseases-itm-2022].

The operational distinction worth knowing is that anthracnose expresses in two forms — foliar blight and basal rot — with different environmental triggers, and these can co-occur on the same green.

Two forms — foliar blight vs basal rot

Per STRI's common-diseases reference, the two forms differ on temperature/moisture trigger profile [stri:diseases-itm-2022]:

Foliar blight — "generally favoured by hot, dry conditions. Symptoms include a yellowing to reddish brown discoloration of leaves and a general thinning of the turf."
Basal rot — "On annual meadow-grass basal rot is most severe in cool, cloudy weather. Basal rot occurs when the crown tissues become infected and scattered plants or small patches of plants turn" [yellow]. Basal rot symptoms "can be observed year-round, often alongside foliar blight symptoms."

Combined symptom note from STRI: "Symptoms of both forms are highly variable, appearing yellow to orange in colour and in an irregular pattern" [stri:diseases-itm-2022]. Diagnostic confirmation typically requires a lab — the field signatures alone are not reliably distinguishable from other yellowing / thinning patterns on poa.

Predisposing stress factors

STRI is explicit that anthracnose is a stress disease [stri:diseases-itm-2022]:

"As it is a stress disease, extremes of moisture favour activity, as do shade, profile compaction, low heights of cut and low nitrogen. Certain ecotypes together with shallow rooted annual meadow-grass can be particularly prone to this disease."

The five operational triggers a supe can read from this list:

Moisture extremes (either over-irrigation or drought stress)
Shade (carbohydrate-starved canopies)
Profile compaction (root volume reduction)
Low HOC (mowing-disturbance pressure)
Low nitrogen (sward weakness)

The last factor matters because it conflicts with the fungicide-loss / cultural-first doctrine on Microdochium (see microdochium-snow-mould): raising N to reduce anthracnose risk is bent-promotion-counterproductive — see §"Nutritional management" below.

Cultural management — STRI ITM doctrine

The STRI ITM reference card on Anthracnose [stri:itm-anthracnose-4b] groups cultural levers as:

Environmental conditions and sward:

"Avoid drought stress"
"Correct poor drainage where there is disease activity during the damper months"
"Avoid surface compaction and undertake compaction management"
"Alleviate disturbance pressures such as a low mowing height and excessive mowing frequency if symptoms appear, or if there is a history of activity during the vulnerable period. Avoid verticutting into the crown of the plant"
"Enhance rooting through a good sand topdressing programme, some aeration and by avoiding drought"
"Improve the micro-climate by enhancing sunshine levels of carbohydrate starved shaded environments and by promoting better air movement"
"Apply suitably proven pigments to help plants survive during periods of stress"

Nutritional management [stri:itm-anthracnose-4b] — note the intentional poa-vs-bent trade-off:

"Excessively low nitrogen levels should be avoided. Higher nitrogen levels to reduce risk of anthracnose will offer short term gain but likely to stifle bentgrass promotion by favouring annual meadow-grass."
"Equal levels of potassium applied during the main season as potassium chloride to nitrogen appear to reduce risk of activity"
"Apply potassium phosphite to strengthen plant defences during and leading up to periods of historical activity"
"Prolonged use of acidifying sources of fertiliser may increase vulnerability to the disease"

Long-term species shift [stri:itm-anthracnose-4b]: "Promotion of more genetically disease tolerant turfgrass. The main medium to longer term solution is to replace annual meadow-grass with bentgrasses. Take advantage of sward thinning by overseeding once conditions are satisfied for their growth."

The bent-overseed-into-thinned-poa lever is the doctrine's strategic capstone — anthracnose damage creates the species-shift opportunity rather than just a remediation problem.

Chemical management

STRI is direct that fungicides have limits in severe outbreaks [stri:itm-anthracnose-4b]:

"Epidemics can be so severe and conditions so stressful that fungicides may only have limited benefit. Practicing integrated management by following good cultural controls and environmental conditions should reduce fungicide dependency and enhance effectiveness. Resistance management should be practiced and include the rotation of fungicide chemistry."

Specific fungicide actives are not named in the STRI reference card — STRI's framing is doctrinal (cultural-first, rotate chemistry, accept limits). Cross-cite fungicide-resistance-management-uk for the FRAC-group rotation discipline that applies to whatever actives are available, and withdrawn-actives-uk-reference for the chemistry-loss baseline.

Quantitative indices — BRI and FLI (model reference)

Eagle's disease model distinguishes two sub-components matching the two field forms. The distinction matters because they have different environmental drivers and different intervention triggers.

Basal Rot Index (BRI) — percentage of individual plants in a sampled area showing crown/basal infection. Rutgers anthracnose research (Crouch et al., operating from Colletotrichum cereale taxonomy) established that basal rot predominates under cool, cloudy, low-light conditions in spring and autumn on poa-dominant greens [rutgers-turf:anthracnose-note]. BRI climbs when:

Soil temperatures are suboptimal (below ~20°C) but canopy is wet
Mowing stress is high (low HOC, frequent cuts) weakening crown
N is deficient, leaving the plant unable to outgrow infection

Foliar Lesion Index (FLI) — percentage of leaves expressing necrotic lesions. FLI is the hot-dry-stress form; it is driven by summer heat accumulation. Using the CDD base 18°C index from degree-day-definitions-uk, FLI pressure rises as CDD accumulates above the dormancy guard [usga:anthracnose-settle-2009].

Operational implication for Eagle model:

| Sub-model | Dominant driver | Primary season | Intervention trigger | |---|---|---|---| | BRI | Cool-cloudy + plant stress | Spring / Autumn | Cultural (HOC lift, K programme, reduce traffic) | | FLI | Hot-dry heat stress | Summer | Irrigation discipline, pigments, fungicide if threshold met |

Both forms can co-occur. STRI notes: "Symptoms of both forms are highly variable…and can be observed year-round, often alongside each other" [stri:diseases-itm-2022]. When Eagle shows both BRI and FLI elevated, the management response combines levers from both columns above.

Source confidence: the BRI/FLI split is US-research-derived (Rutgers, annual bluegrass trials); UK/IE validation against Poa annua parkland greens is limited. Eagle model grades this sub-model LOW (research-grade) until club-level validation data is collected. The qualitative ITM doctrine in §§ above is the actionable UK baseline; BRI/FLI indices are supplementary model inputs.

When to deviate

Supe's own anthracnose action threshold always overrides this entry. Triggers for escalating beyond the cultural-first baseline:

Visible foliar yellowing during hot-dry stretch → tighten irrigation discipline (avoid drought without over-watering), consider pigment application, defer aggressive grooming
Cool/cloudy stretch with poa-dominant sward + history of basal rot → potassium phosphite preventive, escalate fungicide rotation per agronomist advice
Member-event window → known anthracnose-pressure greens go under tighter monitoring; pre-event fungicide may be warranted even if cultural triggers haven't fired
Aggressive verticutting required (e.g. thatch programme) → STRI's specific warning "avoid verticutting into the crown" — if work must proceed, schedule during low-pressure windows and raise N + K leading up to it

microdochium-snow-mould — companion cool-season UK greens disease where the same poa-annua-susceptible doctrine applies; both diseases push toward the bent-overseed species-shift long-term strategy
dollar-spot-management — climate- shifted summer-pressure disease that the foliar-blight form of anthracnose overlaps in operational window (hot-dry conditions); cultural-first IPM doctrine parallel
fungicide-resistance-management-uk — the rotation-discipline framework that STRI's "include the rotation of fungicide chemistry" prescription is one application of
withdrawn-actives-uk-reference — chemistry-loss baseline that makes STRI's "fungicides may only have limited benefit" framing operationally consequential
mowing-heights-cool-season — the HOC-floor discipline; STRI's "low heights of cut" trigger factor is the disease-specific expression of the broader cultural-first HOC-lift doctrine
topdressing-rates-uk-greens — the sand-topdressing programme STRI names under "enhance rooting"
itm-parkland-greens-rA — the R&A GC2030 ITM parkland doctrine; STRI's per-disease ITM cards (this one being 4b Anthracnose) are the disease-specific operationalisation of that broader framework

Anthracnose — Foliar Blight and Basal Rot (STRI ITM)