--- title: Leaf Spot and Leaf Blotch canonical: https://fernland.com.au/problem-solver/leaf-spot-and-leaf-blotch/ dateModified: 2026-08-07 09:38:51 summary: "Leaf spot and leaf blotch cover a wide range of fungal and bacterial pathogens that cause spots, blotches or lesions on foliage across turf, ornamentals and crops." type: article keywords: [Leaf Spot and Leaf Blotch] --- # Leaf Spot and Leaf Blotch > Leaf spot and leaf blotch cover a wide range of fungal and bacterial pathogens that cause spots, blotches or lesions on foliage across turf, ornamentals and crops. Leaf spot and leaf blotch is a broad term covering many different pathogens, including fungal genera such as Alternaria, Cercospora, Septoria, Ascochyta, Curvularia, Cordana, Stemphylium and Helminthosporium, as well as some bacterial pathogens such as Pseudomonas and Xanthomonas species. Rather than one disease, it is a group of look-alike symptoms produced by different organisms on different hosts, ranging from turf grasses and lawns to ornamentals, vegetables and fruit crops. On the plant, most leaf spot pathogens appear as discrete circular, oval or angular lesions on leaf blades, often with a distinct margin and sometimes a yellow (chlorotic) halo. Colour varies by pathogen and host: lesions may be brown, tan, grey, black or reddish, and centres often become papery, straw-coloured or bleached as the tissue dies. Under humid or wet conditions, fine fungal growth (mycelium) or small dark fruiting bodies (pycnidia or sclerotia) can sometimes be seen within older lesions with a hand lens. Bacterial leaf spots tend to look more water-soaked, angular and greasy, often with a yellow halo, and lesions may ooze in wet weather. These diseases occur throughout Australia wherever host plants are grown, and are most active during periods of prolonged leaf wetness, high humidity, warm to mild temperatures and dense canopy or turf cover that restricts airflow and slows drying. Spores or bacterial cells spread by wind, rain splash, irrigation, contaminated tools and equipment, and sometimes insects. Overhead irrigation and extended dew periods are major drivers of outbreaks in both turf and nursery/ornamental production. Management is based on cultural controls: improving airflow and light penetration through pruning or reduced density, avoiding overhead watering late in the day, watering early so foliage dries quickly, removing and disposing of infected leaf material and fallen debris, avoiding excess nitrogen which promotes soft susceptible growth, and rotating or spacing susceptible species to reduce pathogen build-up. Sanitation of tools and mowing equipment between beds or blocks also helps limit spread. Where fungicide or bactericide use is warranted, correct identification of the causal organism and host is important, as products and timing differ between fungal and bacterial leaf spots and between crop groups. ## How to identify - **Leaf lesions:** discrete spots, blotches or streaks on leaves, varying in colour (brown, tan, grey, black, reddish) and shape (round, oval, angular) depending on the causal organism. - **Halos and margins:** many spots show a yellow (chlorotic) halo around a darker or drier centre; bacterial spots often look water-soaked or greasy rather than dry. - **Coalescing damage:** in severe cases spots merge into larger blotches, leaves yellow prematurely, and heavy defoliation or thinning of turf/canopy can occur. - **Fruiting structures:** older lesions may show tiny black dots (pycnidia) or fine fungal growth visible with a hand lens in humid conditions — a useful sign the cause is fungal rather than physiological. - **Field check:** pick affected leaves and place them in a sealed plastic bag with a damp paper towel for 24–48 hours; fungal growth or spore masses developing on the lesion surface confirms an active fungal pathogen. For turf, part the canopy and inspect individual blades close to the crown, where early lesions often start. - **Lookalikes:** nutrient deficiencies, sunscorch and chemical/fertiliser burn can cause spotting or blotching without any fungal growth developing in the bag test, and lesions from abiotic causes are usually more uniform and not surrounded by a distinct halo. Rust diseases produce raised, powdery orange/brown pustules rather than flat spots, and can be distinguished by rubbing a lesion — rust leaves an orange or brown powder on fingers or clothing. ## Registered products we stock - [Tombstone Duo Fungicide](https://fernland.com.au/tombstone-duo-fungicide/) — ProForce - [Sceptre Turf Fungicide](https://fernland.com.au/sceptre-turf-fungicide/) — Colin Campbell Chemicals - [Stellar 250SC Fungicide](https://fernland.com.au/stellar-250sc-fungicide/) — PCT SureFire - [Dacogreen Weathershield Contact Fungicide](https://fernland.com.au/dacogreen-weathershield-contact-fungicide/) — Colin Campbell Chemicals - [Mancozeb DG Fungicide](https://fernland.com.au/barmac-mancozeb-750/) — Amgrow Specialty Agriculture - [Penncozeb 750DF Fungicide](https://fernland.com.au/mancozeb-750df-fungicide/) — UPL - [Chlortan 720 Fungicide](https://fernland.com.au/chlortan-720-fungicide/) — PCT SureFire - [Instrata Triple-Action Turf Fungicide](https://fernland.com.au/instrata-triple-action-turf-fungicide/) — Syngenta - [Chief 625 Topflo Systemic Fungicide](https://fernland.com.au/chief-625-topflo-systemic-fungicide/) — Adama - [Copper Oxychloride Fungicide](https://fernland.com.au/copper-oxychloride-fungicide/) — Amgrow Specialty Agriculture - [Heritage Maxx Turf Fungicide](https://fernland.com.au/heritage-maxx-turf-fungicide/) — Syngenta - [Switch Fungicide](https://fernland.com.au/switch-fungicide/) — Syngenta - [Bumper 625EC Fungicide](https://fernland.com.au/bumper-625ec-fungicide/) — Adama - [Azoxystrobin 250SC Fungicide](https://fernland.com.au/azoxystrobin-250sc-fungicide/) — EnviroMax - [David Grays Copper Oxychloride | Fungicide](https://fernland.com.au/david-grays-copper-oxychloride-fungicide/) — David Grays - [Mancozeb 750 DF | Fungicide](https://fernland.com.au/mancozeb-750-df-fungicide/) — David Grays - [Velista Turf Fungicide](https://fernland.com.au/velista-turf-fungicide/) — Syngenta - [Liquid DEK Fungicide](https://fernland.com.au/liquid-dek-fungicide/) — Colin Campbell Chemicals - [Liquid Thiram Fungicide](https://fernland.com.au/liquid-thiram-fungicide/) — Amgrow Specialty Agriculture - [Medallion Turf Fungicide](https://fernland.com.au/medallion-turf-fungicide/) — Syngenta - [Quali-Pro Evolution Advance | Fungicide](https://fernland.com.au/quali-pro-evolution-advance-fungicide/) — Adama - [Emerald Turf Fungicide](https://fernland.com.au/emerald-turf-fungicide/) — Colin Campbell Chemicals - [Flowable TMTD Fungicide](https://fernland.com.au/flowable-tmtd-fungicide/) — Colin Campbell Chemicals - [Headway Maxx Turf Fungicide](https://fernland.com.au/headway-maxx-turf-fungicide/) — Syngenta - [Patriot SC Fungicide](https://fernland.com.au/patriot-sc-fungicide/) — Adama - [Banner Maxx Turf Fungicide](https://fernland.com.au/banner-maxx-turf-fungicide/) — Syngenta - [Cheers Weathershield Contact Fungicide](https://fernland.com.au/cheers-weathershield-contact-fungicide/) — Colin Campbell Chemicals - [Dedicate FORTE Stressgard Turf Fungicide](https://fernland.com.au/dedicate-forte-stressgard/) — Envu - [Dedicate Turf & Ornamental Fungicide](https://fernland.com.au/dedicate-turf-ornamental-fungicide/) — Envu - [Interface Stressgard | Turf Fungicide](https://fernland.com.au/interface-stressgard-turf-fungicide/) — Envu - [Lexicon Intrinsic | Fungicide](https://fernland.com.au/lexicon-intrinsic-fungicide/) — BASF - [Quali-Pro Enclave | Fungicide](https://fernland.com.au/quali-pro-enclave-fungicide/) — Adama - [Exteris Stressgard | Turf Fungicide](https://fernland.com.au/exteris-stressgard-turf-fungicide/) — Envu - [Rapide Aqua 500SC Fungicide](https://fernland.com.au/rapide-aqua-500sc-fungicide/) — PCT SureFire - [Reserve Stressgard | Turf Fungicide](https://fernland.com.au/reserve-stressgard-turf-fungicide/) — Envu ## Image credits - [Photo: Scot Nelson from USA via Wikimedia Commons (CC0)](https://commons.wikimedia.org/wiki/File:Hibiscus_Bacterial_leaf_spot_caused_by_Pseudomonas_cichorii_(5684575818).jpg) - [Photo: David B. Langston, University of Georgia via Wikimedia Commons (CC BY 3.0 us)](https://commons.wikimedia.org/wiki/File:%27Cercospora_capsici.jpg) - [Photo: Rasbak via Wikimedia Commons (CC BY-SA 3.0)](https://commons.wikimedia.org/wiki/File:Ridderzuring_bladvlekkenziekte_(Rumex_obtusifolius_with_leaf_spot).jpg) - [Photo: Jaiiiiiiii via Wikimedia Commons (CC BY 4.0)](https://commons.wikimedia.org/wiki/File:Coleroa_robertiani.jpg)