====== Bipolaris ====== **Examples of early stage:** {{virology:b:media:bipolaris:bipolaris1.webp?400}} {{virology:b:media:bipolaris:bipolaris2.webp?400}} {{virology:b:media:bipolaris:38b8f39125ce3740.jpg?400}} **Examples of late stage:** {{virology:b:media:bipolaris:11e8f1b02ced2efd.jpg?400}} {{virology:b:media:bipolaris:40e8cdf4d29f5b26.jpg?400}} {{virology:b:media:bipolaris:4b4688d66fec5a0b.jpg?400}} {{virology:b:media:bipolaris:fcb0295a756f4324.jpg?400}} {{virology:b:media:bipolaris:18b0a1b0ca4d0077.jpg?400}} ===== Description ===== Bipolaris manifests physically at the tip of columns in the following stages: * **Initial Stage:** When it first presents, the epidermis color of the affected area turns deep purple without a raised blister, and can have weeping black ooze. * **Progression:** As the infection runs its course or dries out, the affected tissue turns deep black, crusts over, and begins to sporulate. * **Growth Arrest:** The tip is typically destroyed or severely damaged, leading to a terminated tip. If the plant survives, it walls off the infection, resulting in a scarred apex from which pups may eventually emerge, or not. =====Origin ===== Bipolaris is caused by the fungal pathogen //Bipolaris cactivora//. It is active in warm, humid summer weather with cycles of wet and dry soil. Outbreaks are also associated with seasonal transitions, high rainfall, and sudden cold snaps. It is often confused with other top-down fungal pathogens like //Fusarium proliferatum// and //Neocosmospora//, or bacterial wet rot (such as //Erwinia carotovora//). ===== Cultivation Notes ===== * **Environmental Management:** Avoid excessive watering during cold snaps and seasonal transitions. * **Soil & Nutrition:** Ensure proper soil pH and nutrient balance. Hindered nitrogen, potassium, and calcium availability (often caused by pH imbalances or excess of other nutrients) can weaken the plant's defenses. Some growers apply dolomite lime (raises soil pH) or gypsum and epsom salts as part of a winter routine. * **Chemical Treatment:** * **Phosphorous Acid (Phos Acid):** Highly recommended as a preventative and active treatment. For active infections, spray directly on the wound. Some users suggest using up to three times the recommended dose for virulent cases, applying repeatedly until the infection dries, crusts, and turns grey. * **Propiconazole:** Recommended by community authority Gee Bee, though she notes that true Bipolaris may not respond to it, requiring physical removal. Note: Propiconazole is not safe for edible plants (labeled for turf and ornamentals). * **Sulfur Powder:** Generally ineffective at stopping systemic or active outbreaks, as the rot may reappear elsewhere. * **Physical Intervention (Chopping):** If chemical treatments fail or the rot continues to spread down the ribs, cleanly chop the infected tip. Deciding to chop immediately versus "letting it ride" is a common dilemma; some plants successfully throw off the infection and offset naturally, while others will rot entirely if not amputated early. ===== Community Discussion & Citations ===== //The community discussion centers on identifying and treating a severe outbreak of tip rot on Trichocereus cacti. While some members initially misidentified the pathogen as bacterial, the consensus established it as the fungal pathogen Bipolaris cactivora, with community authority Gee Bee noting that Fusarium proliferatum and Neocosmospora present similarly. Treatment strategies are divided between aggressive chemical intervention (using high doses of phosphorous acid or systemic fungicides like propiconazole) and physical amputation ("chopping"). Additionally, growers discussed the role of environmental stressors—such as cold snaps, excessive winter rain, and soil pH/calcium imbalances—as the primary triggers for these outbreaks, while clarifying that pests like mealybugs are likely attracted to the fungal hyphae rather than acting as primary vectors.// ^ Date ^ Speaker ^ Key Insight/Quote ^ | 2026-06-08 (approx) | Gee Bee | "Looks like Bipolaris, but could also be a fusarium proliferatum or neocosmospora. Try propiconazole. If it BP then it may not respond and chop" | | 2026-06-15 (approx) | Gee Bee | "Another fungus that can attack top down and looks like Bipolaris is fusarium proliferatum, and also (less likely) neocosmospora." | | 2026-06-15 (approx) | Gee Bee | "Likley they didn't cause it but were an early warning as they do like to eat hyphae and fungal spores. Courtesy pic, note the mandibles have hyphae in and crumbs are scattered about." | | 2026-06-15 (approx) | Gee Bee | "yeah I posted a ladybug, here is the mealy I meant to post. Not as clear a case but appears to be dining on fungus. I would suggesting treating for fusarium, but i know you don’t like to treat..." | | 2026-06-22 (approx) | Brad Albert | "Bipolaris fungal rot Treat with phos acid" | | 2026-06-22 (approx) | Brad Albert | "no it sporulates The first appearance is this black goopy mess that will eventually dry on its own and go grey and this is when it will release its spores. You can dry it out now with phos acid ive had good success treating these outbreaks" | | 2026-06-22 (approx) | Brad Albert | "easily treatable ive stopped it in its tracks b4 and the cactus just grows thru it" | | 2026-06-22 (approx) | Brad Albert | "i use about 3 times the recommended dose for virulent cases like this ,and i keep applying until it visibly starts to dry and crust and turn grey" | | 2026-06-22 (approx) | Brad Albert | "i made that mistake to start with as well and finally got sick of it. Cracked the shits and nuked it Good luck man 💜🌵" | | 2026-06-22 (approx) | Brad Albert | "spray the shit out of the infection, but in saying that preventable sprays do allay alot of issues over winter" | | 2026-06-22 (approx) | Loo'k Lost-mang | "it is fungal, Bipolaris cactivora is the pathogen, you’re thinking of Erwinia carotovora" | | 2026-06-22 (approx) | Loo'k Lost-mang | "Bipolaris, I would guess calcium availability is being hindered by soil pH or excess of other nutrients, especially with how widespread the damage is" | | 2026-06-15 (approx) | Wilfy Fletcher | "Gee Bee ah yeah good point .. this was in a greenhouse situation ... so very limited what could have caused it .. and the only thing i can find on the plant, in the crevices and on neighbours is mealybugs" | | 2026-06-15 (approx) | Wilfy Fletcher | "Gee Bee oh i treat! my antifungal arsenal is rather impressive these days! ud be impressed! and yeah only 1 in a whole greenhouse with it .. and i find mealybug fluff around it and in the wound 🥴 and on neighouring plants infestations" | | 2026-06-15 (approx) | Wilfy Fletcher | "Gee Bee my point is there shouldnt be mealy in my greenhouse! so they had to have caused it or brought it in" | | 2026-06-22 (approx) | Wilfy Fletcher | "yeah phos acid is a staple in all cactus gardens 😀 or should be" | | 2026-06-22 (approx) | Peter Maxwell | "That looks like bipolaris. Everything I ever had that got it kinda threw it off without treatment; just growth arrested and grew a new tip." | | 2026-06-22 (approx) | Hayley Marie | "Ahh Shucks, Possibly Fungal, cold snaps and excessive water. Frozen tips can cause the cells to expand and burst, the same can happen with wet roots and cold you can mound and raise the soil line. Purple may be recoverable but black may need help and a trim on a warmer day. Depends on if you are willing to let it ride, if you do cut back they may need temp shelter for recovery." | | 2026-06-22 (approx) | Phil Mack | "sometimes if you dont cut it right away youll just be doing chop jobs on it until it eventually nothing or it just dies, etc.... unfortunately it happens sometimes if you cut right away itll stop the infection then somtimes if you leave it alone itll go away on its own. its a crap shoot almost." | | 2026-06-30 | Jim Knowlton | "My understanding is that propiconazole is not recommended on edible plants... It's for turf and ornamentals" | | 2026-06-22 (approx) | Thomas Mitchell | "little bit of dolomite mate usually part of my winter routine. Had these tips before this was applied though." | | 2026-06-22 (approx) | Thomas Mitchell | "the fun of it all brother they have all been fine in the ground for a few years. These few months in Vic been weird. High temps then a few cold snaps mixed in with some rain and then a 22 on Wednesday this week. Cacs are confused haha" | ===== Contributor Confidence ===== //Visible to trusted reviewers only.// ^ Contributor ^ Confidence ^ | Gee Bee | 10/10 | | Brad Albert | 8/10 | | Loo'k Lost-mang | 7/10 | | Wilfy Fletcher | 6/10 | | Peter Maxwell | 6/10 | | Hayley Marie | 6/10 | | Phil Mack | 6/10 | | Jim Knowlton | 6/10 | | Thomas Mitchell | 6/10 | ===== Credibility Notes ===== * **Gee Bee:** Recognized community expert on cactus pathology. Provided precise taxonomic distinctions between Bipolaris, Fusarium, and Neocosmospora, and clarified insect-fungal interactions. * **Brad Albert:** Provided highly detailed, consistent, and actionable treatment protocols (phosphorous acid dosing and application frequency) based on successful personal experience. * **Loo'k Lost-mang:** Demonstrated scientific literacy by correcting taxonomic errors (fungal vs. bacterial pathogens) and identifying physiological factors like soil pH and calcium lockouts. * **Wilfy Fletcher:** Active participant who provided detailed greenhouse observations and treatment experiences, accepting correction when necessary. * **Peter Maxwell, Hayley Marie, Phil Mack, Jim Knowlton, Thomas Mitchell:** Provided consistent, practical observations regarding environmental triggers, safety warnings for chemical applications, soil amendments, and the physical progression of the disease.