Mayonnaise polish on a 5-ft columnar cactus followed by browning/death: unlikely direct cause. Pattern of decline (top-down vs. bottom-up) reveals true issue.
Decline Pattern Diagnosis
Pattern
Cause
Mayo Role
Bottom-up (base first)
Rot from overwatering
Coincidence
Top-down (tips first)
Root damage/underwatering
Coincidence
Uniform sudden browning
Chemical toxicity
Possible (oil clogging stomata)
Mayonnaise Risks (Theoretical)
Oil film blocks gas exchange (stomata)
Rancid oils attract pests/fungi
Acidity (vinegar/lemon) may irritate
But: unlikely to kill established cactus in 3 months
True Culprits
Seasonal watering error (most common)
Root mealybugs (check roots)
Fertilizer burn
Cold damage (Wyoming winters)
Action
Determine decline pattern
Unpot; inspect roots
Treat per pattern (rot vs. drought)
Never use food products on plants
Cacti need water, light, drainage—not condiments. The mayo is a red herring.
