Plant care guide
Prickly Pear Sunburn: Sun Scar or Pad Disease?
Updated
Why does my Prickly pear cactus have sunburn?
Sun damage on a prickly pear shows as pale, bleached or tan patches on the pad faces that took the sun, which later dry into a permanent, corky scar. It usually follows a sudden move from indoors or shade into full sun. Spreading, zoned brown spots that grow until the whole pad dies are a fungal disease, not sunburn.
What to do first
Shade the plant or step it back to partial sun for a few weeks, and check that the soil is not waterlogged or bone-dry. Leave scarred pads in place unless they rot or die, and acclimate gradually next time.
A prickly pear with scorched pads looks like a contradiction. NC State Extension says plants in the genus prefer full sun, and UF/IFAS says prickly pear thrives in full sun. Yet pads do burn.
The cause is usually how fast the light changed. Iowa State University Extension says sun scald on succulents mainly happens when a plant kept in low light moves suddenly into bright or direct sun (Iowa State: succulent problems). A potted prickly pear coming out after a winter indoors is the classic case.
What Sun Damage Looks Like on Pads
Iowa State describes sun damage as brown or tan patches on leaves or stems. On a prickly pear, the pads are the stems. University of Maryland Extension’s excess light page adds that scorch starts as pale, bleached or faded areas. Look for:
- Pale, bleached or tan areas on the pad faces that point toward the sun
- Damage that appeared within days or weeks of a move outdoors or into a sunnier spot
- Shaded pads, or the shaded side of the same pad, still green
- Patches that stay the same size once the plant is shaded
Iowa State says burned areas will not recover. Stems with sun scald callus over, leaving a permanent scar. A firm, dry, tan scar on an otherwise healthy pad is old damage, not an active problem.
Sunburn or Something Worse?
The Texas A&M Plant Disease Handbook lists a fungal disease on Opuntia that is also called scorch or sunscald. Do not confuse it with sun damage.
| What you see | Likely cause |
|---|---|
| Tan or yellow patch on the sunny face, stops spreading in shade | Sun damage |
| Zoned spots that enlarge until the whole pad turns reddish-brown, centre grey-brown and cracked | Fungal scorch (Hendersonia opuntiae) |
| Rusty, corky areas on the pads | Scab, linked to overwatering and poor ventilation |
| Moist, light brown rot with pink pustules | Cactus anthracnose |
| White, splotchy, mold-like patches | Cochineal insects |
Texas A&M says no practical control exists for the fungal scorch, and advises removing pads with anthracnose as soon as noticed. For scab, it recommends more light and lower humidity. NC State describes cochineal as a white, splotchy, mold-like substance that can kill the plant.
What to Do Now
- Cut the light for a few weeks. Move a potted plant to partial shade, or rig shade cloth over a planted one. Clemson Extension’s indoor cacti factsheet advises partial shade for the first few weeks outdoors.
- Check the soil. Clemson says cacti need very well-drained soil. During the growing season, water when the soil has dried slightly. In winter, give just enough to keep the plant from shriveling. NC State warns wet soil causes root rot.
- Leave scarred pads on. Iowa State says scalded stems callus over, so a scarred pad can stay. Remove a pad only if it dies, rots or shows the spreading disease spots above.
- Wear thick gloves. NC State and UF both warn about glochids, the tiny barbed bristles in the areoles that irritate skin.
- Grow a replacement if needed. UF/IFAS says to cut a pad at least six months old, let the cut callus for a week or two, then set it upright about 2.5 cm (1 in) deep in a soil and sand mix.
Acclimate Before the Next Move
Iowa State University Extension’s guide to moving plants outdoors says never to move houseplants from indoors straight into full sun. On succulents, damage to fleshy stems and leaves is permanent. Start in shade and add light over 10 to 14 days. Use cloth or shade material if no shady spot exists.
Indoors, Clemson recommends south or west windows with several hours of direct sun for arid-climate cacti. A plant grown in that light adjusts to the outdoors more easily than one from a dim room.
For watering trouble that looks like damage, see our prickly pear overwatering vs underwatering guide. Our houseplant sunburn guide covers acclimation in more depth, and soft or wrinkled cactus covers pads that change texture.
References
- Iowa State University Extension: Common Problems and Issues of Succulents
- Iowa State University Extension: Moving Indoor Plants Outside for the Summer
- Clemson Cooperative Extension HGIC: Indoor Cacti
- Texas A&M Plant Disease Handbook: Cacti and Succulents
- NC State Extension Gardener Plant Toolbox: Opuntia
- UF/IFAS Gardening Solutions: Prickly Pear
- University of Maryland Extension: Excess Light on Indoor Plants
How this guide was put together: Iowa State University Extension, Clemson Cooperative Extension, Texas A&M Plant Disease Handbook, NC State Extension, UF/IFAS and University of Maryland Extension guidance.