Diffenbachia issues - Ask Extension
Having some foliar issues on 2 diffenbachias that are about 3 yrs old. Started about a month ago on one plant, now symptoms are starting on the other ...
Knowledgebase
Diffenbachia issues #791217
Asked May 17, 2022, 10:59 AM EDT
Having some foliar issues on 2 diffenbachias that are about 3 yrs old. Started about a month ago on one plant, now symptoms are starting on the other (trying to keep them separate). Plants are checked regularly for too much/too little water.
I do not see any insects or insect activity. A few months ago I fertilized with a liquid product.
Talbot County Maryland
Expert Response
This doesn't appear to be due to an insect pest, nor do we recognize symptoms of a particular disease. (There are fungal spores emerging from the dead brown leaf, but this is commonly a secondary issue due to the fungus decaying the dead tissue; these fungi are not necessarily infectious.) How long have the plants been outside (unless they were moved outside just for the photos)? Dieffenbachia are quite sensitive to cool temperatures and prefer to stay at least above about 65 degrees F or cold injury can affect its tissues.
For now, continue monitoring for watering needs while avoiding over-watering and move the plants back indoors overnight unless the lows stay in the mid- to upper 60s or warmer. Keep them shaded as well so the leaves don't sunburn. Trim off those two lower leaves that are dead/dying.
Fertilizing during winter is not needed for most houseplants since their growth rate slows so much due to the limited daylight and dryer air. For the future, you can resume fertilizing around mid-spring or so and end around early autumn. (How often to fertilize during the growing season greatly depends on the formulation you're using, so follow package label instructions.)
We suspect these leaf injuries are abiotic, meaning they are due to environmental conditions and not caused by a pest or pathogen. It almost looks like a physical injury, where the leaves were struck, punctured, abraded, or otherwise physically damaged. Was any type of spray used near the plants just before the leaf damage became evident? (Window cleaner, disinfectant, wasp spray, etc.)
Although damaged leaves do not heal, if new growth looks normal or has less damage, then the issue will probably pass and not cause the plant much long-term stress. If the lower leaf shedding accelerates and new growth isn't keeping up with replacing lost leaves, something more serious with root health is likely to blame. Long-term, repot the plants every year or so to refresh the soil so it doesn't harbor a buildup of minerals from water or fertilizer (which, when excessive, can kill roots).
Miri
For now, continue monitoring for watering needs while avoiding over-watering and move the plants back indoors overnight unless the lows stay in the mid- to upper 60s or warmer. Keep them shaded as well so the leaves don't sunburn. Trim off those two lower leaves that are dead/dying.
Fertilizing during winter is not needed for most houseplants since their growth rate slows so much due to the limited daylight and dryer air. For the future, you can resume fertilizing around mid-spring or so and end around early autumn. (How often to fertilize during the growing season greatly depends on the formulation you're using, so follow package label instructions.)
We suspect these leaf injuries are abiotic, meaning they are due to environmental conditions and not caused by a pest or pathogen. It almost looks like a physical injury, where the leaves were struck, punctured, abraded, or otherwise physically damaged. Was any type of spray used near the plants just before the leaf damage became evident? (Window cleaner, disinfectant, wasp spray, etc.)
Although damaged leaves do not heal, if new growth looks normal or has less damage, then the issue will probably pass and not cause the plant much long-term stress. If the lower leaf shedding accelerates and new growth isn't keeping up with replacing lost leaves, something more serious with root health is likely to blame. Long-term, repot the plants every year or so to refresh the soil so it doesn't harbor a buildup of minerals from water or fertilizer (which, when excessive, can kill roots).
Miri
