Houseplant Leaf Damage: Pests or Disease?

I was wondering if you would know what would cause this type of damage to a leaf on a ZZ plant? I have several other plants with similar damage to their leaves including several calathea, crotons, and pothos. I’m assuming some type of pest, however, the only thing I’ve been able to spot is some fungus knats. Thank you for your time,

Hi Josh,


It’s hard to tell from these pictures what the problem is, could you describe the damage? Brown marks, yellow marks, circles, etc. Until I get more info, spray all parts of the plant with my green solutionIf you don't want to use a commercial chemical product to treat plant pest problems try the “Green Solution.” This is a mixture of water, alcohol, biodegradable liquid soap, and mineral oil. Always test any spray on one or two leaves to be sure it won’t damage the plant. Depending upon how severe the infestation is, you can use these ingredients in varying proportions. If there are only a few pests, dip a Q-tip in alcohol and gently swab them off. For a more widespread problem, start by using a spray of warm water mixed with a few tablespoons of biodegradable soap. If that doesn’t cure the problem, make a solution using 8oz. water & 8oz. alcohol, add two tablespoons of biodegradable soap and two tablespoons of mineral oil. Spray all areas of the plant. Use this solution on leathery leafed plants (except palms), never on fuzzy leafed plants like African Violets or Begonias. For palms, omit the alcohol from the Green Solution. Never spray a plant that’s sitting in the sun or one with very dry soil.    : 50% water, 50% inexpensive rubbing alcohol, a few squirts of biodegradable liquid detergent, a few squirts of mineral oil. Be sure the plants are not in the sun and the soil is not super dry. Protect carpets and furniture. This works well on many plant diseases and plant pests. (until we can determine the exact problem).