Many pests brown spots houseplants owners see come from bugs feeding on leaves and stems. The main culprits are spider mites, scale insects, mealybugs, and thrips. Each one leaves different marks that help you figure out what you're dealing with. Catching them early makes treatment much easier for you.
I learned to spot spider mites plant damage after losing a nice fern to them. At first I thought the yellow patches were from bad watering. Then I saw tiny webs between the leaves. By that point mites had spread to three other plants nearby. Now I check leaf undersides with a magnifying glass when anything looks off. Those fine webs and yellow dots give mites away once you know the signs.
Spider mites make tiny yellow or brown speckles across your leaves. Each dot comes from a mite poking a cell to drink the juice inside. Bad cases show webbing between leaves and stems. Mites love dry warm air and breed fast. A few bugs can turn into thousands in two weeks if you don't act. Misting your plants and keeping humidity up helps stop them from moving in.
You'll find scale insects houseplants often harbor on stems and leaf backs. They look like small brown bumps and don't move once settled. Many people mistake them for part of the plant. Scale jab needle-like mouths into tissue and drain sap all day. This feeding makes sticky honeydew that coats nearby areas and grows black mold. Scrape a bump with your fingernail to check.
I had a scale problem on my citrus tree last year. Sticky spots on the shelf below told me something was wrong before I even saw the bugs. The brown bumps blended in with the bark. It took weeks of scrubbing and spraying to clear them out. Scale hide their eggs under their shells, so you need multiple treatments over time to get them all.
Mealybugs show up as white fluffy masses in leaf joints and along stems. These soft bugs cluster together under waxy coating for protection. Like scale, they make honeydew while feeding. Brown spots appear where they've drained too much sap. A cotton swab with rubbing alcohol kills them on contact. Treat again every few days since eggs hide in cracks.
Thrips leave silvery streaks and tiny black dots on leaves. These thin bugs scrape surfaces to feed. The cells they damage turn brown and papery over time. Thrips are hard to see since adults are barely 1 millimeter long. Yellow or blue sticky traps help you spot them. Shake a leaf over white paper and watch for tiny crawling specks.
All these pests can spread disease between plants as they feed. Their mouths pick up viruses and bacteria from one leaf and carry them to the next. This makes catching bugs early even more important. One sick plant becomes a threat to your whole collection if pests move around freely.
Treat pest problems with insecticidal soap or neem oil on all leaf surfaces. Don't forget the undersides where bugs hide. Spray every 5 to 7 days for three weeks to kill new bugs before they lay eggs. Keep sick plants away from healthy ones until the problem clears up. Check your other plants often during treatment to catch any spread.
Read the full article: Fiddle Leaf Fig Brown Spots: Causes and Fixes
