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Posts Tagged ‘Houseplant Care’

Spiders on your plants aren’t a bad thing. In fact, spiders eat many of the insects that damage house plants, so they really should be left alone. Seeing a spider in the house might be just a bit too much to bear for some, but a house with spiders is more likely to be insect free. (Spiders are not insects.) Though there are dangerous spiders known in the U.S., here in the northeast most spiders living in our homes will be the common house spider, which is relatively harmless.

Spider mites, on the other hand, are critters you definitely don’t want on your plants. Spider mites build webs like spiders and are in the same arachnid family. Some mites cannibalize their own kind, but most prefer plant juices and will pierce a leaf or stem and then suck the plant juices and nutrients from it. This weakens the plant, and large infestations might even kill it.

Plants with spider mites will show small yellowish-brown spots on their leaves. These spots might be quite far apart at first, but as the colony grows leaves will have so many spots that they will appear off color and have a metallic bronze appearance. Small webs on the undersides of leaves and where the leaf meets the stem are where eggs will hatch. To check a plant for these tiny creatures, hold a piece of white paper under a leaf or branch and give the plant stem a couple of good taps. Spider mites will fall off if they are present and appear as small, rust red, moving dots on the paper. (You might need a magnifier.) Mites can travel from plant to plant on a slight breeze, so infected plants should be quarantined or thrown away if inexpensive.

Spider mites like it hot and dry, so keep humidity high by frequent misting and grouping plants together. Keep plants shaded from hot afternoon sun or consider keeping your plants in a sunny room in which the heat has been turned down. Most houseplants will do better at 65° F (18° C) than they will at 75° F (24° C) and you’ll save fuel.

Once spider mites appear on a plant control can be difficult unless spraying is done regularly. Eggs hatch in 4-5 days and mites will reach egg laying adulthood in a week or less. A strong isopropyl (rubbing) alcohol and water solution of 2 parts alcohol to 3 parts water should be sprayed twice weekly for at least 3 weeks.  It is very important to spray the undersides of leaves thoroughly along with the rest of the plant. Houseplants should be inspected regularly, even after spraying, so infestations don’t get out of hand.

Before spraying any plant with alcohol always test a leaf first to see if the plant will be harmed by it. Furry leaved plants should not be sprayed. Always protect surfaces and fabrics from alcohol sprays.

Photo magnification of Two Spotted Spider Mite by USDA-ARS-SEL & EMU, using Low Temperature -SEM

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