Hi Caroline,

This looks like it is thrips insect damage. They are small puncturing insects that make tiny holes in the leaves that leave this speckly white appearance to the leaves and some leaf curl. They are very tiny and rarely noticed, though the one you have captured in the photo does look like it could be a larval stage of thrips. Aphids cause similar leaf mottling but thrips typically leave black speckles behind as well, which are their byproduct. You should look for that as an indicator.

There are blue cards covered with an oily film that can be used in the planting area to identify when the thrips are present. You can minimize the likelihood of an infestation by keeping plants just on the moist side (thrips like dry conditions) and increasing humidity in the growing area. Make these adjustments minor so as not to invite other varieties of problems. Inspect the plants regularly. New infestations are easier to control.

Use the least toxic product that is effective. Good quality insecticidal soap can be used to treat a small occurrence. Use a commercial product rather than a home remedy because dish soap formulas vary and can have a variety of plant-harmful ingredients. Safer makes a good houseplant insecticidal soap. Follow directions carefully, test the product first on just a portion of the plant and keep the plant out of direct sun while it is wet. Be thorough and repeat every ten days until there is no evidence of insect activity on the indicator card.

Thrips spend some phases of their life in the soil and some on the leaves of the plant. You can have multiple stages of development on the plant at one time. Nymphs drop off the plant into the soil and then emerge as adults. Immersing the plant’s container and soil in water for a sustained period of time will have an impact on the insects in the soil but not those on the plant leaves.

NYBG Plant Information Service

Hello! 

We recommend always trying cultural approaches (indicator cards, humidity, moisture, spraying leaves with water) and non-chemical approaches (insecticidal soap). They work by smothering the insects and are easier on the plant, you and the environment. They are also slower to take effect than toxins and rely on repetition and consistent use to be effective, but really do work if you are rigorous. Make sure that you cover every surface of every leaf and stem with the soap. Check back and repeat every ten days until the indicator cards show no new insects.

If they don't work, you can decide whether you want to try a naturally occurring chemical approach (like the spinosad in the Captain Jack product) or chemical insecticides (like the Bonide product).

You should do your best to isolate the affected plants while you treat them. If that is hard to do in your space, you can create temporary isolation chambers for the plants by bagging them in clear plastic recycling bags which will also have the side effect of increasing humidity.

Wishing you luck!

Forgot about commenting on beneficial insects! While they are used indoors for greenhouse operations growing commercial plant products, they are not usually used in a less controlled environment for houseplants.

Thank you! That trash bag trick is brilliant! I have limited light in my NYC apartment and I worried the plants would decline. It's so strange because they are all flourishing with very minimal damage. 

Very happy to help! I know it can feel a bit hopeless.

The insects live mostly in the temperature range of about 50 to 90 degrees F., so you can quickly sanitize by putting microwave-safe items in the microwave for 3 minutes, immerse in boiling water or place outside in the cold overnight. They can travel on clothes and tools, so latex gloves, wiping down tools under hot water, avoid brushing on plants all help. You can also temporarily bag the healthy plants to prevent access.

Thank you again! My plants are all bagged up. Should I also put bags over plant cuttings propagating in water? Can thrips live on plants that are rooting in water? 

It sounds like you are off to a good start!
The thrips will be less interested in the cuttings in water because they don't like a wet environment. Still, you could have some feeding on leaves but not full life cycles of insects. You can pop a clear bag over the cuttings too if they are very close to the potted plants.
Keep your eye on the plants under the plastic covers. Some plants will adore the extra humidity that creates but others that prefer a dry environment will not. You want to make sure that the cure isn't worse than the thrips! Your plants could also need less water than they typically do in the closed environment, so test the soil before you water.

Hello,

Hi! The treatments that you added to your plant's soil are likely to have side effects, just like human treatment routines. These spots are the kind of damage one sees if there is something going on at the roots that the plant is reacting to (water too cold, soil additives that are irritants, build up of fertilizer) but can also happen on epipremnum if the root ball dries out completely even once during the growing season, or the leaves are exposed to too bright light and burn. Burn happens even more frequently when water splashes on the leaves.

In the low-light conditions of winter (October through February), water only as often as is necessary to prevent the soil from drying completely. In general, the plant will need more water in brighter conditions than in a dimmer spot. Wipe off any water that splashes on the leaves.

Average household humidity is adequate, but if the room is on the warm side, particularly if it is above 65" F. in the winter, you will need some supplemental humidity. Mist daily or use a pebble tray to raise air moisture. Keep the plant away from heat vents where sudden sharp additions of warm air will stress the plant.

You are right that your begonia cutting is reacting to too much water (all water). Begonias with hairy leaves are especially prone to rot if they get too wet. It may not be too late to place it back in soil and certainly worth a try! Trim the cutting to just below a leaf, remove that leaf and dip the cut end in rooting hormone. Plant it in a small pot with half peat and half perlite, just moistened, and cover with a clear plastic bag. Then keep it in bright but filtered light and do not water it again until new growth begins in about a month. At that point you can uncover the cutting and water it sparingly. It will be ready to go into a larger pot in standard soil in about six months. This is not an easy time of year to start cuttings because most plants are in a slow growth phase but you never know.