Ask a Question forum: Monstera Deliciosa pest problem

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Name: Linniez
Sydney NSW Australia
Mar 6, 2018 6:50 AM CST
Hi, my monstera deliciosa was recently discovered to have scales - only found a few but noticed when 1 leaf was starting to develop tiny brown holes and such.

I've now cut off that leaf and 1 other adjacent and sprayed pyrethrum on the leaves after bringing it outside for a water (flush).

After spraying on pyrethrum I noticed little black dots appearing randomly on the underside after 1-2hrs which have now appeared on the front side and slowly becoming transparent & bigger after 18-24hrs...did I do something wrong?

Being frantic, last night I then sprayed and wiped all my foliage and stems with white it proctects leaves but also suffocates scales and mealybugs etc.

How can I save my precious monstera? I'm hoping these don't even get bigger and bigger and kill all the leaves...

- indoor plant near a east facing window
- I bring outside once a week or week-half to water but sometimes I top up during the week as there were really hot weeks in the last 1-2months
- when I first repotted about 1.5 months ago it was looking fabulous and I kept the rootball just bigger pot as it was growing roots outside
- I may have misted the plant a couple times during hot days...maybe overwatering it as a result in between waters?
- I put a tiny bit of fertiliser seeds during the repotting
- I sprayed and wiped white oil all over the foliage during repotting also

Any tips and advice would be much appreciated.

Thumb of 2018-03-06/Linniez/60a306
Thumb of 2018-03-06/Linniez/4c8b42

Name: Will Creed
Profess plant consultant & educator
Mar 6, 2018 3:19 PM CST
Scale insects don't make holes in leaves. They make slightly raised brown bumps that scrape off easily with a fingernail. I don't think that is what you have and not what I see in the photos.

There are a number of possible causes for the brown spots on the leaves. They include pyrethrum or white oil toxicity; exposure to too much light and heat outdoors; repotting improperly; misting in the sun or heat; and fertilizer toxicity. Frantic (your word) responses often cause more problems than they solve.

Keep your Monstera indoors close to the east window and leave it there. Outdoor sun and heat are too much for it. There is no need to spray for insects because I don't think there are any. Misting serves no useful purpose and can cause leaf damage if done in direct sunlight or high temps. Fertilizer is intended for healthy plants that are growing vigorously and have depleted their nutrients. Yours has not.

The roots that you saw were probably aerial roots that normally grow outside the pot and are not an indication that the plant needs a bigger pot. It is good that you kept the original rootball intact.

When properly potted, it is best to allow the top half-inch of soil to dry in between thorough waterings.

This is a naturally vining or trailing plant that wants to grow along the ground. It is a struggle to keep it upright because the stems fall under the weight of their large leaves as they grow longer. You can keep using taller and taller supports or you can simply cut back any stems that get too long and unruly. The cut stem sections can be propagated pretty easily in water or damp soil.

Worry less and do less and I think your Monstera will be fine.

Will Creed
Horticultural Help, NYC
Contact me directly at [email protected]
I now have a book available on indoor plant care

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