The most important to get rid of mold on the top of the soil in potted plants is to water correctly. Mold is almost always a sign that the soil is staying too wet - if the soil gets dry on top between waterings, as it is supposed to (actually the drying shouldn’t be limited to the top of the soil,) it won’t get moldy. Here’s some information on watering plants based on testing soil moisture -

Marlie Graves, House plant professional, 30 years. Top Writer 2017, 2018.Answered 9 months agoHow often should I water my houseplants?Originally Answered: How often should I water my plants?

The link appears to be basically an advertisement for a landscape service that is looking to develop business by having people call them with questions. Not a bad idea, but nothing to do with the question.

To answer as succinctly as I can, water your plants when they need it. “How often” depends on too many things like kind of plant, kind of soil, amount of light, temperature, weather, etc etc to have any meaning. Anyone who gives you a “Water every week/ every day/ every month” answer isn’t really helping you at all.

Also, I don’t even know if you mean outdoor garedn, or indoor plants. If you want to know more about indoor plants, here’s an answer I wrote awhile ago -

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However, you might be talking about mold on leaves. The most likely of those would be powdery mildew, for which the best treatment is probably using a commercial fungicide marked for powdery mildew.

Then again, if you see white fuzzy looking patches on the leaves, it may well be that you’re seeing mealy bugs - they often look like mold to people who don’t know what they’re seeing.

Se guardi da vicino le macchie, vedrai degli insetti con le zampe dentro le tende di cotone che fanno.

Queste possono essere eliminate pulendole con alcol diluito - 2 parti di alcol, 8 di acqua. Tienili lontani spruzzando con una miscela di acqua e sapone - 1/2 cucchiaino di sapone liquido puro, come Castille o DrBonner's (non Dawn) in 2 tazze d'acqua. Spruzzare molto accuratamente - sopra, sotto, ai lati, in tutti gli angoli e le fessure - settimanalmente per 4 settimane.

Vedrai molti altri trattamenti suggeriti per le mealie - olio di neem, alcool, spray insetticida, ecc - ma ho fatto questo per 30 anni professionalmente, e questo è il meglio che ho trovato. Qualsiasi cosa vogliate provare va bene, ma qualsiasi cosa sia, fatelo settimanalmente per 4 settimane per rompere il ciclo di vita degli insetti - altrimenti saranno ba-a-ack.