Ladybugs, lacewings, and syrphid flies are natural predators that kill mealybugs. “Encourage beneficial insects like ladybugs and parasitic wasps in your garden, as they feed on mealy bugs ...

The white masses could be mealy bugs, a type of sap-sucking pest ... This is a form of soil solarisation that uses heat to kill pests and disease-causing organisms. Check the growing media ...