Mealybug can in certain instances become a problem on roses, other small shrubs and plants, especially during periods of drought.
It usually is an indication that the plant is not happy at root level. When not enough water is applied for the plant to sustain itself properly or conversely when the soil is clay and water stands.
They are more easily visible in May to July. The adult insect with eggs and crawlers is protected under the white foam-like cover from spraying with a normal insecticides and it is only when the crawlers leave this protection and before making their own canopy that they can be eradicated by spraying.
It is best to brush over them ripping their cover and then spraying with a bio-oil such as Ludwig’s Insect Spray at double the recommended concentration.
Mealybug on roses is easily confused with Cochineal, a sap-sucking insect that feeds on cacti and prickly pear plants. It is actually a scale insect in the suborder Sternorrhyncha, from which the natural dye carmine is derived.