Mealybug, Mealybugs, Mealy Bug, Mealy Bugs
Mealybugs are close cousins of Scale Insects, both of which are common pests of house and garden plants! Lucky for us, Mealybugs are relatively easy to get rid of if you catch them early. They're sap-feeders, typically being concentrated around the roots but you may also see them on your plants' leaves and stems. Sap-sucking behaviour means they can impact the vigour of plants. Mealybugs are common pests of Citrus, Sugarcane, Grapes, Pineapple, Coffee, Cassava, Ferns, Cacti and many more. There are around 30 native species of mealybug in the UK, which around a third live on grasses. Several invasive species have been introduced to the region accidentally.
Many species of mealybug are pests, thriving indoors and in glasshouses.
Eaten by predatory insects outdoors.
Adults: Female mealybugs are most common in plants. They secrete a white 'fluffy' wax, and this almost covers the whole body. They're usually detected from the powdery dusting left over the leaves of plants. They're oval-shaped insects with a textured body covered in white wax. Short, white, protrusions extend from around the body. Male mealybugs look a lot different from the females. They look more like an aphid, but with the wings folded flat and outwards. Little males are produced by females, so they can be rare to see. Nymphs: Very similar to females but smaller.
Symptoms can be variable and are dependent on the species. Balls of a cotton-like wax on plants. Plant surfaces may be covered in a clear sticky clear honeydew. Black sooty mould on plant surfaces. Stunted growth. Premature leaf fall.
Females make a large part of mealybug populations, and they can't fly, unlike males. This means the main route of transmission is by bringing newly bought, infested plants into the greenhouse or garden. Plants should always be inspected carefully before any money spent and purchased from a trusted source. To be extra safe, you can quarantine plants for a month before joining it with others. Regular inspection of plants is advised. Indoor plants should be checked frequently, especially when conditions are warm! Fallen leaves should be collected and disposed of accordingly in case there are eggs or bugs on them. Sometimes it is just easier to dispose of the plant if the infestation is too heavy. For lighter infestations, simply pick off mealybugs with some tissue paper. Heavier infestations may require a disinfectant or insecticide. You can make one from scratch using water, oil, bio-friendly washing up soap and some chilli or garlic. Another option would be to use some rubbing alcohol. Unfortunately, the latter won't get rid of the tiny nymphs and eggs, so reapplication is necessary. Insecticidal soaps may be applied if infestations don't clear up within a few weeks. The ladybird Cryptolaemus montrouzieri offers a solid form of biocontrol for glasshouses. Their larvae look a lot like mealybugs, so don't be alarmed if there seems to be more at first! Chemicals should not be used in conjunction with chemical sprays.
Chemical alternatives include organic sprays (containing natural pyrethrum), winter washes (containing natural plant oils) which are particularly suitable for vines, and the more persistent chemicals containing synthetic pyrethroids. Before any application, make sure to scrape away any wax or dead insects, as this too serves as an added layer of protection. If a chemical option is sought, check with your local garden centre and please take care to follow the manufacturers' instructions. Check with your local regulating body for guidance on active ingredients and their authorisation for use. Plants that are in flower should never be sprayed due to the danger of harming pollinators.