Mealybug Control in Your Garden

Mealybugs (Pseudoccidae) are sap-sucking insects closely related to Scale Insects. These tiny pests feed on plant sap, depriving plants of essential nutrients and weakening their overall health.

More than 200 species of Mealybugs occur in Australia, many of which are native, but there are several introduced species as well. Pest species encountered in gardens are more likely to be introduced than native.

Common pest species include Citrus Mealybug (Planococcus citri), Citrophilous Mealybug (Pseudococcus calciolariae), Hibiscus Mealybug (Maconellicoccus hirsutus), Longtailed Mealybug (Pseudococcus longispinus) and Tuber Mealybug (Pseudococcus viburni). Of these Mealybugs, Citrophilous Mealybug is native, and the others are introduced.

When Mealybug infestations are severe, their feeding damage can also be quite severe, including wilting and distortion of new leaves. Mealybugs excrete a large amount of honeydew, which promotes the growth of Sooty Mould and may damage plants further.

Female Mealybugs are usually oval in shape and less than 5 mm in length. They secrete a powdery ('mealy') waxy substance which covers their bodies, and some species have filaments of wax extending around their bodies. Some species may have very long filaments extending from the rear.

Eggs are usually laid in a sticky mass of waxy threads known as an 'egg sac', and eggs may be pale yellow or orange, depending on the species.

Nymphs are initially yellow-brown in colour and not covered with wax, and are known as 'crawlers'. Female nymphs develop their waxy covering at the second nymph stage.

Adult males are seldom-seen, tiny, winged insects which don't feed and are about 1 mm long.

Female Mealybugs are usually oval in shape and less than 5 mm in length. They secrete a powdery ('mealy') waxy substance which covers their bodies, and some species have filaments of wax extending around their bodies. Some species may have very long filaments extending from the rear.

Eggs are usually laid in a sticky mass of waxy threads known as an 'egg sac', and eggs may be pale yellow or orange, depending on the species.

Nymphs are initially yellow-brown in colour and not covered with wax, and are known as 'crawlers'. Female nymphs develop their waxy covering at the second nymph stage.

Adult males are seldom-seen, tiny, winged insects that don't feed and are about 1 mm long.

• Fruits – especially Citrus, Figs and Grapes.
• Many ornamental plants including Cactus, Fuchsia, Gardenia, Hibiscus, Jasmine and Oleander.
• Many houseplants including Coleus, Ferns, Ficus, Orchids, Palms and Philodendron.
• Greenhouse plants are particularly prone to Mealybug attack, because the warm, humid environment is ideal for Mealybugs.

Mealybugs are sometimes difficult insects to control because of their habit of feeding in secluded parts of plants. Keep an eye out for white cottony masses, sticky residue or Sooty Mould while you are watering your plants. 

Regular monitoring of your plants either indoors or out in the garden, will ensure Mealybug populations don't explode 'overnight'. Managing Mealybugs is much easier if you can catch an infestation in its early stages. Don't wait for an infestation to build up to unmanageable levels.

Prevention is always better than cure. The only way Mealybugs can get into your garden or your house is on a plant. Check plants and cuttings for Mealybugs before bringing them into your garden or into your house.

There are several things that you can do to prevent or minimise Mealybug damage. The trick is to not let them build up in such high numbers that they are causing major damage.

To treat Mealybugs on indoor and outdoor ornamental plants, as well as vegetables like Broccoli, Brussels sprouts, Cabbage, Cauliflower, Beans, Peas and Tomatoes, use Yates Advanced Ready To Use.

For large infestations, use Yates Nature's Way Vegie & Herb Spray Concentrate. Mix in a sprayer and spray all surfaces of the plant thoroughly, repeating every 5-7 days if required. These are contact sprays, so ensure you cover the plants and pests thoroughly, including on the undersides of leaves.

• When watering, closely examine the foliage and stems of your plants. Look out for any indications of yellowing or stunted growth, as these may be signs of an infestation by Mealybugs. If you spot any suspicious symptoms, check for the presence of Mealybugs or other sap-sucking pests.
• Look out for Sooty Mould developing. The presence of Sooty Mould is an excellent indicator of sap-sucking insect activity.

• Check plants and cuttings for Mealybugs before bringing them into your garden or house.
• Prune dense foliage to minimise sheltered feeding spots.
• Ants protect Mealybugs from predators and parasites in return for a feed of honeydew. Prevent Ants climbing trees by banding trunks with horticultural glue. This sticky barrier acts as a deterrent for the Ants, preventing them from accessing the tree and the Mealybugs. By disrupting the symbiotic relationship between Ants and Mealybugs, you can reduce the protection provided to the pests and limit their population growth.
• Prune heavily infested foliage and dispose of it. Where possible, isolate infected plants, and treat with a suitable insecticide and return to its location once the pests are controlled.
• Healthy plants are better at fending and recovering from insect attacks. Water and feed indoor plants, outdoor plants, and potted plants regularly to ensure optimal health. 

• Several species of native parasitic wasps (see Beneficial Wasps).
• Beneficial insects such as Lacewings and Ladybird species.
• The Native Ladybird Beetle, Cryptolaemus montrouzieri, is a commercially available biological control. This beetle has been exported to other countries where it is known as 'Mealybug Destroyer'.