Hemiptera : Pseudococcidae

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Mealybugs get their common name from the white, powdery or ‘mealy’ wax material which covers the bodies of the adult females and nymphs of most species. Females and nymphs of many species also have white waxy filaments extending from the edges of their body.

Mealybugs are related to scale insects, and just like scale insects they are sap suckers. When Mealybugs are in large numbers, their feeding damage can 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.

 

Best Treatment for Mealy Bugs

Mealybugs are sometimes difficult insects to control because of their habit of feeding in secluded parts of plants. The first thing you might notice is sooty mould building up. Keep an eye out (see Monitor) for sooty mould while you are watering your plants. If you find sooty mould, then you should see if you can find what caused it.

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 (see How to Prevent Mealybugs Appearing). The trick is to not let them build up in such high numbers that they are causing major damage (see Symptoms of Mealybugs).

Regular monitoring of your plants either indoors or out in the garden, will ensure that a major infestation of Mealybugs doesn’t occur ‘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.

To treat Mealybugs on indoor and outdoor plants, try Yates Nature’s Way Vegie & Herb Spray. This is a contact spray, so ensure you contact the pests thoroughly for the product to be effective. Repeat weekly, if required. 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.

What are Mealy Bugs &
How to Get Rid of Them

Mealybugs (Pseudoccidae) are sap sucking insects related to scale insects. 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.


Description

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.


Life Cycle

Female Mealybugs of some species (e.g., Longtailed Mealybug) lay live young (i.e., ‘crawlers’) under their bodies, but most species lay eggs into a waxy egg sac. Adult females lay 300 to 600 eggs over a period of 1 to 2 weeks.

Nymphs hatch and, if they are destined to become females, pass through three nymphal instars before adulthood.

Male Mealybugs have four nymphal stages. Males only feed in their first and second instars and then pass through two non-feeding instars. The last two stages are completed inside a waxy cocoon that is produced by the second-instar nymph. Adult males only live for a few days. Their only role in life is to find females and mate with them.

The full life cycle takes from 6 to 12 weeks depending on the species, and there may be several generations per year.

Adult females and nymphs tend to feed in sheltered parts of plants such as between fruits and leaves that are touching, inside leaf sheaths, the base of stems, and sometimes the roots.

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Image above: Paw Paw heavily infested with mealy bug

What Plants are Impacted by Mealy Bugs

  • 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.
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Image above: Mealy Bug nymph, and adults exuding honeydew

Symptoms of Mealy Bugs

  • Wilting and distortion of new leaves.
  • Leaf and bud drop.
  • Mealybugs exude excess plant fluids as honeydew, which promotes the growth of unsightly sooty mould on the affected plants.
  • Dense sooty mould can affect plant photosynthesis which can result in leaf drop.
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Image above: Aglaonema sp. infested with Mealy Bug

How to Prevent Mealy Bugs Appearing

Monitor

  • Look out for sooty mould developing. The presence of sooty mould is an excellent indicator of sap sucking insect activity.

Prevent

  • Don’t bring them in. Check plants and cuttings for Mealybugs before bringing them into your garden or house.
  • Prune dense foliage to minimise sheltered feeding spots.
  • Honeydew attracts ants, which protect the Mealybugs from predators and parasites in return for a feed of honeydew. Prevent ants climbing trees by banding trunks with horticultural glue.
  • Mealybugs may breed in weeds. Control weeds.
  • Prune heavily infested foliage and dispose of it.

Natural enemies

  • Several species of native parasitic wasps (see beneficial wasps).
  • Naturally occurring lacewings and ladybird species.
  • The native ladybird beetle Cryptolaemus montrouzieri is a commercially available Mealybug predator. This beetle has been exported to other countries where it is known as ‘Mealybug Destroyer’.

Recommended Products to Control Mealy Bugs

Yates PestOil

For control of citrus leaf miner, scales, mites, mealy bug, aphids and white fly on citrus, grapes, fruit trees, roses and ornamentals.


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