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Mealybug

Australia has a large number of native mealybug species, including members of the genera Paracoccus, Ferrisia and Pseudococcus. Pest species in field crops include peanut mealybug and solenopsis mealybug.

Scientific name

Maconellicoccus hirsutus (peanut mealybug), Phenacoccus solenopsis (solenopsis mealybug). Family: Psuedococcidae (various species)

Description

  • Female adults are about 3mm long.
  • Female adults and nymphs are oval and covered in a white waxy coating giving them a mealy appearance.
  • Males are small aphid-like winged insects.
  • Peanut mealybug colonies form on shoots, stems, leaves and peanut kernels, and develop into white masses.
  • Ants can nurture mealybug colonies, collecting honeydew while keeping predators away.

Distribution and habitat

Widespread; generally prefer warmer conditions.

Hosts

In field crops, hosts are primarily peanut, cotton, mungbean and sunflower. Mealybugs are also found in a wide range of horticultural crops, garden plants and weed species.

Damage

Mealybugs pierce and suck on plant tissue. Damage is often worse in stressed plants. Symptoms include:

  • reduced plant vigour and shortened season
  • stunting
  • distorted shoots/leaves
  • reduction in flowers/seeds/fruit
  • honeydew contamination and sooty mould
  • peanut kernels of infested plants may collapse and turn black
  • 'hot spots' of dead plants.

Life cycle

  • Females lay egg sacs containing hundreds of eggs.
  • Young nymphs (called 'crawlers') are highly mobile.
  • Only males have a pupal stage.
  • Many generations can occur within a year.
  • Can hibernate over winter on host plants or in soil.

Monitoring and thresholds

Can affect any plant stage but is often difficult to detect until colonies are well advanced. Often:

  • infestations are close to paddock edges or in poorly drained areas
  • in peanuts, colonies are found at the base of plants on the taproot and pods.
  • in cotton, early infestations of solenopsis mealybug cause 'hotspots' of dead plants.

Natural enemies

Mealybug ladybird, other ladybirds and predatory beetles, lacewing larvae, parasitoid wasps.

Control

Practice good farm management and hygiene by:

  • preventing mealybugs moving into farms and fields that are currently mealybug-free
  • restricting movement of people and machinery in infested areas
  • regularly washing clothing and equipment that may transmit crawlers
  • keeping fields and non-crop areas free of alternative host plants.

Mealybugs are very difficult to control with chemicals as:

  • their waxy coverings repel sprays
  • they hide in sheltered areas of the plant
  • they quickly develop resistance to pesticides groups
  • most pesticides that are toxic enough to affect mealybugs will impact on beneficial populations.

Further information