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Pest & Disease Factsheet - Mealybugs

Vines, tomatoes and tropical plants are among those at risk.

Mealybug: citrus, Planococcus citri - image: Martin Lagerwey/Flickr
Mealybug: citrus, Planococcus citri - image: Martin Lagerwey/Flickr
 

There are four common mealybug species found in the UK, the most common being citrus mealybug, Planococcus citri. The vine mealybug, Pseudococcus viburni (syn. affinis), can be found on cactus, passiflora and tomato, while the long-tailed mealybug (Pseudococcus longispinus) is found on tropical plants and the New Zealand flax mealybug (Trionymus diminutus) (pictured below) is found on phormiums and cordylines.

Non-native mealybugs found on imported plant material include the bougainvillea mealybug (Phenacoccus peruvianus), coffee mealybug (Planococcus lilacinus) and the golden root mealybug (Chryseococcus arecae). Notifiable pests include the lantana mealybug (Phenacoccus parvus) and root mealybug (Rhizoecus hibisci). Carefully check imported stock. Some root mealybugs, such as Rhizoecus falsifer, are not notifiable.

Mealybug: New Zealand flax, Trionymus diminutus

How to distinguish them

Female mealybugs are wingless, immobile, up to 5mm long and covered with waxy threads that can be white, brown or pink. Males are winged, about 1mm long and shorter-lived than the females.

Biology

Female mealybugs, when mature, can lay up to 500 eggs in a white, woolly egg mass. The long-tailed mealybug produces live young. On hatching, the young disperse and find suitable feeding sites. On average, from egg to adult takes four weeks at 26°C and eight weeks at 20°C.

Symptoms

Many pests are host-specific.

Nymphs and adult females suck plant sap, causing distortion, yellowing, defoliation and honeydew that supports sooty moulds. Heavy infestations can kill a plant.

Treatment: biological control

The Australian predatory ladybird Cryptolaemus montrouzieri feeds almost exclusively on mealybugs and is effective in large pest colonies. Adults are about 4mm long, mostly brown or black with a distinctive orange head. The white larval stage grows up to 1cm in length and looks like an oversized mealybug. Adults and larvae feed on pests. After mating, females can lay up to 500 eggs in the mealybug masses. Cryptolaemus work best between 21°C and 30°C in bright, sunny conditions.

Parasitic wasps are also available. Leptomastix dactylopii is effective against Planococcus citri. It lays its eggs into the third larval and adult stages. Leptomastix epona is effective against Pseudococcus viburni (syn. affinis) (pictured below). Both wasps are yellow-brown and about 3mm long.

Female Anagyrus pseudococci are brown and about 2mm long. They will mainly control Planococcus citri but will also attack Pseudococcus viburni (syn. affinis).

Parasitic wasps are best used in conjunction with Cryptolaemus.

Mealybug: vine, Pseudococcus viburni - image: BENHS

Treatment: cultural control

  • -Avoid encouraging lush growth. Pests can multiply quicker on plants with higher nitrogen levels.
  • -Install yellow sticky traps to snare winged males.
  • -Check for honeydew deposits, sooty mould growth and ant activity.
  • -A pheromone trap is available for the winged males of Planococcus citri.
  • -Quarantine and check imported stock.

Treatment: chemical control

Active ingredient Deltamethrin
IRAC code 3
Formulation Various including Decis* (Bayer)
Action(s) Contact insecticide with residual activity — incompatible with biological controls.

Active ingredient Flonicamid
IRAC code 9C
Formulation Mainman* (Belchim)
Action(s) Selective feeding blocker — compatible with some biological controls.

Active ingredient Nutrient-based plus additional natural products
Formulation SB Plant Invigorator (Fargro)
Action(s) Contact insecticide with physical action — compatible with some biological controls.

Active ingredient Pyrethrins
IRAC code 3
Formulations Pyrethrum 5EC (Agropharm), Spruzit (Certis)
Action(s) Short-term knockdown product. Re-introduce predators after seven days.

Active ingredient Spirotetramat
IRAC code 23
Formulation Movento* (Bayer)
Action(s) Contact and ingested insecticide — compatible with some biological controls.

Fully updated by Dove Associates

* Extension of Authorisation required for use in ornamental plant production outdoors and/or under protection.

Use plant-protection products safely. Always read the label and product information before use. Dove Associates shall in no event be liable for the loss of or damage to any crops or biological control agents caused by the use of products mentioned.

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Parent Category: Gardening Fact Sheets
Category: Fact Sheets 2017
Last Updated: 02 October 2017
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