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Australian bug

Icerya purchasi

Cottony cushion scale / Fluted scale (Eng.), Australiese wolluis (Afr.)

These bugs secrete honeydew which can result in sooty mold. Most damage on the host plants is a result of sap depletion.

This species is a common cosmopolitan pest which originated from Australia. Females are easily recognized by the white, fluted attached egg sacs. Females can lay eggs without the need to mate with males - a self-fertilizing hermaphrodite.

Detection

Appearance
-Eggs are orange, oval, and laid in white, fluted wax egg sacs. There can be as much as 400 eggs per egg sac. -First instar nymphs (newly hatched) are 0.5 mm in size, red in colour with black legs and antennae. -Second instar nymphs are 1.0-1.5 mm in size, reddish-brown with black legs and antennae. -Third instar nymphs are similar in appearance to second instars, but 3-4 mm in size. -Adult females are 3-5 mm in size, oval and convex. The egg sac gradually grows from the body of the female and reaches a length between 5-10 mm. -Adult males are very rare and similar size as females, reddish-brown with greyish wings and tufts of long setae at the posterior end of the abdomen.
Symptoms
-Citrus trees: Heavy infestations can result in twig dieback and both leaf and fruit drop. They don't cause direct damage to the fruit as they feed on the stems and foliage.
Activity
Diurnal

Personality

Order
Hemiptera
Family
Margodidae
Metamorphosis
Incomplete
Distribution
Found all over South Africa, Australia and California.

Biological treatment

The ladybird beetles, Rodolia cardinalis and Rodolia ferruginea are imported natural enemies of I. purchasi. Both larvae and adults feed predate on all life stages of I. purchasi. I. purchasi also have a symbiotic relationship with ants. Ants act as bodyguards for the bugs and in turn they are rewarded with sweet honeydew. Ant control is therefore essential for successful biological control, because the ladybird beetles won't be able to predate on I. purchasi unless the ants disappear.

Chemical treatment

Insecticides containing pyriproxyfen or neonicotinoids can be used to control infestations. Stem application of neonicotinoids can ultimately form a chemical barrier which will reduce the numbers of those moving up the trunks. No specific treatments are registered to control the pest, because chemical control is seldom required.

Attracts this pest

There are at least 80 known host plants in southern Africa. Host plants include the following: roses, citrus, mango, mulberry, guava, Accacia spp., Casuarina spp. and Lantana camara.

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