Scale insects

Pest description:

Avocado scale – Fiorinia fioriniae (Targioni-Tozzetti)

Found on many different host plants in the world
Feeding damage occurs on the fruit and leaves, and is caused by the immature stages that are light brown in colour
Female avocado scales have a transparent exoskeleton, are orange-brown in colour and 1.0 – 1.3 mm in length
Immature males have a white exoskeleton and are elongate-oval in shape
Very little research has been done to date on the biology and control of avocado scale in South Africa
In other parts of the world, 3 – 4 generations have been monitored per year in avocado orchards

Heart-shaped scale – Protopulvinaria pyriformis (Cockerell)

One of the most damaging scales on avocado leaves
No damage is not done to the fruit
The protective layer (± 3 mm wide) of the female heart-shaped scale is hard, brown and heart-shaped with dark radial stripes
A waxy egg-sack is often visible under the female scales with 200 – 300 eggs per sack
The male form of the scale has not been seen in South Africa
Two generations of heart-shaped scale can be monitored throughout the avocado season in the Nelspruit area.
Nymphs or crawlers are light green
They emerge from eggs during November and March
It takes roughly 5 – 7 months from egg to adult stage, depending on temperature

Honeydew

Plant sap that scale insects feed on is full of plant sugars
Sap is excreted by scale insects in the form of honeydew
Ants feed on, and spread, the honeydew and protect scale insects on the trees against predators in a mutualistic relationship
The sweet honeydew excretion acts a food source for ants
Sooty mould is observed when Ascomycete fungi (mainly Cladosporium and Alternaria) grow on the honeydew
Fungal growth limits the effective area of photosynthesis on the leaves and can lead to tree decline or defoliation in all cultivars

More information:

Suggested scout methods:
- Scout the underside of leaves and especialy rough-skinned cultivar fruit for scale insects
Control options:
- The waxy covering of scale insects protects them against contact insecticides
- Contact insecticides must be sprayed on the immature stages (crawlers)
- Scales are controlled by oils, systemic pesticides or biological control agents such as parasitoid wasps and Coccinellid beetles
- Registered product labels

Heart-shaped Scale:

Soft-brown Scale: