The cottony cushion scale, Icerya purchasi , poses a challenge to crops in many tropical and subtropical regions, particularly on citrus. Find out how to identify this mealybug, understand its lifestyle, and most importantly, how to effectively combat it using biological solutions.
What is cottony cushion scale?
Native to Australia, the cottony cushion scaleg, scientifically known as Icerya purchasi , is a large scale insect of the Margarodidae family. Its accidental introduction to California in the 19th century caused considerable damage to citrus crops, marking the beginning of its reputation as a pest.
Due to trade, this species has now spread widely in tropical and subtropical regions. It can also appear in greenhouses in temperate zones , where favorable conditions allow it to proliferate.
Morphology
Adult female are up to 10 mm long and oval in shape. Their reddish -brown bodies are covered in a white, granular wax that provides natural protection. These females produce a white ovisac, a waxy sac that contains the eggs, and can reach 1 cm in length.
Unlike females, males, which are rarer, are small, yellowish, and have wings that allow them to migrate from one plant to another to fertilize females.
The larvae are initially red and oval, but they quickly become covered with a thin white waxy layer as they develop.
Reproduction and life cycle of Icerya purchasi
Each year, thecottony cushion scale can produce between two and four generations , which promotes rapid population multiplication. The females, hermaphrodites, have the ability to self-fertilize in the absence of males, a mechanism that allows them to maintain their presence even in unfavorable conditions.
An adult female can lay more than 500 eggs in two to three months. These eggs, which are bright red in color, are protected in an ovisac made of wax. Fertilized eggs give rise exclusively to females.
After hatching, the young larvae, initially mobile, move towards the leaves to feed before gradually migrating to the branches, where they reach maturity.
Prolonged periods of drought or the reduction of natural predators promote significant infestations and make the management of this pest more complex.
What are the host plants of the cottony cushion scale?
The Australian mealybug attacks a wide variety of plants, including:
- Citrus fruits (Citrus)
- The mango tree
- Acacias (Acacia spp.)
- Casuarinas (Casuarina spp.)
- Pittosporum (Pittosporum spp.)
- The brooms
- Mimosas
- The rose bushes
Do you need a solution for cottony cushion scale?
Damage caused by the cottony cushion scale
This scale insect feeds on plant sap , weakens trees and causes shoots to dry out, leaves to fall and the bark to become deformed. These injuries sometimes reveal oozing , a sign of an advanced attack.
A common side effect of infestation is the production of honeydew, a sugary substance that promotes the development of sooty mold . This black coating on the foliage reduces photosynthesis.
Ants , attracted by the honeydew, also make the situation worse by protecting the scale insects from natural predators .
Prevention and biological control of the cottony cushion scale
To effectively combat the cottony cushion scale, several practices can be adopted:
- Preserve natural plant cover in orchards to maintain a habitat favorable to predators.
- Introduce natural predators, such as the Australian ladybird Rodolia cardinalis , to control scale populations.
- Plant with suitable spacing to ensure good sunlight and reduce areas prone to infestations.
- Prune trees regularly to limit the spread of the infestation.
- Reduce chemical interventions in order to preserve the natural enemies of the cochineal.
Agrobiotop solutions against the cottony cushion scale
At Agrobiotop, we design natural treatments and solutions for the control of garden pests, such as cottony cushion scale. Do not hesitate to contact us for any treatment protocol. Here are our recommended products:
Biostimulants
Physical barrier action against crop pests
- CHITOPROTECT (Basic substance)
- Chitosan
- BENTOBIO (Physical barrier action against pests)
