Cottony Cushion Scale: Essential Facts and Insights Simplified

Cottony Cushion Scale (Icerya purchasi) is an invasive pest that has long been a problem in the United States. Originally a pest of citrus plants in California, this scale insect has expanded its reach to feed on various ornamental plants such as Nandina, Euonymus, Boxwood, and Rose source. It is essential for gardeners, farmers, and horticulturists to be aware of Cottony Cushion Scale and its impact on plants.

Easily identifiable by their unique appearance, female Cottony Cushion Scales are rusty red with black legs and antennae, measuring around 4.5mm in length source. The males are smaller, around 3mm long, with a slender, reddish-purple body and metallic blue wings. Males also differ from females in that they have piercing and sucking mouthparts. The scale gets its name from the white, cotton-like wax it secretes when molting source.

As the Cottony Cushion Scale infests a plant, it can severely impact the overall health of the plant, often leading to stunted growth and even death. Thankfully, there are natural enemies like the vedalia beetle (Rodolia cardinalis) that help control the scale population. Both adults and larvae of these beetles feed on all stages of Cottony Cushion Scale, keeping their numbers in check source.

Overview of Cottony Cushion Scale

What Is Cottony Cushion Scale?

Cottony cushion scale (Icerya purchasi) is a pest that affects various plants, including citrus trees. Female cottony cushion scales are rusty red with black legs and antennae, measuring about 4.5mm long, while males are smaller (3mm) and reddish-purple with metallic blue wings. These pests have piercing/sucking mouthparts which can cause damage to plants.

Some key characteristics of cottony cushion scale are:

• Rusty red color in females
• Slender and reddish-purple appearance in males
• Cottony egg sac secreted by females

Icerya Purchasi Life Cycle

The life cycle of Icerya purchasi consists of several stages:

1. Egg: Females lay 600-800 eggs within a cottony egg sac. Hatching can take a few days in summertime or up to 2 months in winter.
2. Crawler: Newly hatched nymphs are red with dark legs and antennae. At this stage, they feed on plant tissues.
3. Mature nymph and adult: The nymphs molt several times, leaving behind white, cottony molting skins. As they become adults, individuals differentiate into either female or male.

In summary:

The presence of cottony cushion scale on plants can be harmful, so proper management and control measures should be taken to protect them.

Damage Caused by Cottony Cushion Scale

Symptoms on Leaves and Twigs

Cottony cushion scale, a pest native to Australia, causes damage to various plants, including citrus trees and ornamentals ¹. Symptoms include:

• Leaves: Curling, yellowing, and dropping off
• Twigs: Stunted growth and dieback

Fruit and Crop Damage

When cottony cushion scale infests fruit crops, it causes:

• Reduced fruit size and quality
• Deformed growths on fruit surfaces
• Premature fruit drop

This can directly impact crop yields and decrease market value.

Infestations and Dieback

Infestations of cottony cushion scale lead to several issues in the affected plants:

• High honeydew production: The scale insects excrete honeydew, which attracts ants and encourages sooty mold growth on leaves and fruit.
• Dieback: Due to their feeding on plant sap, heavy infestations can cause twig and branch dieback, and eventually lead to plant death.

Early detection and management of cottony cushion scale is crucial to minimize the damage caused to plants.

Biological

Cottony Cushion Scale Management and Monitoring

Monitoring Techniques

To manage Cottony Cushion Scale effectively, it’s crucial to monitor their population. These are some techniques:

• Visual inspection: Examine the plant’s twigs and branches for egg sacs, nymphs, and adults. Keep an eye out for white, cottony masses.
• Crawlers monitoring: Watch out for the nymphs, which are red with dark legs and antennae. They hatch within a few days in summer and up to 2 months in winter.

Sanitation and Pruning

Practicing sanitation and pruning can help control the scale population:

• Prune infested branches: If infestations are limited to specific parts of the plant, remove them to prevent spreading.
• Increase canopy exposure: In hot climates, pruning canopies open can reduce scale populations by exposing them to heat and parasites.

Cooperative Extension Resources

For more assistance and best practices, Cooperative Extension services are available to provide support and guidance. Reach out to your local county extension office for personalized advice on managing Cottony Cushion Scale in your area.

Interaction with Other Species and Environmental Factors

Ants and Honeydew

Cottony cushion scales secrete a sugary substance called honeydew. Ants are attracted to this honeydew, and they protect the scale insects from predators.

Some examples of these predators are:

• Ladybugs
• Green lacewings

Sooty Mold and Defoliation

The honeydew also promotes the growth of sooty mold. This black fungus affects plant aesthetics and can suppress plant growth. Defoliation may occur in heavily-infested plants.

Temperature and Reproduction

Reproduction in cottony cushion scales is influenced by temperature. Egg hatching may take a few days in summer, but up to 2 months in winter. Warmer temperatures accelerate their lifecycle.