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Scale Insects are a gardening Foe!!!!!!!!!!!!!!!!!!!!!!
Scale insects are a diverse group of small, sap-feeding pests that can cause significant damage to plants in Florida landscapes. These insects are known for their protective coverings, which can make them difficult to detect and control. They affect a wide variety of ornamental plants, trees, and shrubs commonly found in Florida gardens, often leading to issues such as yellowing leaves, dieback, secondary mold infestation, and reduced plant vitality.
Scale Insects are divided into 2 main categories - armored and soft bodied. Armored scale have, as you would imagine, a hard waxy covering that is also made up of previous cast skins. This "armor" protects the insect and a female's eggs, which are laid just under the armor. Adult armored scale generally do not move once they begin to feed. They are smaller than soft bodied scale. Lastly, they do not produce honeydew as a byproduct of their feeding on plant material.
Soft scales are different in the ways already discussed. They do still have a waxy covering, but it can not be removed, and is generally the same color as the actual insect. Soft scale females can reproduce without males, making their population number jump significantly in single growing seasons. Because they create honeydew, host plants are more likely to contract molds and potentially diseases. Honeydew also invites ants to the plant and a symbiotic relationship is formed between the two insects. The ants provide protection from predators to the scale, while the scale's honeydew feeds the ants.
Florida is home to numerous species of scale insects, but some of the most prevalent include:
Armored Scales
Species: Lepidosaphes spp., Fiorinia externa (Oleander scale), Hemiberlesia lataniae (Koch’s scale), Lepidosaphes beckii (Purple Scale), Lepidosaphes gloveri (Glover Scale), Pinnaspisas pidistrae (Fern Scale), Unaspis citri (Snow Scale),
Characteristics: Armored scales have a hard, protective shell that shields them from environmental factors and predators. Do not create honeydew. Generally, only first instars are mobile.
Host Plants: Common hosts include citrus, crape myrtle, and various palms.
Soft Scales
Species: Icerya purchasi (Cottony cushion scale), Saissetia oleae (Olive scale), Ceroplastes rusci (Fig Wax scale), Saissetia neglecta (Carribean Black Scale), Coccus hesperidum (Soft Brown Scale), Ceroplastes floridensis (Florida Wax Scale), Coccus viridis (Green Scale), Phalacrococcus howertoni (Croton-scale)
Characteristics: Soft scales lack the hard covering seen in armored scales and produce a sticky, sugary substance known as honeydew, which can encourage the growth of sooty mold.
Host Plants: Soft scales target a wide range of plants including ornamental trees, shrubs, and fruit crops like avocado and citrus.
Mealybugs
Technically mealybugs are a form of scale. But their white waxy appearance tends to make them seem like their own category. I have a whole post on mealybugs you can see by CLICKING HERE.
Scale insects feed by inserting their needle-like mouthparts into plant tissues and withdrawing sap. This can lead to several visible symptoms:
Yellowing or stippling of leaves (due to sap loss and chlorophyll degradation).
Leaf drop and premature defoliation.
Stunted growth and poor plant health.
Sooty mold growth on leaves and stems due to the honeydew excreted by soft scales.
Honeydew accumulation, which may attract ants.
Severe infestations can lead to the death of affected plants, especially when left untreated for extended periods.
Management Strategies
Cultural Practices
Pruning: Remove heavily infested branches and leaves to reduce the scale population.
Proper Plant Care: Ensure that plants are well-watered and fertilized to maintain their overall health, making them less susceptible to pests.
Monitoring: Regularly inspect plants for signs of scale insects, particularly the undersides of leaves and stems.
Biological Control
Predatory Insects: Natural enemies, such as ladybugs, mealybug destroyer larvae, lacewing larvae, and parasitic wasps (e.g., Encarsia species), can help control scale populations.
Nematodes: Soil-applied nematodes, like Steinernema spp., may target scale insect larvae in the soil.
Chemical Control
Insecticidal Soaps: These are effective against soft scales and mealybugs but must be applied directly to the insects for success. Insecticidal soaps work by breaking down the protective waxy coating of the pests.
Horticultural Oils: Oil-based treatments can smother both armored and soft scale insects, blocking their respiratory openings.
Rubbing Alcohol: We have been able to semi-successfully control soft bodied scale and mealybugs with direct application of rubbing alcohol to the insects. It is best done with a cotton ball or small paintbrush. In large infestations, this could prove to be overly time consuming. It also works only by direct contact. Any insects missed will survive the treatment.
Systemic Insecticides: Products containing imidacloprid or other systemic insecticides can be effective in controlling scale insects, particularly for trees and shrubs.
Integrated Pest Management (IPM)IPM focuses on combining various methods—biological, cultural, and chemical—to keep pest populations below damaging levels. Regular monitoring is crucial to determine the most appropriate action at the right time.
Preventing scale insect infestations requires vigilance in plant selection from nurseries. Ensuring the introduction of pest-free plants, especially in nurseries and garden centers, can significantly reduce the risk of scale insect establishment. Furthermore, promoting biodiversity by planting a variety of species can limit the impact of a single pest. Higher biodiversity attracts more insects to the garden. This may seem like a bad thing. But, beneficial predators will be attracted to the garden to help take care of the unwanted gardening foes. This is free pest management.
In the future, research into more targeted biological control agents, like parasitoid wasps or entomopathogenic fungi, offers hope for more sustainable management practices. Additionally, developing resistant plant varieties could be another step toward reducing the prevalence of scale insects in Florida landscapes.
Resources:
https://edis.ifas.ufl.edu/publication/CH195
https://mrec.ifas.ufl.edu/lso/entomol/ncstate/scaleint.htm