Welcome, fellow cactus and succulent enthusiasts! Today we’re going to talk about a common pest that affects many of our beloved plants – scale insects. These small, sap-sucking insects can cause significant damage to cacti and succulents if left untreated. They can cause the yellowing of leaves, leaf drops, and even plant death in rare cases.
Understanding how to identify, treat, and prevent scale insect infestations is vital for maintaining the health and vitality of your cacti and succulents. This article will provide you with all the information you need to protect your plants from these pesky pests. So, let’s get started!
Scale Insect Identification
Scale insects (Coccidae) are small, usually about 1/8 to 1/4 inch in size, and can be found on the stems and leaves of cacti and succulents. They are typically oval or circular in shape and can be found in a variety of colors, including brown, gray, black, or white. They can be difficult to spot as they often blend in with the plant’s color. Most species of scales have waxy or armored coverings, solidifying to form fish-like “scales,” hence the name. They are immobile and often appear as small bumps on the plant.
Not all bumps on a cactus or succulent are scale insects, as some cacti and succulents have natural bumps or growth patterns. Therefore, it’s important to pay attention to any changes in the appearance or health of your plant, as well as to look out for the other symptoms of scale infestation, which will be discussed in the next section.
Types of Scale Insects
Scale species can vary in terms of their appearance, behavior, and the types of plants they infest. However, they are usually divided into two main types.
- Armored scales: These insects have a hard, protective shell or “scale” covering their bodies. They do not have a visible body and live under the protection of their own scale. Examples include the Euonymus scale, Oystershell scale, Pine needle scale, and San Jose scale.
- Soft scales: These insects have a softer, waxier covering on their bodies and can often be seen with the naked eye. They can secrete a honeydew substance that can attract ants and sooty mold. Examples include the Brown soft scale, Cottony maple scale, European elm scale, Fletcher scale, and Magnolia scale.
Mealybugs are actually also a type of scale insect (family Coccoidea), but they’re distinct enough in their appearance and required treatments that they’re usually treated as a separate group.
Life Cycle of Scale Insects
Scale insects have a relatively simple life cycle, which typically consists of four stages: egg, crawler, nymph, and adult.
- Egg: Scale insects begin their life cycle as eggs, which adult females lay. These eggs are usually small, round, and difficult to spot. They are typically laid on the leaves or stems of plants and can be found in clusters or singly.
- Crawler: Once the eggs hatch, the insects enter the crawler stage. This is a mobile stage, where the insects are able to move around the plant and find a suitable feeding site. Crawlers are usually small and can be yellow, white, or brown in color.
- Nymph: After the crawlers find a feeding site, they will settle down and begin to feed. At this stage, they are called nymphs. They insert their mouthparts into the plant and begin to feed on the sap. As they feed, they will grow and molt, shedding their skin as they grow.
- Adult: Once the nymphs have completed their growth, they will enter the adult stage. At this stage, the insects will fully mature and have reached their final form with antennae. Adult scale insects are usually immobile and are characterized by the protective covering or waxy coating on their bodies. They will continue to feed on the plant foliage of the host plant and reproduce, laying eggs to begin the cycle again.
Symptoms of a Scale Insect Infestation
Scale infestations can cause a variety of symptoms in cacti and succulents. Some of the most common symptoms to look out for include the following:
- Yellowing or discoloration of leaves: Scale insects feed on the plant sap, which can cause the leaves to turn yellow or discolored.
- Leaf drop: Heavy infestations can cause leaves to drop prematurely.
- Sticky residue on leaves or branches: Scale insects excrete honeydew, which can attract ants and create a breeding ground for sooty mold.
- Slow growth or stunted growth: Scale insects can drain a significant amount of energy from a plant, which can inhibit its growth.
- Black or sooty mold growth: This leftover fungus from honeydew is a good indicator of the presence of scale insects.
Not all these symptoms are specific to scale infestation and may be caused by other factors such as disease, under-watering or over-watering, or environmental stress. Therefore, it’s important to pay attention to any changes in the appearance or health of your plant and to look out for other signs of scale infestation.
Treatment options for Scale Insects
Scale infestations can be a bit tricky to treat, but with the right approach, you can effectively control and eliminate these pests from your cacti and succulents. There are two main types of treatment options: chemical and natural.
- Horticultural oil: This oil is sprayed onto the leaves of plants to suffocate and kill scale insects. It works by smothering the insects and their eggs and can also help control other types of pests, such as spider mites and aphids.
- Insecticidal soap: This is mixed with water and sprayed onto plants to control scale insects. It works by penetrating the insects’ protective wax coating and disrupting their cell membranes, causing them to die.
- Neem oil: This is extracted from the seeds of the neem tree and has insecticidal properties. It works by disrupting the insects’ hormone systems, which can prevent them from reproducing and feeding.
- Rubbing Alchohol: When applied to a plant surface, this solution kills most pests on contact.
- Dish Soap: An easy option is to simply use a spray bottle and fill it up with soapy water or dish soap and spray the leaves of your houseplant with it.
- Biological control: This involves introducing natural enemies or parasites of scale insects to control the infestation. For example, ladybugs and lacewings eat scale insects, and parasitic wasps and nematodes can also be used to control scale insects.
Usually used as a last resort, chemical treatments (insecticide or pesticide) can be highly effective in controlling scale insect infestations, especially when used in combination with other control methods. They can provide quick results, which can be beneficial in cases where the infestation is severe, or the plants are under stress. In addition, they are widely available and easy to use, which makes them accessible to many people.
However, they are not selective and can harm other beneficial insects and microorganisms in the soil. And overuse or misuse of systemic insecticide can lead to the development of resistant populations of scale insects, making it harder to control them in the future.
Preventing scale infestations is key to keeping your cacti and succulents healthy and pest-free. Some of the best practices for preventing scale insect infestations include:
- Regularly inspecting your plants: Regularly inspecting your plants can help you catch scale infestations early, before they become a major problem. Pay attention to any changes in the appearance or health of your plants, and look out for the common symptoms of scale infestations.
- Quarantine new plants: Before introducing new plants to your collection, it’s a good idea to quarantine them for a few weeks. This will give you a chance to inspect them for any signs of pests or diseases and to treat them before they have a chance to spread to your other plants.
- Maintaining healthy plants: Healthy plants are less likely to be affected by pests and diseases. Be sure to provide your plants with the proper light, water, and nutrients they need to thrive.
- Keep the environment clean: Cleaning the environment regularly can help prevent scale infestations. Remove any fallen leaves, debris, or other plant material from around your cacti and succulents, as this can provide a breeding ground for pests.
- Use natural predators: Scale insects have natural predators such as ladybugs, beetles, and lacewings, consider introducing these beneficial insects to your garden to help control the population of scale insects.