Scale insect infestations refer to the presence of scale insects, small, sap-sucking insects, on the leaves, branches, and stems of plants. Scale insects are known for their hard or soft protective shells that cover their bodies and for excreting a sticky residue called honeydew.
Symptoms
- Sticky residue or honeydew on the leaves, branches and surrounding surfaces: Scale insects excrete a sticky residue called honeydew, which can attract ants and cause the growth of sooty mold.
- Discoloration or yellowing of leaves: Scale insects can cause leaves to turn yellow or brown as they feed on the sap of the plant.
- Wilting or stunted growth: Scale insects can cause plants to wilt or stunt as they feed on the sap and weaken the plant.
- Presence of scales on the leaves and branches: Scale insects can be seen as small, round or oval-shaped bumps on the leaves and branches of the plant.
- Black sooty mold: Scale insects can attract ants that feed on the honeydew, and this can lead to the growth of black sooty mold on the leaves and branches of the plant.
- Brittle or distorted leaves: Scale insects can cause leaves to become brittle or distorted as they feed on the sap of the plant.
- Crawling nymphs: Scale insects have crawler stage nymphs that are mobile and can be seen moving around on the plant.
- Infestation can be heavy and can cause severe damage to the plants and even death if not treated in time.
It’s important to note that the symptoms of a scale insect infestation can vary depending on the specific type of scale and the plant it is infesting, and can be similar to other pest or disease symptoms.
What is a Scale Insect
Scale insects are small, oval or round insects that are usually less than 1/8 inch long. They can be difficult to spot because they are often found on the undersides of leaves and on the stems of plants. The appearance of scale insects can vary depending on the species and the stage of their life cycle. Some common characteristics of scale insects include:
- Hard or soft shells: Some scale insects have hard, protective shells that cover their bodies, while others have a softer, more flexible covering.
- Coloring: Scale insects can be various colors, including brown, yellow, gray, or white.
- Shape: Scale insects can be oval or round in shape.
- Size: Scale insects are small, usually less than 1/8 inch long.
- Sticky residue: Scale insects excrete a sticky residue called honeydew that can attract ants and cause the growth of sooty mold.
- Nymphs: Scale insects have nymphs that are crawlers, those are mobile, and can be seen moving around on the plant.
It’s important to note that many types of scales can look similar and can be difficult to identify without a microscope. It’s also important to consult an expert to identify the specific type of scale and to know how to deal with them.
Treating Scale Insect Infestations
There are several ways to deal with scale insects, including:
- Physical removal: Scraping off the scales by hand or with a soft brush can be effective for small infestations.
- Horticultural oil: This is a type of oil that smothers the scales and can be used to control light infestations. It’s important to make sure that the oil you use is labeled as safe for use on the plant you are treating.
- Insecticidal soap: This is a soap-based pesticide that can be used to control light infestations. It works by breaking down the scales’ protective waxy coating.
- Neem oil: This is derived from the neem tree and can be used as a natural pesticide to control scale infestations.
- Pesticides: There are several pesticides that can be used to control scale infestations, including imidacloprid, dinotefuran, and pyriproxyfen. These are to be used as a last resort. It’s important to carefully read and follow the instructions on the pesticide label and to make sure that the pesticide is safe to use on the specific plant you are treating.
- Biological control: Some natural predators such as ladybugs, lacewings, and parasitic wasps can be introduced to control scale populations.
It’s important to keep in mind that some of these methods may not be effective in certain cases or on certain types of scales. Consultation of an expert or entomologist is advised before taking any action. Additionally, it’s important to prevent future infestations by keeping plants healthy and avoiding overcrowding.
Physical Removal Methods
Physical removal of scale insects can be an effective method for controlling small infestations. Here are a few ways to physically remove scale insects:
- Pruning: Cut off and dispose of any heavily infested branches or leaves.
- Scraping: Use a small, sharp tool, such as a credit card or a toothbrush, to scrape off the scales from the stems and leaves of the plant. Be sure to scrape the undersides of leaves as well as the tops.
- Washing: Use a strong stream of water to wash off the scales from the plant. This method is particularly effective for controlling crawler stage of scales.
- Dabbing: Use a cotton swab or a soft toothbrush dipped in rubbing alcohol to gently dab the scales on the plant. This method is particularly effective for controlling soft scales.
It’s important to be careful not to damage the plant while removing the scales, and to repeat the process as needed to ensure that all of the scales have been removed. Keep in mind that physical removal may not be enough to control heavy infestations and may need to be combined with other methods such as horticultural oil, insecticidal soap, or neem oil. Also keep an eye out for the scales’ crawler stage, as they are mobile and can move around on the plant, spreading the infestation.
Horticultural Oil
Horticultural oil is a type of oil that can be used to control scale insect infestations. Here are the steps to use horticultural oil to control scale insects:
- Choose an oil labeled as safe for use on the specific plant you are treating. Some common types of horticultural oil include mineral oil, neem oil, and canola oil.
- Check the weather forecast. Do not spray when the temperature is above 90 F or when the humidity is high. It is also best to avoid applying horticultural oil on hot, sunny days, as it can cause leaf burn.
- Mix the oil with water according to the label instructions. Most horticultural oils need to be mixed with water at a ratio of 2-3% (2-3 tablespoons per quart of water)
- Apply the oil solution to the plant using a sprayer. Be sure to cover the entire plant, including the undersides of the leaves, where scale insects are often found.
- Repeat the treatment as necessary. Some scales have multiple generations in one year and some can have overlapping generations. Repeat the treatment every 7-10 days until the scales are gone.
- Be aware that horticultural oil can also harm beneficial insects and mites, so it’s important to avoid applying it during times when these organisms are active.
It’s important to note that horticultural oil can be toxic to some plants, so it’s important to read the label carefully and to test the oil on a small, inconspicuous area of the plant before treating the entire plant. Additionally, it’s recommended to use an Integrated Pest Management (IPM) approach, which includes using a combination of different control methods such as cultural, physical, biological and chemical methods to manage the scale insects populations.
Insecticidal Soap
Insecticidal soap is a soap-based pesticide that can be used to control scale insect infestations. Here are the steps to use insecticidal soap to control scale insects:
- Choose an insecticidal soap labeled as safe for use on the specific plant you are treating.
- Check the weather forecast. Do not spray when the temperature is above 90 F or when the humidity is high. It is also best to avoid applying insecticidal soap on hot, sunny days, as it can cause leaf burn.
- Mix the insecticidal soap with water according to the label instructions. Most insecticidal soaps need to be mixed with water at a ratio of 2-3% (2-3 tablespoons per quart of water)
- Apply the soap solution to the plant using a sprayer. Be sure to cover the entire plant, including the undersides of the leaves, where scale insects are often found.
- Repeat the treatment as necessary. Some scales have multiple generations in one year and some can have overlapping generations. Repeat the treatment every 7-10 days until the scales are gone.
- Be aware that insecticidal soap can also harm beneficial insects and mites, so it’s important to avoid applying it during times when these organisms are active.
It’s important to note that insecticidal soap can be toxic to some plants, so it’s important to read the label carefully and to test the soap on a small, inconspicuous area of the plant before treating the entire plant. Additionally, it’s recommended to use an Integrated Pest Management (IPM) approach, which includes using a combination of different control methods such as cultural, physical, biological and chemical methods to manage the scale insects populations.
Neem Oil
Neem oil is a natural pesticide that can be used to control scale insect infestations. Here are the steps to use neem oil to control scale insects:
- Choose a neem oil labeled as safe for use on the specific plant you are treating.
- Check the weather forecast. Do not spray when the temperature is above 90 F or when the humidity is high. It is also best to avoid applying neem oil on hot, sunny days, as it can cause leaf burn.
- Mix the neem oil with water according to the label instructions. Most neem oils need to be mixed with water at a ratio of 2-3% (2-3 tablespoons per quart of water)
- Apply the neem oil solution to the plant using a sprayer. Be sure to cover the entire plant, including the undersides of the leaves, where scale insects are often found.
- Repeat the treatment as necessary. Some scales have multiple generations in one year and some can have overlapping generations. Repeat the treatment every 7-10 days until the scales are gone.
- Be aware that neem oil can also harm beneficial insects and mites, so it’s important to avoid applying it during times when these organisms are active.
It’s important to note that neem oil can be toxic to some plants, so it’s important to read the label carefully and to test the oil on a small, inconspicuous area of the plant before treating the entire plant. Additionally, it’s recommended to use an Integrated Pest Management (IPM) approach, which includes using a combination of different control methods such as cultural, physical, biological and chemical methods to manage the scale insects populations.
Pesticides
Pesticides can be used to control scale insect infestations, but it’s important to use them with caution. Here are the steps to use pesticides to control scale insects:
- Choose a pesticide labeled as safe for use on the specific plant you are treating and for the specific type of scale insects you have. Some common pesticides for scale insects include imidacloprid, dinotefuran and pyriproxyfen.
- Read the label carefully and follow the instructions for mixing and applying the pesticide. Make sure to wear protective gear such as gloves, goggles and mask, as per the instructions.
- Apply the pesticide according to the instructions, using a sprayer or a duster. Be sure to cover the entire plant, including the undersides of the leaves, where scale insects are often found.
- Repeat the treatment as necessary. Some scales have multiple generations in one year and some can have overlapping generations. Repeat the treatment as per the instructions on the label, usually after 7-10 days.
- Be aware that pesticides can also harm beneficial insects and mites, so it’s important to avoid applying it during times when these organisms are active.
It’s important to use pesticides only as a last resort and to carefully read and follow the instructions on the pesticide label to minimize any potential risks. Additionally, it’s recommended to use an Integrated Pest Management (IPM) approach, which includes using a combination of different control methods such as cultural, physical, biological and chemical methods to manage the scale insects populations. It’s also important to monitor the plant after the treatment to see if the infestation is under control, and if not, consult with an expert for further advice.
Biological Control
Biological control is the use of natural predators, parasites, or pathogens to control scale insect infestations. Here are the steps to use biological control to manage a scale insect infestation:
- Identify the specific type of scale insect infestation you have. Different natural enemies are effective against different types of scales.
- Research the natural enemies of the specific scale species you have. Some common natural enemies of scale insects include ladybugs, lacewings, parasitic wasps, and predatory mites.
- Purchase or obtain the natural enemies from a reputable supplier. Make sure they are the correct species for the scale infestation you have.
- Release the natural enemies into the infested area according to the supplier’s instructions.
- Monitor the infestation to ensure that the natural enemies are effectively controlling the scale population.
- Repeat the release of natural enemies as needed until the scale population is under control.
It’s important to note that biological control can be less effective in certain cases, such as when the infestation is heavy, or when the natural enemies are not well adapted to the specific area or environment. Additionally, the effectiveness of biological control can be reduced by the use of pesticides, so it’s important to avoid using pesticides when using biological control. Consultation of an expert or entomologist is advised to determine the most effective methods for controlling scale infestations in your area, including the use of different types of natural enemies.