Scale are insects named for their shell-like wax casings that suck sap from plants. Scale, whiteflies, mealybugs, and aphids are a part of the superfamily Coccoidea. The most common types of scale are soft and armored. Soft scale tends to look more fluffy or gummy while armored scale is very waxy. Frank, S. (2021). Cottony maple leaf scale, Pulvinaria acericola, ovisacs on dogwood leaves. Cottony Maple Leaf Scales Producing Eggs. Retrieved February 18, 2022, from https://entomology.ces.ncsu.edu/2019/05/cottony-maple-leaf-scales-producing-eggs/. Armored scale is typically smaller than soft scale and appears flatter. This flatness can make it harder to identify on a plant. United States National Collection of Scale Insects Photographs, USDA Agricultural Research Service, Bugwood.org. (1979). Greedy scale (Hemiberlesia rapax). Retrieved February 18, 2022, from https://www.ipmimages.org/browse/detail.cfm?imgnum=5113037. A couple of key differences between the two types of scale are indicated by the following chart. Palmieri, M. (2013). Soft Scales Vs. Armoured Scales. Up to scale. Retrieved February 18, 2022, from https://www.landscapemanagement.net/up-to-scale/. Life cycle stages of scale includes egg, nymph aka crawler, and adult. The female scale insect will lay eggs underneath their scale covering. Once the egg hatches you have a nymph aka crawler. This crawler will move to a new spot to start feeding on sap. Once a crawler starts feeding, the shell will start developing and the legs disappear completely (in armored scale). It is generally understood that once a crawler picks a new spot that they do not move. Adult males are more similar in appearance to fungus gnats. Soft scale can produce asexually through a process called parthenogenesis. Armored scale usually mate sexually which requires the adult males to fly to the females. Scale has a fairly long life cycle of 3 or more months. King Quenson. (2021). Scale insect life-cycle. How to Manage the Scale Insects. Retrieved February 18, 2022, from https://www.kingquenson.com/ar/Company_News/How-to-Manage-the-Scale-Insects.html. An instar is just a phase between two distinct periods when an outer layer or covering is shed or added to. This helps to estimate the age of the scale. Held, D. (2019). Armored scale completed all three of the nymphal instars. Controlling Scale Insects and Mealybugs. The Alabama Cooperative Extension System. Retrieved February 18, 2022, from https://www.aces.edu/blog/topics/lawn-garden/controlling-scale-insects-and-mealybugs/. Scale damage on a plant can manifest in sticky honeydew (from soft scale), black sooty mold forming on honeydew, yellowing/dying leaves, and dying leaves/branches. Stevens, R. E., & Cranshaw, W. (2020). Honeydew, excreted by brown soft scale, which has collected on a nearby leaf. Brown Soft Scale – A Common Insect Pest of Indoor Plants – 5.599. Colorado State University Extension. Retrieved February 18, 2022, from https://extension.colostate.edu/topic-areas/insects/brown-soft-scale-a-common-insect-pest-of-indoor-plants-5-599/. Nature Garden. (n.d.). Mock-orange leaves covered with armored scale insects. Sooty mold, techniques and organic treatments to avoid it. Retrieved February 18, 2022, from https://www.nature-and-garden.com/gardening/sooty-mold.html. Combatting scale once it has infected a plant requires a lot of patience and continued care. Depending on the severity of scale and the cost of the plant it can be easier to just toss it. Trimming infested leaves and stems can help. If you can get your finger underneath the shell-like cover, you can usually pry the scale off of the plant. To treat scale, use a combination of neem oil and isopropyl alcohol. Apply neem oil to the whole plant once a week for the next 3-4 months. Make sure to apply it in the evening to avoid foliage burning. Use warm water and either castile or dish soap to act as an emulsifier with the neem oil concentrate. If your neem oil comes premixed do not worry about adding anything in. Concentrate: 2 cups warm water 3/4 tsp neem oil concentrate 2-3 drops of free & clear dish soap or castile soap Alcohol needs to be diluted into a spray before use on foliage. Spray the whole plant once a week for the next 3-4 months in addition to the neem oil. I would recommend using the alcohol and neem oil on different days e.g., Monday and Thursday. Alcohol spray: 1/2 cup isopropyl alcohol 70% 4 cups water Additionally, if you see any scale try using a cotton swab with alcohol on it to remove the insect. The earlier you can catch a scale outbreak among your plants the easier it will be to contain. I have personally dealt with scale on a large H. nummularioides and despite my best and constant efforts I was not able to salvage the plant. References:
Mahr, S. (n.d.). Scale insects. Wisconsin Horticulture. Retrieved February 19, 2022, from https://hort.extension.wisc.edu/articles/scale-insects/ Held, D. (2019, June 17). Controlling scale insects and mealybugs. Alabama Cooperative Extension System. Retrieved February 19, 2022, from https://www.aces.edu/blog/topics/lawn-garden/controlling-scale-insects-and-mealybugs/
0 Comments
Leave a Reply. |
Archives
March 2024
Categories
All
|