Soft Scales and How to Treat Them

 

The purpose of this article is to educate you about soft scale insects and how it's best to treat them. I know most people want to call an arborist or a pest control company to come spray their trees once and be done with it. I get that, but it probably won’t work. It takes persistence over multiple weeks in the spring, and may need to be treated over several years as annual maintenance. 

 

The bad news is that if you ignore the problem, you risk extensive dieback and tree death. Also, hiring someone else to do the job right can be costly and require repeat visits.

 

The good news is the products and equipment needed to do it yourself are relatively cheap, and it's easy enough if you know what to do. The focus of this video is how to spray your trees with organic pesticides and how to remove these insects from your trees by hand.

 

Before I get into it, I think the best way for you to begin is to schedule a consultation with me and I can help you make a plan based on your expectations and budget. I can also point out a lot of little things that cause poor tree health and make your trees more attractive to scales. If you think you can manage it by yourself, I hope this video helps.

 

What is it?

 

Soft scale is an insect. It’s a pest of trees and shrubs, and it's becoming a big issue around parts of Reno and Sparks this year. Most people don’t realize it’s an insect because it doesn’t really look like one. 

 

I started seeing it a few years ago, but this year it seems to have gotten worse. At this time, the scale causing the most problems in Reno is believed to be Kuno scale, but European Fruit Lecanium scale or Oak Lecanium scale may also be present.

 

After hatching, it spends a few weeks as a crawler and then picks a spot to remain fixed for the rest of its life, and begins to grow a protective covering while feeding on the sap of your tree. This causes unsightly and sticky sap dripping we call honeydew. I can attract ants and sooty mold.

How bad is it?

 

A small amount of scale won’t hurt your trees. You can tolerate having some on your trees each year. Removing all of them is not necessary, but you need to reduce their populations. They hurt your trees by sucking the sap. You’ll first notice thinning foliage. Leaves will be smaller, curled, or fall off. Then, branches will die back. In the worst cases, trees can die completely.

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Treatment

 

For treatment, most people first ask, “what do I spray?” I’ll get to that. But first, know that using pesticides is just one of the ways of controlling these pests, and it's not always the most effective method. For example, a more effective method for controlling soft scales is removing them by hand. But on larger trees this isn’t very practical, so spraying is also necessary. Timing is important so you’ll also want to monitor for crawlers using sticky tape. In general, you’ll want to use both methods whenever possible.

 

Spraying

 

Protecting your trees from soft scales is difficult. Since it primarily affects flowering and fruiting trees, it’s not safe to use synthetic insecticides, contact or systemics. These types of pesticides are extremely toxic to birds and pollinators. It’s recommended to use only horticultural oil or insecticidal soap, and both of these products need to make direct contact with the recently hatched scale crawlers to kill them. And the crawlers are only present for a short time in the spring before they start to mature and become resistant to spraying.

 

Equipment

 

For trees less than 10’ tall, I recommend buying a 1 gallon handheld pump sprayer like this one from Lowe’s or somewhere else. They only cost about 15 dollars. 

 

For trees up to 20’ tall or so, I recommend the M6 six-gallon battery-powered backpack sprayer from a company called MY4SONS. You can order them online and they custom build them. If you already have power tools from Dewalt, Milwaukee, Kobalt, etc., they can even install a compatible battery receiver so you can use the batteries you already have. I have mine set up for Kobalt batteries. You’ll also want to get their 14’ spray telescope. This lets you easily spray up to 20 feet or more. 

 

Pesticides

 

For insecticidal soap, buy the concentrate, not the ready-to-use (RTU) that comes prediluted. The concentrate will require mixing, but you'll save money, and you'll be able to mix it at a more concentrated amount that will be more effective. I recommend the safer brand or the southern ag brand if you have a regular residential property. If you’re managing a large property or many properties, you’ll save money buying M-Pede in a larger quantity. If you have hard water, it won’t mix properly. Buy gallons of distilled water from any grocery store.

 

Monitoring

 

Since spraying is only effective for a narrow window in the spring when recently hatched crawlers are active, you'll want to monitor for crawler activity to know when to spray. Use any light-colored tape and wrap it around 2-3 infested branches to create a 5”’ long sticky band trap. Check them daily or every few days. Use a 10x hands lens or use your phone if you have a good zoom lens. 

 

Mechanical Removal

 

If your trees are small enough that you can reach all or most of the affected branches, I highly recommend removing them by hand wearing gloves, which we call mechanical removal. I use chemical resistant gloves with a long cuff, but you could also use regular dishwashing gloves too. It helps if you spray them first to weaken or loosen them. You can use plain hose water, horticultural oil, or insecticidal soap. If you use oil or soap, you should wear gloves. This method is gross and tedious, but it works and your trees will appreciate the immediate relief. 

 

If your trees are too large or tall for this mechanical removal, then you should still remove the insects you can reach, but you’ll mostly have to rely on spraying. 

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Equipment Needed

 

1 gallon handheld sprayer

M6 six-gallon battery backpack sprayer from MY4SONS

Batteries for backpack sprayer

14’ spray telescope from MY4SONS

Monterey Horticultural oil

Safer Brand Insecticidal soap concentrate

Southern Ag Insecticidal soap concentrate

Distilled water

Measuring spoon

Chemical-resistant gloves or dishwashing gloves

White electrical tape or masking tape

10x hand lens