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How to Use a Hand Lens

Being able to see small insects or fungal fruiting bodies up close often helps me diagnose a plant problem. Recently, I was at a tree nursery and the owner showed me scale insects on a red maple tree twig.

Updated:

July 6, 2022

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Figure 1. Magnification reveals the purple color of a Japanese maple scale. Photo: Emelie Swackhamer, Penn State

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By just looking at it, the insects looked grayish-white and appeared to be an armored scale because there was no honeydew or sooty mold. I suspected it might be a Japanese maple scale, but I wasn’t sure. So, I dug out my trusty 10X hand lens and took a closer look. Japanese maple scales overwinter as females under the scale covering. The female’s bodies are purple and so are the eggs. I used a pencil to flip some of the scale coverings over and was able to see the purple bodies underneath. Bingo! Japanese maple scale (Figure 1).

Having a hand lens allowed me to identify the problem quickly, so the grower could react to it and protect his trees. Of course, you can always confirm an insect identity by sending a sample to our Penn State insect ID expert, Dr. Michael Skvarla.

A 10X lens will allow you to see important features to identify a wide range of insects and disease signs. I use my hand lens to examine scale insects, spider mites, insect eggs, fungal fruiting bodies of needle cast disease, and many other plant problems. To see really small objects like eriophyid mites or nematodes, a dissecting microscope with optional top and bottom lighting is better than a hand lens, but I am often amazed at how much a simple 10X lens can help.

It is pretty easy to get a 10X hand lens. 20X power is nice but will probably cost a little more. You can order a hand lens from an online store and some garden centers carry them. A regular magnifying glass works well too.

To use a hand lens, I prefer to put the lens up against my face, stabilize it against the bridge of my nose and bring the plant sample in as close as needed to get it into focus (Figure 2). I always use my left eye because it is my dominant eye. I sometimes see people holding a hand lens at arm’s length and trying to see through the small glass lens from afar. That method never works well for me. If you’ve never used one, it is a good idea to practice using your hand lens so when you need its abilities, you will be ready. I like to practice looking at twigs, interesting moss, and of course, insects, and fungi!

Figure 2. Hold the hand lens up to your eye and move the plant closer until it comes into focus Photo: Clay Swackhamer

If you want more practice using your hand lens, bring it to one of our in-person pest walks this summer! We are holding pest walks at 10 sites across Pennsylvania in August and September. We will focus on insects, diseases, and weeds of ornamentals, turf, and right-of-way areas. Here is information about the schedule. I hope to see you and your hand lens there!

Landscape Pest Identification Walks in August and September 2022

These hands-on educational programs cover the identification and management of insects, diseases, and weeds affecting ornamentals plants, turfgrass, and right-of-way areas. Each location is held from 12 noon to 4:00 p.m., rain or shine. Each 1-hour session is worth two Pennsylvania pesticide recertification credits for the respective categories—Core, Cat. 05, 06, 07, 10, 18, 23, and PC. You are not required to stay for the entire four-hour event if you only want to attend one or a couple of sessions. ISA CEUs will also be available. Each location’s registration site has a detailed agenda. You may also register by calling 877-345-0691.

For grogram questions contact Emelie Swackhamer, exs33@psu.edu, 610-489-4315.