Apps for Measuring Herbivory

For iOS Users: LeafByte

Read the instructions here first, then read my notes below. Basically, you put a piece of paper with scale dots behind the leaf, take a picture, and the app does the rest. If your leaf has any damage to the edge, you can use your finger to draw in where the edge would have been, so that the missing area is estimated correctly.

The developer also has a very helpful FAQ page that is worth reading.

• My experience has been that the automatic background removal is pretty good, and should need either no tweaking or only minor tweaking on your part.

• I recommend that you print out the white-background scales that are linked in the instructions (also here), and carry them with you to place behind leaves. If you use these print-outs, LeafByte will automatically detect the scale and you will not need to worry about setting the scale. Technically, LeafByte can work without the scale dots, but it uses them to figure out what parts of the image are leaf and what parts are background. So if you don't use the scale dots, it does a poor job of identifying holes in the leaf.

  • I do not recommend using the black-background scale unless you know you need to measure an especially light-colored leaf. Most of the plants I see commonly are really not light enough to require it, and if the leaf is too dark the black background works very poorly. (note there's a setting you need to change to use the black background, see FAQs if you need this)

• LeafByte is sensitive to shadow, so try to avoid shadows around the edges or in holes. If the leaf is curling, it can help to flatten it with a clear acetate sheet (provided in your care package).

• Pay close attention to the instructions for drawing in a missing edge with your finger -- it's easy to do, and important for correctly estimating leaf area.

• When you've taken the picture, double-check that the areas it highlights as being eaten match up with your visual impression. If it isn't capturing all the holes, you need to try again with better lighting.

• When you're satisfied that the estimate is reasonable, write down the numbers that LeafByte shows you in your field book: % eaten, leaf area, and area eaten. (This is more foolproof than trying to save the data to the app.)

For Android Users: BioLeaf

BioLeaf has a very nice built-in tutorial that you can access when you install it. Basically, you put a white piece of paper behind the leaf, take a picture, and the app does the rest. If your leaf has any damage to the edge, you can use your finger to draw in where the edge would have been, so that the missing area is estimated correctly.

Download the app and work through the tutorial (it should take you < 5 min). At that point you'll be ready to rock'n'roll!

When you've taken the picture, double-check that the areas it highlights as being eaten match up with your visual impression. If it isn't capturing all the holes, you need to try again with better lighting.

When you're satisfied that the estimate is reasonable, write down the % eaten number in your field book. This is more foolproof than trying to save the data to the app.

FAQ's

I have access to both iOS and Android. Which app is better?

Both apps work perfectly well, and both are quite easy to use, so it really doesn't matter much. But if I had to choose, I'd recommend the Android app BioLeaf. It is a little bit easier to use, a bit less sensitive to shadow, and it does not require printing out scale dots. (It's true that BioLeaf does not provide absolute leaf area, but for our purposes just having % herbivory is fine.)

How should I reference this app when writing my paper?

Here are links to the primary papers describing the development and verification processes for each app. You should cite these papers just as you would any other publication (we'll be learning how to incorporate citations in class).
LeafByte
BioLeaf

What if I just can't get the app to work?

First, I think this unlikely -- I have extensively tested both apps, and I find them user-friendly and fairly foolproof. But if you do run into problems, simply take photos of your leaves against a white background, making sure that all of the herbivore damage is visible and shadows are minimal. If the leaf is curly, use a clear acetate sheet to keep it as flat as possible. Both LeafByte and BioLeaf can analyze photos saved on your phone. If the app stops working the field, you can troubleshoot the app later using those photos. If you need help troubleshooting, reach out to me.