Garden Detective

What’s bugging his sage?

Garden Detective: What’s causing the holes in these sage leaves? The most likely culprits: Snails (or slugs), caterpillars and katydids.
Garden Detective: What’s causing the holes in these sage leaves? The most likely culprits: Snails (or slugs), caterpillars and katydids.

Experts tackle readers’ garden questions.

Q: Help! Something is eating my sage and I can’t figure out what it is. Any advice on how to get rid of this problem?

Patrick Harris, Sacramento

Sacramento “Bug Man” Baldo Villegas: I would like to ask all kinds of questions to Patrick about the pictures that he sent. However, without having information to go by, the damage that I see on the sage might be due to three types of critters: Snails and/or slugs; caterpillars; or katydids (also known as longhorned grasshoppers). My guess is in that order.

Here are more details about each.

Snails and slugs: They usually feed at night and are common in areas that are shady and humid. Go out in the evening and see if you see any sign of these critters. These two animals “walk” with their stomachs and they are called gastropods. They usually leave behind a slime trail that is silvery in appearance, especially on the underside of the leaves. An easy fix is to put some snail/slug baits such as “Sluggo,” which contains iron phosphate – a fertilizer that stops snails and slugs quickly. Sprinkle some of the granules around the sage and check the following day; likely, you will see dying individuals.

(Editor’s note: Be careful using snail bait around pets. Metaldehyde, a common ingredient in many snail baits, is poisonous to dogs. Sluggo uses pet-friendly iron phosphate instead of metaldehyde as its active ingredient. Any uneaten bait will degrade and become part of the soil.)

Caterpillars: There are many types of caterpillars; most will blend with the foliage and be hard to see. What I do is I shake the plants and I look for anything that falls down in the soil. If they are green or brownish, you will be able to see them very clearly.

If you see caterpillars, then just pick them off and put them in a jar with soapy water – problem solved. I usually squish them and don’t bother about the soapy water.

Katydids: These longhorned grasshoppers are generally green. They love the new leaves. The nymphs or immature katydids are usually very hungry and they will eat anything that is green if they are hungry and their favorite host plants are not around. They love citrus and roses!

Do the same thing I described for caterpillars. Look for anything that jumps from one stem to another. The adult katydids do fly, so look for flying critters as well. I usually catch them and squish them, but you can drop them in soapy water.

I do not like to use pesticides if I can help it. I generally like to remove the damaging pest out of the garden physically or use the least toxic manner available to combat it.

Baldo Villegas is a retired state entomologist and master consulting rosarian.

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