- Author: Paula Pashby
I have been trying to take really good care of all my plants this summer, doing all the things that they should like. The plants look healthy, but many have different types of leaf damage.
The main culprits are Whiteflies, Harlequin Bugs, Earwigs, and Slugs/Snails.
The damage may look similar, and this is just a starting point, so here are a few tips on identifying which bug is causing what type of damage.
Whiteflies
Whiteflies can seriously injure plants by sucking juices from them, excrete sticky honeydew, and cause yellowing or death of leaves. Outbreaks often occur when natural biological control is disrupted! (ie pesticides that kill beneficial garden insects)
Biological Control: Spiders, lacewings, ladybugs, big-eyed bugs, praying mantis
Harlequin Bugs (a type of stink bug)
Injures the host plants by sucking the sap of the plants. Damage on leaves and stems looks like uneven discolored spots around a hole. Young plants may wilt, turn brown, and die. Mature plants may survive but growth is slowed. Damage on fruits such as squash, tomatoes, and okra appear as dark holes surrounded by bumps, pits, or white-yellowish spots.
Biological Control: Parasitoid Wasps, minute pirate bugs, praying mantis
Earwigs (often called Pincer bugs)
Leaves appear jagged and full of holes. Plants become ragged overnight, and some leaves will only be partially eaten.
Most Effective Biological Control: Tachnid Flies
Slug/Snail
Large, ragged holes in tender leaves and flowers. Traces of slime on chewed leaves or along the ground. Seedling leaves one with only a small stem remaining.
Biological Control: Parasite Wasps
Leafcutter Bee (these are good guys)
Leafcutter bees cut the leaves of plants for forming nest cells and rarely destroy plants. They are very beneficial to the garden! The cut looks like a crescent or almost perfectly circular shaped hole on the outer edge of the leaf.
What about pesticides?
- Choose products that are least harmful to natural enemies—such as insecticidal soaps and oils—and combine their use with the other practices listed above.
- Good coverage, including the underside of leaves, is essential. Repeat applications might be required.
- Avoid using pesticides if natural enemies are present.
Sources:
Good Bugs, Bad Bugs: Jessica Walliser, Copyright 2001
Garden Insects of North America: Whitney Cranshaw and David Shetlar, Copyright 2018