Staying Ahead of Garden Pests

How to Identify and Deal With Common Garden Pests

Jun 28, 2018
Red Aphids

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Normally I don’t go looking for trouble, but it is the best way to head off potential problems in the garden. Keep your eyes open when you are weeding and you may be surprised by the kinds of pests you find. Look for telltale signs like holes in leaves, egg masses, and webs.

Scouting for Pests

Leaf miners tunnel between leaf layers in chard, spinach, lamb’s quarters, and beet greens leaving a light green meandering trail behind. Often you don’t notice them until you cook up the greens and find a lot of tiny worms. Yuck!

Cutworms are one of the many critters that do their dastardly deeds at night. In the morning you’ll find plants chewed off at the soil line leaving only stubs behind.

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Sometimes if you dig around the base of the plants you’ll find a fat cutworm sleeping it off and you can remove him from the premises in any way you choose.

Another nighttime visitor is the slug. If large ragged holes are appearing in your hostas and petunia leaves, the slugs have been dining there. The only tip they leave are the silvery trails of dried mucus they slid out on.

We’ve all seen green aphids on plants in the springtime, but every summer we get a crop of red aphids on our heliopsis plants.

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They are easy to dislodge with a strong spray of water and usually don’t come back.

I love my swallowtail butterflies, but after hosting about 20 of their caterpillars, my dill patch is looking pretty ragged.

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Hopefully, it will have time to spring back before the cukes are ready to pickle.

Beetlemania

My sweet potatoes and morning glories share a pest, the tortoise beetle.

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It has a hard shell and quietly rasps round holes in the leaves. Sometimes I find a few on the tomatoes and eggplants. In the past we have had the golden tortoise beetle which looks like it has been gilded with gold leaf—very shiny and too pretty to kill.

Flea beetles are tiny black hoppers that eat small holes in the leaves making them look like they have been hit with mini-buckshot. Their larvae, white grubs with brown heads, are 3/4 inch long - much larger than the adults. They live in the soil and eat plant roots.

If you grow asparagus don’t ignore it over the summer. Make sure to check for asparagus beetles. There are two kinds. One is black and white and appears very early in the spring. The other one is bright orange and it is active right now (mid-summer), laying eggs on the fronds which hatch into fat slimy worms that hungrily defoliate the plants. Like many beetles they tend to drop when when disturbed so stick a small container of soapy water under them and shake the frond a bit and they will fall right into it. The larvae cling on tighter and have to be squished.

 Since we keep the young cucumber and squash plants covered with reemay to discourage the beetles from attacking the plants before they are strong enough to survive, the early cucumber beetles were at a loss.

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I found them sitting on potatoes and tomatoes not finding much to eat. This kept the population down a bit so when we finally uncovered the plants as they started to blossom they were not overwhelmed with bugs.

There are a few squash bugs starting to show up and lay eggs on the underside of the zucchini leaves.

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We try to squish these eggs daily to keep future generations of bugs to a minimum.

Mexican bean beetles are something I have not had to contend with yet which is a blessing. One female can lay over 500 eggs! If your bean leaves are being skeletonized check the underside for clusters of yellow eggs and crush them. Handpick the beetles or knock them into a bucket of soapy water and squish or drown the spiny yellow larvae.

We went a little overboard on seed potatoes this year so we have beds of potatoes growing all over the garden. No potato bugs so far but I keep checking. Colorado potato beetles will not only eat potatoes but other nightshades as well including tomatoes, eggplants, peppers, and petunias—that is most of my garden! Like the bean beetles they lay masses of yellow eggs on the undersides of the leaves. When the brick red larvae hatch they eat large amounts of foliage. By now you know the drill—handpick the adults and squish or drown them and their offspring.

Plant Diseases

While you are scouting be sure to check for signs of plant diseases, too.

Hot, humid weather is perfect for encouraging fungal and bacterial diseases, so watch those tomato leaves.

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Powdery mildew will start showing up soon, too.

If your cukes suddenly wilt and no amount of water revives them, you probably have cucumber wilt caused by the cucumber beetle. Remove and destroy these plants and start some new ones in another spot. There is still time for you to harvest some cukes before fall. Cover the young plants with a lightweight row cover until they start to flower. Late plantings often are not as bothered by the beetles as the early cukes are.

Be vigilant; if you stay ahead of the bugs you will be able to keep them under control without resorting to using chemicals. 

For more pest and disease advice, check out our Pest and Plant Disease Library.

About This Blog

Get inspired by Robin Sweetser's backyard gardening tips. Robin has been a contributor to The Old Farmer's Almanac and the All-Seasons Garden Guide for many years. She and her partner Tom have a small greenhouse business and also sell plants, cut flowers, and vegetables at their local Farmer's Market.

Reader Comments

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Garden Pests

Something is killing the marigolds by stripping off all the leafs
leaving just the stem and the flowers, which needless to say
kills the plant. Help. :)

Marigold pest

It could be the below pests:
Aphids. ...
Earwigs. ...
Caterpillars. ...
Leafminers. ...
Snails and Slugs. ...
Spider Mites. ...
Thrips. ...
Whiteflies.

Slugs or earwigs get my vote,

Slugs or earwigs get my vote, especially if the damage is happening at night. Try putting out shallow containers half-filled with cheap beer to lure the slugs to a drunken death. For earwigs mix up equal parts soy sauce, vegetable oil, and corn syrup or molasses. You only need about 1/2 inch of this mix in a shallow container. Bury the containers up to their rims near your plants. In the morning check the containers and you will see who the culprit is.

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