How to Identify and Manage 9 Common Gladiolus Pests

Gladiolus are particularly vulnerable to those pests that affect bulbs and rhizomes as well as corms, which are the underground structures these plants grow from. These storage structures look similar to bulbs but lack the onion-like layers that true bulbs have.

In our guide to growing gladiolus, we cover cultivation instructions for these showy perennials.

In this guide, we’ll be diving into the most common types of pests that may affect your plants, how to identify them, and what you can do to control them.

Here’s what’s coming up:

1. Bulb Mites

Belonging to the Rhizoglyphus genus, various species of bulb mites are tiny pests that will infest many different bulb and corm plants, including daffodils, hyacinths, tulips, and garlic, as well as gladiolus.

Bulb mites are itty bitty, between 0.55 and 0.75 millimeters long, with translucent, oval white bodies with amber or brown legs. They move slowly, and upon closer inspection, it’s not uncommon to mistake these pests for insect eggs.

The mites themselves feed on the corms and also provide entry points for the introduction of secondary bacterial and fungal pathogens.

Symptoms of a bulb mite infestation are varied. In the case of a large infestation, or a secondary infection from soilborne fungal or bacterial pathogens, the bulbs may fail to sprout or their growth may be stunted and warped.

You’ll need to dig up the corm to inspect it, as this is the only way you’ll know for sure that the pests are present.

Unlike other pests, bulb mites don’t have a dormancy period. This means they may be present and active throughout the year, with the most activity seen during the growing season.

If you dig up your gladiolus to store during the winter months, infested corms will spread these pests to other bulbs in your greenhouse or storage shed.

Before planting, ensure that you check carefully for mites, but obvious damage may also be caused by other types of pests, bruising, or improper storage over the winter.

Bulb mites are notoriously hard to control once they’ve become established, and in the case of a bad infestation, entire plants should be dug up and destroyed. Do not compost infested plant material.

2. Caterpillars

You may find a few different types of caterpillars munching away at your gladiolus. Cutworms and the zebra caterpillar (Melanchra picta) are the most common, and management for both is the same.

Cutworms and zebra caterpillars are both the most active in May. Cutworms are nocturnal and are most active at night, while M. picta is active during the day.

“Cutworm” is a generic name given to caterpillars in the Noctuidae family that feed on young plants by cutting them down at the soil line. They aren’t picky eaters and feed on a wide variety of host plants, eventually growing into adult nocturnal moths.

Cutworms are smooth-skinned with green, brown, gray, or black coloration when in their larval form. They are roughly two inches in length when they are fully grown.

All larval cutworm species are similar in appearance and will curl into a “C” shape when they’ve been disturbed or knocked to the ground.

Zebra caterpillars are much more colorful and easier to spot. Mature larvae have long, yellow stripes on their bodies with a dark orange head.

They also belong to the Noctuidae family, but don’t feed in the same manner as cutworms. Instead, these caterpillars feed directly on the foliage, moving around and munching wherever they please.

Thrips are sap-sucking pests. They have a mouth that works like a straw, piercing foliage and stems to suck out the sap. Without intervention, these pests will weaken your plants and potentially spread to other vulnerable plants in your landscape.

Gladiolus thrips are active starting in the early spring when new shoots are forming. Symptoms of an infestation may include stunted shoots, leaves with a withered, bleached, or spotted appearance, and the flowers that are distorted and damaged.

You’ll most likely notice these pests in one of their pupal forms, hiding in the sheaths of the leaves or flower stalks.

Gladiolus thrips go through pre-pupa and pupa stages before turning into adults. Their bodies have burnt orange coloration in both pupal stages, with bright red “eyes.”

In the pre-pupa stage, the thrips have short wing pads and undeveloped wings that aren’t large enough to provide lift. Their antennae point forward, and they don’t move unless disturbed.

In the second stage, the thrips have longer wing pads, underdeveloped wings, and antennae that fold back over their heads. They will move slowly and hide unless disturbed.

Unlike the citrus mealybug, obscure mealybugs have a much thicker layer of white wax on their backs. The filaments on their bodies are also longer, extending much farther outward than those on other species.

These pests are also sap-suckers, and they excrete honeydew onto the leaves of their host plant. Honeydew can cause sooty mold, which is unsightly.

These kinds of mealybugs don’t stop their activity in the winter like other pests.

The two most common plant bugs that infest gladiolus are the tarnished plant bug, Lygus lineolaris, and the four-lined plant bug, Poecilocapsus lineatus. These bugs are sap-suckers, feeding on the sugars within your plant’s stems and foliage.

These pests emerge in mid-May. When they are young, they’ll hide within the sheaths of your gladiolus.

Both species are easy to spot when they are young. P. lineatus nymphs are small and have bright reddish-orange coloration, with light-colored stripes on their wing pads.

L. lineolaris nymphs are a lemon-lime color and will develop five black dots on their backs.

6. Root-Knot Nematodes

In the genus Meloidogyne, root-knot nematodes are a pest that can affect many different host plants. They are microscopic, parasitic roundworms that infect the roots. While some types of nematodes are beneficial, these will negatively impact your plants.

The more temperate and tropical your USDA Hardiness Zone, the more likely you are to encounter these pests. They thrive in moist, warm soil and will strike in the summer growing months.

But how do you know if you have an infestation of root-knot nematodes? Unfortunately, by the time your plant signals that there is an issue, it might be too late.

Root-knot nematodes will create lesions on the corms. These open lesions invite bacteria and fungi to enter your gladiolus, eventually rotting out the corm and killing the plant.

During an active nematode infestation, your gladiolus will look sick – yellowing or wilted leaves and stunted growth are the most common symptoms. None of these symptoms are unique to this type of infestation, but there are other signs you can look for.

Are there other plants around your gladiolus that are also looking sick? If you dig up your plants and inspect the roots, do you see unnatural-looking galls – swollen circular growths – all over them?

These are hints that you’re dealing with root-knot nematodes. So let’s talk about control.

Luckily, these nematodes spread slowly, so you might be able to act before the infestation spreads to the rest of your garden.

However, there isn’t a way to rid your gladiolus of these pests once infested, so it’s best to remove them from the garden altogether and dispose of them in your trash can or firepit.

The leading solution for home gardeners is to decrease parasitic nematode populations within the soil, then rebuild the soil to fight off these pests naturally.

7. Slugs and Snails

These slimy creepy-crawlies are no fun. And they are particularly awful when it’s warm, wet, and rainy.

Slugs and snails will usually strike in the spring or summer, but the damage they cause is always the same: holes in the foliage, usually appearing overnight.

The best way to manage slugs and snails is to hand-pick them off, or set up beer traps around the planting area to kill these pests en masse.

Beer traps are easy to set up – just grab a can of cheap beer (not the good stuff!) and pour it into a shallow bowl or saucer. Set it outside in the late afternoon, and come back the following morning to dispose of the dead slugs and snails that have drowned.

Check out our guide to managing slugs and snails for more options.

8. Tulip Aphids

Tulip aphids, Dysaphis tulipae, are pests that target and feed on the bulbs or corms of ornamental plants like tulips, irises, and gladiolus.

They can strike both planted bulbs and bulbs in storage. Additionally, when the infested plant begins to grow above ground, these parts will become a target for the aphids too.

While aphids are generally easy to eradicate, they should be taken seriously if you notice them on your plant. Aphids are notorious for spreading viruses when they feed, causing more significant issues that are harder to manage.

If the plant begins to grow stunted and distorted, you’ll know if your gladiolus corm is potentially infested with aphids. Tulip aphids will move to the aboveground growth soon after it emerges from the soil.

You can control tulip aphids by using your favorite insecticidal soap. If you notice an infested corm while moving your plant out of storage, immerse it in an insecticidal soap dunk before planting, and this should clear it up.

When your gladiolus has started growing aboveground, spray it thoroughly with your insecticidal soap. Spray in every nook and cranny to avoid missing any of these pests.

As you can guess from their name, these spider mites have spots that flank their bodies on either side. It’s difficult to see without a microscope. With the naked eye, these mites will look brownish.

Spider mites are teeny-tiny arachnids that feed on the contents of your plant’s foliage. They are sap-suckers, and they leave behind silvery patches on the leaves when they’ve finished feeding.

These mites will infest plants in the summer when the temperature is high, and the weather is dry. They form colonies, building tiny protective webbing all over the plant. This webbing can give your plant a dusty look from afar because it’s so small.

To control a spider mite infestation, you can use a few different methods.

First, if you’re partial to chemical solutions, a good neem oil concentrate or insecticidal soap will damage the colony without harming beneficial insects.

If you lean more towards biological control, introducing a beneficial predator mite like Phytoseiulus persimilis will do the trick. P. persimilis is an excellent choice because it feeds on the two-spotted spider mite at every life stage.

You can find these predator mites at Arbico Organics in containers of as little as 2,000 and up to 10,000. If the infestation is severe, you should apply a knockdown spray of neem oil at least 7 days before releasing these predatory mites.

Check out our guide to controlling spider mites if you find you’re dealing with these pests regularly. There are a lot of good tips and tricks in there that can help!

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