Getting to the Root of the Problem – Learn to Identify Vegetable Insect Pests

Along with growing a vegetable garden comes the possibility of vegetable insect pest attacks. Many of them love root vegetables while others prefer vegetables grown above ground. To follow are some of the most damaging vegetable pests one should watch for in their garden. After reading this blog, please have a look at the Top 5 Blog for June 2024. This Top 5 will give you some environmentally friendly insect pest strategies and ammo to use this spring.

Cutworms

Cutworm larvae (caterpillars) are voracious nocturnal plant feeders that will attack just about any young vegetable stem. The larvae look like fat worms, smooth, and brown, grey or green in color. The signature identifier is seedling plant stems cut off at the soil line without an insect in sight. During the day, the culprits are hiding just under the soil around their chosen seedlings. Lightly rake the soil and you will expose the larvae. If disturbed, they will curl up into a tight ‘C’ shape. When they are out at night, hand pick by the light of a flashlight and drown in a bucket of soapy water.

There are many species of cutworms. On the prairies there is only one generation per year. The adults are moths that have dark grey or brown wings.  The moths do not cause damage but do lay hundreds of eggs on just about any plant and leaf litter in your vegetable garden. Even the weeds! When the larvae hatch, they feed for several weeks, pupate in the soil in June and emerge as adults in August and early September. The adult moths then lay eggs before winter in the soil, on weeds and piles of debris.

One effective cutworm deterrent is to create small plant collars from toilet paper rolls. Push the rolls into the ground to a two-inch depth around germinating seeds or newly planted seedlings. You can also make collars from milk cartons, tin cans, yogurt or fruit cups. Keep these collars on your plants until the plants have filled the collars. Cutworms are not fond of tougher, older plant stems. Using a flashlight at night, you can also handpick the culprits and drown them in a bucket of soapy water!

Onion Root Maggots

Your onions are yellowing, wilting and falling over. When you pull one up, there are holes in the bulbs, some bulbs are rotten and many tiny ‘worms’ are inside.

The adult onion root maggot looks like a regular ¼ inch long housefly that has an incredibly keen sense of smell. The female lays eggs in mid-May to early June at the base of their larvae’s favorite plants to snack on. These plants are onions, leeks, garlic, chives and shallots. They are especially fond of wet, fertile soil as an incubator for their eggs. When the eggs hatch ten days later, again it is the cream colored larvae that cause the plant damage. The hungry larvae can feed for up to three weeks, moving from bulb to bulb.

On the prairies there are two generations per year.

The second generation adults appear at the end of summer into early autumn.  Their eggs produce larvae that do not do as much damage as the first generation. They pupate in the soil over the winter and emerge as adults in the spring.

Do your homework in winter and search out resistant onion varieties. Bunching onions are resistant. Onion Root Maggots prefer white onions over yellow or red. Clean up well in fall – Do not compost affected plants – throw them in the garbage.

Do not plant onions, shallot or garlic bulbs too close together in their rows. If planted close together the larvae can easily travel from bulb to bulb.

Imported Cabbage Worm aka -White Cabbage Butterfly (Previs rapae)

This insect’s larvae not only likes cabbage but other brassicas as well; radish, kale, broccoli, brussel sprouts, horseradish, bok and pak choi and kohlrabi.

The adults are the small white butterflies that we see flitting about in spring. The male has one spot on each upper wing; the female, two black spots on each upper wing.

Their life cycle consists of just four stages. The adult moth will lay her tiny oval, yellowish white eggs on the underside of the outer leaves of the host plant. Usually a cabbage! The eggs hatch in a week and the larval stage begins feeding.  This is the stage that can cause a lot of damage. The caterpillars are 25-30 mm long, green and velvety with pale yellow lines along the back and sides. As they feed, large jagged, irregular holes are left behind and they may even tunnel into the heart of the host plant. After about a month the larvae become a chrysalis and in two more weeks an adult moth will emerge.

Carrot Rust Fly

The Carrot Rust Fly is the most serious pest of carrot crops. They can also damage celery, celeriac, parsley and parsnips. Symptoms above ground include dying leaves, bronze-colored leaves, stunting and leaf wilt.

The adult flies are slender, measuring 6 mm long (tiny) with an orange head, black body and yellow legs. The wings are dark and transparent. The male has a rounded abdomen tip and the female’s abdomen tip is pointed. They can track the scent of carrots from one mile away.

Carrot Rust Fly can have one to three generations per year. They overwinter as pupae in grass, debris, topsoil or within old carrot roots left in the garden. The adults will emerge in May and June. They lay up to 40 very tiny white eggs (1mm) on the soil or near the base of host plants. Hatching in 10 days the yellow brown larvae (maggots) quickly grow to 6 mm long. They then burrow into the carrot roots where they leave rusty red tunnels as they feed. They feed for several weeks, then pupate. Adults emerge 25 days later, (mid-July  and August). The second generation cycle begins with the adult females laying eggs.  A possible third generation emerges in fall. This can be a stretch in some areas as really most second generation eggs rarely reach the adult stage. Some will reach the pupal stage by the start of winter.

Avoid planting your carrots, parsnips, celeriac and celery in long rows. This makes it easy for the larvae to travel from root to root. Intersperse rows with companion plants that repel the fly such as French Marigolds, Oregano, Cilantro or Rosemary.

Wireworms

Wireworms are the larvae of Click Beetles. There are thousands of species of this beetle all over the world. Click Beetles make a clicking sound when grabbed or turned upside down and can jump at least 3 m when startled. Wireworms identify as 1.25 to 4 cm. hard bodied, wire-like, yellow to brown larvae. Once the larvae have hatched in the spring, they can spend a few months or up to 4 years in the soil before pupating!

The larvae prefer grass roots but do like potatoes in particular, carrots, beets, radishes, turnips, parsnips, and rutabaga.

Their damage can be very extensive as they eat seeds in the soil, stems, roots and tubers. They spend the growing season in the soil, boring into larger stems, roots and tubers.

Above ground identifiers of wireworms are irregular dying patches of plants. If this is occurring in your lawn or vegetable garden pull up two to three different plugs of lawn/plants and examine the roots /tubers for the larvae. Wireworms can also attack fruit and fruiting plants.