Gardeners across the globe face a constant challenge: dealing with damage to their beloved crops and flowers. Among the most persistent pests is the imported cabbageworm, whose adult butterflies are notorious for their sheer numbers and prolific egg-laying habits. These pesky insects have a particular fondness for plants in the Cruciferae family, but they won’t discriminate – they’ll happily munch on a wide variety of flowers, weeds, and other plants as well.
If you’re tired of watching your garden suffer at the hands of these unwanted visitors, then let’s explore some strategies to help you regain control.
What Are Imported Cabbageworms?
The cabbage white butterfly (Pieris rapae), also known as the imported cabbageworm or small white, is a medium-sized species commonly found in temperate climates. While adult butterflies are generally harmless, their larvae can wreak havoc on plant life. In fact, the caterpillars have a voracious appetite that can quickly reduce large, healthy leaves to mere veins and stems.
This butterfly was first spotted in Canada in 1860 and rapidly spread across North America within six years, earning its widespread presence across the continent today.
The larval stage of the imported cabbageworm feeds on plant foliage, causing significant damage as it burrows into the heads of broccoli and cabbage. As a result, gardeners must exercise caution when preparing these plants for consumption if they’ve been infested by these pests.
Furthermore, the butterflies’ copious consumption and waste production can lead to substantial contamination and staining of crops, particularly in cases of large-scale infestations.
The Lifecycle of Cabbageworms
The metamorphosis of a butterfly from its egg stage to a fully formed adult typically takes approximately 42 days. This remarkable transformation is followed by an average lifespan of around three weeks for the mature butterfly. The frequency of generations within a given season, however, is influenced by factors such as temperature.
In colder climates, it’s common to observe three distinct generations, while warmer regions like northern California may experience up to five and more southern locations potentially seeing eight or more. Interestingly, in places like Florida, certain species of cabbageworms are present year-round due to the region’s unique climate.
Eggs
Female monarch butterflies deposit their eggs individually on the undersides of leaves or foliage, sometimes clustering them in small groups. At first glance, the tiny white orbs may appear identical to the naked eye. However, upon closer inspection with a microscope, the eggs reveal themselves to be bullet-shaped and standing upright, their original white hue gradually giving way to a faint yellow as they mature.
Larva
The larval stage of this insect’s life cycle is characterized by a soft, velvety green caterpillar that may display faint yellow stripes. As it matures, the caterpillar grows plump and approximately one inch in length. Unfortunately, this stage is also the most destructive, marked by ceaseless eating and defecation that can have devastating effects on your crop.
Pupa
Pupation, the transformative process by which caterpillars morph into butterflies, typically unfolds on food crops. However, it’s not uncommon to find these cocoons on a diverse range of plants, including the fragrant and flavorful basil. In fact, the pupation stage often takes place on the underside of basil leaves, where it’s camouflaged by cottony strands that provide exceptional protection.
The caterpillar’s silk production is so impressive that it can even curl the leaf around itself for added security.
Adult
With an adult wingspan spanning up to two inches across, this striking butterfly boasts a crisp white body adorned with distinct black dots. While the patterns of these dots subtly differ between males and females, their overall appearance remains a captivating sight. In its relatively short three-week lifespan, the female butterfly assumes a prominent role, actively flitting from plant to plant as she lays up to 400 eggs during this period.
In contrast, it’s the adult male that typically takes center stage in terms of daytime activity. Beyond egg-laying duties, these adults also take pleasure in sipping nectar, leading them to visit a variety of plants – not just those where they lay their eggs.
Host Plants of the Imported Cabbageworm
When it comes to these unwanted visitors, many assume that only a select few plant species are at risk. However, the truth is that many plants can be affected by this pest’s life cycle. To effectively manage the issue, it’s essential to observe the insects’ behavior and identify which specific plants they’re targeting for egg-laying or caterpillar feeding. Some common hosts include cabbage, kale, broccoli, Brussels sprouts, kohlrabi, cauliflower, and horseradish.
Damage by Cabbageworms
Without proper control measures in place, imported cabbageworm populations can explode, leading to catastrophic consequences for your crops. These voracious pests consume leaves relentlessly, causing irreparable damage by excavating holes that can ultimately lead to leaf loss or a premature demise as the plant is unable to provide the necessary nutrients. In extreme cases, the plant may be left a mere skeleton, marking its eventual demise.
Controlling Cabbageworms
To prevent damage caused by imported cabbageworms, it’s essential to implement control measures at the start of each season, ideally before the butterflies begin to appear on your prized plants. This proactive approach helps minimize the impact of these common pests and ensures a healthy crop yield.
Hand Pick
For smaller gardens or individual plant enthusiasts, this approach is both efficient and effective. It requires minimal manpower – just a few minutes of your time each day. Simply pluck the aphids from the affected plants and dispatch them with a quick squish or crush. Alternatively, if you’re a chicken keeper, you can delight your feathered friends by offering them as a tasty treat. Your chickens will surely appreciate this wormy indulgence, and you’ll be rewarded with their grateful clucks.
Floating Row Covers
To effectively deter butterflies from landing on your garden beds in the first instance, consider utilising physical barriers. These are particularly effective when used on elevated planters. You can either create your own or purchase pre-made options. However, be prepared to take swift action once you open the cover as adult cabbage butterflies may quickly respond by entering your space, especially if left unattended.
Companion Planting
When it comes to deterring cabbage moths, some plants are more effective than others. To repel these pests, you’ll want to focus on plants that are compatible with brassicas or other crops you’re trying to protect. Certain herbs and flowers have been shown to deter imported cabbageworms, including lavender, thyme, dill, onions, garlic, marigolds, and peppermint. By incorporating these plants into your garden, you can create a barrier that cabbage moths are less likely to cross.
Another strategy is to use trap crops. This involves intentionally planting a crop that cabbage butterflies prefer for egg-laying purposes, thereby distracting them from your primary crop. Nasturtiums are an excellent choice for this method, as they’re easy to grow and can be contained in pots to prevent over-spreading.
Neem Oil
While neem oil is an effective solution for many gardening woes, its benefits shouldn’t be underestimated. This natural substance not only kills pests by disrupting their feeding and reproduction habits but also makes foliage unpalatable to unwanted insects like imported cabbageworms. Although it can provide some relief, neem oil may not be enough to completely eradicate large infestations on its own. A multi-faceted approach that incorporates other methods is often necessary.
Furthermore, neem oil’s applications extend beyond pest control – it can also help combat a range of fungal diseases in the garden. Its versatility and eco-friendly nature make it an invaluable addition to any gardener’s toolkit.
Bacillus Thuringiensis
Bt, a naturally occurring bacteria found in soil, is a non-toxic threat to humans and animals but a formidable foe to certain insect larvae. Its potent properties make it an attractive option for gardeners seeking to control pests without harming themselves or other beneficial creatures. Available in concentrated form or as a convenient spray, Bt is a reliable choice when integrated into your growing routine.
To reap its benefits, simply mist your plants evenly in the evening, allowing the liquid to drip off the foliage. Be sure to apply this treatment to both sides of the leaves. Notably, Bt should be used with caution around swan plants and milkweed, as monarch caterpillars may be present and require protection. With proper application, Bt can prove a valuable ally in maintaining a healthy and balanced garden ecosystem.
Parasitic Wasps
Beneficial wasps like Trichogramma brassicae don’t pose a threat to humans, as they focus on laying eggs on the larvae and pupae of caterpillars instead of stinging us. These wasps are readily available for purchase in packs containing eggs, pupae, or adults, both online and offline. Once introduced into your garden, these wasp eggs will hatch and the resulting larvae will feed on the caterpillar itself, providing a natural form of pest control.
Insecticidal Soaps
When tackling cabbageworms, most insecticidal soaps prove effective when sprayed directly on the pest. It’s crucial to check the product you’re using to ensure it doesn’t have residual effects that harm beneficial insects and pollinators. The market offers both natural and chemical-based options, with the former generally being more environmentally friendly. To create a DIY solution, combine one teaspoon of mild dish soap with 1 liter of water in a spray bottle, then aim directly at the target.
This homemade approach allows for precision targeting while minimizing environmental impact.
Pyrethrum
While pyrethrum is derived from natural sources, it can still pose a risk to beneficial insects, albeit for a relatively short period of several hours at most. On the other hand, its knockdown properties allow it to swiftly incapacitate pests on contact, unlike neem oil which requires time to take effect. As a result, pyrethrum is often employed as a fast-acting solution to eliminate feeding butterflies, and its efficacy can be optimized by applying it liberally to targeted plants.
Cornmeal
A peculiar yet effective method for controlling imported cabbageworms involves using cor meal. To implement this approach, start by thoroughly wetting the affected plant with a spray bottle or hose. Next, liberally sprinkle cornmeal over the foliage, taking care to cover all areas evenly. As the worms feed on the cornmeal, they will expand and ultimately succumb to their own consumption.
Diatomaceous Earth
In situations where rainfall is unlikely, consider employing diatomaceous earth as a natural pest control method. This approach can be especially effective in small areas, where the benefits of this powder are truly remarkable. For those unfamiliar with diatomaceous earth, it’s worth noting that this substance is actually fossilized remains of aquatic organisms rich in silica.
To utilize it effectively, simply sprinkle the dry powder over your plants and allow its unique properties to take effect. As cabbageworms crawl across the treated area, their bodies will absorb the fats and oils, ultimately leading to desiccation and a reduction in infestation.
