Beloved as they are, butterflies can sometimes strike fear in the hearts of gardeners. Species like the Large White (Pieris brassicae), Small White (Pieris rapae), and Cabbage Moth are known troublemakers. While their elegant flutter near cabbage plants may not be the most welcome sight for gardeners, it’s crucial to acknowledge their role in the ecosystem and discover ways to coexist with these winged creatures peacefully.
The Large White butterfly showcases stunning white wings with black tips, while its underside features a pale green hue, providing camouflage when at rest. Females can be distinguished by the presence of two black spots and a black line on the upper side of the forewing. Introduced in summer, second-generation Large White butterflies exhibit larger sizes and more distinct black spots.
When it comes to diet, Large White butterflies actively engage in plant pollination by feeding on nectar.
Now, let’s turn our attention to the Large White caterpillars.
These remarkable creatures begin their journey as yellow pin-shaped eggs, typically laid in groups of 20 to 60 on the underside (and occasionally the upper side) of cabbage leaves. After approximately ten days, the eggs hatch, revealing greenish-yellow larvae adorned with black dots and sparse, short dark hairs. Three distinctive yellow stripes grace their bodies, positioned above the legs and along the back.
Large White caterpillars, unlike other caterpillar species, employ a distinctive defense mechanism. Instead of relying on leaf twisting or cobweb ball formation, they have developed a unique strategy. By feeding on cabbage leaves, these caterpillars accumulate mustard oil, making themselves unappetizing to predators like birds. This clever adaptation serves as a deterrent, reducing the chances of being preyed upon. However, it’s important to mention that birds are known to indulge in pupae from the last brood, which hibernate during winter.
Let’s take a closer look at the Small White butterfly and its caterpillar, as they have distinct characteristics from the Large White butterfly.
The Small White butterfly is smaller in size, with a wingspan ranging from 3 to 5 cm. Compared to the Large White, the spots on its wings are smaller and have lighter, uneven edges, giving them a unique appearance.
When it comes to the Small White caterpillar, it starts its life when the butterfly lays pale yellow eggs individually. The caterpillars are green in color with delicate yellow lines that give them a velvety appearance. Unlike the caterpillars of the Large White, they do not accumulate toxic substances and are actually preferred by birds as a food source. This is why Small White caterpillars often hide deep within the cabbage heads to protect themselves from birds and other predators, unlike the fearless Large White caterpillars that crawl even on the outer leaves of cabbage.
As the Small White caterpillar grows and consumes nutrients, it eventually reaches its maximum size and searches for a suitable place to pupate. Typically, the pupa is formed away from the food plant, such as on a fence, tree trunk, or building. It attaches itself with a silk sash and cremaster for support. Interestingly, you may even find a chrysalis in a greenhouse.
Let’s also explore the nocturnal moth and its caterpillars, notorious for their love of feasting on our precious crops.
Cabbage Moth (Mamestra brassicae) Body length: 19–23 mm. Wingspan: 40-50 mm
Appearance-wise, the forewings of the Cabbage Moth are dark with varying shades of brown, similar to other cutworm species. A distinguishing feature is a kidney-shaped spot on the wing edges, partially surrounded by white. These characteristics help identify the Cabbage Moth.
This butterfly thrives in high humidity, so if your garden is located in a lowland or near a water source, or if the months of May and June are cool and damp, the chances of encountering a Cabbage Moth increase.
When it comes to diet, Cabbage Moths feed on flower nectar, serving as vital pollinators. They fly at night and seek shelter in grass, along the shaded sides of fences, tree trunks, and other secluded spots during the day. These nocturnal butterflies are unsung heroes in the pollination of plants, holding second place after bees. With the decline in bee populations, the role of night butterflies in preserving plant species becomes even more critical. However, this significant contribution often goes unnoticed outside scientific journals where environmentalists highlight the importance of insects in ecosystems.
In many sources, the Cabbage Moth is labeled a malicious pest that must be eradicated to prevent hunger. However, it’s essential to consider the credibility of the information source. Whether it’s an agronomist working with vast mono-cultivated areas or a website promoting pesticides, the perspective can significantly influence the portrayal of this butterfly.
Let’s examine if there’s more to the story.
The life cycle of the Cabbage Moth follows a pattern similar to the Cabbage White. It overwinters in the pupal stage, with the autumn generation of caterpillars burrowing into the ground for pupation (in contrast to Cabbage White, which attaches its chrysalis with a silk thread to a fence or tree trunk). In April-May, the butterfly emerges from the overwintered pupa. The female lives for an average of 2-3 weeks, lays eggs, and then passes away. Depending on weather conditions, there can be 2-3 generations of Cabbage Moths per year.
What do Cabbage Moth caterpillars look like? The adult caterpillar of the Cabbage Moth grows to a length of 35-40 mm. Its body color can range from greyish green to dark brown or black. One distinctive characteristic is the presence of a pattern of dark spots on its back, which sets it apart from caterpillars of other species.
What do the Cabbage Moth caterpillars eat? Cabbage Moth caterpillars display an omnivorous diet. They typically consume aggressive plant species such as pigweed, bindweed, and sow thistles, which they effectively control. However, due to the destruction of natural food sources and the prevalence of monocultural fields, these caterpillars have adapted to feeding on cultivated crops. They have developed a taste for cabbage, beets, poppy seeds, carrots, corn, lettuce, flax, buckwheat, and more. It’s no surprise that the well-nourished leaves of cabbage are particularly enticing to these caterpillars.
So, after examining three types of butterflies whose caterpillars share our love for radishes, watercress, bok choy, broccoli, cabbage, and cauliflower, the question arises: how can we coexist with these caterpillars in our gardens?
Traditional agricultural practices recommended by agronomists include deep autumn plowing, inter-row cultivation, weed destruction, and chemical treatments. Following these recommendations may indeed help protect our crops. However, they come at the cost of disrupting soil health and natural predator-prey dynamics. Moreover, the use of chemicals can have negative effects on human health.
Therefore, let’s take a different approach.
Instead of completely eliminating all wild elements from our gardens, let’s create pockets of wilderness and incorporate many flowering plants rich in nectar. These plants will not only provide food for butterflies but also attract their natural enemies. Birds, lizards, hedgehogs, bats, and parasitic ichneumon wasps (such as Apanteles glomeratus L., Pteromalus puparum L., and Trichogramma evanescens Westw) are among the beneficial insects and animals that help regulate butterfly populations. These tiny wasps lay their eggs directly on caterpillars or pupae, becoming a formidable force in controlling pests. In fact, they can destroy up to 90-95% of cabbage caterpillars and other species.
By cultivating a garden that supports a diverse range of species and avoiding the use of chemicals, we can attract these natural allies and maintain a balanced ecosystem. Instead of being the sole enemies of caterpillars, we can allow nature’s invisible superheroes to work their magic.
I urge caution when it comes to the use of chemicals, even bioinsecticides. While biological products are generally better than heavy chemicals, it’s important to use them sparingly and only in emergency situations. The primary goal of a conscious gardener should be to create optimal conditions for all insects, birds, and mammals.
So, how can we overcome our fear of caterpillars in the garden and still ensure a thriving cabbage crop? Here are some recommendations to consider:
Embrace the garden as part of a dynamic ecosystem where species coexist and keep each other in balance.
Physical Barriers: Use fine netting or horticultural fleece to create a barrier that excludes adult butterflies from reaching your brassica crops. Set up a frame or hoops to support the netting, ensuring it reaches the soil and is sealed tightly to prevent any gaps. Investing in metal arcs and mesh may initially require some expenses, but it provides long-lasting protection for years to come. In the spring, you can add an additional layer of garden fleece on top of the mesh to protect against temperature differences. Take the time to design and implement a reliable barrier that keeps your crop safe and gives you peace of mind.
When selecting the ideal netting, it’s crucial to consider your garden’s specific requirements. Netting comes in various options, each serving its unique purpose. Some feature larger holes, perfect for shielding crops against birds, deer, and other wildlife. However, for safeguarding cabbage and deterring butterflies while still allowing sunlight and moisture to reach your plants, ultra-fine garden mesh, also known as Netting Pest Barrier, is the way to go.
You can easily find mesh with integrated hoops, but it’s essential to carefully review the product specifications, paying close attention to height and the number of hoops included. Sometimes, objects may appear larger in photos than they are in reality. While regular-size hoops suffice for smaller crops like Rocket Salad (part of the Brassicaceae family), larger plants such as kale or broccoli require larger hoops to ensure ample space for growth and flourishing.
Companion Planting and Understanding Butterfly Behavior: You may wonder, how does a butterfly that feeds only on nectar know which plant to choose for its caterpillars? During the search for a suitable food plant to lay eggs on, butterflies rely on chemical signals. When an insect flies a short distance from a potential food plant, it detects volatile chemicals (similar to a smell) that serve as its main guide. As the butterfly gets closer to the plant, it also assesses the visual signals, such as the color and size of the host plant. But that’s not all.The butterfly uses special receptors on its legs to check the ‘taste’ of the plant. Researchers have observed that butterflies make multiple landings on the foliage to ensure that the host plant is suitable for their caterpillars.
Now, you may think this is all fascinating, but how does this knowledge help gardeners protect their cabbage crop?
By planting companion plants with strong smells, such as marigolds, calendula, and onions, next to your cabbage, you can mask the scent of the cabbage plant. Additionally, these companion plants visually confuse the butterfly. Moreover, using tall plants with openwork foliage, such as dill and medicinal chamomile, can further confuse the butterfly. Each time it lands, it will find itself on a different plant that doesn’t meet the criteria for its caterpillars’ food.
While companion planting may not provide 100% protection for your cabbage crop, they can significantly reduce the number of caterpillars.
Using decoys to trick cabbage white butterflies is an interesting and practical approach to protect cabbage crops. While it may not be scientifically proven, it is a reasonable method that requires minimal effort.
By creating white objects, such as replicas made of white film or disposable paper cups, and hanging them over the cabbage plants on sticks that sway in the wind, you can create the illusion of an already occupied plot, deterring butterflies from laying their eggs on your plants.This method takes advantage of the butterfly’s behavior of seeking out plots with ample food supply for their offspring. When they see the white decoys, they may assume that the area is already populated by other butterflies and choose to fly to a neighboring plot instead.
Implementing this technique can be an interesting project for children, as they can actively participate in making the decoys and observing the behavior of cabbage white butterflies.
Crop Rotation. To protect cabbage crops, it’s crucial to rotate them each year. Some pests, like cabbage moth caterpillars, burrow into the ground for pupation, while others, like flea beetles reside in the upper soil layer. If we neglect crop rotation and cover beds with nets, hibernating insects can still damage young plants from the inside.
To practice crop rotation effectively, avoid growing cabbage in the same spot each year. Instead, plant cabbage in beds where legumes, onions, garlic, cucumbers, or potatoes were grown the previous year. However, avoid planting cabbage in areas where other cruciferous vegetables like radishes, arugula, bok choy, and watercress were previously cultivated.
Protect Your Garden with Sacrificial Plants: Nasturtium to the Rescue.
Have you ever heard of the clever technique of using sacrificial plants to attract and divert pests? Nasturtium, with its enticing charm, is a top contender for this role. Planting nasturtium under fruit trees serves as a cunning strategy to deter ants from spreading aphids across the tree, while also capturing the attention of large white and small white butterflies. To optimize its impact, plant nasturtium away from your precious crops. Choose a spot along the garden’s border or pathway and create a captivating flowering strip. Within this designated area, sow the seeds of easy-to-grow, nectar-rich annual plants such as phacelia, cosmos, dill, and other delightful varieties. This enchanting haven will not only allure butterflies but also attract their natural enemies, ensuring a harmonious balance within your garden.
These tips will safeguard your precious cruciferous crop and transform your perspective on butterflies in the garden. By embracing the intricate harmony of the ecosystem, the life of a gardener becomes more engaging and captivating than ever before!
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