Cabbage worm infestations can be a major problem for gardeners who grow brassica crops, such as cabbage, broccoli, and cauliflower. These pests, which are the larvae of the cabbage butterfly (also known as the imported cabbageworm or Pieris rapae), feed on the leaves of the plants, causing holes and damage that can severely impact the health and yield of the crop.
Symptoms
- Holes in the leaves of the plants, which can range from small pinpricks to large, ragged tears
- Green or yellowish-green worms (about 1 inch long) on the leaves and stems, which are the larvae of the cabbage butterfly
- Damage to the head or heart of the cabbage or other brassica plant, which can include wilting, discoloration, and stunted growth
- Frass (insect droppings) on the leaves and nearby surfaces, which can appear as small black or brown pellets
- Damage to the flowers and buds of the plant, which can prevent proper pollination and reduce yield
- Some cabbage worms can be hard to spot, as they can blend in with the leaves and stems, making it difficult to detect them before they cause significant damage.
It’s important to keep an eye out for these symptoms and take action to control the infestation as soon as possible, as cabbage worms can quickly multiply and cause significant damage to your garden.
What is a Cabbage Worm
A cabbage worm is the larva of the cabbage butterfly, also known as the imported cabbageworm or Pieris rapae.
- They are green or yellowish-green in color
- They can grow up to 1 inch in length
- They have a smooth and plump body
- They have black spots on their body, which can be seen clearly when they are still
- They are active and can be seen moving around on the leaves and stems of the plants
- They have a pair of black dots on the front of their head, which are the eyes
- They have three pairs of true legs and five pairs of prolegs
- Their shape is similar to a worm, and they can curl up when touched or disturbed.
It’s important to note that cabbage worms are often hard to spot, as they can blend in with the leaves and stems, making it difficult to detect them before they cause significant damage.
Treating a Cabbage Worm Infestation
It may be necessary to use multiple methods to effectively control a cabbage worm infestation in a garden. For example, handpicking may be helpful in the early stages of an infestation, but using insecticidal soap may be needed as the infestation becomes more severe.
Handpicking
- Look for worms on the leaves, stems, and heads of the plants
- Use gloves or a tool like tweezers to remove the worms from the plants
- Dispose of the worms in a container of soapy water or by dropping them into a bucket of soapy water
- This method can be time-consuming and may not be effective if the infestation is severe
- It can be helpful to do this early in the morning or late in the evening when the worms are more active and easier to spot
- It’s a good idea to check the plants regularly, at least once a week, to catch the infestation early and prevent it from spreading.
Using Insecticidal Soap
- Spray the plants with insecticidal soap, which suffocates the worms
- Be sure to follow the instructions on the product label for proper application and safety precautions
- This method can be effective in controlling small to moderate infestations, but may not be as effective for large infestations
- Insecticidal soap can be harmful to beneficial insects, so it’s important to use it only when necessary and to avoid applying it when beneficial insects, such as bees, are present
- It’s a good idea to spray in the evening, as the soap will not dry out as quickly, and the worms will be more active and easier to reach.
Using Bacillus thuringiensis (BT)
- Apply Bacillus thuringiensis (BT), a naturally-occurring bacteria that is toxic to worms, to the plants
- BT can be found in liquid or powder form and should be applied according to the product label instructions
- This method is considered safe for use in organic gardens and can be effective in controlling moderate to large infestations
- BT is specific to certain types of worms and caterpillars, so it will not harm beneficial insects or other beneficial organisms in the garden.
- it’s important to follow the instructions on the product label, as over-application can lead to resistance in the worms.
Using Neem oil
- Spray the plants with neem oil, which can act as an insect repellent and also disrupt the life cycle of the worms
- Neem oil should be applied according to the product label instructions
- This method can be effective in controlling moderate to large infestations
- Neem oil is also safe for beneficial insects and other beneficial organisms in the garden
- It’s important to follow the instructions on the product label and avoid applying neem oil in direct sunlight or when the temperature is high, as it can cause burning and damage to the plants.
Using Companion Planting
- Planting certain companion plants, such as nasturtiums, dill, or calendula around your brassica plants can help repel cabbage worms
- This method can be effective in preventing or reducing infestations, but may not be as effective in controlling existing infestations
- Companion planting can be used in conjunction with other methods to increase the effectiveness of controlling the infestation.
- It’s important to research which plants are best for your specific situation and to consider the overall health and well-being of the garden ecosystem.